Fuel pump or transmission?

[bm23]

I have been having this issue on and off and it was previously fixed by filling the gas tank up. I can drive at around 2000 rpms in first and sometimes second, but once I get out on the road, I cant make it past 30 mph due to it lurching. It's a 95 350 tbi and the fuel pump has never been replaced.

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[Schurkey]

There's two dozen things this could be, so don't limit your diagnosis to fuel pump and transmission.

WHAT IS YOUR FUEL PRESSURE when the engine is running poorly?

When was the last time you replaced all the "tune-up" parts? Cap, rotor, plug wires, spark plugs, air filter, fuel filter, and then verified initial timing, timing advance, and cranking compression of all eight?

Does the hot-air valve on the air cleaner snorkel work right?

How often do you buy "Top Tier" (high detergent, which is NOT octane related.) fuel, or use a fuel system detergent like Techron?

How old is the O2 sensor?

Connect a scan tool, look at the data stream especially when the engine is acting up.

I think this is very unlikely to be transmission-related, but what color is the trans fluid? Is the fluid level correct when fully warmed-up?

I had a misfire--stalling--low power issue with my TBI; resolved by installing a new distributor shaft. The magnets and pickup coil had failed.

 

[RichLo]

^ yea

It very well could be the fuel pump but you'll want to test fuel pressure before replacing it.

I also doubt its the transmission.

 

[stutaeng]

How do you check for fuel pressure on the TBIs? I helped my buddy on his '90 truck.

He thought it was the fuel pump because he didn't see fuel on the bowls. We did more digging and found he did not have spark at plugs or coil. We then disconnected the fuel lines and fuel squirted out, so that ruled out fuel.

Finally narrowed it down to ICM or distr. pick up coil. New distributor came with both parts, and that solved the problem with no start.

Is there a way to check for actual pressure while running?

^ yea

It very well could be the fuel pump but you'll want to test fuel pressure before replacing it.

I also doubt its the transmission.

 

[PlayingWithTBI]

Is there a way to check for actual pressure while running?

Yes, you can get a kit from the auto parts store, that goes where the fuel filter does, or install you own permanently. Here's a link to an AFPR, fuel pressure adapter, and gauge, scroll down to see them.
http://www.rvmorsemachine.com/product.htm

Here's what mine looks like, you have to bend the MAP sensor vacuum tube down a little to clear the adjusting screw.

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Installed on the motor (5.7L) set @28PSI with a 28PSI spring, LOL.

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[Schurkey]

https://actron.com/content/gm-tbi-fuel-pressure-tester

 

[stutaeng]

Yes, you can get a kit from the auto parts store, that goes where the fuel filter does, or install you own permanently. Here's a link to an AFPR, fuel pressure adapter, and gauge, scroll down to see them.
http://www.rvmorsemachine.com/product.htm

Here's what mine looks like, you have to bend the MAP sensor vacuum tube down a little to clear the adjusting screw.

You must be registered for see images attach

Installed on the motor (5.7L) set @28PSI with a 28PSI spring, LOL.

You must be registered for see images attach

Awesome! Maybe the OP needs to invest in one of these. Isn't TBI something like 12 psi?

 

[PlayingWithTBI]

Isn't TBI something like 12 psi?

Yes, GM specs 9 - 13PSI but 11 - 13 is optimal. In order to get my AFR down to ~14.7 stoichiometric with a WBO2, I needed more fuel - more pressure = more fuel.

 

[90lsx]

I had a problem similar to that, it ended up being the hose that connected from the pump to the hat.

 

[Postmech]

Fuel filter ?