Electric Lift Pump Noise driving me nuts

[maynardogle]

About three years ago, I bypassed the old mechanical pump on my 84 K/5 and installed a Holly Red Head electric pump. I used the little fuel hose jumper spot that is on the inside frame rail on the passenger side and the Holly pump installation bracket that has a rubber sleeve to isolate the pump from the bracket. Pump has worked great for three years, no problems. Maybe its just me but lately the buzzing from the pump seems to be getting louder. I think the pump buzz is actually louder than the engine at idle. I only used the Holly Red head because it was available (free) from a race car builder buddy. I know the later K5 diesels came with an electric pump. Are these fairly quiet ? They are only $59 at my parts shop. Anybody already fight and win this battle? I don't want to hear fuel pump buzz drown out the beautiful sound of my clacking engine.

 

[longbedder]

I put a NAPA electric pump on my 6.2L when my mechanical pump failed. I told the guy at the counter it was for a 1994 diesel Suburban with a 6.5L, and got a stock replacement unit. It's made by Carter.

I cannot hear it at all while the engine is running in either my pickup with the 6.2L or my actual '94 Burb.

 

[Kain]

had a carter in my camaro it was way quieter than the holley red i have on my Blazer

 

[campfire]

I put a NAPA electric pump on my 6.2L when my mechanical pump failed. I told the guy at the counter it was for a 1994 diesel Suburban with a 6.5L, and got a stock replacement unit. It's made by Carter.

I cannot hear it at all while the engine is running in either my pickup with the 6.2L or my actual '94 Burb.

Same here. I asked for a pump for a 1988 V-series Suburban and found it much, much quieter than my other aftermarket fuel pump.

 

[maynardogle]

OK... I will go that route.

 

[maynardogle]

Finished the swap today. What a difference. With the engine off and the new pump on, I can barley hear the humming of the thing from its location on the frame rail. However, I was surprised at the massive drop in fuel pump pressure. I have a digital gauge on the output of my 2 micron Racor filter and before the swap it read between 7 and 11 psi. With the new pump it reads 3 psi at idle and under 2 psi at full throttle. Truck still feels like it has the same performance so I guess 2 psi is enough.

 

[longbedder]

Hmmmm....2-3PSI is probably not enough (especially since you know you were getting 7-11 before). The injection pump will run even with a failed lift pump on a 6.5l, but will die an early death because it's straining to feed itself. I would make sure there are no obstructions between the tank and filter output, and make sure the lift pump is getting full battery voltage - if both of these are true, then your lift pump may be bad even though it's new.

 

[campfire]

Hmmmm....2-3PSI is probably not enough (especially since you know you were getting 7-11 before). The injection pump will run even with a failed lift pump on a 6.5l, but will die an early death because it's straining to feed itself. I would make sure there are no obstructions between the tank and filter output, and make sure the lift pump is getting full battery voltage - if both of these are true, then your lift pump may be bad even though it's new.

I agree. Quiet is good, but low pressure isn't.

Full disclosure: I don't have fuel pressure gauges in any of my rigs, so I have no idea what pressure values I'm running. But I run off of the mechanical pumps and just use the electric for priming. & diagnostic use.

 

[maynardogle]

Another interesting byproduct of this swap has been easier starting.. I've had this truck for over 10 years and it has always had intermittent problems with cold starting. Most days the glow plugs cycle and I hit the starter and it catches and runs in less than a second. Then there are the occasional days when it starts, runs for three seconds and dies. Then it takes almost a full minute of cranking to get it running again and for the first minutes it lopes, surges and finally settles down. I have researched this forum and the consensus is that this is a symptom of an IP that has lost its prime and air has gotten into it somehow. Oddly, ever since this lift pump swap, I haven't had a single hard start episode. Now I am wondering if the factory pump has a one-way valve in it or something about the lower pressure is involved. Nothing has changed except the lift pump. I even used the old hoses. As for the pressure thing, I have decided to swap out the fuel element in the Racor and see if that makes any difference on my dashboard gauge. I also have a little mechanical fuel pressure gauge that I will install inline under the hood to check pressure on the input side of the filter. Details to follow....

 

[campfire]

Another interesting byproduct of this swap has been easier starting.. I've had this truck for over 10 years and it has always had intermittent problems with cold starting. Most days the glow plugs cycle and I hit the starter and it catches and runs in less than a second. Then there are the occasional days when it starts, runs for three seconds and dies. Then it takes almost a full minute of cranking to get it running again and for the first minutes it lopes, surges and finally settles down. I have researched this forum and the consensus is that this is a symptom of an IP that has lost its prime and air has gotten into it somehow. Oddly, ever since this lift pump swap, I haven't had a single hard start episode. Now I am wondering if the factory pump has a one-way valve in it or something about the lower pressure is involved. Nothing has changed except the lift pump. I even used the old hoses. As for the pressure thing, I have decided to swap out the fuel element in the Racor and see if that makes any difference on my dashboard gauge. I also have a little mechanical fuel pressure gauge that I will install inline under the hood to check pressure on the input side of the filter. Details to follow....

Yep...sure does sound like air is getting into the lines. That is what prompted me to install my first priming pump. I run it for 10 seconds or so to pump the air bubble back to the tank before I start the engine. This has worked so well I haven't actually gotten around to fixing the original leak. Though it finally has gotten big enough to occasionally see fuel weeping, so now I know where it is.


But you're saying you didn't change the usage pattern of the pump (ie, you didn't start running the pump ahead of time to pump the bubble through?). If nothing but the pump changed, I'll bet you resolved the leak that was letting air into the circuit in the first place. Maybe a coupling wasn't seated, maybe your old pump leaked. It doesn't sound like a coincidence...

 

[maynardogle]

Nope.. I have the electric pump on a toggle switch (left side) and I have always waited for the glow plug light to go out, then hit the starter (right hand) and the toggle switch simultaneously. I never thought that running the lift pump for a few seconds prior to start would push the bubble back around to the tank. I didn't think that was how the DB-2 pump input and return worked. As I was driving today I was thinking I need to research how the DB-2 works, I've always wondered why this pump doesn't have a page on this forum, or over at DP.

 

[campfire]

Nope.. I have the electric pump on a toggle switch (left side) and I have always waited for the glow plug light to go out, then hit the starter (right hand) and the toggle switch simultaneously. I never thought that running the lift pump for a few seconds prior to start would push the bubble back around to the tank. I didn't think that was how the DB-2 pump input and return worked. As I was driving today I was thinking I need to research how the DB-2 works, I've always wondered why this pump doesn't have a page on this forum, or over at DP.

Running the pump for a time (without the fuel solenoid engaged) is the GM-approved way of bleeding air out of the system. With my mechanical pump the instructions are to disconnect the fuel solenoid wire and crank the engine for a set amount of time. It's a bunch easier to simply hit the switch and let the electric pump do all the work. If you pump the air bubble into the IP....well, you know how that all works out.