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Old 07-16-2008, 02:16 PM
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S10 Fuel Problem

Howdy,

New to the site. Hopefully I'll soon be asking advice on a 69' Roadrunner or 59' Apache, but for now this S10 is giving me fits.

I have a 90 2.5L, 5sp, tbi. Spun a bearing and bought a 2.5L engine from a 90, auto, tbi. Popped in the engine using the wiring harness from the auto.

Everything works. Runs great when you prime the tbi, but will not start\run on its own.

No fuel, or power at injector. Checked it with a noid light.

Fuel pump runs when you jump the relay, or power the test wire. But it doesn't stir on its own via the ignition. Not even the 2sec burst. It does have power to the relay. Have tried 3 relays.

Have swapped out ECMs and proms. Still, no dice.

What activates the signal to the relay? What sends the signal to the injector?
Just the ECM, or ignition module?

Appreciate any help. Iím almost ready to replace the harness. Just donít see why the auto harness wouldnít work. I find no loose wires. I did adapt one tranny plug to work on the 5sp.


Thanks,

Rob

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Old 07-16-2008, 05:42 PM
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Quote:
Originally Posted by RobMc
Howdy,

New to the site. Hopefully I'll soon be asking advice on a 69' Roadrunner or 59' Apache, but for now this S10 is giving me fits.

I have a 90 2.5L, 5sp, tbi. Spun a bearing and bought a 2.5L engine from a 90, auto, tbi. Popped in the engine using the wiring harness from the auto.

Everything works. Runs great when you prime the tbi, but will not start\run on its own.

No fuel, or power at injector. Checked it with a noid light.

Fuel pump runs when you jump the relay, or power the test wire. But it doesn't stir on its own via the ignition. Not even the 2sec burst. It does have power to the relay. Have tried 3 relays.

Have swapped out ECMs and proms. Still, no dice.

What activates the signal to the relay? What sends the signal to the injector?
Just the ECM, or ignition module?

Appreciate any help. Iím almost ready to replace the harness. Just donít see why the auto harness wouldnít work. I find no loose wires. I did adapt one tranny plug to work on the 5sp.


Thanks,

Rob
There are two relays one for start and one for run. The start relay comes on for 10-15 seconds when the igintion switch is armed. The start relay counts down for about 10 to 15 seconds then shuts off. The computer contols the run relay it switches it on when it reads an RPM tach output from the distributor.

It sounds like your not getting voltage to the start relay when the switch is turned on. Probably a wiring or connector problem given that you can actualte the relay with an outside voltage source.

Bogie
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Old 07-17-2008, 09:40 AM
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the ecm doesn't pulse the injectors unless it sees pulses from the ignition.

did you convert the truck to auto or something?
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Old 07-17-2008, 07:13 PM
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Thanks for the replies.

No, I didn't convert, but the new engine ran an automatic. I mated it to my 5sp. I did notice the ignition module on the automatic distributor has a different part# than the one one the 5sp distributor. Could that cause problems?

Appreciate the help.

Rob
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Old 07-17-2008, 07:23 PM
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Quote:
Originally Posted by RobMc
Thanks for the replies.

No, I didn't convert, but the new engine ran an automatic. I mated it to my 5sp. I did notice the ignition module on the automatic distributor has a different part# than the one one the 5sp distributor. Could that cause problems?

Appreciate the help.

Rob
Yeah, it's hunting for a converter lock up and tracks throttle position against manifold vacuum against RPMs against gear selection.

Bogie
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Old 07-22-2008, 10:57 PM
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Well, I wound up swapping distributors. Had different plugs. Same issue, still runs fine when you pour fuel down the TBI, but no dice on its own.

I pulled the injector and it's getting fuel from the pump when cranking.

Testing the red and blue wires to the injector I found that the red wire is grounded and the blue won't pulse when connected to a 12v source and cranking. Both ECM fuses are good.

Any ideas?

Appreciate the help.

Best,

Rob
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