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Penmaenmawr · 07-11-2013, 09:43 PM

The under floor fuel pump on my 345 is obnoxiously noisy, and obviously constantly on when the engine is running: is it normal to be so obtrusively loud? If so, can anything be done to quieten it, as in rubber mounts or other sound insulation? Are there quieter pumps available? I couldn't find anything via a search, but cannot think I'm the first to deal with this.

cwf · 07-11-2013, 10:53 PM

Well, you'll know when motor quits if it was pump issue.

Pumps can be noisy. Especially in heat. Also, alcohol in fuel is killing us slowly. Your pump may be a warning shot...

I would investigate replacement.

Swap In new one and see if it works better. Sound isolation easy. Check the fuel lines are not hardening and transmitted to frame.

dznf0g · 07-12-2013, 08:42 AM

Quote:

Originally Posted by cwf

Well, you'll know when motor quits if it was pump issue.

Pumps can be noisy. Especially in heat. Also, alcohol in fuel is killing us slowly. Your pump may be a warning shot...

I would investigate replacement.

Swap In new one and see if it works better. Sound isolation easy. Check the fuel lines are not hardening and transmitted to frame.

These ethanol statements are just killing me. We have been using ethanol in fuels in the midwest since the early 80's. Were there pump issues, and corrosion issues back then? Yes. All, Cars and trucks have been built to a 10% max ethanol for decades. WE HAVE NO ISSUES WITH PUMPS IN THE INDUSTRY due to 10% ethanol. And GM alone has over 6 million E85 capable vehicles on the road......AGAIN....no ethanol issues. This is an urban legend which will not die with those who have relatively recently had ethanol pushed on them as an fuel oxygenator over the carcinogen, MTBE.

I have been using E10 in all my outboards, cars, yard equipment, gennies....for DECADES. ZERO ISSUES
.

ScrapIrony-2 · 07-12-2013, 01:30 PM

We replaced our fp a couple of years ago...the new one is a little quieter, but not much. Since it mounts to the frame, a rubber/neoprene/cork damper might work...haven't tried that, yet. The 454 pretty much overrides the fp noise.

Penmaenmawr · 07-12-2013, 04:18 PM

Thanks for the comments. I won't get pulled into the ethanol issue, except maybe to say it seems like something from a socialist planned economy, combined with more farmer welfare

Good suggestion on hardened fuel lines. I'll price a new fuel pump. This one sounds like Daffy Duck combined with a chain saw. I mounted my compressor on rubber and foam, which made a little difference, but the main thing thaqt helped there was getting everythng leak free, so the compressor doesn't come on any more. Unfortunately that doesn't seem to be an option for the fuel pump. Why does it have to run continuously? Isn't it possible to modify the system to run intermittenly to build up pressure with no return flow? I don`t understand the bypass flow thing, or whatever it might be called. It seems really inefficient to be pumping something 25 feet forward then 25 feet back constantly.

dadstoy · 07-12-2013, 07:41 PM

Quote:

Originally Posted by Penmaenmawr

Thanks for the comments. I won't get pulled into the ethanol issue, except maybe to say it seems like something from a socialist planned economy, combined with more farmer welfare

.

Really?

raveson · 07-13-2013, 07:39 AM

My old pump made a racket. Replaced the carb with a TBI that came with a new pump pressuring at 18psi. All is quiet now. Changing over to fuel injection has not only increased performance, but also improved mpg by 20%! Worth the money not only for the mpg but high elevation travel. Try replacing the filters inline and at the carb, might quiet it down.

Penmaenmawr · 07-13-2013, 01:31 PM

Quote:

Originally Posted by raveson

My old pump made a racket. Replaced the carb with a TBI that came with a new pump pressuring at 18psi. All is quiet now. Changing over to fuel injection has not only increased performance, but also improved mpg by 20%! Worth the money not only for the mpg but high elevation travel. Try replacing the filters inline and at the carb, might quiet it down.

That would be my ultimate solution for sure, and I'd very much like to hear how you went about it. I've had several GM TBI fuelled trucks, and they've always been reliable and economical. Whenever I look into this however, the choices (buy an old 454 Suburban or go to one of the many aftermarket manufacturers of TBI's) seem so uncertain that my head starts spinning. There's always someone who has had a terrible experience with any of the aftermarket TBI's, but ripping one out of an old GM truck seems to involve a level of expertise I lack, and there's not apparently a "how to" step-by-step guide to doing it that I have found.

raveson · 07-15-2013, 06:25 AM

Install is not simple. All the old air pumps have to come out and new sensors installed in the manifold and exhaust. Fuel return lines also must be added. The instructions were good from the manufacturer. I purchased the system complete from Holley direct. They were helpful with tech questions and problems. Kit cost was about $2,200. If you are not a good engine mechanic (I'm not), get one to help as it took two of us about 5 full days to install. The cost and trouble to install was well worth it!

Penmaenmawr · 07-15-2013, 08:46 AM

Quote:

Originally Posted by raveson

Install is not simple.

Honest at least!

Quote:

All the old air pumps have to come out and new sensors installed in the manifold and exhaust. Fuel return lines also must be added. The instructions were good from the manufacturer. I purchased the system complete from Holley direct. They were helpful with tech questions and problems. Kit cost was about $2,200. If you are not a good engine mechanic (I'm not), get one to help as it took two of us about 5 full days to install. The cost and trouble to install was well worth it!

I assume you've covered quite a few miles since then and had no problems, so looks as if Holley will be my choice. Good instructions are essential for me, as I try to save my brain for when I might really need it. Looks like a Winter-time job.

Keyair · 07-15-2013, 10:52 AM

On the Ethanol issue, my biggest problem has been fuel line disintegration but that maybe just age too...
I have replaced all of the flexible lines I can reach easily, but there are a couple more to do.

My rear mounted fuel pump is not that noisy, and I don't hear it once the engine is running. The way it is mounted is kinda odd to my eyes... its on like a skirt of rubber that hangs off the frame rail.
Pic.

Its been my experience that pumps are noisier if:
1/ improperly mounted
2/ suffering a blocked pipe or filter causing cavitation
3/ old and tired.

Vane style pumps are quieter than diaphragm style too I think, but they are generally used in FI and high pressure situations.

The stock GM TBI setup is pretty good, and cost effective if you are a hunter/scavenger type of guy like me... but the aftermarket FI setups are sweet and probably better if that is an option. Here in CA, its not.

Penmaenmawr · 07-16-2013, 08:53 PM

Quote:

Originally Posted by Keyair

................
My rear mounted fuel pump is not that noisy, and I don't hear it once the engine is running. The way it is mounted is kinda odd to my eyes... its on like a skirt of rubber that hangs off the frame rail.

Interesting installation. That certainly would reduce noise transmitted through the frame, and I bet was done by someone with a pump as noisy as mine!

Quote:

..............
Vane style pumps are quieter than diaphragm style too I think, but they are generally used in FI and high pressure situations.

Can a vane pump be used in combination with a pressure regulator to maintain a suitably low pressure for a carb? (I don't really know what I'm talking about.

)