Need help with starting problem.
- Thread starter src76ta
- Start date
More testing leading to more questions. Following procedures for testing fuel pump relay circuit I got to the bottom section that targets the oil pressure switch. With engine running at normal temp I disconnected the fuel pump relay and it continued to run. Next step to reconnect relay with ignition off and probe fuel pump test terminal. Ligth on means bad oil switch. No light means no trouble. I got no light. Problem is that my starting issue is intermittent. I decided to try and unplug the oil switch with the car running to see what happened. It ran. Then I unplugged the switch with engine off. The oil gauge pegged to the right and the car would not start. Also there was no fuel pump prime noise. I cant find anything in the TTA supplement but there is a direct relation between the fuel pump and the oil switch. I'm thinking the switch is shorting out and screwing with the entire fuel pump loop. First thing monday I'll be on the phone tracking down a new oil switch. I hope these are still available.
Advance auto 25 bucks.
http://www.partsamerica.com/PartDet...IE&MfrPartNumber=OP24501&PartType=417&PTSet=A
http://www.partsamerica.com/PartDet...IE&MfrPartNumber=OP24501&PartType=417&PTSet=A
TTA oil/Fuel switch
.. been following your post.. .. and THIS is a very good post for how much info your put into it and others can get a benefit from.
Check this with the description of the unit your after as the picture and info from the GM files listed shows it as a small Switch. This is the only one now listed in the current GM info. The number for the switch they show for 3.8lt (not stipulating Turbo or not) is 25036378 or using delc's numbers is D1816. GM current retail around US$11.95
It is described as a fuel pump & Engine Oil Pressure switch.. three prong. is around 1.5 inches tall. This might also help.
Good luck.
.. been following your post.. .. and THIS is a very good post for how much info your put into it and others can get a benefit from.
Check this with the description of the unit your after as the picture and info from the GM files listed shows it as a small Switch. This is the only one now listed in the current GM info. The number for the switch they show for 3.8lt (not stipulating Turbo or not) is 25036378 or using delc's numbers is D1816. GM current retail around US$11.95
It is described as a fuel pump & Engine Oil Pressure switch.. three prong. is around 1.5 inches tall. This might also help.
Good luck.
The oil pressure switch interfaces with the fuel pump wires.
Now a better test is to connect a fuel pressure guage to the rail and see if the rail is holding pressure. If not, you have bad injectors.
The oil pressure switch should have no bearing on your fuses being dead.
And you can have leaky injectors that OHM out correctly.
Put a guage on the car and confirm operation.
Now a better test is to connect a fuel pressure guage to the rail and see if the rail is holding pressure. If not, you have bad injectors.
The oil pressure switch should have no bearing on your fuses being dead.
And you can have leaky injectors that OHM out correctly.
Put a guage on the car and confirm operation.
You can have leaky injector(s) that wont hold good pressure, but thats not gonna keep the car from starting. From running good yes.
All 6 would have to be completely dead in order for it to not start. Then all of the sudden they all start working and the car runs fine, no way.
If the fuel pump relay works, there will be pressure at the rail. That doesnt mean the cars gonna start. It still has to go thru the oil pressure switch.
All 6 would have to be completely dead in order for it to not start. Then all of the sudden they all start working and the car runs fine, no way.
If the fuel pump relay works, there will be pressure at the rail. That doesnt mean the cars gonna start. It still has to go thru the oil pressure switch.
The oil pressure switch will not cause a no start condition. The power running through the switch is there to back the fuel pump relay up in the event it or the 12V relay drive from the ecm fails.
Termial C on the oil pressure switch and terminal A on the fuel pump relay both feed circuit 120(tan/wht) which is the power for the fuel pump. It does not run power through either one but is simply a backup should one fail.
The oil pressure switch will not stop a car from running should the oil pressure drop UNLESS the fuel pump relay is also bad.
