eaglescout526

Well the wiring for the fuel pump from the relay goes right through the bulk head under the booster and clutch master. So unless the tar in there is creating resistance, then the FP or splice "N" is also causing an issue.

Makes me wonder if we wiggled something. But yes the voltage at the FP is still odd. Thankfully you don't have to adjust the pressure regulator. Not fun nor easy to remove the throttle body. I mean bad things can still show good resistance, my guess is resistance was the common sign of a bad injector. Well we can keep trying to see if we can get better voltage to the FP and then go from there. But I am happy to see the engine wants to fire without fuel down the TB.

Unless the injector is dirty. Not sure how much of a difference but the more grounds the better.

Question is. Do we suspect the fuel pump at fault? Or the injector?

I will say this. We are hell of a lot farther than what we were. Almost seems like the injector is trying to spray.

Timing test should help with that too, if the injector is spraying at all. I have a spare injector but am unsure if it works or not. I think Ωhm might know more about the injector timing light test than I would.

Not looking for anything specifically, just parts or pieces to assemble some kits for those who want to add cruise control to their trucks.

Ok so I went a did a little test of my own with the injector harness. I used a test light and tried a couple things. I attached the clip to power of the battery and found one is ground and remains lit until the engine cranks. I tried the other prong of the injector harness and got nothing, not even a dim light. Switched the clip to ground post and got nothing on the prong that lit up and nothing during crank. Moved to the next one and got nothing during crank, course its so bright outside that even if the test lamp did dimly light, I didn't see it. But if I recall, your test noid remained lit constantly, I'm still waiting on my noid light to test it better than using a test light.

I missed that. Brain is kinda burned from the ECU thread.

Usually that is a culprit for a no start condition. The aftermarket CPS's are a hit or miss and can fail right out of the box.

Alright once you get a reading, lets get back at it tomorrow. Also ive been studying the 86, 87 and 88 electrical schematics. Everything connected to the ECU connector is the same for all years, so I would imagine the 87-90 years could be an upgrade over the 86 ECU.

Yeah but with key on we won't see any voltage run down the line for start up phase. Power will be present for one second and them gone. It won't be until the engine is running(or relay jumped) when we will see constant power at the splice and else where in that line.

But weren't we seeing 10V earlier today at those splices? Wait did you get the 10V with the relay or the jumper?

We could test for resistance and voltage, Supposedly the wiring shows it is apart of that FP relay splice "K" so it should have either the 10V(from earlier) or battery voltage and I would guess that the ECU controls the ground for the pulse. I can try to do a test light tomorrow and see if I can get that dim pulse and rewatch your video to see.

Correct, we have ruled out just about every damn thing except two things. Is the ECU switching the injector? Or is the injector faulty and not pulsing fuel like it should? We have kinda ruled out the fuel pump but not exactly.

So unless the ECU isn't switching the injector fully, or the injector isn't wanting to operate correctly, it just won't fire or at least it tries to.

I don't think the orientation matters for the injector, at least I haven't seen anything that denotes orientation for it.

Lol lets not do that again shall we? No blockage in the fuel line so that's good, pretty cool to learn that it just pours right out during crank. So I'm not sure how the ECU controls the injector, my guess is the ECU has a switch or control chip inside that switches on/off for the ground of the injector to pulse. Other than checking for the Ωhms resistance, I am not sure how else to test it. I mean it was tough to tell if the ECU was truly switching the injector with the noid. I might have to take a test light and see if I can see what this dimming looks like.

Have you tested your CPS for Volts AC? Should put out above 3.5VAC. Huh, I mustve not submitted my reply when I typed what to check.

Ah good, you caught the keeping it plugged into the harness. I thought about mentioning that. Well when it does the prime, fuel will come out of the hole in the TB for the injector for a second. When you go to crank or apply voltage to the pump it should just come out, we aren't looking for pressure, more or less seeing if fuel flow is obstructed or not and seeing if maybe the injector could be at fault.

Hold off on that for a moment. I remembered something from when I rebuild my throttle body. If you were to remove the injector there are two holes, one for input and the other for return. I am wondering if we can observe how the fuel comes out from there.

Basically like fuel was just trickling down the TB. Or kinda like when you have fuel in a carb and enough comes out and the engine kinda catches but its not enough to keep going?

Very well could've been. Still need to figure out this fuel problem. So pump constantly running with 12V applied and relay in place, it kinda wants to start but it acts like its not getting enough fuel to meet the demand of starting. Sound right? So I wonder if power loss is at that bulk head met with resistance from the tar inside. Just a working theory for now.

Heyyyyy the ISA works!! I know that sound after shut down anywhere. I think we are moving away from the bad ECU idea.

Yes and no, I would hold off on the pump thing until we get this fuel injector thing figured out but it could be the pump, but 3-4 volts still doesn't sound right unless that's all it really needs but if that was the case then why would they have put a ballast on the later years?