Fuel pump

[Dylan88]

Will be getting a new fuel pump was just wondering if I should get the whole assembly or just the pump itself? What's the differences ?

Thank you for your help its a 91 gmc 1500 2wd

 

[kennythewelder]

I always change just the pump, but only use Delphi, or AC delco. I have had issues with the cheap pumps not lasting.

 

[Dylan88]

Awesome thanks alot. I'm cutting a trap door in the box since its a rusty crappy work truck haha

 

[Dylan88]

It runs but barely idles gotta pump it crazy to keep it going. Weak pump im assuming. Runs when you spray starter fluid

 

[PlayingWithTBI]

Did you put a pressure gauge on it to see what kind of pressure you have? Does your fuel gauge work OK? After checking your pressure and, if your gauge is good, then get a replacement pump (I'd get an AC Delco EP-381, 155LPH instead of ~75), suction sock, and fuel filter for it. When you change it, clean all the grounds and connections.

 

[Dylan88]

Just did the fuel filter and o2 sensor . I'll have to get that pump and a new sock thank you

 

[Dylan88]

A higher pressure pump won't hurt anything or run different ?

 

[L31MaxExpress]

A higher pressure pump won't hurt anything or run different ?

It will run and actually have power. Regulator sets the pressure not the pump.

 

[Schurkey]

Did you put a pressure gauge on it to see what kind of pressure you have? Does your fuel gauge work OK? After checking your pressure and, if your gauge is good, then get a replacement pump (I'd get an AC Delco EP-381, 155LPH instead of ~75), suction sock, and fuel filter for it. When you change it, clean all the grounds and connections.

^^^ Yup.

And REPLACE THE IN-TANK WIRE HARNESS. Clean the mating connectors as needed.

Typically about $20 for an aftermarket harness. The wires may be long, but they'll work.

Photo 1. New harness (top) vs. OEM harness (below) Available at any auto parts store--I got mine at NAPA. This photo is from my Lumina, but GMT400 is similar.

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Photo 2. Corroded OEM wire with swollen insulation, vs. new wire (harness inside fuel tank.)

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The new pump should come with a short section of hose, be sure to use "Fuel Injection" clamps on the new hose. This hose is "special" in that it's rated for SUBMERGED use in gasoline. Most fuel hose isn't. (Must meet SAE 30R10 specification)
http://www.napabeltshose.com/~/media/napa/documents/napa-submersible-hose.pdf?la=en

Photo 3. What ****** hose clamps do to fuel hose; along with "Fuel Injection" hose clamps.

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For the record, I won't do fuel pump work without testing pressure, volume, and voltage (as close to the tank as practical--generally by inserting a test wire into the closest connector to the tank)with the pump RUNNING. The supply side voltage is typically about 1.5 volts below alternator voltage. Also test the ground side of the pump harness. There's typically about 1 volt on the ground side. (voltage across the pump is low because GM uses under-sized wire for the fuel pump circuit--but more than 2.5 volts below alternator voltage with engine and fuel pump RUNNING is cause for investigation.)

 

[Reega]

Be ready to buy an assembly unit though, when I changed mine a few years back, the metal fittings were the fuel line attach to the assembly had essentially welded themselves together, it wasn't the threads but the tip of the line just past the O rings. I destroyed the assemble getting them loose. Also new O rings.