Question Fuel pump

[Kevin D Pem]

Check for fuel like above stated.
Isolate wires with tape, so they don't keep shorting out.
Ohm out all fuses relating to fuel system, ECM is part of fuel system. Fuel pump has it's own fuse.

There will be a connector outside of the throttle body should you need to replace the injector. I would likely replace injector as a fix of the wire will be iffy.

Don't replace parts until you have found the problem!!!

OMT: the tank pump is high pressure, compared to external pumps.

 

[GypsyR]

Good clarification.
The wires to the injectors appear to have overheated some. A bit of fuel spray in that area isn't kind to those wires either. So I'd note that for future attention maybe I see nothing to effect your actual problem.

By looking at the throttle body and the year I'm guessing that you have a Chevy 454 and not a Ford. I'm more of a Ford guy but also have fuel issues. The main one is that fuel pumps often "stick" after sitting and not running for a very long time. Sometimes you can unstick one by tapping on it. In cars you can sometimes do that by hitting the gas tank where the pump is while someone tries to start the car. Unfortunately RV tanks are rather heftier and the shocks from such hammering don't travel to the pump as well. But though it's not much fun to do It costs zero dollars and takes only a few minutes with a helpful. If about ten good bonks around the center of the tank where pump is have no effect, a hundred more hits aren't going to either. It's something to try real quick and move on. I have had it work a couple of times. In such cases it's a good rule to believe that same fuel is going to stick again and should be replaced but it might get you going.

Sometimes fuel pumps "varnish up" with old gas to the point where no amount of beating or even solvents will recover their function. Replacement is the only fix. Also if that has happened the tank generally needs to be cleaned out too.

Being electrical, sometimes pumps just quit. Like a light bulb going out. Only one fix for that too.

My older Ford has a "fuel pump relay". If it doesn't work, neither does the pump. During some troubleshooting I found that the relay was fine but one of the wires where it plugged in was corroded to the point it had green stuff on it. Not good. And like anything else electrical, there's a fuse. I don't know the specifics of your GMC/Chevy/whatever but it's a safe bet you also have a fuse and pump relay somewhere you could check out. A 12 volt test light is your friend there. If you are getting power to and from those two then you are fairly safe in saying you have a pump problem or the wires to the pump. (Mice, chipmunks, etc chew wires). If no power to those components you'd back up to the ignition switch. A bit rare, but it can happen the ignition switch doesn't power up things correctly, particularly on GM vehicles.

 

[karindryan]

1) Ok so first check fuel pump as you explain
2) wrap wires in electrical tape?
3) what does “ohm out” mean? (As a used this world is new to me so am learning lingo!)
4) by ECM do you mean throttle body?
5) replace fuel injector now or wait for complete diagnosis?
6) tank pump better than external pump

QUESTION: how likely is it that I will have to drop tank to replace pump if that’s the issue? Mechanic friend says he thinks may not be required to drop tank…

 

[karindryan]

Good clarification.
The wires to the injectors appear to have overheated some. A bit of fuel spray in that area isn't kind to those wires either. So I'd note that for future attention maybe I see nothing to effect your actual problem.

By looking at the throttle body and the year I'm guessing that you have a Chevy 454 and not a Ford. I'm more of a Ford guy but also have fuel issues. The main one is that fuel pumps often "stick" after sitting and not running for a very long time. Sometimes you can unstick one by tapping on it. In cars you can sometimes do that by hitting the gas tank where the pump is while someone tries to start the car. Unfortunately RV tanks are rather heftier and the shocks from such hammering don't travel to the pump as well. But though it's not much fun to do It costs zero dollars and takes only a few minutes with a helpful. If about ten good bonks around the center of the tank where pump is have no effect, a hundred more hits aren't going to either. It's something to try real quick and move on. I have had it work a couple of times. In such cases it's a good rule to believe that same fuel is going to stick again and should be replaced but it might get you going.

Sometimes fuel pumps "varnish up" with old gas to the point where no amount of beating or even solvents will recover their function. Replacement is the only fix. Also if that has happened the tank generally needs to be cleaned out too.

