Electric pump would not energize on start

[milkyway]

1998 Mercruiser 5.0 L mercarb 2bbl

my electric fuel pump runs when it is hard-wired directly to the battery so i know it is not broke, but it does not energize when you turn the ignition to on, prior to start. it used to. what is the problem? thanks in advance.

 

[Don S]

Re: Electric pump would not energize on start

but it does not energize when you turn the ignition to on, prior to start. it used to. what is the problem?

It shouldn't have been coming on. It should only run when the starter is engaged, or the oil pressure is above approx. 3 psi.

 

[dubs283]

Re: Electric pump would not energize on start

so, in the past, you would hear the fuel pump run with the key in the "run" position prior to turning the engine over to start it??

the fuel pump wiring for that engine should energize the fuel pump circuit during cranking, then the oil pressure switch energizes the fuel pump when the engine is running

does the engine run at all??

 

[milkyway]

Re: Electric pump would not energize on start

the engine has been difficult to start. i could not smell any gas in the carb despite my manual priming with the throttle. so i hard wired the pump to force gas into the carb, the engine started right away but died after 15 seconds. engine died and it would not start again.

i am trying to rule out the pump before attempting to overhaul the carburetor. i will also first check the antisiphon valve for blockage.

so the electric pump you said should not run until i crank the engine? well, it used to run prior to start. but it also did not energize prior to start. so now my best guess between the 2 is that it should energize, but then now i r ealize i am mistaken. so it is normal that the pump not energize. also, the pump does not run when i jump the 2 wires at the oil pressure switch. it used to run when jumped. i must have another problem.

the carburetor has not been serviced for 6 years - only yearly blasting of carburetor cleaner.

any suggestions? i need to run the engine for winterization.

thank you

 

[Don S]

Re: Electric pump would not energize on start

Check the connections of the wires on the oil pressure switch. It's located above the block mounted oil filter on the port side aft part of the engine.
They are known to corrode and fall apart if water gets on them. Especially if it's salt water.

 

[milkyway]

Re: Electric pump would not energize on start

i will check all connections. thank you.

 

[skipper6567]

Re: Electric pump would not energize on start

If it has electronic distributor,computer controled.Its probly the ignition modulator under distributor cap.It will just kill the motor randomly. may start run for a week and then not start for a day then all is ok..it can be intermitent is what Im saying. if your oil pressure sensor is good then I would bet its something with ignition. you said you smell gas,well that means no spark. if its the tbi model be carefull,it just keeps spitting fuel out those injectors and if you suddenly get a spark..bang! valve covers get bigger!!