Fuel delivery issue 1997 k2500 7.4 vortec - random not starting

[Piratehunter]

back in April while driving, the truck quit while turning a corner. tried to start it, would fire and flutter a bit, but then die. several attempts till battery died too. hauled to a garage, they found too low of fuel pressure, replaced fuel pump and filter. All is good for 5000 miles.

last week while in back country hunting the truck dies in the woods, same behavior, would fire and flutter, no power and dies. haul to a garage and test, too low fuel pressure...recommend pump and filter again. haul it home to home town garage, 120 miles. it starts up and runs great for them, they start and stop several times, all is good, leave it running for a bit, dies, and starts the fire and flutter issue again. that is as far as we've gotten so far.

anyone seens this and/or recommendations on troubleshooting? Thanks.

 

[Piratehunter]

this problem must be going around, found and following this tread too https://www.gmt400.com/threads/fuel-starvation.55479/

 

[454cid]

I wonder if this is a passlock issue....that'll keep it from starting, but I'm not sure if it can effect an already running engine.

 

[Schurkey]

Before you install ANOTHER fuel pump and filter:

1. How much trash is in the filter?
2. Was the tank cleaned-out? Number-One cause of early fuel pump failure is debris in the gas tank.
3. Measure voltage and amperage of the fuel pump when running. The "fuel pump" is not just a pump, it's also an electric motor. Wiring problems, poor connections, etc. will screw-up fuel delivery. Voltage MUST be measured as close to the pump as practical. Amperage can be measured anywhere in the circuit--but you might as well measure it in the same place you're getting your voltage readings. IDEALLY, you'd use a low-amperage current probe, and an oscilloscope so you can see the amperage draw of each bar on the motor armature, and calculate motor RPM, too.
4. No point in installing a fuel pump and not installing the in-tank wire harness (as applicable).

 

[stutaeng]

I think the fuel pressure regulator can also affect fuel pressure. If the spring inside the FPR loses stiffness, it allows more fuel to pass into the return line, and therefore, fuel pressure will be lower. This wouldn't cause intermittent low pressure problems though.

 

[Erik the Awful]

I would suspect a wiring issue - most likely a wire broken internally. If it was shorting I would expect a blown fuse.

If the sock is missing from the bottom of the fuel pickup, I could see debris being the problem.

 

[Carlaisle]

Since the same problem keeps recurring, you are most likely looking for something that has remained unchanged over the life of this problem. If the FPR has not been checked, it should be. The pump starving for fuel can present as low pressure, so check to be sure there are no issues in the tank. If the tank was not verified to be clean last time, replace the filter again so you know that won't be the problem this time. What is the voltage/amperage drawn by the pump? What fuel pump did you install? Was it an AC Delco, Walbro, or some chinesium special? You would not be the first person to install multiple new parts that failed shortly after installation. Many pumps fail due to an over current condition caused by a bad ground. You might consider running a dedicated ground from the battery to the pump to eliminate this as a potential source of future frustration. This last option is probably the most likely culprit and easiest to test and is what I would try first.

 

[Piratehunter]

Since the same problem keeps recurring, you are most likely looking for something that has remained unchanged over the life of this problem. If the FPR has not been checked, it should be. The pump starving for fuel can present as low pressure, so check to be sure there are no issues in the tank. If the tank was not verified to be clean last time, replace the filter again so you know that won't be the problem this time. What is the voltage/amperage drawn by the pump? What fuel pump did you install? Was it an AC Delco, Walbro, or some chinesium special? You would not be the first person to install multiple new parts that failed shortly after installation. Many pumps fail due to an over current condition caused by a bad ground. You might consider running a dedicated ground from the battery to the pump to eliminate this as a potential source of future frustration. This last option is probably the most likely culprit and easiest to test and is what I would try first.

thanks for all the recommendations. The original fuel pump ran for 114000 miles with a couple of filter changes over time. when it went out, tank was full, it was replaced with a Delphi hp10001, full assembly and filter. I’m not sure if the shop completely dropped the tank and verified it was clean. it went about 5000 miles till same symptoms on 1/4 tank. It’s back at the same shop, new ownership and mechanics willing to honor warranty.

this is a ‘97 with the 7.4 vortec, I believe the FPR is inside the plenum, how is it tested?

Thanks everyone for all the responses.

 

[454cid]

this is a ‘97 with the 7.4 vortec, I believe the FPR is inside the plenum, how is it tested?

It's on the back of the fuel rail. It does have a short piece of vacuum hose that can rot, I've been told..... I've never been deep enough to check my 99 and it's pushing 300K miles.

 

[81nascar]

Since the same problem keeps recurring, you are most likely looking for something that has remained unchanged over the life of this problem. If the FPR has not been checked, it should be. The pump starving for fuel can present as low pressure, so check to be sure there are no issues in the tank. If the tank was not verified to be clean last time, replace the filter again so you know that won't be the problem this time. What is the voltage/amperage drawn by the pump? What fuel pump did you install? Was it an AC Delco, Walbro, or some chinesium special? You would not be the first person to install multiple new parts that failed shortly after installation. Many pumps fail due to an over current condition caused by a bad ground. You might consider running a dedicated ground from the battery to the pump to eliminate this as a potential source of future frustration. This last option is probably the most likely culprit and easiest to test and is what I would try first.

I'm with him.. I think you have a wiring/ground problem possibly causing the pump failure..