Greetings,
I was hoping some of you fine folks could help me out with an issue concerning a 1988 LX Coupe. The car was originally a four-cylinder car, which has been converted to an eight-cylinder car. I purchased the car during the transition period. I have the V8 engine harness in place with the appropriate computer (speed density), but I’m not able to get the car to start. The fuel pump is not turning on when I turn the key on. I have checked both the pump and the relay, both check out fine. Here’s another issue, I can turn the fuel-pump on to pressurize the system, by just adding a jumper wire in place of the fuel pump relay, but I don’t believe the computer or the fuel injectors are working because the engine will turn over, but will not run on its own. I am able to spray carb cleaner in the throttle body and get the engine to fire, still the car will not run on its own. I do have fuel at the fuel rails and I have spark, which is what leads me to believe that my injectors aren’t working and/or the computer isn’t working. At this point, its hit or miss for me, I’ve been checking wiring diagrams and really just racking my brain here and I keep coming up short of success. Any ideas or suggestions would be greatly appreciated!
Join the club, I am in the same boat. I have a 91, when I turn the key to the on position the pump does not prime. I did not think to jump the relay at the connector though, should have tried that. I had a problem four months ago similar to this and it was a clogged fuel filter. Now this time it won't even prime. I have so far replaced the fuel pump relay and the ignition switch. I have ordered a new fuel pump, a new TFI Ignition Module (wierd I know but it plays a part), and a EEC Power Relay. Hopefully one of those will fix the problem. I will let you know how I make out and I hope you will do the same. I would try the Fuel Filter first and reset the computer(remove positive cable from battery).
Thank you for the reply. Good to know I'm not the only one with this problem. I have connected 12v directly to the pump and it pumps just fine and I've replaced the relay, haven't replaced the TFI module, but I'm going to try a new EEC relay tonight and see if that changes anything. When I replaced the 4-cyl fuel lines with V8 fuel lines, I replaced all the fittings and filters in the process, so I can eliminate that. I'll keep everyone posted.
What is the part/model number of the EEC relay. I went to Autozone to pick one up today and the guy gave me a blank look. I figured it is the same as the fuel pump relay but I may be wrong. My car is stuck at my friends house which is 40 minutes away so i can't really just go out and check. I am amassing all the parts then going to drive down there and try them one by one. At least most of the parts are cheap to try to fix this problem with the exception of the fuel pump.
BORG-WARNER - Microprocessor Relay Part No: R648
That is what O'reilly has as the part number, but I think it might be for the 4-cylinder. You can have the person at AutoZone look up the relay by calling it a Microprocessor Relay or a ECM relay. Hope this helps you out.
If it's not an HO motor, and you're using a Mustang computer, then the injector order will be wrong. The stang HO is 13726548 while the non HO is 15426378. If this is the case, you can cut and splice, or get an injector harness from a non-HO of the same vintage, like out of a Crown Vic or a truck...
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1992 Deep Emerald Green Mustang GT Hatch, 5 speed, 2.73s, Mac fenderwell cold air intake, '93 Cobra MAF, Mac 70mm throttle body & spacer, Explorer intakes, Mac unequal headers & offroad pipe, Magnaflow catback, Walbro 110lph fuel pump, Jet adjustable FPR, MSD Blaster coil, Accel 8mm wires, FRPP aluminum quadrant, UPR firewall adjuster, stock cable, Granatelli upper control arms.
Waiting to go on: Granatelli lower control arms, and GT40 Iron heads!
Did you check the inertia switch in the trunk? If it's out, it will also cause the pump not to prime. If you have to click it in, that means it was keeping the pump from turning on. You should also check the wires to the harnesses for the injectors for voltage, but Id say the main problem right now is your fuel pump not turning on. I guess also try checking the harness to the fuel pump for voltage, kinda sucky reach though.
