Bad Fuel Pump?

[MrTruck805]

Hi All,

My 89' 350 TBI with about 215k miles has been having some symptoms that leads me to believe it's the fuel pump, but I figured I'd post here before attempting that not so simple part replacement.

The engine is dying often but not all the time at idle / low RPMs.
While on the freeway it will sometimes throw Code 44 for running too lean, but clear a minute or so later.
Throttle response just doesn't seem normal, especially when accelerating or going uphill.

I had recently replaced the IAC, Fuel Filter, and O2 Sensor, so I don't think they are the problem. When the truck is running OK at idle I see a very steady 7 PSI on the fuel pressure gauge.

Anything I should check out before dropping the gas tank to replace the fuel pump?

Thanks!

 

[rampage]

7 PSI is too low, I think it should be closer to 10 but someone will chime in with the correct range. When my pump was going out I could hear it making a rattling noise. After I removed it I could see the shaft was loose.

There’s a rubber hose that attaches to the fuel pump and is prone to split. The OEM hoses were not meant to be used with ethanol based fuel and it deteriorates them. That would be my first guess. But as long as you’re there you might as well replace the pump. Do your symptoms change with a full tank?

 

[dyeager535]

Yep, 7 is too low, assuming the gauge is correct. 9-13 is what GM says is acceptable, but folks have stated that under 10 is noticeable.

Could be the in-tank hose, as mentioned. If you are sure the gauge is correct, drop the tank.

 

[rampage]

And to make life easier when dropping the tank you can empty it by using the pump. Disconnect the fuel line at the filter and connect a hose onto the fuel line coming from the tank and drop the other end into a suitable container(s). Use the fuel pump relay bypass wire under the hood on the firewall to make the pump run constantly.

 

[MrTruck805]

7 PSI is too low, I think it should be closer to 10 but someone will chime in with the correct range. When my pump was going out I could hear it making a rattling noise. After I removed it I could see the shaft was loose.
There’s a rubber hose that attaches to the fuel pump and is prone to split. The OEM hoses were not meant to be used with ethanol based fuel and it deteriorates them. That would be my first guess. But as long as you’re there you might as well replace the pump. Do your symptoms change with a full tank?

Yeah, I do get the feeling that it dies at idle less when the tank is full.