HELP!! Electrical Issue

[87TIGN]

Ok so I have an 87 GN and I am having some MAJOR issues right now. About 2 weeks ago I put a new intake on the car and took it for a ride. It rode great and felt great. I got on the highway and hit about 3/4 throttle and it started to sputter so I got off the throttle and if I hit the throttle again it would bog down and it finally died. I could not get it started on the side of the road so I had it towed home. Once home I checked the ignition control module (even put a new one on) and no change. Next I tried a new coil pack and nothing. Next I tested the crank position sensor and put a new one on, nothing. Checked and rebuilt the cam sensor, nothing. All the while I have had no spark. Engine cranks fine just no spark. So I proceded to check all the wires on the ICM harness everything checks out ok but ground did not read out as continuous so I soldered in a new ground on the harness and this didnt fix anyting either. Next I hooked up a noid light and found I have no injector pulse (light not on at all). So I went to the computer next. Picked up a computer for 75 bucks and this didnt fix it either. (I know the best way to fix a GM is to throw money at it )So next I probed all the wires on the computer (I know best readings are taken with the car hot at closed loop but seeing as how the car wont start I had no choice) and everything seemed to check out ok. I had power on all the injector lines and the main harness power. Next I went to the injector harness itself. I had power on the individual injector clips so I went to the harness at the back of the intake. On this harness I read the pink/black wire (power) and had the 11-12 volts but it read continuous to ground... So I figured that maybe I had a direct short but I had no blown fuses. I checked the pink/black wire on the other sensors and they all read the proper voltage with key on but also read contiuous to ground. I than proceded to take the wire bundle that comes from the computer to the injector harness apart and inspect all the pink/black wires and there are no broken or frayed wires that I can see. Please help me. I am at my wits end with this car and I dont know where to go. I have probebly 10-12 hours in the car and it feels like I have gone nowhere. Any suggestions would be much appreciated.
Thanks
Andrew

 

[garyk1970]

tripple check the ecm fuse(s) in the underdash fuse block...very easy to look over....

 

[garyk1970]

if the new fuse blows as soon as you turn the cra on or later...start unhooking solienoids ie; boost,evap canister,etc...
check the oil pressure sensor too if the ign is shorting out....post back.

 

[notacarlo]

since GaryK brought up sensors, it got me thinking.

I don't remember for sure, someone WILL correct me.

The oil pressure sensor. If that has no signal or becomes disconnected, I believe the car will not start. (as a safety precaution if you lose oil pressure)

 

[87TIGN]

since GaryK brought up sensors, it got me thinking.

I don't remember for sure, someone WILL correct me.

The oil pressure sensor. If that has no signal or becomes disconnected, I believe the car will not start. (as a safety precaution if you lose oil pressure)

You know its funny you say that because yesterday when I tried cranking I had no oil press on my gauge. It is a mechanical gauge however so it may not get a great reading on startup. When the car originally shut down I had perfect oil press readings on my gauge (boust 15-20 psi hot). Is there an oil press relay that could be shot? Would no oil press cause no spark no fuel?

 

[87TIGN]

tripple check the ecm fuse(s) in the underdash fuse block...very easy to look over....

I triple checked the ecm fuses under the dash yesterday after all was said and done and all were ok.

 

[notacarlo]

You know its funny you say that because yesterday when I tried cranking I had no oil press on my gauge. It is a mechanical gauge however so it may not get a great reading on startup. When the car originally shut down I had perfect oil press readings on my gauge (boust 15-20 psi hot). Is there an oil press relay that could be shot? Would no oil press cause no spark no fuel?

Kill spark...I think so. Kill fuel, no. For giggles remove the three wires on that switch and tie them together....try to start the car. (by tie I mean link together)

 

[87TIGN]

I will try doing that this week and let you know what happens.

 

[BlackBandit]

Disconnecting the oil pressure sensor WILL NOT prevent you from starting the car. It's wired to act as a fail safe that allows you to start your car if the fuel pump relay goes south. Did you pinch any wires when you put the intake on? Did you hook up all your grounds? I don't have a schematic in front of me but I would guess that those pink wires have a coil in between them and ground. If you're using a "beep checker" for continuity it'll read through a good bit of resistance. If you're checking with an ohmmeter how many ohms do you have? (pink to ground)

 

[87TIGN]

Disconnecting the oil pressure sensor WILL NOT prevent you from starting the car. It's wired to act as a fail safe that allows you to start your car if the fuel pump relay goes south. Did you pinch any wires when you put the intake on? Did you hook up all your grounds? I don't have a schematic in front of me but I would guess that those pink wires have a coil in between them and ground. If you're using a "beep checker" for continuity it'll read through a good bit of resistance. If you're checking with an ohmmeter how many ohms do you have? (pink to ground)

Just did the beep check but I can do an ohm test. How many ohms should there be? I just did a cold air intake (big mouth kit) not an actual intake manifold.

 

[BlackBandit]

Depends on the coil. (assuming there is one) Does your SES light come on when you turn the key on? Also, are you getting your reference voltage at the sensors? (crank, cam, ect.) Are you sure you're getting all the power to the ECU? Check the orange wire going to the battery and as mentioned before check fuses. Could also be a fuse to the ccci.