It is a high-output motor with a matching speed-density V8 computer. I have checked the injectors and I have 11.0v at the red wire. I am going to pickup a noid light to check and see if they are firing from the distributor. I'm now looking at the problem as maybe the TFI module on the distributor. I am also going to look into the fusable links and make sure they are all ok. I do not have ANY voltage at the fuel pump wiring harness in the trunk. The inertia switch was the first thing checked, it is pushed in. Thanks for the feedback. I'll let you know what I find after trying these things I mentioned this afternoon.
After checking the fusable links, starter relays, distributor and all the ground wires, I still don't have a working fuel pump. The noid light came up negative on the injectors too, so I have two problems to deal with. I have come to the conclusion that the wiring harnesses between my 88 coupe and the engine harness (which is supposedly from an 88 hatch) are not compatible. I'm having more problems than successes. I have decided to strip dash and engine harnesses out of the car and get a matching set out of a donor car. Everyone will say that's what I should have done to begin with, but I guess you live and learn. Thanks for the input everyone. Dan I hope you get your car working, if anything, you should try to jumper the orange wire and the yellow wire at the fuel pump relay. If you turn the key on with it jumpered and the fuel pump primes the car, then you have a short, if it does not work, then your problem will be more tedious to find. Best of luck!
Thanks, I will be getting the parts today and installing them tomorrow. Looks like I will be doing it in the rain, all well. Good luck with your car, I will post another message here if I figure out my problem. I will jump those wires and see if it primes. If I can not figure it out I will see if I can install a manual switch to turn the fuel pump on and off. At this point I don't care what it takes I want my car back. Right now I am driving my friends car, a 97 Ford Escourt Station Wagon with Winnie the Pooh and Tiger stickers on it, awsome.
I dug a little deeper and found that someone had a problem with the connector itself on top of the fuel pump. Supposedly one of his spade connectors came loose on the pump. May be something else to check out. Also my friend and I have been looking over the wiring diagrams to figure a way to bypass half the relays and other wiring in the car. Here are a few solutions we came up with.
Solution #1 (Quick, Dirty, and Really DANGEROUS - No Inertia Switch)
Run a wire from the positive side of the starter solnoid to a toggle switch and connect that switch to the Pink/Black wire under the drivers seat. Throw the switch pump comes on you drive.
Solution #2 (A little nicer, but still no Inertia Switch - DANGEROUS)
Buy a new Fuel Pump relay. Run a wire from the Yellow wire that connects to your aftermarket radio or any switched 12v wire and put a female spade on the other end and connect it to the new relay where the Orange/Light Blue wire would have. Then from the relay where the Pink/Black wire would have connected run a wire between the new relay and the female connector under the seat to the Pink/Blue Connector. Put a female connector on one end and a male on the other. Then run a gound from the ground on the new relay. Now when you turn the key to the on position pause for a second to allow the fuel system to prime then start the car. This will allow the pump to turn on and off with the key instead of a toggle.
Just some more suggestions. I am still looking as to how I can buy a universal inertia switch to add to the mix.
Update--
My car is now running. I have not yet replaced the harnesses with the ones that I purchased from a 91 GT, I still have plans on doing so, but I was able to finally figure out the issue with why the fuel pump wouldn't prime and why the injectors wouldn't fire. I feel really stupid for this, but then again, it wasn't obvious, it was a ground wire. In fact, it was the ECM ground wire that sits under the starter solenoid. It was never obvious because it doesn't have a ring style ground clip, it has a single wire connector, which was, at the time, very misleading, so I left it alone, not finding anything to plug it into. After going over a few more schematics of what goes where, I noticed an ECM ground wire exclusive to the driver side, which prompted further investigation and come to find out, the connector I left alone, was the culprit. Running a jumper wire from the connector to the negative of the battery prompted several relays to kick, which didn't happen before and the fuel pump to prime, also never happened before. At the turn of the key, the car roared to life, much to my suprise and my excitement. I have a copy of the schematic with the connector I was so confused about, if anyone else has this problem, feel free to PM me and I'll get that schematic to you. Dan, best of luck buddy with your wiring woes, I'm sorry to hear that your harnesses are cooked, you could probably pick one up on ebay pretty cheap. Best of luck to you.
88 Coupe 302 won't start 
