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Articles .: Ford F-Series 1953 - 1979 .: 53-79 F-Series Drivetrain, Transmission, & Axle .: Installing A 1987-93 Mustang SEFI 5 Liter V8/AOD Drive Train into A '61- 79 F100 - F250 Truck


By Donald R. Haulsee


I acquired a 66 F100 as part of a trade. The truck was a short wheel base stepside and the body was in good shape. Unfortunately, the 240 6 cylinder engine had broken timing gears and the transmission extension housing on the Cruisamatic was cracked. I also had a Mustang 5.0 SEFI engine with an AOD sitting in the corner of the garage. I saw no reason to spend more money on an engine and transmission for the truck when I had a perfectly good drive train sitting there in the garage. To my surprise, the drive train bolted onto the existing cross members without drilling any holes. What I thought would be a difficult project, turned into a relatively simple conversion.

The truck has excellent drivability, performance,and fuel consumption. The AOD combined with my 3.70 ratio rear axle gives approximately 1900 rpm @ 60 mph. Combined city/highway gas mileage is in the range of 18-20 mpg. As can be expected from EFI, the engine starts easily in all weather conditions.

The late model Mustang HO V8 drive train is readily available in junkyards and from local trading magazines for a low price. A local quality wrecking yard quoted an 89 V8 with 80,000 miles for $400 with a 100 day warranty. A used Mustang AOD transmission can be purchased for as low as $200. This drive train can be easily retrofit, complete with computer controls into any F100 series truck that was available with an FE block V8 or a small block V8 even if the truck was originally equipped with a 6 cylinder engine. By carefully scouting through several Pull-It-Youself wrecking yards, I was able to gather virtually all of the parts to assemble the truck for a very low cost.

I used a lot of parts from other Ford cars. In particular, I found that Crown Victoria/ Grand Marquis parts were very useful and very plentiful in Pull-It-Yourself yards.

The difficulty of installation will be affected by environmental standards in your area. In my case, I have not installed the air pump, catalytic converters, or the charcoal canister. Outside of that, the entire computer system is operating.

The wiring of the computer system is not overly complex. I will give the wiring connections that I used, however, the harnesses do change slightly from year to year. The Electrical/Vacuum troubleshooting manuals available from Helm have enough information to wire the truck. You will have to refer to the Engine Controls, Power Distribution and Start/Ignition sections to find all of the connections.

I recommend the Crown Victoria computer harness over the Mustang harness because the solenoid, battery, computer, and relays are located in compatible locations. If you must have a Mass Air unit, then I recommend that you add the additional wires for Mass Air to the Crown Victoria harness rather than struggle with locating parts where the Mustang harness wants to put them. The late model mustang web site, The Corral (, has instructions on adding MAF to a Speed Density Mustang harness.


87-93 Mustang 5.0 V8

87-93 Mustang Air Cleaner Hose

87-93 Mustang AOD (Mustang AOD's and 351W AOD's have more clutch plates)

87-93 Mustang AOD TV linkage

87-88 5.0 Mustang Speed Density Computer (If you use Mass Air, get MAF Meter Also)

86-89 5.0 Crown Victoria Computer Harness (Modify harness with Mass Air)

86-89 5.0 Crown Victoria TAD/TAB solenoids and EGR Valve Positioner

86-89 5.0 Crown Victoria Exhaust Manifolds with Pipe Flanges

86-93 V8 O2 Sensors

86-89 5.0 Crown Victoria O2 Sensor Harness

86-89 5.0 Crown Victoria Air Cleaner

87 Up Mustang Fuel Pump Relay (Other car lines will also work)

87 Up Mustang Fuel Pump Inertia Cut Off Switch (Other car lines will also work)

TFI Compatible Ignition Coil

V8 AOD fill tube

V8 AOD torque converter

V8 AOD torque converter cover

V8 AOD wiring harness

V8 AOD Flex Plate

V8 AOD Flex Plate to Crankshaft Bolts

V8 AOD Torque Converter Nuts

V8 AOD Engine Plate

86-88 5.0 MAP Sensor (BAP Sensor For MAF Conversions)

