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Old 07-09-2020, 10:32 PM
SeaHarlequin SeaHarlequin is offline
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How to diagnose potential bad pump?

Hi - I'm trying to determine whether I have a bad fuel pump.

I have a late model Atomic 4 engine. The engine has an electronic fuel pump (Facet pump). There is a fuel pressure gauge just after the in-line fuel filter (after the fuel pump) and just before the carb.

I'm getting intermittent shutdowns, both from idle and while in gear. I've observed that these shutdowns are related to lack of fuel pressure -- the PSI will drop to 0 and the engine will run happily until it exhausts the gasoline in the carb.

I've attached a multimeter and can measure current going to the pump when attempting to start the engine (at least 5 amps which should be sufficient, right?). A few times during today's session, the pump apparently behaved and fuel pressure registered for a bit. There was no discernible pattern to the length of time of runs -- sometimes it'd run for 15 minutes before stopping, other times 3-5 minutes. The last few tries, it has not responded to these attempted starts.

I've tried uncapping the gas tank to let air in to rule out a clogged intake tube.

Since the fuel pump is a relatively significant resource sink (both in terms of cost and crawling in there to install a new one), I'm trying to rule out other possibilities before doing so. Are there other steps I can check to rule out other culprits which could result in fuel not making it to the pressure gauge (and carb)?

I'm not sure if this is related: I thought I could short across the OPSS switch to activate the pump but the multimeter showed no reading unless I tried to start the engine. If needed, I can bring a DC power supply and supply power directly to the pump but I was hoping there was an easier way to test the pump.

Thanks!
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