I have a 65 mustang that I did a 5.0 EFI swap in a few years back. I did the swap myself and have been a mechanic forever but cant figure this one out. Its all 1990 efi parts. The car has worked great for years but when I went to get it out for the first time this year it wont start. I have spark, and fuel pressure to the rails, it wont fire on starting fluid. I have an in line h.p. fuel pump. And like all efi cars, the fuel pump use to prime itself when you turned the key on. Now it wont do that. Checked fuses, swapped relays and found that if i pull the relay with the key on and stick it back in, it starts the fuel pump, but runs continuously even after it builds pressure. But with fuel and spark it still wont start, nothing has changed with the timing. I checked for bad connections everywhere and tripped and reset the inertia switch and the fuel pump still wont run. What am I missing? Fuel...spark...didn't check compression, couldn't imagine it being bad I parked the car last year with it running perfectly.. Any help would be greatly appeciated, thanks Guys!
Starting Problems
- Thread starter Steve Ford
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You have power at the pump?
Have you tried to start it with starting fluid?
I suspect the injectors are not firing but that is a guess, do you have one of those noid light things to check the injector power? There is a cranks but no start thread I will post a link to that may help, you said you used an efi setup.
I see @a91what beat me to the 'check the codes' part of my post, well done.
http://forums.stangnet.com/787471-cranks-ok-but-no-start-checklist-fuel-injected-mustangs.html
Have you tried to start it with starting fluid?
I suspect the injectors are not firing but that is a guess, do you have one of those noid light things to check the injector power? There is a cranks but no start thread I will post a link to that may help, you said you used an efi setup.
I see @a91what beat me to the 'check the codes' part of my post, well done.
http://forums.stangnet.com/787471-cranks-ok-but-no-start-checklist-fuel-injected-mustangs.html
I have obd-1 plugs for my solus scanner, no codes, I even used a dummy reader to try and get codes, all 0's. No codes in system. I pulled the cold air intake off and sprayed starting fluid right into the plenum, nothing. No power to the fuel pump unless I pull the relay and insert it again, can feel the relay click and the fuel pump runs continuously, wont even shut off when it reaches prssure. I dont get it. Has spark, wont start on ether, only thing I can think of is the cylinders are loaded up and washed out so theres not enough compression. The plugs were wet.
Run through the no start checklist, check your grounds, code reader not communicating worries me.
you'd think I'd cought that!
ok so I had some more time to work on it, it will fire on ether now very briefly, just enough to sputter and I have power going to the injectors but no pulse on the other wire. I only tested the two front injectors since the rest are miserable to get at. I get 00 for codes, can only do key on engine off obviously though. so im assuming the ecu isnt communicating. The fuel pump runs every other key cycle. and runs continuously and wont shut off unless I cycle the key. I pulled the ecu and reconnected it to make sure the connections were good. Loosened grounds, cleaned, and tightened up again. Bad ECM im thinking? The battery tender I had on the car, stopped working and I replaced it, wonder if it shorted out and was enough to fry the computer.
I'm leaning bad ECU here. Have another handy to try?
What ECU and vehicle wiring are you using?
What ECU and vehicle wiring are you using?
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Computer will not go into diagnostic mode on 86-90 models 5.0 Mustangs
Disconnect the battery positive terminal before making any resistance checks.
The voltage drop in the ground cable will cause incorrect resistance readings.
How it is supposed to work:
The black/white wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self test mode. If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. Since it is a dedicated ground, it passes through the computer on its way to the computer main power ground that terminates at the battery pigtail ground. It should read less than 1.5 ohms when measured from anyplace on the engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.
What sometimes happens is that the test connector black/white wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.
The STI (Self Test Input) is jumpered to ground to put the computer into test mode. Jumpering it to power can produce unknown results, including damage to the computer. The ohm test simply verifies that there are no breaks in the wiring between the test connector and the computer input.
How to test the wiring:
With the power off, measure the resistance between the computer test ground (black/white wire) on the self test connector and battery ground. You should see less than 1.5 ohms.
If that check fails, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the black/white wire and pin 46 on the computer wiring connector: it should be less than 1.5 ohms. More than 1.5 ohms is a wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1.5 ohms. More than that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.
See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.
If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More than 1.5 ohms is a wiring problem
The following is a view from the computer side of the computer wiring connector: it is for an A9L, A9P computer.
Diagram courtesy of Tmoss & Stang&2birds
Check out the diagram and notice all the places the black/white wire goes. Almost every sensor on the engine except the MAF is connected to it.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine
See the graphic for the 10 pin connector circuit layout.
Disconnect the battery positive terminal before making any resistance checks.
The voltage drop in the ground cable will cause incorrect resistance readings.
How it is supposed to work:
The black/white wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self test mode. If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. Since it is a dedicated ground, it passes through the computer on its way to the computer main power ground that terminates at the battery pigtail ground. It should read less than 1.5 ohms when measured from anyplace on the engine harness with the battery pigtail ground as the other reference point for the ohmmeter probe.
What sometimes happens is that the test connector black/white wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.
The STI (Self Test Input) is jumpered to ground to put the computer into test mode. Jumpering it to power can produce unknown results, including damage to the computer. The ohm test simply verifies that there are no breaks in the wiring between the test connector and the computer input.
How to test the wiring:
With the power off, measure the resistance between the computer test ground (black/white wire) on the self test connector and battery ground. You should see less than 1.5 ohms.
If that check fails, remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the black/white wire and pin 46 on the computer wiring connector: it should be less than 1.5 ohms. More than 1.5 ohms is a wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1.5 ohms. More than that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.
See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix for the computer internal signal ground.
If the first ground check was good, there are other wires to check. Measure the resistance between the STI computer self test connector (red/white wire) and pin 48 on the computer main connector: it should be less than 1.5 ohms. More than 1.5 ohms is a wiring problem
The following is a view from the computer side of the computer wiring connector: it is for an A9L, A9P computer.
Diagram courtesy of Tmoss & Stang&2birds
Check out the diagram and notice all the places the black/white wire goes. Almost every sensor on the engine except the MAF is connected to it.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds
(website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine
See the graphic for the 10 pin connector circuit layout.
Thanks for all the help so far, I just went down and the thing fired up, could hear and feel a slight miss through the exhaust when I revved it, might have just been loaded up from screwing around with it. I let it run for about 2 minutes shut it off, now it wont start again. I was able to communicate briefly with the ecm when it was runnng, it established a connection but lost it before I could get any codes. Everything is very intermittent with it. Sometimes the fuel pump will prime other times it doesn't, sometimes the relays click on and off with the key, other times they don't.
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