86-89 5.0 Crown Victoria Drive Shaft

69 F100 302 Engine Mounts

66 - 76 F100 V8 Radiator

69-76 F100 302 V8 Radiator Hoses

83-84 Thunderbird Turbo Coupe Inline High Pressure Fuel Pump

Purolator Inline Universal Low Pressure Electric Fuel Pump PRO #42S

86 Up Mustang 5.0 EFI Fuel Filter

25 Feet 5/16" Steel Tubing

10 Feet 5/16" High Pressure Fuel Hose

24 Fuel Injection Hose Clamps

87-93 Mustang 5.0 Fuel Filter

Assorted Wire Ties and Clips

#10 gage electrical wire

#14 gage electrical wire

#10 Drill Point Sheet Metal Screws

Electrical/Vacuum Troubleshooting manual For 1988 Mustang

Electrical/Vacuum Troubleshooting manual For 1988 Crown Victoria



Remove the hood, air cleaner, radiator, choke cable, throttle cable, and the exhaust system back to the transmission cross member. Remove the drive shaft, speedometer cable, and transmission shifter linkage. Remove any accessories such as windshield washer reservoir, pump, or existing emissions control hardware on the fender aprons.



Since the existing system is low pressure, ALL rubber fuel lines must be replaced with high pressure fuel injection hose with high pressure clamps The high pressure fuel line clamps don't have the slots for the worm in the hose band and can be tightened further than normal hose clamps.

Drain the fuel system. The easiest way is to disconnect and remove the rubber hose directly under the tank. The fuel system will empty quickly so be prepared with several small fuel cans.

Disconnect the fuel supply line from the engine. Remove the rubber line that connects the suction line to the pump.

If the truck has an in cab tank, swing the back of the seat forward to get access to the top of the fuel tank. Disconnect the wiring and the fuel line to the fuel sender unit. Remove the sender from the tank and allow all residual gasoline to evaporate from the sender unit before modifying the unit for a fuel return line. Drill a 1/2" hole in the cab floor approximately 1" to the side of the existing fuel line. This hole will be used for the return line.

If the truck has a frame mounted tank either at the rear or behind the cab, remove the tank completely.


Attach an engine hoist to appropriate lift points.

Remove the nuts from the engine mounts.

Support the transmission with a jack and remove the through bolt from the mount. Remove the two bolts holding the transmission cross member in place. Slightly lift the transmission with the jack and pull the cross member out.

Lower the transmission slightly and begin hoisting the engine and transmission out. The combination needs to be hoisted out with a transmission down attitude.



Engine Bay View - Top
Engine Bay View - Front

Engine/Transmission AssemblyAssemble the engine and transmission as a package. Connect the TV linkage and install the exhaust manifolds. If a serpentine belt drive is used, make sure that the engine has the correct reverse rotation water pump. I chose to use a single V-belt since my truck didn't have any power equipment. Install the 69 F100 engine mounts and transmission mount.

If converting a 6 cylinder truck, unbolt the 2 engine mount supports and move them back toward the firewall into the second set of bolt holes.

Lift the engine with an appropriate hoist. The engine will need to be put in at an appreciable "transmission down" angle. Plug the transmission drive shaft opening with an old yoke to prevent fluid loss and dirt contamination. Install the engine and transmission. Install the transmission cross member.

Drive Shaft

Pull the yoke out from the end of the transmission so that approximately 1.5" of yoke is exposed and measure drive shaft length from yoke center to yoke center. Take the drive shaft to a drive shaft shop and have it modified for length and yoke connection. A long wheel base Crown Victoria drive shaft was usable on my 114" wheel base truck without length modification, however, I did have to change the rear universal joint. I was able to use the existing gear on my speedometer cable although I had to reroute the cable to clear the dual exhaust.Radiator

I highly recommend that a heavy duty V8 radiator be installed. I used the radiator from a 76 F250 big block and it bolted right in. Radiator hoses took some matching and a little trimming. I used molded 90 degree heater hose with a splice kit to connect the heater tubes to the heater core.Transmission Cooler Lines

Fabricate new transmission cooler lines from the transmission to the radiator. It's best to do this before the exhaust system is installed because wrench clearance to the transmission tunnel area gets tight.Vacuum System

