Pollo Dustino
Newbie
Vehicle
1998 GMC K2500 Suburban 4x4, 5.7L V8
Work Done
New fuel pump, Tru-Grade brand, P/N D5331028 (With California emission. With Module Code GFN. Without Low Lubricity Fuel System Sender. Wiring Harness Included. Internal Strainer Included)
New fuel filter
Locking gas cap
Concern
I bought the vehicle surplus from my job in August of 2022. Never had an issue starting, fired up virtually instantaneously. Had the factory fuel pump which could be heard outside the vehicle when running. One day I was driving and the vehicle stalled, would not restart. Could not hear the pump and it would not respond to kicking the fuel tank. Had it towed to my storage yard and I replaced the pump. After priming the fuel system it would start up, but not always instantaneously like it used to. It would have to crank a little bit.
I tend to let the vehicle sit as it is not my primary vehicle. I bought it for camping. Since purchasing it I've only driven around 700 miles total.
After sitting for a while it would start to take longer and longer to start, and I'd have to prime the system five or six times before cranking and it often still would not start up. It would fire the initial prime and that would be it, just keep cranking. I replaced the fuel filter about fifty miles ago as it appeared to be original.
When I got it out of storage a few weeks ago I had to dump a little bit of fuel system cleaner down the throttle body in order to fire it over. Once it fired up it ran fine. Drove it home and it's been parked in my driveway since then.
Two days ago I tried to take it out for my daily errands, but it would not fire over. Since I was running late I hopped in my other car instead. When I got back I tried to start the Suburban and it fired up immediately.
Yesterday I took it out to run some errands and had to prime it a few times before it started. When getting on the freeway it had very low power. I drove it around on surface streets and didn't notice a loss of power, but when I was going up and over a long freeway overpass I went wide open throttle and the engine would not rev over 3000 RPM. I parked it once I got home and have not driven it since.
This morning I busted out my Maddox-brand fuel pressure gauge from Harbor Freight and my volt meter to check the pressure and voltages at the pump. See the chart below:
The "LOADED" test is a brake stand in drive up to 2000 RPM. The pressure drops back down to 51 PSI immediately when letting off the throttle back to idle.
I have a copy of the shop manual and spec for fuel pressure is 60-66 PSI. So going off specs alone I have low pressure. I do not have my vacuum gauge here at home so I do not know what engine vacuum is. I do not hear any vacuum leaks but I know that's not an accurate test.
I have not yet attempted to block off the fuel return line.
One issue I know I need to resolve is a bad fuel pump-to-fuel tank seal. The new pump was an absolute witch to install and it took tremendous force to get the pump to seat in the tank with a new o-ring. When I fill the tank to maximum fuel leaks out around the pump during turns, so I think I rolled or tore the o-ring during installation. Would a leak in this area cause a hard start concern due to a "vacuum leak" into the tank? Same question for the locking fuel cap. I do not have an adapter to test the cap.
The fuel pump voltage is also odd to me. I'm measuring 13.85 volts at the battery with the engine running, but only a steady 12.66 volts at the pump connector. I am not familiar with how GMC powers the pump, is it a regulated voltage down to 12.66?
I am not against doing a new regulator and spider assembly due to the age of the vehicle. The truck needs a new radiator and complete front end rebuild so I'm already getting parts together.
1998 GMC K2500 Suburban 4x4, 5.7L V8
Work Done
New fuel pump, Tru-Grade brand, P/N D5331028 (With California emission. With Module Code GFN. Without Low Lubricity Fuel System Sender. Wiring Harness Included. Internal Strainer Included)
New fuel filter
Locking gas cap
Concern
I bought the vehicle surplus from my job in August of 2022. Never had an issue starting, fired up virtually instantaneously. Had the factory fuel pump which could be heard outside the vehicle when running. One day I was driving and the vehicle stalled, would not restart. Could not hear the pump and it would not respond to kicking the fuel tank. Had it towed to my storage yard and I replaced the pump. After priming the fuel system it would start up, but not always instantaneously like it used to. It would have to crank a little bit.
I tend to let the vehicle sit as it is not my primary vehicle. I bought it for camping. Since purchasing it I've only driven around 700 miles total.
After sitting for a while it would start to take longer and longer to start, and I'd have to prime the system five or six times before cranking and it often still would not start up. It would fire the initial prime and that would be it, just keep cranking. I replaced the fuel filter about fifty miles ago as it appeared to be original.
When I got it out of storage a few weeks ago I had to dump a little bit of fuel system cleaner down the throttle body in order to fire it over. Once it fired up it ran fine. Drove it home and it's been parked in my driveway since then.
Two days ago I tried to take it out for my daily errands, but it would not fire over. Since I was running late I hopped in my other car instead. When I got back I tried to start the Suburban and it fired up immediately.
Yesterday I took it out to run some errands and had to prime it a few times before it started. When getting on the freeway it had very low power. I drove it around on surface streets and didn't notice a loss of power, but when I was going up and over a long freeway overpass I went wide open throttle and the engine would not rev over 3000 RPM. I parked it once I got home and have not driven it since.
This morning I busted out my Maddox-brand fuel pressure gauge from Harbor Freight and my volt meter to check the pressure and voltages at the pump. See the chart below:
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The "LOADED" test is a brake stand in drive up to 2000 RPM. The pressure drops back down to 51 PSI immediately when letting off the throttle back to idle.
I have a copy of the shop manual and spec for fuel pressure is 60-66 PSI. So going off specs alone I have low pressure. I do not have my vacuum gauge here at home so I do not know what engine vacuum is. I do not hear any vacuum leaks but I know that's not an accurate test.
I have not yet attempted to block off the fuel return line.
One issue I know I need to resolve is a bad fuel pump-to-fuel tank seal. The new pump was an absolute witch to install and it took tremendous force to get the pump to seat in the tank with a new o-ring. When I fill the tank to maximum fuel leaks out around the pump during turns, so I think I rolled or tore the o-ring during installation. Would a leak in this area cause a hard start concern due to a "vacuum leak" into the tank? Same question for the locking fuel cap. I do not have an adapter to test the cap.
The fuel pump voltage is also odd to me. I'm measuring 13.85 volts at the battery with the engine running, but only a steady 12.66 volts at the pump connector. I am not familiar with how GMC powers the pump, is it a regulated voltage down to 12.66?
I am not against doing a new regulator and spider assembly due to the age of the vehicle. The truck needs a new radiator and complete front end rebuild so I'm already getting parts together.