I see. Hmm, absent computing the mileage on the pump, anybtips on determining its the fuel pump or jet pump, if a visual inspection doesnt show anything?

Jet pump / transfer pump troubleshooting
 

The only way would be measure the pressure on the return line to the jet pump. I think supposed to be 15-20 psi but that's fuzzy memory. It's easier to open the tank and disconnect the hose and activate the pump. (Hose pointing into the tank). It should spray like Fire hose.

On second thought: pull outlet hose and hook directly to a pressure gauge. I don’t know what the psi is supposed to be but significantly more than 50. 60? 70?

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Thanks for the suggestions Andrew!

Not been in the mood to fiddle with it lately, but will update when I do get around to it.

The first thing I would do is prop up the left side sender with a couple of sticks and have a look to see if there is any fuel spraying out of the jet pump feed.

After that if you can prop up the pump on the other side far enough to see if there is fuel flowing from the relief valve (on end of the third hose going back to the fuel pump well) that should give you an idea of weather or not the pump is providing enough flow for the jets.

Have a rag handy. The spray out the o-ring went right into my phone camera as i was taking a video to show people that exact diagnostic.

That is the best way to see if the o-ring has failed though. Not difficult and instantly know.

If it's not spraying, there could be blockage in the jet pump and bypass the bump though the pressure relief valve.

That all said if your pump is old that's the prime suspect.

Old pump will push less and less force over time, the FPR hides this detail from you until the jet pump doesn't get enough flow to siphon from left to right and you get identical symptoms of jet pump failure.


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Thank you gents, for the additional info!

Hope to get around to this soon.