The center of the upper intake on the SEFI engine will have one large fitting with two smaller connections that face the firewall and a single large fitting that faces the front of the engine. The large fitting that faces the firewall normally connects to the vacuum tree and supplies the power brake booster. The MAP sensor is usually connected to the vacuum tree also. The two smaller fittings are connected to the fuel pressure regulator and to the line that supplies the EVP, TAD, and TAB solenoids. The single large fitting facing forward connects to the charcoal canister purge valve. If you vehicle is not equipped with a charcoal canister, then this line needs to have a small breather filter attached beyond the canister purge solenoid. The injectors and Idle Air Bypass Valve are calibrated for the additional air coming in from the canister purge. An orifice may be required in the canister purge line to control air flow if the canister is not used.Throttle Cable

The throttle connection posed a very difficult problem. My 6 cylinder cable was barely long enough, but unfortunately, the exposed portion of the throttle cable was too short to fit onto the 5.0 throttle bracket. I modified the cable by splitting the steel casing lengthwise at the end with a hacksaw and then peeling the casing back like a banana until the correct length of cable was exposed for the 5.0 throttle mounting bracket. I used hose clamps and sheet metal screws to clamp the cable to the throttle bracket. I also had to add a throttle return spring since the truck cable didn't have an integrated spring like a Mustang. I'm not happy with this arrangement, but it seems to work acceptably.Transmission Shift Linkage

The shift lever on a Mustang AOD is set up for a floor shifter. The simple install here is to install the Mustang floor shifter, but, the lever is pretty far away from the steering wheel and the shifter requires a large hole in the floor. Using the existing column shifter will require that the shift lever in the transmission be replaced with a column shifter lever or that an extension lever be attached. I made a 90 degree lever that I bolted onto the existing lever. The shifter linkage barely had enough adjustment to connect. Low gear is not accessible now from the shifter and further modification is necessary.Air Cleaner

I mounted a Crown Victoria air cleaner on the right fender apron about 6" from the battery. I rotated the upper and lower halves of the air cleaner housing 180 degrees with respect to each other. The clamps on the unit don't have the raised section to latch onto, but the air inlet is now unobstructed. When installed normally, the inlet opening was almost completely covered by the raised inner fender. I used a Mustang air cleaner right angle hose to connect it to the throttle body. The straight end of the hose had to be trimmed to fit. If I were to use a Mass Air System, then I would have mounted the air cleaner closer to the battery and mounted the MAF directly behind the air cleaner. A round K&N air cleaner will make a simpler install.Exhaust System

I chose to use the cast iron exhaust manifolds from a Crown Victoria because they easily cleared all cross members and had the O2 sensors mounted in the top of the manifolds while the Mustang headers are more bulky and have the O2 sensors in the H-pipe. However, my installation shows that there is a lot of room and the Mustang headers/H-pipe would probably clear the frame and crossmembers, but would probably interfere with the column shifter linkage. Alternatively, O2 sensor bosses could be welded into the existing down pipes.


High Pressure RequirementsThe existing fuel system is a low pressure (~4psi) system. SEFI requires a 40 psi differential pressure across the fuel injectors so some modifications need to be made. Since the system is low pressure, ALL rubber fuel lines must be replaced with high pressure fuel injection hose with high pressure clamps The high pressure fuel line clamps don't have the slots for the worm in the hose band and can be tightened further than normal hose clamps.

Fuel Tank

Fuel tank
A truck with an in cab tank will require 2 fuel pumps. I haven't found anyone who makes a cost effective tank that will accept an in-tank pump.

If your truck has either a rear or side fuel tank then I strongly suggest that you replace the fuel tank with a tank from a late model EFI truck. Although the fuel gage sending unit may need to be replaced in a late model tank, many headaches with the fuel system can be avoided. The resistance values used in late model fuel sending units are completely different from those used up until 1985. The resistance at "FULL" in a pre 85 truck is most probably 10-12 ohms while it is 150-160 ohms in a post 85 truck.Fuel Pump Selection

I experimented with modifying the in cab tank sender unit to hold an in-tank pump, but finally settled on a dual pump arrangement. The problems that I had with the in-tank pump were difficulty in mounting it and, and most of all, NOISE. The in cab tank seemed to act as an amplifier and made the pump sound very loud. The in-line Thunderbird high pressure pump has no suction capability and cannot pull fuel up the fuel pickup tube. A small universal low pressure electric fuel pump is needed to ensure that the in-line pump always has fuel available. The in-line pump has a capacity of approximately 88 liters/hr and the low pressure pump has a capacity of 110 liters/hr. With a stock Speed Density setup, I haven't seen any problems with fuel system capacity.Fuel Return Line

