Crank no start. Fires immediately with starting fluid. 50psi fuel pressure. (Page 1/2)
imjoeking MAY 25, 06:21 PM
Howdy. In a bit of a pickle with my L67 swapped 86 GT Auto. For reference, I have a brand new (and beautiful I might add) swap harness from P-Body Motorsports that I installed last year. A couple months ago, my fuel pump suddenly went out. Relay clicked but would not prime with the key on. Towed it home, dropped the tank, and saw the in tank wiring melted in the connector. Previous owner installed a 340lpm pump without beefing up the wiring. I followed FieroAustin's beefed up fuel pump wiring I didn't want to cut into my wiring harness so, I just installed a switch to manually switch on and off the new relay, at least temporarily so I know everything works.

New AEM340 pump works, and I have 50psi of fuel pressure at the rail. But the car will not start. It'll run if you dump a can of starting fluid into the intake but will die soon after. The only thing I can think of is that my injectors aren't firing but I find it unlikely that both my fuel pump and injector circuits went out at the same time. Both injector fuses are good. Also tried two different PCMs. My buddy said I could try "bleeding" the rail because he says he heard air by the fuel pressure regulator. Cracked open the return line with the pump running and the sound got a bit quieter and it sounded like it wanted to start for a second but we couldn't make any more progress there. I also can't find any info on bleeding being an issue with these motors, only diesels, and I never had to bleed anything when I swapped out my old rail.

Since I bypassed the PCM relay control, could the 3800 PCM possibly be looking for a signal from the fuel pump relay before starting? I looked over countless pinouts and diagrams and I couldn't find anything that could lead to that, but I could easily be missing something.
olejoedad MAY 25, 06:54 PM
There is no feedback loop from the FP relay.

Look at the ICM, it needs to see crank rpm to turn on the injector trigger circuit.
imjoeking MAY 25, 11:28 PM

Originally posted by olejoedad:

There is no feedback loop from the FP relay.

Look at the ICM, it needs to see crank rpm to turn on the injector trigger circuit.

That's what I figured. What specifically should I be looking for?

[This message has been edited by imjoeking (edited 05-25-2024).]

olejoedad MAY 26, 04:00 AM

Originally posted by imjoeking:

That's what I figured. What specifically should I be looking for?

Corroded terminal, broken or pinched wire.
I don't recall which wire signals the PCM, as I am traveling and do not have my pinouts with me.

If your ICM/coils are remote mounted, be sure there is a heavy gage ground wire from the ICM plate to the engine block.
imjoeking MAY 27, 12:43 AM
Well. Came out to a completely dead battery. Worked fine the other day. Oh well.

Anyways, I (think) I figured out what wire I needed to look at. Pin D on the ICM harness plug. Did a continuity check on it and the corresponding pin on the PCM connector and it checked out. Engine ground and ICM ground is also good too. I'm unable to turn the engine over and hook up a scan tool until I get the battery warrantied later this week. You'd think since the motor starts and even revs with starting fluid the ICM and crank sensor would be good, right? All 6 injectors are showing the correct resistance too.

L67 Swap / 3.1 Pulley / S1X Cam

XxdjxX89 MAY 31, 10:34 AM
While having someone crank the car back probe injector harness at the fuel injector and make sure one side has solid power and the other is being pulsed
imjoeking JUN 05, 10:45 PM

Originally posted by XxdjxX89:

While having someone crank the car back probe injector harness at the fuel injector and make sure one side has solid power and the other is being pulsed

Connected a noid light to all 6. All failed. I also replaced the crank sensor to rule that out and because it gave me issues before. Still nothing. ICM was replaced last year with a refurb. Also tried with another PCM

Where do I go from here? All of my grounds seem good, no shorts or cut wires from the ICM/CPS to the PCM. I know my injectors aren't getting power, but why!!!! The harness is brand new and I didn't touch it when I did my fuel pump rewire. Unless somehow when my in tank connector failed it took out everything - without blowing fuses - which I doubt lol. I'm at a loss.

Here's a picture of my ICM ground wire in case anyone is curious. It's looked like that since I've owned the car so it should be fine, but maybe I'm just missing something simple....

L67 Swap / 3.1 Pulley / S1X Cam / 4T65EHD
Kansei KNP wheels / Hiro Performance Coilovers / WCF Camber arm / Fiero store front + rear sway bars

olejoedad JUN 06, 01:26 AM
If your noids didn't pulse when cranking.....

There should be 12v Key On the pink wire on each injector - terminal B
The PCM triggers each injector by grounding the wire at terminal A.
The PCM needs to have 12v Battery and 12v Key On.
The PCM needs to have good grounds.
The PCM case should not have direct contact to ground when mounted.

longjonsilver JUN 06, 06:45 AM
Your problems sound similar to mine. First i had random stalling - no warning - just a 3800SC running perfectly or not at all. Then she wudnt start at all. After trying everything that i cud think of, i finally hauled her to Jelly2m8 and he traced it down to three bad connections between the ECM and the ICM. Put in a known good harness, and she fired right up. Now he is trying to fix various and assorted issues. During all that, we found out that my TB was not from a 2002GTP like the rest of the car, but from an older supercharger. The MAF was NOT from a 2002 and was sending a wrong signal to the ECM that Ryan Gick had programmed for a 2002. That was probably why she was running rich and overheating the trunk (i melted clothes in the trunk - the carpet had been taken out fortunately) even tho i have the 1/2" space, the heat shield, and the exhaust tape. Hopefully when i get these issues sorted out i will have a reliable car. Blessings to you on your car.

Astronomy says we will find a coded signal from outer space. Then we'll KNOW that life exists there, for coded signals aren't by chance.

Biology says there are coded genetic signals in every cell, but we KNOW that no intelligence created life.

I'm the original owner of a white ' 84 2M4 purchased Dec 10, 1983 from Pontiac. Always garaged, no rust, 3800SC, 4-wheel drifts are fun!

imjoeking JUN 06, 06:38 PM
12v to the injectors. All 4 PCM grounds pass continuity. OBD has no power. PCM is mounted between the firewall and center console. PCM fuse is good. I don’t think I have 12v or key on 12v to the PCM. My radio and all my other electronics work

Looking at a pinout im seeing that C1-20 should be my +12v for the PCM and OBD. All it says for destination is “power distribution”. Where does the PCM get power from? Is it the white block underneath the drivers side speaker? And how did it run with starting fluid?

[This message has been edited by imjoeking (edited 06-06-2024).]