XJ6 & XJ12 Series I, II & III 1968-1992

Fuel pump is noisy using left tank but not right tank

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Old Mar 16, 2019 | 12:23 PM
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Default Fuel pump is noisy using left tank but not right tank

Greetings,

My ‘87 XJ6 fuel pump started getting noisy and vibrating when I’m using my left fuel tank. When I switch to the right tank, it quiets down. When I switch back to the left, it gets noisy again. The car runs fine when it’s using either tank but the fuel pump sounds like it’s struggling with the left.

Does anyone have suggestions on what this could be? A clogged return valve on the left side maybe? If it is, can it be cleaned rather than replaced? The left return valve is only a few months old.

Thank you,

Danny
 
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Old Mar 16, 2019 | 01:42 PM
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Danny, my pump got noisy too, I ordered a new one, no luck, I ordered a used one, no luck.

Went to a salvage yard and pulled one from a 1986, what did I have to lose, $6.00 or return it for a $6.00 credit.But the noise stopped. Has been running quietly since last year.

dang! I got lucky. Replace the pump and keep replacing it until you hit a good one.

 
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Old Mar 16, 2019 | 03:56 PM
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Usually pumps get noisy from flow starvation. This restricted flow causes cavitation and that causes the noise. Why that tank is starving the pump needs to be investigated. A clogged screen, collapsed line or partially clogged / stuck switch over value all should be investigated. If I was a gambling man I'd bet on a rust chip blockage in the switch over valve.
 
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Old Mar 16, 2019 | 04:07 PM
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I would get a length of tubing and two barbed unions and temporarily plumb it right to left and left to right. The return vales will be going to the other side so just do it for a few minutes with you back there watching. If it is now noisy on the other side it is definitely the pump. If not, it is something else, most likely a restriction somewhere. Anything with fuel can get gummed up. Take the retun valve out and test it by blowing through it while someone works the switch inside. If it is gummed up you might try spray carburetor cleaner and see if that helps. Good luck.

Jeff
 
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Old Mar 16, 2019 | 05:04 PM
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Thank you, all, for your feedback.

Since the pump is quiet when I’m running the right tank, I think it’s likely not the pump itself but you never know. My changeover valve got clogged with fuel debris not that long ago and caused one of the tanks to overflow. Cleaning it solved the problem.

After I figure out the problem, I’ll post what the issue was.

Danny
 
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