Because a SEFI engine has a fuel pressure regulator that maintains pressure by dumping fuel back into the tank, the fuel system MUST have a return line. This means that an additional line must be run back to the fuel tank. I modified the fuel sender unit so that it contained a fuel return line by drilling a 5/16" hole through the sender flange housing and then soldering a 5/16" tube in place. Anyone who has sweated a few plumbing fittings won't have a problem doing this. I also put one of the rubber nipples on the return line that are commonly seen on fuel injection pump assemblies to make sure the return fuel doesn't create foam inside the tank.Fuel Pump Connection

Both of my fuel pumps are mounted on the outside of the frame rail under the drivers door of the cab. I used the existing fuel line from inside the tank to just under the cab floor as the supply for my pumps. The existing fuel line from the steering box back to the frame rail under the tank was used as part of the return system. I bent two steel fuel lines to follow the shape of the engine cross member. These lines start near the steering box and end just under the starter solenoid. I put a final bend into each line to angle the line toward the #1 cylinder location. A Mustang in-line fuel filter, located next to the steering box, connects a new steel line that follows the outside of the left frame rail from the pumps under the drivers seat area of the cab to the new supply line mentioned above.

Connect the engine fuel supply and return lines to the fuel lines run earlier. The forward most line on the engine is the supply. I cut the original supply lines, NOT THE FUEL RAILS, 2-5 inches beyond the spring lock couplers and used fuel injection hose and hose clamps. Fuel injection hose clamps don't have the slots for the worm in the hose band and can be tightened further than normal hose clamps.


DON'T BE INTIMIDATED!!This is probably the part that really keeps most people from doing this conversion. Actually, wiring connections are pretty straight forward. The EEC IV computer harness is pretty much a stand alone system. To make the computer come alive, only 5 connections need to be made. To give the computer control of the fuel pump an additional 3 wires need to be hooked up. For the power hungry, an additional connection is required to allow the computer to turn off AC under WOT. To route the oil pressure and water temperature gages through the wires supplied in the engine harness, two more connections are required. The neutral start switch requires two more connections and if desired, cruise control requires two more connections. In total, perhaps 12 or 13 wires need to be connected, however, when approached from a system point of view, its not overwhelming. Check out Appendixes A, B, and C for generic harness connections.

Wiring Identification And Harness InstallationDisconnect and mark all wires that went to the engine and transmission.

The following wires should be identified in the old harness:

Ignition Power To Coil (Resistance wire - CAUTION) Red/Green

Starter Relay To Coil Red/Blue

Temperature Sender Red/White

Oil Pressure Sender White/Red

Neutral Start Switch wires Red/Blue or White/Pink

Backup Light Wires (If So Equipped)

Starter Solenoid wire Red/Blue

I also suggest that you lay out your computer harness across the firewall while the engine is out. The harness can be mounted to the firewall much easier with the engine out. I chose to mount the TAD/TAB solenoids, EGR valve positioner, vacuum accumulator, and the MAP sensor on the right side of the firewall directly above the heater hose connections. The EEC relay, fuel pump relay, inertia switch, and ignition coil were mounted on the left fender apron. I mounted the computer on the left fender apron, however, I have reservations about its reliability in the engine compartment since Ford chose to put all engine computers under the dash.

I ran an additional 10 gage wire from the starter relay parallel to the harness over to the area of the relays to power the O2 sensors and to be the power source for the relays. I put a 20 amp inline fuse in this wire. I also used a generic Bosch relay to supply clean 12 volt power on ignition to the EEC relay. I was concerned that the ignition coil supply was a resistance wire and didn't want to take a chance on the EEC relay not engaging cleanly. In addition, the O2 sensors need to be powered by a high amperage ignition switched wire.


To start with, the computer harness connects to the starter relay for power and has a ground connection that should be connected to the negative battery terminal. The computer is sensitive to ground integrity so don't skimp and connect the harness to sheet metal. On a Crown Victoria harness, these connections are exactly where needed. When using a Mustang or Thunderbird computer harness, the battery and solenoid need to be relocated to the drivers side of the truck. In this case, the alternator and solenoid wiring needs to be lengthened also. All of the other connections will be made in the three connectors that are located next to the computer in a Crown Victoria harness. For a Mustang harness, the fuel pump connections are located next to the computer and the other connections are in the two connectors near the master cylinder.

