Fuel pump noises/slight cavitation

(Douglas) #1

After about 2 months, REDCAT is running again! I got everything put back together in my fully refurbished fuel system. Many thanks to everyone who provided me insight and advice as I worked through the project! The car is running great and took only a few cranks to fire right back up like I left it off.

One question that I have: now that the system is running again, the fuel pump is noisier than it was before. I believe there is slight cavitation occurring and obviously I want to address that before I drive much at all/do any lasting damage to my otherwise perfectly working pump.

One thing I did to my system: I added a high flow fuel filter (listed as 100micron) between the sump tank and the fuel pump. This was a step advised by Kirby and some others on this forum and after seeing what the inside of the sump tank looked like (before I cleaned it up), I agree and think it’s a very good call since it will obviously get rusty etc. again in time. Nonetheless, I’m wondering if I didn’t get a high enough flow filter to put in the line. Anyone have any insights on what level filter would be acceptable pre-pump.

I should add that I may be able to mount the new filter a bit lower than it is right now. Currently fuel flows out of the sump tank and has to go uphill a bit to the new filter and then curve around and down to meet the pump in its usual spot.

(Greg) #2

I originally had my sump to fuel pump going vertical too. And although my pump wasn’t noisy, it did seem to make a weird noise every once in a while.

It was a huge PITA, but i rerouted it like this. I bought (3) 1/2" ez coils to make sure the 1/2" hose did not kink. The noise seemed to go away. Still wasn’t sure i didn’t have a kinked hose, so I fabbed a way to test fuel pressure, and am getting a steady 33 PSI at the fuel rail, so I claim success. Oh, and I bought longer screws to attach the metal plate cover. And it’s SO tight with the 1/2" hose going behind surge tank, that I didn’t connect the bottom bolt. Top is well connected to battery tray.

Regarding filter, I too added a WIX filter between surge and pump at Kirby’s recommendation. But I opted for a screen filter rather than a standard filter. WIX 33248. I don’t think your filter would be causing problems (unless the sump/tank are full of crud?) since you just put it in.


(Douglas) #3

(Greg) #4

that looks good to me? Not too much gravity to fight.

Wow, what a better idea than what I did! And that’s quite a fancy looking filter. And I see the Ez coils! :):grin:

What pump did you buy? I am using a Bosch and they tend to be quieter.

(DavetheLimey) #5

Doug, If you look up “Another Fuelish Idea” in the archives you can see a picture of the WIX 33248 mesh screen- if that is actually the one you picked.
The 100 mesh screen is rated at 149 microns, which is coarser than the screen inside the sump tank. Did you literally “Add” the can filter to the system, or did you first remove the screen inside the sump?

(Douglas) #6

Just added a photo of how I ran it–goes out of sump tank down to floor loops up above normal post-pump filter then makes two turns to get back to the pump.

The turns are tight but they are definitely not kinked and I have ezcoils on them. The 100 micron pre-filter has the purple on the edges. Seemed like the path of least resistance to me but then again I’m not quite sure.

What does cavitation sound like exactly?? The noise I’m getting (maybe I can record it) sounds like a couple of pebbles/rocks bumping/scraping something. It seems like it’s all noise from the fuel pump but I also haven’t ruled out contributing vibrations yet.

(Douglas) #7

There was no screen in my sump when I took it apart!! So now my system has the filter I bought (see picture above) as the only thing between sump and pump. I don’t know if the car once had a screen and PO removed it or whether it just never had one.

I found the filter I put in on eBay–it was about $30 and seemed to have good reviews. It’s also cleanable apparently though I doubt I would mess with that over buying a new one.

(Douglas) #8

My pump was in good shape so I left it alone. It’s the original that was supplied with the car based on its markings. Maybe it isn’t in quite as good shape as I thought though.

And thanks–yeah the run seemed pretty reasonable–it does go up hill before the new filter but I can’t imagine that or the run’s length would give the pump trouble. Maybe the noise will die down after I run the car more/fill it full of fuel.

I just put in 3 or 4 gallons to test it all out and check for leaks. Haven’t driven it yet but will tonight probably. It idled in driveway well for 15 minutes last night before I called it a night. Maybe the filter needs to saturate a bit more first–will have to keep investigating.