HTH,
Steve
Termial C on the oil pressure switch and terminal A on the fuel pump relay both feed circuit 120(tan/wht) which is the power for the fuel pump. It does not run power through either one but is simply a backup should one fail.
The oil pressure switch will not stop a car from running should the oil pressure drop UNLESS the fuel pump relay is also bad.
HTH,
Steve
Here is a pic of the fuel pump relay wiring diagram so you can see what I'm saying(Chart A-5 from the 20th TTA suppliment)
http://img.photobucket.com/albums/v201/tta850/DSC00871.jpg
http://img.photobucket.com/albums/v201/tta850/DSC00871.jpg
GMC-YA ..ya may wanna look at the schematic.
Something doesnt sound rite. The car fires.. yet stays running.. and the only time the conditions surfaces is when the car is shut off. Initially would sound like a cam sensor problem. Since the cam sensor is used to fire the #1 injector. But the fact he never messes with the cam sensor and the motor fires up again.. would indicate an electrical issue.
The oil pressure sender kills fuel not ignition. the way to verify this is with a simple fuel pressure guage.
Bo.. TTAmeasap.. had a problem once car would not start.. problem was his fuel pressure was so high the injectors wouldnt fire.
So If I owned the car, I would put on a simple fuel pressure guage on the rail and confirm fuel pressure at the rail while cranking. This is the step to make before changing parts and possibly introducing more problems.
The way symptoms are fixed is by taking readings and measurments when ever possible. Then replacing parts and confirming the condition has disappeared. If not.. you'll build a new car looking for a simple problem.
Still the dead fuses in the fuse box are strange. Sure the test lite was properly grounded?
HTH
Something doesnt sound rite. The car fires.. yet stays running.. and the only time the conditions surfaces is when the car is shut off. Initially would sound like a cam sensor problem. Since the cam sensor is used to fire the #1 injector. But the fact he never messes with the cam sensor and the motor fires up again.. would indicate an electrical issue.
The oil pressure sender kills fuel not ignition. the way to verify this is with a simple fuel pressure guage.
Bo.. TTAmeasap.. had a problem once car would not start.. problem was his fuel pressure was so high the injectors wouldnt fire.
So If I owned the car, I would put on a simple fuel pressure guage on the rail and confirm fuel pressure at the rail while cranking. This is the step to make before changing parts and possibly introducing more problems.
The way symptoms are fixed is by taking readings and measurments when ever possible. Then replacing parts and confirming the condition has disappeared. If not.. you'll build a new car looking for a simple problem.
Still the dead fuses in the fuse box are strange. Sure the test lite was properly grounded?
HTH
First off TTA850 thank you for posting that pic, can you take a pic of the ecm wiring and email it to me, CLee1595@aol.com thanks.
Second, the last post I made was incorrect, sorry for the confusion. Please refer to the first post I made about it instead.
Now, the oil pressure switch CAN cause a no start IF the fuel pressure reley is not working, that was the reason I asked if he heard the fuel pump prime. If his relay is bad and the oil pressure switch only works intermittently then the car will only start intermittently.
This sounds exactly like what is going on by this quote right here. That and he said the times the car wouldnt start he notice the oil pressure gauge had pegged over, and the extended starting times.
Now does this mean that a new OPS will fix the problem, NO of course not. As I said before none of this explains the no power at the fuses situation. So yes there could be and underlying electrical issue here.
Razor your last post about checking while CRANKING is a good idea. But this must be done during the no start. Now if he does this while there is no pressure on the rail he can use it to check and see if his fuel pressure realy is working. Which would totally throw the oil pressure switch fixing this out the window.
Your previous post about checking to see if the rail was holding pressure wouldnt prove anything, Especially if he checked after the car had started allready since there would of still been pressure there.
src76Ta - Check all your grounds.
Chris
Second, the last post I made was incorrect, sorry for the confusion. Please refer to the first post I made about it instead.