Ford decided that the entire computer system should be powered from a single relay. They called it the EEC power relay. This relay has a black casing and is made into the harness. It has a large gage yellow wire that is directly connected to the battery side of the starter solenoid. It has multiple red wires that then power the computer and various subsystems.

ECC Relay

The EEC relay is engaged by supplying 12 volts from the ignition switch in the "ON" position to a red/light green wire located in one of the harness connectors. The r/lg wire can be identified by checking for continuity at the ignition coil connector since it also powers the coil. Be careful not to use the wire which supplied the original coil for either the EEC relay or the O2 sensors since it is a "RESISTANCE" wire. Under load, the wire has enough resistance to reduce voltage to the O2 sensors, ignition coil, and EEC relay to less than 9 volts. Either replace the wire completely or use it to switch another relay for clean, FUSED 12 volt power.

The ignition coil and TFI module also need to be powered while the starter is engaged. Connect the red/blue wire in the harness to the starter solenoid wire. This wire is also connected to the neutral start switch. Refer to the neutral start switch section for more detail.


The power to the heated O2 sensors should come from outside of the EEC relay. The Crown Victoria harness has a gray fuse link to the O2 sensors which needs to be connected to a good 12 volt ignition switched source. The O2 sensors also need to be grounded. The Mustang harness and the Crown Victoria harness grounds the O2 sensors in different ways so they will need to be connected between the harnesses. The Mustang harness grounds both O2 sensors through a single orange wire located in the multi-wire white plug at the rear of the engine. The Crown Victoria harness grounds each O2 sensor individually to the block near the air injection manifold location without going through the multi-wire plug. This sounds complex but it really isn't. Simply connect the engine O2 ground wire to the two wires in the Crown Victoria O2 sensor harness and then ground them to either the engine or the frame.


The fuel pump is powered by another relay. This relay is controlled by the computer by grounding the relay coil. Normally, the same yellow wire that supplies the EEC relay supplies the fuel pump relay. EEC relay "ENERGIZED" power is supplied by the EEC Power relay through the inertia switch to the relay coil. When the relay is grounded by the computer, the yellow wire is connected to the fuel pump wire. The relay needs to have a switched source of coil power because the computer drops its control back to ground when it powers down. If an ignition switched coil power source is not used then the pump will run continuously. When the system is wired properly, the fuel pump will run for 2 seconds when the ignition is turned on. After 2 seconds, the computer turns the pump off unless it detects rotation of the distributor through the TFI module. Grounding the tan/light green wire on the self test plug should make the pump run if the ignition is "ON".

The inertia safety switch disconnects the power to the relay coil, turning the fuel pump off, in the event of an accident. The inertia switch is wired in the coil relay circuit so that it doesn't have to handle large current flow.INSTRUMENT CONNECTIONS

The engine harness has the wires for both the temperature and oil pressure gage. The wires in the existing truck harness can be connected at the harness connection point by matching wire colors. The temperature gage is red/white and the oil pressure is white/red. The instruments used in a late model Mustang have different ohm resistance than the instruments used in a classic truck. The sending units on the engine will need to be replaced with the ones from the old truck engine in order for the gages to work properly. The instrument wires do NOT need to be connected for the computer to work properly.NEUTRAL START CONNECTIONS

The harness to the AOD transmission will have four wires. Two wires are for the neutral start switch and two are for the backup light switch. The neutral start switch needs to be connected to prevent the engine from starting in any gear position except Neutral and Park. The computer wants to know when the transmission is in gear so it also monitors this connection. The computer will operate correctly without being connected to the switch, but, a fault code (#67) will be set.

