1997 GMC K1500 hard start when hot

[cdm1993]

I've got a 1997 GMC K1500 with the 5.7 and 4l60E.

When hot (mostly on warmer days above 80F) and the air conditioning has been running the truck occasionally goes into high idle mode when at a stop light. Under acceleration, it bucks and searches for gears, and when entering the highway the torque converter wont lock up. If I shutdown and try and start it, it will not start. It will continue to crank unless I goose the accelerator while cranking, and then it will start; occasionally entering high idle again. There is a distinct smell of fuel when I do this to start it back up.

Maintenance info:
Has 270,000 miles on original engine and transmission.
Transmission fluid and filters changed on time and has not been neglected.
Fuel pump changed 5 years ago at 160,000 miles.
Fuel filter changed 20,000 miles ago.

On cold days, this rarely happens. Any idea whats causing this? Thanks.

 

[BigJakeChevy]

Hello, I just went through this with a friends 98 vortec. We tested fuel pressure and there was definitely a leak. Once we took the plastic plenum off it was obvious the pressure regulator was bad. We ended up replacing the original injection system with the upgraded spider that relocates the injectors at the valves. Hot start issue gone and idle is perfect. Truck noticeablely better off the line too.

 

[dogememe]

99% chance you need a new fuel injection assembly with fuel pressure regulator. Do the extra work and change lower intake gaskets if they haven't been changed before.

 

[Warstud]

I would test or replace the Coolant Temp Sensor

 

[cdm1993]

Originally Posted by BigJakeChevy
Hello, I just went through this with a friends 98 vortec. We tested fuel pressure and there was definitely a leak. Once we took the plastic plenum off it was obvious the pressure regulator was bad. We ended up replacing the original injection system with the upgraded spider that relocates the injectors at the valves. Hot start issue gone and idle is perfect. Truck noticeablely better off the line too.

Originally Posted by dogememe
99% chance you need a new fuel injection assembly with fuel pressure regulator. Do the extra work and change lower intake gaskets if they haven't been changed before.


Interesting. I replaced the intake gaskets and upgraded the injector assembly (SCPI to MFI conversion DELPHI FJ10566), but this was at 204,000 and 3 years ago. Is there a lifespan to the upgraded spider assembly?

Originally Posted by Warstud
I would test or replace the Coolant Temp Sensor


I will check that out.

 

[dogememe]

Originally Posted by cdm1993
Originally Posted by BigJakeChevy
Hello, I just went through this with a friends 98 vortec. We tested fuel pressure and there was definitely a leak. Once we took the plastic plenum off it was obvious the pressure regulator was bad. We ended up replacing the original injection system with the upgraded spider that relocates the injectors at the valves. Hot start issue gone and idle is perfect. Truck noticeablely better off the line too.

Originally Posted by dogememe
99% chance you need a new fuel injection assembly with fuel pressure regulator. Do the extra work and change lower intake gaskets if they haven't been changed before.


Interesting. I replaced the intake gaskets and upgraded the injector assembly (SCPI to MFI conversion DELPHI FJ10566), but this was at 204,000 and 3 years ago. Is there a lifespan to the upgraded spider assembly?

Originally Posted by Warstud
I would test or replace the Coolant Temp Sensor


I will check that out.

It should last longer than that, go rent a fuel pressure tester from O'Reilly and make sure that it's working like it should.

 

[cdm1993]

I changed the coolant sensor and the problem seems to be fixed. I also checked the fuel pressure and it is at 51 PSI with key in ignition, and just above 51 when running. I used an Actron fuel pressure tester.

 

[dogememe]

Does the fuel pressure remain after key is turned off or does it bleed down?