Fuel Starvation.

[wb292]

I have a 91 K1500 RCSB with a 350 and a 5 speed. Last week it started stumbling and stalling. No codes. So I assumed the fuel pump was failing. I replaced it and the filter. It ran good until yesterday. About 700 miles on the new pump and filter. It started loosing power like it was starving for fuel. I got a CEL with codes 24 and 44. It can't rev above 2300prms. I shut it off at a gas station and tried again after a few minutes and it ran good for about 20 miles. It then ran good for another 20 miles or so. I repeated this until I got home. about 130 miles total. I went through the TBI about a year ago with new filters on the injectors. But did not replace them. Should I be thinking the fuel pump relay? Maybe injectors? I plan on testing the fuel pressure this weekend. But It ran good for the the twenty miles each time. Any help would be appreciated.

 

[evilunclegrimace]

It is possible that there is water in the system. These trucks have a 5 micron screen in the filter and it will not allow water to pass. If there is enough water in the system that gas will push the water up against the screen and cause drivabilty issues like stumbling and stalling. Once the truck is shut off and the pressure bleeds down the water will lay in the bottom of the filter and the truck will start and drive normally until the water is pushed up against the screen and the truck shuts down,

 

[wb292]

Ok I will check that out. Here is Arizona it’s not very likely. Water is pretty scarce. I’ll be pulling the pump this weekend and will look in the tank.

 

[evilunclegrimace]

Ok I will check that out. Here is Arizona it’s not very likely. Water is pretty scarce. I’ll be pulling the pump this weekend and will look in the tank.

Just pull the filter and drain it into a clean catch pan and see if there is any water in the filter.

 

[Nad_Yvalhosert]

Before you reload the parts cannon, try another new fuel filter. They're darn cheap, and if you possibly picked up anything from the bottom of the tank, its gonna clog up the filter.

 

[Nad_Yvalhosert]

Now, code 44 indicates the engine is running lean. That would apply, not only if there is low pressure, but low volume as well.
GM doesn't have a Schrader valve on TBI trucks, there is one I bought from Snap On a couple years ago. It installs in place of the fuel filter. I'd hate to recommend you buy one, only to use it once, but it is a good diag tool...

 

[Nad_Yvalhosert]

I have no idea what code 24, lack of VSS, has to do with your issue. Might be a fluke... disconnect the battery, and work on diagnosing the fuel problem.

 

[Schurkey]

Connect a scan tool, look at the data stream. Find out what the computer is trying to tell you.

The scan tool will show if the VSS is accurate, or whether the signal is missing entirely. And the fuel trims should show rich-command if the pump is weak. While you're in there, you can verify all the rest of the sensors, and the computer outputs.

Fuel pressure test is just about mandatory.

How old are the usual "tune-up" items? Spark plugs, plug wires, cap 'n' rotor, PCV valve, air filter, etc? Ignition timing set properly, and ignition advance works? EGR works like it should?

 

[wb292]

This engine has about 15K on it. I installed all new ignition components including a new distributor with the build. EGR and air pump were deleted both on the engine and in the chip. After shutting it off a couple of minutes it runs perfectly for about 20 miles. It pulls strong and I climbed a 6 % grade for 11 miles on my way home. So I’m leaning toward the pump or the relay. I borrowed a fuel pressure gauge from a friend and will check it this weekend. I’m going to try to rig a longer hose on it so I can watch the pressure while driving. I don’t own a scan tool guess I should invest in one soon. I have another Wix filter in the shelf. I’ll try it also.

 

[PlayingWithTBI]

Here's a fitting you hook up to the back of the TB, then you can hook up a hose with 1/8" NPT to a pressure gauge so you can see it while driving under acceleration. When done, just put the gauge there on the fitting to be able to monitor periodically.

Our fuel psi guage to fuel line adapter mounts inline directly to your GM tbi throttle body!!!

Our fuel psi guage to fuel line adapter mounts inline directly to your GM tbi throttle body!!!

marine-performance-parts.com

Here's an example of one with an AFPR, the OE hose fittings screw right in.

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