The trucks existing harness most likely has a red/blue wire that went through the old neutral start switch to the starter solenoid. Connect the ignition switch side of this wire to one of the white/pink wires in the transmission harness and to the red/blue wire in the computer harness (mentioned previously) so that the ignition coil and TFI module are powered during start. Connect the white/pink wire in the computer harness and the other white/pink wire in the transmission harness to the red/blue wire that goes to the solenoid. The computer has to see the resistance of the solenoid coil in order for it to determine gear status.AC WOT CONTROL

The computer harness contains the wiring connections to the AC clutch and pressure switch. Connect the green wire (most likely) from the truck harness to the light green/pink wire in the computer harness. The computer harness has a relay that it uses to turn the AC off during WOT. The AC connection does NOT need to be made in order for the computer to work properly.


Some versions of the EEC computers have integrated cruise control. The Mustang does not while 87 up Crown Victoria's and Thunderbirds do. Mass Air Mustangs use the VSS to control transition to adle as the car stops. Simply connect the wires from the VSS sensor to the dark green/white and black/white wires that connect to pins 3 and 6 on the EEC computer. The VSS sensor does NOT need to be installed to have the computer operate correctly unless you are using a Mass Air system.EXTRA WIRES

I know this is scary, but there will be some wires that are not connected. Depending on the year harness, there may be wires for a brake on/off switch, speed control command switch, vehicle speed control solenoid, and data output link.

Fuel Pump Relay Terminals


Before installing the computer and powering up, there are several quick electrical checkouts that can be done to make sure that major wiring errors don't exist.

The first check is to make sure that 12 volt power is available to the TFI connector at the correct terminals with the switch in "RUN" and "START".

Disconnect the EEC computer.

Disconnect the connector to the TFI module on the distributor.

Unplug the fuel pump relay

Disconnect the "S" wire at the starter solenoid

Hold the TFI connector so that the terminals face out with the locking tab to the right.

The connector pins are referred to as #1 at the bottom up to #6 at the top.

Insert a straight pin into the terminal being probed.

Use a VOM to check for +12 volts on pins #2 and #3 with the ignition switch in "RUN"

Use a VOM to check for +12 volts on pins #3 and #4 with the ignition switch in "START"

If OK, connect all connectors except EEC and fuel pump

Use a VOM to check for +12 volts on the red/green wire at the ignition coil in "RUN" and "START"

Use a VOM to check for +12 volts on the red wire at the TAD and TAB solenoids, EVR, Canister Purge Solenoid, and at the Idle Speed Air Bypass Valve in the "RUN" position

Turn ignition switch to "OFF"

Disconnect the O2 sensors from the O2 sensor harness.

Turn ignition switch to "RUN"

Use a VOM to check for +12 volts on the gray wire in each harness sensor connector

Turn ignition switch "OFF"

Check that the black/light green wire in each sensor connector has ground continuity

Reconnect the O2 sensors.

Ensure the left O2 sensor connector has the dark blue/light green wire.

Connect the EEC computer and the fuel pump relay.

Verify that all fuel lines are installed and tight.

Turn the ignition switch to "RUN"

Fuel pump should run for 2 seconds

If the fuel pumps don't run, see the 'No Start - Fuel System' section below

Cycle the ignition switch from "OFF" to "RUN" several times to build fuel pressure

Take a deep breath and START THE ENGINE


So it didn't start? Don't give up just yet. I hope that you remembered to put fuel back in the tank. We did drain it in an earlier step.

Seriously, several of my conversions didn't start immediately. After weeding out simple things like wiring errors and defective pumps, I traced the problems to a defective distributor stator in one case and a defective fuel pressure regulator in another case.No Start - Fuel System

The first thing to check for is fuel pressure. There is a Schrader fitting (looks like a tire stem) on the fuel pressure regulator where pressure can be checked. The regulator is just behind the throttle body and should have a vacuum line attached. Remove the protective cap and attach a high pressure gage. Fuel pressure should be approximately 40 psi engine off and 36 psi engine running at idle. If you don't have a high pressure gage then depress the stem carefully. Fuel should flow freely out of the fitting.

I suggest the following steps to debug a fuel system problem.

Check that both fuel pumps run. If only one pump runs, then the other pump is either defective or incorrectly grounded. If only the high pressure pump runs when the key is turned to run, then fuel is not being primed. Without a low pressure pump, the in-line high pressure pump will NEVER pick up the fuel. If only the low pressure pump runs, then there is not enough fuel pressure to spray fuel through the injectors. If both pumps run, but the fuel pressure is low or nonexistent. check the pickup tube in the tank for holes or obstructions. Also verify that you have the suction side of the low pressure pump connected to the existing pickup tube in the tank.

