OK, here's the deal. A couple of months ago I moved my stock lift pump to the frame rail. Everything has been working great, but over the weekend the fuel pump started to sound different. My fuel pressure would be around 8 psi at idle, used to be 14.5, so I changed the fuel filter and everything is back to normal. Today going to work it starts to sound funny again. My fuel pressure is down to around 8 psi. I rev the engine and the fuel pressure jumps back to normal when it idles back down it goes to 8 and back to 14 this repeats itself a couple of times all along I can here the pump sound change in pitch.

Either the pump is going bad or it's electrical, that my best guess.

Anyone have any other ideas?

One other thing, it doesn't seem to do it when I'm on the highway only around town driving. Could sloshing fuel have an effect on it? I have about 3/4 of a tank.

Thanks for any help.

 

I'm no expert by any means not even a novice.

Saying that I would check two things if it were me.

First you mentioned wiring. Did you buy a premade kit or did you hook them up your self? If you did it your self did you solder the connections an put shrink wrap on them? If not I would correct this first.

second, you could be getting a little air in the line. double and tripple check all your fittings. Make sure you didn't crack a banjo washer.

Good luck, I'm sure someone with more experience will chime in.

Wade

 

Banho washers were new, but I'll take a look anyway. I wonder if not lubing the fuel filter gasket would cause a leak? I'm starting to wonder if I did lube it with diesel fuel prior to install. You know when you do something simple enough times you take it for granted that you've done it correctly.

 

I never lube mine before installing it. Haven't had a problem in 66K miles. Check the electrical connections at the pump. Do you have mechanical or electrical gauges? If electrical, double check all connections. It might also be your sender if it's electrical. If you can, try hooking a different gauge (like a mechanical one you can swap out real quick with) and see if that matches the reading your getting.

 

I have a Briar Hopper mechanical gauge hooked up to the top fuel filter port. I don't have my pillar gauges in yet.

The change in pump noise pitch goes along with the action of the gauge needle.

So either I'm getting air from somewhere or it's electrial? Sound about right?

 

I read here where the ECM controls the lift pump. Could this be the reason I'm seeing the strange pressure reading on my gauge?

I also wonder if my ez is affecting the lift pump operation?

 

The EZ should have NO effect on the LP.

The ECM controls the LP, but only at startup. When you first turn the key, the LP will operate at low pressure for 10 seconds, or until the engine starts. Once the engine's running, the ECM leaves the LP alone-- it runs the same speed all the time.

I'd test your electrical leads closest to the LP. Odds are that your wiring is fine and your LP isn't. When the LP goes bad, it will sound like it's turning slower, like it's having to work REALLY hard just to spin.

Justin

 

My pump did the same thing, then proceeded to go to teh 3psi level, and 0 at anything above an idle. Shutting it down and restarting brought the pressure back up for a minute or two. I did the filter thing too, and thought everything was OK, for about a day. Then it started doing it again. I didn't feel like dealing with the warranty so I just disconnected it and installed a FASS. I'm betting your pump is on its way out.

Chris

 

Thanks for the info everyone. I have a back up fuel pump I'm going to throw on the truck and see what happens. I'm not sure exactly how to test the electrical part of the lift pump so this is the next best option.

 

Mike,

Any updates?

 

Na, I'm still at work, I won't be able to do anything till tonight.

 

let me know

 

Mike,

Did you get the problem resolved? If so, what was the trick?

 

Sounds like it might be the check ball in the pump -- it could be coming out of its seat. It's a common problem in the LP, and before it goes completely, it'll send the pressure at idle and speed all over the gauge, or give relatively consistant but completely weird readings (like 6 psi at idle and 16 psi at speed). Had a couple of LP's do this, and I remember being able to hear different pitchs in one of them.

 

Seen the same thing with my last lift pump Gear Poet.

That thing had great pressure (14 @cruise) then you would lean into the throttle a bit and she would drop to 2 psi and stay there till you shut the truck off and restarted it.


Jason