mr2george

Everything is pretty much complete. I have the efi dash harness, engine harness, fuel tank. This is all in an 85 4x4. It cranks and fires bit will only run for a second. I dont think its getting fuel through the injectors. It has fuel to the rail and the cold start. What could be my problem? Thanks!

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DeathCougar

im assuming you have the AFM hooked up? And no air leaks?

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mr2george

Yes the afm is hooked up. Doesn't seem to be any leaks

superjoe83

make sure you have 12v to the single plug on the injector resister with the key on. Since its running on the cold start injector, this tells me that the fuel pump is working when cranking at least

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mr2george

I just checked the resistor with an ohmeter and got 12 volts. Anyone else have a clue what it could be? I don't think its getting an injector pulse.

mr2george

We checked the injector connector and got .01 volts. Then we checked the same wires at the ecu plug and got 12 volts. Any ideas? Maby some wires got cut somewhere in the harness.

dcg9381

No that's the correct behavior.
The injectors are fired by pulsing them to ground. They're actually a single bank of injectors altough the ECU indicates two different banks.

Are you getting cranking RPM on the tach when hitting the starter?
Sure you have fuel pressure?

One way to test for injector trigger is to put a test light across the terminals of the injector connector. Crank the truck. You should see that light go on and off very fast - it might be best to use an LED test light.

ECU needs cranking RPM to know to trigger the injectors... i'd suspect that it's not getting cranking RPM indications from the ignitor if you have no tach deflection and no injector trigger.

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mr2george

Ya i'm pretty sure i'm gettting fuel pressure it reaches the cold start and the rail ive cracked both lines. We checked to see if the tack works and it does it jumps up to about a 700 rpm's when it starts for a second.

dcg9381

Check for the ground pulse, as I've indicated.

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mr2george

ya theres definately no pulse through the injector plug we just checked it with a test light

dcg9381

OK. You're checking across the terminals at the injector plug, with the injector unplugged, correct?

If so - that would indicate that your ECU isn't getting cranking RPM. If you have access to a FSM, I'd go through the "no fuel" diagnostic procedure - but what I'd be looking for is the signal out of the ignitor coming into the ECU that tells the ECU that the truck is cranking... I can probably detail out which pin that is if you need me to. The input is either a 12v or 5v square wave.. I forget which.

You can simulate cranking if you've got spare distributor. Just turn the truck "ON" connect the distributor and give it a spin. I've hooked mine up to an electric drill before to check tach and other operations.

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mr2george

Ya if you could tell me which wire it is to check on the ignitor or ecu that would be great

mr2george

I found out we don't have power running from the harness that runs across the valve cover too the ingnitor.

dcg9381

OK, resolve that issue and see what happens.. :-)

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mr2george

Y would we not have power there though? What does this harness do it looks it ties into the injector harness from the coil. its three wires

dcg9381

I don't understand the question.
The ignitor isn't passive (unpowered). It's job is to take the VR signal out of the distributor, translate it to a square wave and send it to the ECU. The ECU then makes decisions about timing and tells the ignitor when to fire the coil.
Here's a photo of how it works.. Just assume the megasquirt in the photo is the stock ECU:

http://lakebox.dnsalias.com/photos/1...igncontrol.htm

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mr2george

ok well there seems to be 3 plugs on the ignitor, one smaller one, and two bigger ones, one of the bigger ones goes to the distributor, the smaller one plugs into the harness right by the ignitor, the other one that doesn't have power thats supposed to runs across the valve cover and ties into the harness under the upper intake plenum. I checked this plug on a 4 runner and it had power to 2 of the three terminals with the key on. Mine has no power at any of them with the key on.

dcg9381

You really need a wiring diagram from the right year of truck. You can't just hook up a 12v probe or volt meter to various wires and decide what needs power, especially since the signal wires generate 12v square waves (which can show as 12v or 0v depending cranking / engine position).

My advice is to get the FSM, map out the wires to the ignitor - there should only be one "power" wire to a switched ignition source.

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