Also did you notice a few points where I added metal lines? One is right past the normal fuel filter. I just couldn’t make that 180 degree turn without being nervous about kinking there.

(DavetheLimey) #9

I have no idea what filter you used, so can’t form an opinion!
Cavitation is a whining sound that could sound like a power steering pump which is low on fluid.
Remove filter and see if your noise goes away!

(Greg) #10

If there was no screen in the sump, then those bits of crud would be getting through the fuel pump and could have worn it a bit. Probably ended up in main fuel filter. Did you change that? If it’s clogged, it could also make the fuel pump noisy.

If I were you, I’d put in a new pump. They aren’t terribly expensive. Be warned though, I really like the Bosch, and it’s quieter and superior. But it’s a tiny bit bigger, so you’ll have to slit the foam sock around it to fit it.

yeah, i see the metal line. I just ran a longer hose, but your way is cleaner.

(Douglas) #11

Yes of course–here’s the filter I bought. Not advertising in any way just sharing link to show which one I have: https://www.ebay.com/itm/AN6-AN8-AN10-Inline-Fuel-Filter-High-FLOW-100-Micron-Cleanable-SS-Black-purple/192638544431?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Interesting that it’s a whining sound–not a way I’d describe what I’m hearing right now. Thank you very much for the help and input!

Will have to try bypassing filter to see–just got to be very careful not to spill gas in my finally clean and smell free trunk!

(Douglas) #12

Would you be able to mention/message me exactly which Bosch you got and from where? Thank you for the help!

I did change the main fuel filter. OEM spec but brand new!

The foam sock was gas soaked from a leaky hose before I did all my work so it went out. I fabricated a new one so it will be easy enough to customize it/raw materials again for a slightly larger pump.

I definitely wish I had bought more hose than I did. Had to get creative in large part because I was “working with what I had” and decided I didn’t have the money or patience to buy more hoses…

I do worry a bit that something I did has changed the pump’s life as the noise is louder now than before I did this work. But maybe there’s junk in the pump from before like you say–if it’s on its way out anyhow then I’m not too worried.

Definitely need to setup fuel/air mixture monitoring soon though as I don’t want the pump or anything else to let me run lean. I won’t punch it in the car for now anyhow too just to be safe and save the hassle of burnt pistons!

(Greg) #13

Bosch 69536 is the pump I went with. It’s turbine tech, which is supposed to be better than the other kind.

(Douglas) #14

Got it–thank you again!

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #15

Maybe it fell off and is rattling around in your surge tank!

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #16

I used a regular cheap-a$$ 1/2" metal inline fuel filter in my '83 along with the OEM Lucas
roller pump. Ran nice and quiet. IMHO, any 1/2" filter is going to flow plenty, as this system flows through 5/16" lines later on.

Something you definitely should check: The mounting of the fuel pump. It’s supported in foam and clamped, but it can sometimes slide down so the outlet end contacts the floor of the trunk. It gets very noisy indeed in that situation. I couldn’t get mine to stay up no matter what I tried, so I finally just wrapped a worm screw clamp around the body of the pump so it couldn’t slide down through the foam any more.

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #17

I opened my Lucas roller pump by unfolding the aluminum tabs and pulling the guts out. One thing that struck me about the design is that I could not see anything other than friction preventing the entire pump from spinning in the housing. So while I was in there, I drilled and tapped for a tiny screw that would positively prevent the pump from turning. Not too difficult to do IIRC, but just the same, I recommend that anyone buying a new pump go for the Bosch turbine type instead.

(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #18

BTW, whenever fiddling with these pumps, make doubly sure to check the polarity on the connections. They are two different size spade connectors IIRC, but we had some reports a while back that replacement pumps had the sizes reversed. You do NOT want your pump running backwards.

(scrimbo) #19

A little silicone seal will hold pump to the foam …if pump slides down it can put pressure on lower hose and can crack spigot on pump

(Douglas) #20

I seriously thought I might find it there! But during my full refurb I pulled the sump tank out of the car and opened it all up and treated the inside of it etc. so definitely no screen in there. Possible that PO did away with it though.