If the pumps don't run, then the next step is to determine if the inertia switch, fuel pump relay, or pump wiring is at fault. A quick test is to run a wire directly from the positive terminal on the battery to the fuel pumps. If the pumps don't run, then the pumps are either defective or incorrectly grounded.

If the pumps run when connected directly to the battery, then disconnect the tan wire from the computer to the relay and attach a wire to the relay terminal and ground it. If the pumps don't run, then the inertia switch is tripped, the relay is wired incorrectly or else the relay is defective.NO START - IGNITION SYSTEM

So you have fuel pressure, but the engine won't start. First, rerun the electrical checks for the TFI unit and the coil from the startup section. Testing the TFI module and stator is difficult. The tests below may not always identify a defective module.

Connect a 12 volt test light from the negative coil terminal to the negative battery terminal and crank the engine. The test light should flicker as the engine cranks. The flickering test light indicates that the TFI module is probably operating correctly and collapsing the primary winding in the coil during engine crank. If the test light does not flicker, check the coil as specified below, and if the coil is OK, replace the TFI module.

Even if the TFI module is operating, the stator assembly may be defective. On one of my conversions, the stator assembly was loose in the distributor, and fired the TFI module at random times. Unfortunately, the stator is not easy to check or easy to remove from the distributor. The distributor gear has to be pressed off the shaft to remove it.

Disconnect the wiring to the ignition coil. The resistance from the positive terminal to the negative terminal on the coil should be 0.3 to 1.0 ohm's. The resistance from the negative terminal to the positive terminal should be 6,500 to 11,500 ohm's. Replace the coil if it is outside of these limits.Pull the spark plugs and check for fouled plugs. Verify that all high voltage connection are in good shape. Black sooty plugs are an indication of excessive fuel. Check the fuel pressure regulator diaphragm and the MAP or BAP sensor vacuum connections. If running Speed Density, then the MAP sensor should be connected to engine vacuum. If running Mass Air, then the BAP sensor should be vented to atmosphere.ENGINE STARTS - ROUGH IDLE

Make sure that the LEFT O2 sensor is in the left manifold. If the left and right sensors get transposed, the engine will idle rough and may also exhibit bucking type behavior about 2 minutes after startup as the computer switches to closed loop control.

Also check to see if the fuel pressure regulator diaphragm is leaking.

Clean the two connectors that attach the engine harness to the computer harness.Now its time to get the code scanner and the timing light out. The scanners are available at most auto stores for about $35. Set the timing to factory specifications (10 degrees BTDC) with the SPOUT disconnected. Connect the code scanner and do a KOEO test and a KOER test if possible.

Work the codes as necessary to clear them. A genuine FORD Emissions Manual (Volume H) for your year harness and engine is invaluable in sorting out the codes.

Troubleshooting beyond this level is out of the scope of this article.


HO - High Output

AOD - Automatic Overdrive

O2 Sensor - Oxygen Sensor

Mass Air - 89 up Mustang 5.0's measure air flow with a meter

Speed Density - 87-88 Mustang 5.0's compute air flow based on engine speed and air density. Performance modifications to an SD engine are limited because fuel and air tables are stored in the computer and can't be easily modified. In reality, the computer can handle most changes as long as the cam is not changed.

MAF - Mass Air Flow Meter

TV Linkage - Throttle Valve Linkage. An AOD uses this to determine engine load and thus shift points.

TAD Solenoid - Thermacter Air Diverter Solenoid. Diverts air pump air to the catalytic converters.

TAB Solenoid - Thermacter Air Bypass Solenoid Bypasses all air pump air during certain engine conditions.

EGR Valve Positioner - Exhaust Gas Recycle Valve Positioner. Sometimes referred to as EVP. Supplies a variable vacuum to the EGR valve as necessary.

TFI Module - Thick Film Integrated Ignition Module. This and the stator take the place of points in the distributor. It is the rectangular gray box bolted to the side of the distributor.

MAP Sensor - Manifold Air Pressure Sensor. Speed Density injection must know the manifold pressure to accurately calculate air flow into the engine.

BAP Sensor - Mass Air Flow injection uses this sensor to correct for ambient air pressure. 5.0 MAP's and BAP's are essentially interchangeable.

