No spark no injector pulses- Question for the wiring experts (Page 1/3)
Dennis LaGrua JUN 09, 09:55 AM
I have a 4.9L swap and the engine started and ran fine with the harness. Discovered that the transmission was bad so we pulled it out and had it rebuilt. Put everything back together, engine cranks but no spark and it appears that there are no injector pulses as well. Scan tool says defective neutral range switch so we replaced it. Still no start. I suspect that the ECM /system somehow is not getting any power. Could be a ground or power problem so I could use some tips to troubleshoot. What a PITA.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

theogre JUN 09, 12:24 PM
Ignition type... HEI? DIS?

ECM/PCM won't start injection w/o seeing Ignition first.

Both Ignitions at crank time is "dumb" and under ICM control. ECM doesn't start ignition control till see 500-600 RPM.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Dennis LaGrua JUN 09, 04:00 PM

quote
Originally posted by theogre:

Ignition type... HEI? DIS?

ECM/PCM won't start injection w/o seeing Ignition first.

Both Ignitions at crank time is "dumb" and under ICM control. ECM doesn't start ignition control till see 500-600 RPM.



I hear what you are saying but it looks like the ECM may be without power. Tomorrow I will check all of the switched 12V inputs that supposed to be there. The engine uses a distributor but inside is the ICM and the cam sensor.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

greenturnedblue JUN 09, 09:07 PM
the ECM provides the CEL right? So if the ECM is uncommunicative the CEL wont come on when you turn the key to ACC
Dennis LaGrua JUN 10, 08:29 AM

quote
Originally posted by greenturnedblue:

the ECM provides the CEL right? So if the ECM is uncommunicative the CEL wont come on when you turn the key to ACC



Thank you. Thats a very good point . The CEL light goes on when the ignition is turned to on but then turns off. To make sure we will double check to see that the power and ground feeds are all good. It could also be that the power is not getting to the ignition module or the ignition module has failed. I just wish this was OBD2 as the diagnostics are better but the solution right now seems to be to check the power sources to everything

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Rodrv6 JUN 10, 09:27 AM
Always check power and ground circuits. Is it possible a ground wire didn't get hooked back up during transmission installation?

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Rod Schneider, Ball Ground, Ga.
"You can't have too many toys!"
1988 Fiero GT
1988 Porsche 928S4
1987 Corvette
2016 Mustang EcoBoost
Van's RV-6 airplane

Dennis LaGrua JUN 11, 09:37 AM

quote
Originally posted by Rodrv6:

Always check power and ground circuits. Is it possible a ground wire didn't get hooked back up during transmission installation?




Its on the to do list. But since I work on the cars P/T it may be a week or so before I get to it.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

sanderson231 JUN 12, 06:17 PM
Hook up a scan tool and see if the TPS reading changes when the gas pedal is pushed. That will show if there is power to the PCM. However it could be that there is no power to the ignition module.

It had a no start problem on a 3800 that sat for a few months. It had spark, fuel injector pulses and good fuel pressure. There were no codes set on the scan tool. Out of desperation, I changed the crank position sensor and cam position sensor and the car started. I theorized that the PCM was getting bad signal from the crank position sensor and the timing was way off.
Dennis LaGrua JUN 14, 11:49 AM

quote
Originally posted by sanderson231:

Hook up a scan tool and see if the TPS reading changes when the gas pedal is pushed. That will show if there is power to the PCM. However it could be that there is no power to the ignition module.

It had a no start problem on a 3800 that sat for a few months. It had spark, fuel injector pulses and good fuel pressure. There were no codes set on the scan tool. Out of desperation, I changed the crank position sensor and cam position sensor and the car started. I theorized that the PCM was getting bad signal from the crank position sensor and the timing was way off.



Been away for a few days now back. Focusing on missings grounds an power right now. The crank position sensor on the 4.9L is in the distributor. There is a probably a way to check it with an ohm meter but haven't gotten that far

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

sanderson231 JUN 15, 08:35 PM
The power to the distributor comes from the ignition switch through E3 of the C500 connector. After it passes through the C500 connector there is a 0.5mm fusible link ("H") on the way to the distributor. If this fusible link is blown there is no power to the distributor or ignition module.