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Gmc 3500 Help

VegasHeat

By VegasHeat
in Ask A GM Technician

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VegasHeat Enthusiast

VegasHeat

Posted
Posted

Thank goodness I found this site...maybe somebody here can help.

 

I have a 1993 GMC 3500 with a 454cid. Last summer I had problem where the truck would start initially for five seconds then die. I could re-start the truck and it would gradually run longer...five seconds...seven seconds....ten seconds...fifteen seconds...then stay running. When it died....it was like the fuel pump shut off (I'm pretty sure that was what was happening). I didn't have a problem until November and then it did it everytime I started it (I only drive it one day on the weekends).

 

The truck has sat over the winter and I am experiencing the same problem. I initially thought that that oil pressure sending unit was not registering and the truck would die after the initial prime (I can hear the fuel pump when I turn the ignition on). The truck starts and then dies. The other issue is that the oil pressure gauge is pegged. It starts and shows 30lbs and then pegs and dies.

 

Today after starting the truck and going through the five, seven, ten and fifteen second startings, I got the truck to run and staying running....but it eventually stumbles...drops rpms and dies. Today also I started to get a check engine light everytime it starts and after it is running for five seconds.

 

This problem seemed to occur right after I changed the thermostat, which seems coincidental. I have changed the oil and filter today, no difference. I haven't changed the oil pressure sending unit, not sure if it's the problem.

 

I'm sorry for the long post and I really appreciate any help with this frustrating situation.

95 chev Enthusiast

95 chev

Posted
Posted

I'm no expert, and I may be way off base on this, but try changing out the fuel filter. It is cheap and easy to do and the results may suprise you. Although I don't think that a clogged fuel filter would make the check engine light come on, you never know. I only suggest the filter change because I was experancing some hard starting and stalling/stumbling issues and it turned out to be the filter. Mine is a 95 chevy 2500 with the 5.7 engine.

VegasHeat Enthusiast

VegasHeat

Posted
  • Author
Posted
have you concidered scanning the pcm for codes,taking it to a garage?

 

I have considered taking it to a shop and I don't have a scanner, but was hoping I would be able get some suggestions here and I don't know if it would make it there. If it was as simple as changing the oil pressure sending unit, I would be kicking myself for having it towed to a shop, diagnosed and fixed. That's why I came to this site hoping someone would have suggestions. I will take it to a shop as the last resort.

 

Thanks Chev95 for the suggestion on the fuel filter. Tomorrow I will change the fuel filter and probably the oil pressure sending unit.

 

Does anybody know if the symptons warrant these changes, or do they not fit? Thanks for any other suggestions, they are greatly appreciated.

ZZ327 Senior Enthusiast

ZZ327

Posted
Posted

pull off your air cleaner and see if the fuel injectors are spraying fuel in the Throttle body. If its got high miles it might be time to change your PCV valve and o2 sensor(s) that are inline after the exhaust manifolds, and check your EGR valve on the Intake too.

VegasHeat Enthusiast

VegasHeat

Posted
  • Author
Posted
pull off your air cleaner and see if the fuel injectors are spraying fuel in the Throttle body. If its got high miles it might be time to change your PCV valve and o2 sensor(s) that are inline after the exhaust manifolds, and check your EGR valve on the Intake too.

 

 

Thanks ZZ327, it is spraying fuel into the throttle body, but I think the fuel pump is cutting off after it primes the system (that's why I was thinking it was the oil pressure unit). After a while of starting and dies....it will run for a few minutes....but then dies. It was running for a few minutes this afternoon and then all of a sudden it sputtered and died. Then it will start right back up and run for a few minutes and sputter again and die. The initial times I could tell the fuel pump shut off and that's what killed it. I'm wondering if it's more than one problem.

 

I will change the PCV valve and 02 sensors and check the EGR valve....thanks for the input.

  • 2 weeks later...
VegasHeat Enthusiast

VegasHeat

Posted
  • Author
Posted

Ok...scanned the codes and it was the knock sensor. The wire had come off. I cleared the codes. I changed the oil pressure sending unit and now have good oil pressure. I have checked the EGR, seems fine.

 

The truck still takes five or six times to start and will finally run but will intermittently die. I drove the truck around for twenty minutes the other day after I had it running and it would die on deceleration.

 

Took the truck back, parked it and the next morning it is back to the five or six times to start it. It runs for a tens seconds then dies.

 

I took the air cleaner off and watched the throttle body injection and both injectors spray fine and when the truck shuts off it is not because of lack of fuel....it's like someone turns the key off.

 

I checked for codes and there aren't any. I did change the fuel filter....no change.

 

Any more ideas?

VegasHeat Enthusiast

VegasHeat

Posted
  • Author
Posted
Have you checked the Idle air control valve?

 

Took it out and cleaned it yesterday.

 

Today went to start it and it took about twenty minutes and twenty tries to get it running. Each time it would run a little longer. Its almost as if it doesn't want to start until the motor is warm. When it dies, it is like someone turned off the key. Still no codes. I can hear the fuel pump running until it dies.

  • 1 month later...
VegasHeat Enthusiast

VegasHeat

Posted
  • Author
Posted

Here's an update and thanks to those that gave suggestions in an effort to help.

 

I finally bit the bullet and changed the fuel pump. I was dreading it because I didn't want to drop the tank or take the bed off. I decided to lift the bed and I changed the fuel pump and the truck fired right up. Only $49.00, which is much better than a tow to the dealership.

 

I was told by several people that if you constantly run the fuel tank under a quarter tank that the fuel pump remains uncovered by fuel and it burns out. Don't know the validity, but it makes sense to me.

 

Once again, thanks to all that gave suggestions, it truly is greatly appreciated!

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