EFI - Electronic Fuel Injection. In EFI, the injectors are typically fired in banks. Truck 5.0's are EFI.

SEFI - Sequential Electronic Fuel Injection. In SEFI, each injector is fired at a specific crank position. All 86 and up Mustangs, Crown Victorias, and Thunderbird 5.0's are SEFI.

Serpentine Belt - An accessory belt drive where a single belt drives all accessories.

Idle Air Bypass Valve - Air bleed valve, controlled by the computer, that provides air flow for idle and cold start.

Canister Purge - Fuel vapors from the gas tank are accumulated in a charcoal canister. The purge valve draws those vapors in at engine start.

EEC - Electronic Engine Control Computer

EEC IV - Fourth Generation Electronic Engine Control Computer

EEC Relay - Relay to power EEC in Start Position

VSS Sensor - Vehicle Speed Sensor. Sensor that is bolted to transmission at speedometer cable location that senses vehicle speed. Used primarily for cruise control, however, Mass Air Injection uses VSS to stabilize idle operation.

Stator - Hall Effect switch located in the distributor.

SPOUT - TFI output signal to computer. This connection allows the computer to control engine ignition timing. When disconnected, ignition timing is fixed to the base timing as set by a timing light.

KOER Test - Key On Engine Running EEC computer test

KOEO Test - Key On Engine Off EEC computer test

AC - Air Conditioning

WOT - Wide Open Throttle

APPENDIX A Mustang Harness Connections

Based on 1988 MUSTANG wiring schematics:

When you look at the primary harness that goes from the engine to the computer, you should have 3 connectors that tie back into the main wiring harness. One connector is next to the computer and the other two are at the drivers side firewall next to the master cylinder. The one by the computer is connector #135 the two others are #201 and #403.WIRES


# 135 (The one by the computer) should have 5 active pins with a total pin count of 8. They are as follows

wire # Color Function

657 Tan Cluster EEC Malfunction Light(2.3 ONLY)

687 Gray/yellow ignition switch "RUN" Power To Oxygen Sensors

97 Tan/lt green Computer Control fuel pump relay

359 black/white Transmission neutral sense switch

361 red Power from EEC relay to fuel pump relay

#403 should again have 5 active pins with a total pin count of 8

258 white/pink low oil level sensor

348 lt green/pink thermostatic switch to AC

32 red/lt blue Ignition start Power to Distributor module

11 dk grn/yellow Tachometer gage feed from - coil connection

16 red/ lt green Ignition switch "RUN" To EEC Relay

#201 should have 6 active pins with a total count of 8

33 white/pink Starter relay energized(thru clutch T to #32)

39 red/white Temperature gage

31 white/red Oil pressure gage

199 lt blue/yellow Transmission Neutral Sensor switch Return

150 dk grn/white Trans speed sensor

563 orange/yellow Trans speed sensor

787 pink/black fuel pump relay status(mass flow ONLY)

(turn on EEC in run position)(fuel pump coil power) (computer grounds this to turn relay on)

APPENDIX B Thunderbird Harness Connections

Based on 1988 TBIRD wiring schematics:


# 455 (The one by the computer) should have 4 active pins with a total pin count of 8. They are as follows

wire # Color Function97 Tan/lt green Computer Control fuel pump relay/Self Test37 yellow Power to Fuel pump thru relay

361 red Power from EEC to inertia switch & pump relay787 pink/black fuel pump relay status

#143 should have 8 active pins with a total pin count of 832 red/lt blue start power to TFI module

16 red/ lt green ignition switch "START" To Coil and EEC Relay

687 Gray/yellow ignition switch "RUN" Power To Oxygen Sensors39 red/white Temperature gage

31 white/red Oil pressure gage376 brown/white Ignition Switch "RUN"

657 Tan Cluster EEC Malfunction Light


#201 should have 3 active pins with a total count of 8

348 lt green/pink thermostatic switch to AC

150 dk green/white Trans speed sensor

563 orange/yellow Trans speed sensor

APPENDIX C Crown Victoria Harness Connections

Label all electrical wires as they are released. Disconnect the battery cables, temperature gage sender, oil pressure sender, choke heater (if equipped), neutral start switch, coil power supply, and starter cable to solenoid. Disconnect the engine ground wire also.

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