Cavitation Issue, please help
 

Hello,
I am trying to diagnose an issue that might be cavitation. I am having this problem with my Aeromotive A1000 fuel pump and ATL fuel cell. The car runs great at idle, but when accelerating the car skips/sputters, and the pump changes tones, it sounds like it is pulling air, but Aeromotive tech support believes it is cavitation. The pump is mounted under the cell with Aeromotive filters before and after. Initially my thought was that the pump did not seem to be gravity fed since the fuel feed was on the top of the cell. Aeromotive Tech support said that one the pump primes, as long as it is mounted under the cell, it will act gravity fed. Does that sound right to people? I am now questioning the fuel filters being too restrictive, the pick ups being too small, or just a major issue with the tuning of the car (which would not explain the change in fuel pump tone). Thank you very much for your help.

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I would start off by testing fuel pressure under load. Are you seeing any dips in pressure when the pump tone changes and the sputtering is occuring?

Yes, that is my fault for leaving that out. The minute we go under load we lose major pressure, which Aeromotive says the cavitation would cause.

How large of a fuel filter are you running (micron rating) pre and post pump? Either testing with no pre pump filter for a very short time or upgrading to a larger one would be my next step. It deffinetly sounds like cavitation is your problem.

The pump is having to draw fuel up the pickup so it is not gravity fed or acting like it's gravity fed. Having a pusher pump in the tank would help that situation. ATL or Fuel Safe makes and in-tank setup. You don't need a huge pump since it will only need to keep a slight amount of positive pressure on the primary pump. Another way is to use a high-volume, low-pressure carb type pump as a lift pump to feed the primary injection pump. Something like the Holler blue. These pump work much better as lift pumps than any of the high pressure injection pumps. I've used the Holley blue feeding a surge tank which gravity fed the primary injection pump on my road race car with great success.

Have you checked the fuel filers? Any crap left in the cell when it was mounted got one or both clogged up?

Being below the fuel cell means the fuel is siphoned down to the pump which indeed is going to have the same characteristics as a gravity feed. I think the problem is likely the filter on the inlet side of the pump too restrictive. My pool pump also cavitates when the filter basket on the inlet starts to get plugged :D

I had the identical problem with an A1000 on my old turbo Z car; it was indeed that the fuel filter before the pump was clogged. I was using an 85 micron pre and 10 micron post filter and I had it mounted almost identically to the way you have described.

Not really. While it is siphoning after the line is primed the siphon, by definition, means there is a vacuum in the line pulling the fuel up the feed out of the cell. When something is gravity fed there is the actual mass of the fuel pushing it down the line.

What's the difference? Not much for a pump that is designed as a sucker pump. But for a pump that is designed to have positive pressure on the inlet side there's a big difference.

Thanks for the info. This disagreement between Ludwig and Tom93 is the same disagreement the Aeromotive Techs and I have. I will be checking the filters tomorrow, but does anyone have any more info to support or disagree with these two?

I have an A1000 pump and it is gravity fed without any issues. Past experience with cells has been that it is pretty easy to clog up the prefilter, and then you get cavitation. Also make sure that if you have foam in the cel that you aren't sucking the block into the outlet. In the cheapie Summit cell I have the foam block had tipped down into the sump and was flush against the outlet. The pump was strong enough to pull the foam into the outlet where it scrunched up and restricted flow.

Also, has others have said, make sure that the prefilter is at 100micron or larger. Another way to check would be to just take the prefilter out and see if the problem goes away (though I wouldn't run it that way long).

-Andy M.

As I'm just doing this now...is it better to use a low or high pressure pre-pump with the A1000? I just ordered a fuel safe in-cell surge tank with the low pressure pre-pump builtin feeding to an A1000 mounted on top of the cell.

If you place the pump a set distance below the tank you will have the same PSI (minus a very small pressure drop for friction of the longer siphon hose) at the end of the line whether you are siphoning or gravity feeding. Its simple physics, you dont have the entire tank of gas pushing down on the line of the gravity feed, nearly all the fuel is pushing down on the tank itself. Only the tiny hose size area directly above the gravity feed is pushing down the line. There really will be no difference if you think about it from a physics point of view.

Ultimately siphon feed is not the reason for the cavitation.

Another possibility on the fuel filters - when I put inline filters on my Cosmo twin pump setup the douche bags at Tognotti's gave us inline fuel filters for carbueretted engines instead of fuel injected ones, so the flow was restricted by orders of magnitude. The pumps were pushing so hard against them that the fuel was almost boiling from the friction/pressure. Blew two 30 amp fuses before we finally figured out they'd given us the wrong part numbers.

Just another story that might help you, maybe not......