Electric Fuel Pump Kaputt?

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Simon Wootton

Cadet
Joined
May 16, 2001
Messages
15
Hope someone can help. Merc 4.3 LX with electric fuel pump. I was having intermittent problems but now more permanent! No fuel pressure so no fuel to carb.<br /><br />So far I have shorted out the oil pressure switch wires - after establishing healthy oil pressure - to no avail. I have no manual so can't trace the wiring properly. I see two purple wires at the oil pressure switch and a purple and black at the pump. I have definite continuity between one lead at the switch and the black lead at the pump - but nothing at the purple wire at the pump.<br /><br />As access is poor in my engine bay I can't easily see if there are any relays etc. that may explain where to look next.<br /><br />Grateful for any ideas!<br /><br />Simon
 
L

loadnet

Petty Officer 1st Class
Joined
Aug 27, 2003
Messages
225
Re: Electric Fuel Pump Kaputt?

- Remove both wires from the pump terminals and clean em real good, then stick em back on.<br /><br />- While spinning the engine over, ground a test light and stab the pump wires one at a time to see if you're getting juice TO the pump.<br /><br />*Got juice to the pump while spinning the engine over?<br /><br />- Run a jumper ground wire from the other pump terminal to batt ground. - then repeat test above. You may only have a badly grounded pump terminal causing this headache.<br /><br />*No juice to the pump? and not knowing which wires are supposed to be hot or ground?<br /><br />- Grab your positive side batt terminal with aligater clip from test light and stab the black wire terminal at the pump. (it should be ground)<br /><br />*If the test light lights up?<br /><br />- Run a positive jumper wire direct from the batt to the purple wire and see if the pump runs.<br /><br />*Pump doesn't run? while feeding it juice manually and has good ground?<br /><br />- Replace the pump.<br /><br />*Pump runs but engine won't start?<br /><br />- Remove and pressure test the pump.<br />Should have 4 to 7lbs pressure coming out of it for Non FI engines.
 
R

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Electric Fuel Pump Kaputt?

hello<br /> follow the captains advice and buy a manual. some engines are using a pump relay that will fail occasionally. without looking at yours I cant tell. the purple wire should have 12 volts with the key on and the oil pressure switch closed/bypassed.the black is ground. <br /> a lot of those pumps failed. it may be just as quik to remove it ,bench test it and clean the pump intake screen if it is still a good pump.<br /> good luck and you gotta buy a manual.
 
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Simon Wootton

Cadet
Joined
May 16, 2001
Messages
15
Re: Electric Fuel Pump Kaputt?

Thanks Guys - Sorry! I forgot to say that the pump runs OK on the bench.<br /><br />I'll go and play with it again and report back.<br /><br />Thanks!
 
S

Simon Wootton

Cadet
Joined
May 16, 2001
Messages
15
Re: Electric Fuel Pump Kaputt?

Thanks ctak - going to the boat in a few days and will check this out! Will I feel sick if the kill switch is the culprit!<br /><br />Simon
 
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