Now, the oil pressure switch CAN cause a no start IF the fuel pressure reley is not working, that was the reason I asked if he heard the fuel pump prime. If his relay is bad and the oil pressure switch only works intermittently then the car will only start intermittently.
This sounds exactly like what is going on by this quote right here. That and he said the times the car wouldnt start he notice the oil pressure gauge had pegged over, and the extended starting times.
Now does this mean that a new OPS will fix the problem, NO of course not. As I said before none of this explains the no power at the fuses situation. So yes there could be and underlying electrical issue here.
Razor your last post about checking while CRANKING is a good idea. But this must be done during the no start. Now if he does this while there is no pressure on the rail he can use it to check and see if his fuel pressure realy is working. Which would totally throw the oil pressure switch fixing this out the window.
Your previous post about checking to see if the rail was holding pressure wouldnt prove anything, Especially if he checked after the car had started allready since there would of still been pressure there.
src76Ta - Check all your grounds.
Chris
To check fuel rail pressure when the car won't start may take several tries. Will I need to bleed pressure between attempts? Are there any spacific grounds that come to mind? There is a chance that my craftsman test lite may have been giving me false reports. I was using it over the weekend and was getting no light from a known hot fuse. Sorry for that misinformation. I need to go back now and retest the fuel pump relay to verify my first findings. Do they want power put to the fuel pump test terminal as indicated in the first step of the fuel pump relay diagram,or is that only if the car won't crank? I'm somewhat confused about that step.
src76ta - There is the ground coming off the negative battery cable that goes to the engine, it sould be between the turbo bracket and the head. At least that is where it is on my car. The other grounds are at the back of the intake, coming off the main wiring harness to a stud on the intake.
I've been thinking about this today, you said the car would go to a no start sometimes after it had allready been started. What doesnt make sense is that the car sould of at least hit off of what was left in the rail if the injectors and plugs were firing. When it doesnt start do you know if the plugs are getting spark and the injectors are pulsing?
I think we might of gotten ahead of ourselves here, Julio is right lets get the basics.
I've been thinking about this today, you said the car would go to a no start sometimes after it had allready been started. What doesnt make sense is that the car sould of at least hit off of what was left in the rail if the injectors and plugs were firing. When it doesnt start do you know if the plugs are getting spark and the injectors are pulsing?
I think we might of gotten ahead of ourselves here, Julio is right lets get the basics.
Tested fuel pressure and got 37-38 psi while running. Got the no start to occur and had 40psi. The gauge is on now and i'll check it later today. while cranking the third time when the car woulden't fire it coughed and stumbled and then fired. This is the first time for this symptom.
- Joined
- May 9, 2002
What is the number on the fuel pressure regulator? "237" (45 PSI) is stock, your fp is more typical of a GN 233 regulator.
Next time you have knock retard, add octane to see if it goes away on its own, no sense changing parts until you know whether or not higher octane reduces or eliminates knock retard.
Best Regards
Your reference to knock retard I'm guessing goes back to the original problem. Boostjunkie came out and did some tuning of the basics on the car. New fuel filter,set IAS. and scanned for codes. We drove the car and verified the knock. At his suggestion, we replaced the injectors with a set of rebuilt stock ones. This elimanated the knock. However, This is when the no start trouble appeared. Not to say that it could not have been there before. I had only had the car for a few months and only put about 6 miles on it. This is my first exposure to turbo cars but I new the noise was not normal. The problem seems to be mutating. When it first began, the no start condition would persist for 10 to 15 tries. Sometimes pulling the fuses or disconnecting the battery would get it to start . Now when the no start occurs, two or three tries and it fires. Also this last time it spit and coughed as it was attempting to start. Thats a first for that.I need to thank all the guys on this forum for being patient with me and sticking with me. This will be a really fun car when it runs right. I have to admit, it really sucked when it woulden't start in the tech line at TA Nationals this year.