 

[turbolou]

Reply

Check pin connectors at the harness going to the side of the control module for good contact. Tighten them up a bit with a pick tool. You indicated no spark or inj.pulse.Are you getting an RPM cranking signal, Do a good visual inspection of the crank sensor wires . peal the tape off & make sure there isn't a break in the wiring or connector. Did the crank sensor get damaged during installation.Ground wires on back of the head don't just look to see if they are attached physically put a wrench on the bolts to make sure they are tight.Rebuilt the cam sensor? are you sure the reluctor index tang isint missing or broken off. Have you tried another cam sensor. good luck

 

[87TIGN]

Depends on the coil. (assuming there is one) Does your SES light come on when you turn the key on? Also, are you getting your reference voltage at the sensors? (crank, cam, ect.) Are you sure you're getting all the power to the ECU? Check the orange wire going to the battery and as mentioned before check fuses. Could also be a fuse to the ccci.

SES light does come on with key on. there is reference voltage at the crank and cam sensors. I am pretty sure there is power to the ECU I did check to orange wire and had power to the computer and the SES light is on so that is a good indicator. Checked all the fuses under the dash and they are all in good shape.

 

[87TIGN]

Check pin connectors at the harness going to the side of the control module for good contact. Tighten them up a bit with a pick tool. You indicated no spark or inj.pulse.Are you getting an RPM cranking signal, Do a good visual inspection of the crank sensor wires . peal the tape off & make sure there isn't a break in the wiring or connector. Did the crank sensor get damaged during installation.Ground wires on back of the head don't just look to see if they are attached physically put a wrench on the bolts to make sure they are tight.Rebuilt the cam sensor? are you sure the reluctor index tang isint missing or broken off. Have you tried another cam sensor. good luck

The harness has good contact with the CCCI but I will double check. Not 100% sure on the rpm signal. I get low RPM lights on the dash when cranking however. I will check the wiring on the crank sensor but when I replaced the old one all the wres looked to be in good shape. I will definitly try tightening the ground bolt on the back of the intake. I originally thought it was the cam sensor that was cuasing my problem so I ordered the RJC kit and when it got here I pulled the sensor apart and the tang on my was ok. So because I had it all open already I filed the old tang off and put the new one in place. However I have not tried a new cam sesnor all together. If I am getting good reference voltage at the cam sensor that I shoudl be ok right?

 

[turbolou]

Reply

The harness has good contact with the CCCI but I will double check. Not 100% sure on the rpm signal. I get low RPM lights on the dash when cranking however. I will check the wiring on the crank sensor but when I replaced the old one all the wres looked to be in good shape. I will definitly try tightening the ground bolt on the back of the intake. I originally thought it was the cam sensor that was cuasing my problem so I ordered the RJC kit and when it got here I pulled the sensor apart and the tang on my was ok. So because I had it all open already I filed the old tang off and put the new one in place. However I have not tried a new cam sensor all together. If I am getting good reference voltage at the cam sensor that I shoudl be ok right?

Only if its timed correctly. & the hall effect sensor in the cap is OK. What bothers me is you have no spark or injector pulse. That almost has to be in the crank trigger circuit. I remember when Jason Cramer's race car died at BG & he replaced one bad crank sensor with another. I bet he'll never forget that one. I also have had loose crank damper bolt causing the damper to move forward & lose the crank sensor signal. Also ran into a worn crank keys a few times. Use the hooked end of a stretched coat hanger & do a real good shake & wiggle test on all the wires to see if that doesn't do something. Guaranteed when you do find the problem it will be something stupid & probably a result of human error caused by busy little fingers.

 

[Blazer406]

Per the "no-start" diagram.... if you have fuel pressure....but no spark at all.....it says:

Check circuit 839 which is pin "M" on the CCCI connector.....Pink/Black wire - Fuel Pump/CCCI/Injector fuse. Check for "open". If circuit is OK....CCCI module faulty.....or connection faulty.....

 

[87TIGN]

Got it figured out. Someone on the board had suggested to look at the crank signal wiring and I had a buddy of mine playin around with the car with his oscillascope and saw there was no crank signal. When he checked the harness connector the female end of the pin was splayed open so the crank sensor was getting no ground. He pulled the connector apart and fixed the problem, car started right up. Huge relief for me, I am so extatic that its running again!! Thanks for all you help guys.
-Andrew

 

[turbolou]

reply

Only if its timed correctly. & the hall effect sensor in the cap is OK. What bothers me is you have no spark or injector pulse. That almost has to be in the crank trigger circuit. I remember when Jason Cramer's race car died at BG & he replaced one bad crank sensor with another. I bet he'll never forget that one. I also have had loose crank damper bolt causing the damper to move forward & lose the crank sensor signal. Also ran into a worn crank keys a few times. Use the hooked end of a stretched coat hanger & do a real good shake & wiggle test on all the wires to see if that doesn't do something. Guaranteed when you do find the problem it will be something stupid & probably a result of human error caused by busy little fingers.

Glad you found it, I bet that one you won't forget soon.