Being electrical, sometimes pumps just quit. Like a light bulb going out. Only one fix for that too.

My older Ford has a "fuel pump relay". If it doesn't work, neither does the pump. During some troubleshooting I found that the relay was fine but one of the wires where it plugged in was corroded to the point it had green stuff on it. Not good. And like anything else electrical, there's a fuse. I don't know the specifics of your GMC/Chevy/whatever but it's a safe bet you also have a fuse and pump relay somewhere you could check out. A 12 volt test light is your friend there. If you are getting power to and from those two then you are fairly safe in saying you have a pump problem or the wires to the pump. (Mice, chipmunks, etc chew wires). If no power to those components you'd back up to the ignition switch. A bit rare, but it can happen the ignition switch doesn't power up things correctly, particularly on GM vehicles.

Super helpful thanks!!

 

[karindryan]

Good clarification.
The wires to the injectors appear to have overheated some. A bit of fuel spray in that area isn't kind to those wires either. So I'd note that for future attention maybe I see nothing to effect your actual problem.

By looking at the throttle body and the year I'm guessing that you have a Chevy 454 and not a Ford. I'm more of a Ford guy but also have fuel issues. The main one is that fuel pumps often "stick" after sitting and not running for a very long time. Sometimes you can unstick one by tapping on it. In cars you can sometimes do that by hitting the gas tank where the pump is while someone tries to start the car. Unfortunately RV tanks are rather heftier and the shocks from such hammering don't travel to the pump as well. But though it's not much fun to do It costs zero dollars and takes only a few minutes with a helpful. If about ten good bonks around the center of the tank where pump is have no effect, a hundred more hits aren't going to either. It's something to try real quick and move on. I have had it work a couple of times. In such cases it's a good rule to believe that same fuel is going to stick again and should be replaced but it might get you going.

Sometimes fuel pumps "varnish up" with old gas to the point where no amount of beating or even solvents will recover their function. Replacement is the only fix. Also if that has happened the tank generally needs to be cleaned out too.

Being electrical, sometimes pumps just quit. Like a light bulb going out. Only one fix for that too.

My older Ford has a "fuel pump relay". If it doesn't work, neither does the pump. During some troubleshooting I found that the relay was fine but one of the wires where it plugged in was corroded to the point it had green stuff on it. Not good. And like anything else electrical, there's a fuse. I don't know the specifics of your GMC/Chevy/whatever but it's a safe bet you also have a fuse and pump relay somewhere you could check out. A 12 volt test light is your friend there. If you are getting power to and from those two then you are fairly safe in saying you have a pump problem or the wires to the pump. (Mice, chipmunks, etc chew wires). If no power to those components you'd back up to the ignition switch. A bit rare, but it can happen the ignition switch doesn't power up things correctly, particularly on GM vehicles.

 

[karindryan]

Yes Chevy 454. Ok —so test fuel line into throttle bottle first to see if fuel is coming in while turning over? Then check pump relay and fuses? And then tap hard ten times under middle of fuel tank (which is half full) while someone else tries to start? Correct order?

 

[karindryan]

Yes Chevy 454. Ok —so test fuel line into throttle bottle first to see if fuel is coming in while turning over? Then check pump relay and fuses? And then tap hard ten times under middle of fuel tank (which is half full) while someone else tries to start? Correct order?

 

[karindryan]

Throttle body not bottle!! Altho that’s kind of funny

 

[Kevin D Pem]

Ohm out = check fuse with volt/Ohm meter. (No vm just replace fuse with new on for testing).

ECM =engine control module.

If you think you see copper tape wire.

On some vehicles an access hole can be made in the floor, however dropping the tank is preferable.


As stated above by gypsyR find the relays and check them. Unlike a car they could be anywhere, not in a dedicated box.

Fuel pressure may also be a problem two of the pumps I have replaced the pressure regulator was in the pump, others are in the engine compartment.

 

[karindryan]

Ok thanks very much! Very helpful.