502 MPI-- no power to cool fuel pump!!
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I'm really frustrated; 1999 gen VI 502 MPI; after replacing both exhaust manifolds, and installing new distributor rotor, cap, and spark plugs, went to start the engine up. it started, ran for 3 minutes, then died and could not be restarted. Half tank of fuel onboard-- only 2 months old gas. Checked all wiring everywhere, removed distributor cap and checked everything, all ignition components, throttle cables, etc-- everything I could think of-- everything was in order. Then noticed that the cool fuel pump was NOT "buzzing" for about 3-5 seconds when I turned the ignition switch on each time-- like it did in the past. checked all wiring to and from the computer, and after that-- sprayed some starting fluid (I know-- not supposed to but I was desperate to rule out the ignition system as a problem)-- the engine started up and ran fine!!! Shut it down and restarted a few times to check for reliability-- it fired up all times.
The next day, put it on the hose again to fire it up before a lake trip-- nothing; will not start and no "buzz" from the fuel pump. Removed the power cable from the fuel pump to check for voltage-- cannot get any reading. Checked all wiring from the fuel pump to the relay and also switched out the relay-- nothing.
Tomorrow I will wire power directly to the fuel pump to see if I can rule it out, but does anyone have any suggestions or experience with this type of problem??
Thanks!
The next day, put it on the hose again to fire it up before a lake trip-- nothing; will not start and no "buzz" from the fuel pump. Removed the power cable from the fuel pump to check for voltage-- cannot get any reading. Checked all wiring from the fuel pump to the relay and also switched out the relay-- nothing.
Tomorrow I will wire power directly to the fuel pump to see if I can rule it out, but does anyone have any suggestions or experience with this type of problem??
Thanks!
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I've seen quite a few 502 Mags where the pink power lead going to the relay had a break in it. Remove the relay and make sure that one of the pink wires has power. If not, check it's fuse. There is a fuse holder that has 6 wires going to it. It looks like a plug with a cap on it, but it has 3 small fuses in it. 1 for the ignition, 1 for the fuel pump and 1 for the ecm..
You should also get power to the small wire opposite of the gray wire in the relay plug. I can't remember it's color....maybe green. It's a small 18 or so gauge wire. It will get power for 3 seconds when the key is turned on. It will also get power once the engine starts to crank and the ecm sees some rpm (60 rpm i think)
Eddie
You should also get power to the small wire opposite of the gray wire in the relay plug. I can't remember it's color....maybe green. It's a small 18 or so gauge wire. It will get power for 3 seconds when the key is turned on. It will also get power once the engine starts to crank and the ecm sees some rpm (60 rpm i think)
Eddie
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check the fuel pump relay socket,,they've been know to burn up a little at the contacts,,especially the relays w/ the smaller pins
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I'm having this same issue with a 500EFI that I just had rebuilt and put back in the boat. Sometimes I turn.the key and hear the fuel pump run and sometimes it doesn't run. Seems to be intermittent. Would I be.looking for the same wirea, etc. as mentioned above for the 502?
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If this is MEFI 3 there should be a 15 amp fuse for the fuel pump. I would check that out first . Maybe some one can pull up the diagram for you and if I recall correctly 3 fuses another for ECM 10 amp / knock module and ECM / DLC 15 amp. Had to think about that one to be correct sure about it. Maybe SB can pull up the diagram for it.
Last edited by BUP; 04-24-2016 at 05:33 PM.
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there is a connector on the harness that has a cover over it, with three fuses inside, as stated ^^^^^^^&
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^^^^^ re read me post as I had to think about it and redid it after posting - getting old and my laptop not doing right currently freaking virus BS.
what about your carter fuel pumps ?? what happen to those in another thread ?
what about your carter fuel pumps ?? what happen to those in another thread ?
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If this is MEFI 3 there should be a 15 amp fuse for the fuel pump. I would check that out first . Maybe some one can pull up the diagram for you and if I recall correctly 3 fuses another for ECM 10 amp / knock module and ECM / DLC 15 amp. Had to think about that one to be correct sure about it. Maybe SB can pull up the diagram for it.
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Thanks for the suggestions---I did check the fuses, both visually and with a continuity tester, and they were fine. I pulled the relay and no sign of burning on the pins-- I even switched them and no success. Supplied power to the fuel pump and it ran, so looks like I have a bad wire or ecm ( not good!).
Eddie; you mentioned that you have seen some 502's with broken pink wires-- by any chance do you remember where the break was so I can focus on looking in that vicinity? Hate to slice up my tightly wound wiring harness unless I absolutely have to....
Eddie; you mentioned that you have seen some 502's with broken pink wires-- by any chance do you remember where the break was so I can focus on looking in that vicinity? Hate to slice up my tightly wound wiring harness unless I absolutely have to....
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Or the pump driver in the ECM