norton

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!

Young Performance

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

sutphen 30

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

splashandburn

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?

BUP

iTrader: (9)

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.

F-2 Speedy

iTrader: (6)

there is a connector on the harness that has a cover over it, with three fuses inside, as stated ^^^^^^^&

BUP

iTrader: (9)

^^^^^ 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 ?

splashandburn

So I'm guessing these fuses are all going to be located at the back of the motor with all the wiring harnesses? I took a quick look there earlier but didn't see anything obvious. I take a hard look in the morning. The fuse can't be bad if its intermittent so are you thinking a corroded connection inside the connector?

norton

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....

F-2 Speedy

iTrader: (6)

Or the pump driver in the ECM