What's normal for inline HP fuel pump noise?

[joeydurango]

Just finished up a ~2200 mile road trip in my recently "completed" '72 K10. Running a 5.3 LM7 and a 4L60, pretty standard swap. We ran stock tank, gravity feed to basic inline filter, then to a Walbro high-pressure fuel pump, and a second, nicer inline filter. For the first several hundred miles on the new setup - before leaving on this last big trip - the pump's noise was consistent, a quiet whine you could hear when you were stopped but nothing loud or obnoxious. We left on our trip and after about 400 miles, the pump's whine increased in both pitch and volume, until you could hear it while driving at 40mph. I assumed it was having trouble getting fuel and changed out the first inline filter - it was packed with large detritus from the tank (thanks, guy who brazed in the fitting!). This quieted the pump back down to normal volume and pitch, and it was great for the next ~1000 miles. Then back came the noise - and I swapped out the filter again, only to have no effect on the pump. We ended up driving another 400 miles back home to finish the trip, with the pump making what seemed to me quite a lot of noise. Drove fine, no starvation or anything, just noisy. So:

The noise is annoying but I can deal. Just want to make sure I'm not burning up the pump. Has anyone else noticed a lot of variation in the sound of Walbro pumps? Or is this an automatic "something's not right, check it out"?

The one other thing that appears to have an effect is ambient air temp. Every time it's been excessively noisy, it's been 90 or above. I changed the first filter just as it cooled off for the night, and then drove around on the coast for the next week. Here at home it's not often super-hot. On the last leg of the drive back, it was hot before AND after I changed the filter, and no difference was apparent in the pump noise. Does this make any sense at all, or is it coincidence? Thanks guys!

[Blackpony]

With external pumps the outside temperature will affect the noise output of the pump. Where is the pump mounted? I would suggest to make sure it gets plenty of airflow to help keep it cool.

[encasedmetal]

x2. I use large external pumps on my late model builds and if it's a hot day (especially sitting in traffic- they start screaming. you also don't want to run the tank below 1/4 level or you risk burning up the external pump that way too

[joeydurango]

That's all good to know, thanks!

We've been filling up at 1/4 (1/8 in extreme cases), even though I know in our tank there are several gallons sloshing around even when the gauge reads completely empty. I figure the pump shouldn't have to "pull" from the tank, I just want gravity to do its job feeding the pump. It does seem a little louder when the tank is less full.

The pump is mounted on the inside of the frame rail as close as possible to the tank. Plenty of airflow, and it does appear to be loudest when going slow, in traffic, when it's hot. Going through Moab yesterday it must have been 100*, and waiting in a turn lane it was sure making some noise.

As long as this is normal I won't worry about it. Just didn't know what to expect...

[encasedmetal]

Originally Posted by joeydurango

That's all good to know, thanks!

We've been filling up at 1/4 (1/8 in extreme cases), even though I know in our tank there are several gallons sloshing around even when the gauge reads completely empty. I figure the pump shouldn't have to "pull" from the tank, I just want gravity to do its job feeding the pump. It does seem a little louder when the tank is less full.

The pump is mounted on the inside of the frame rail as close as possible to the tank. Plenty of airflow, and it does appear to be loudest when going slow, in traffic, when it's hot. Going through Moab yesterday it must have been 100*, and waiting in a turn lane it was sure making some noise.

As long as this is normal I won't worry about it. Just didn't know what to expect...

"normal" is relative. I will say external pumps don't last as long as internals. does your filter have a washable element?

[joeydurango]

Not sure about the second inline filter. Definite no on the first filter (the one I've replaced a couple times), it's a $5 basic 3/8" inline filter.

When you say they don't last as long - is that short-term enough that I should carry around another pump for replacement on the side of the road? Would hate to just give up the ghost while on top of some mountain pass or something.

[encasedmetal]

Originally Posted by joeydurango

Not sure about the second inline filter. Definite no on the first filter (the one I've replaced a couple times), it's a $5 basic 3/8" inline filter.

When you say they don't last as long - is that short-term enough that I should carry around another pump for replacement on the side of the road? Would hate to just give up the ghost while on top of some mountain pass or something.

don't last as long meaning the pump gets more tired a time goes on- you should start noticing a slight drop in fuel pressure when it's starting to go. washables are good cause you don't have to replace them, you just soak them and brush with something like a tooth brush to clean it.

[BR3W CITY]

Do you know what the Micron rating on the filter is? I'm wondering if you have too small of an orifice, causing the pump to fight the filters. When you add heat and load, it gets worse.

My 255 whined occasionally until we switched the feed from -6 to -8. I have tank foam, and fill up as soon as it gets to the foam (about 1/3 left)

[ls1nova71]

Originally Posted by BR3W CITY

Do you know what the Micron rating on the filter is? I'm wondering if you have too small of an orifice, causing the pump to fight the filters. When you add heat and load, it gets worse. )

This^^^^ There isnt a $5 3/8 filter on the market that I know of that is the right size, micron wise. I bet youre restricting it too much.

[joeydurango]

Good to know. You guys have any source for inline filters you know are the correct micron size? Don't recall seeing micron size ratings on anything I've looked at. I'd be willing to try something different.

[ls1nova71]

http://www.robbmcperformance.com/products/filters.html This is what I'm using, 100 micron, made in the USA and less than $30.

[BR3W CITY]

I have the Earls 40 Micron billet inline filter. I think it was $22.

I have bad luck with ALL pre-filters tho, except the "Sock" on intank pumps. I just run a single filter after the pump, and thats it.

[joeydurango]

Thanks guys, that's super helpful. Will try one of those options out, and if the pre-filter just doesn't work out long term I'll try BR3W's route. This forum is awesome!

[Hart_Rod]

Another thing to check is the gauge of wire you are running to the pump. I would use no smaller than 10 gauge via a relay. I would not run it through the truck wiring system. Connect the power wire directly to the battery with a 30 amp fuse or circuit breaker and then trigger it via the ecm.