HELP i have a gremlin onboard
 

Hello OSO Forum
I need your Help.
I have a gremlin onboard and going to AA meetings will be my next step unless you guys can help.
I know someone has had this problem before.
Here is the situation
Of the 2000 twin 502 mag mpi engines one likes to shut down.
Im having an intermittent fuel pump shut off on the port engine (Two fuel pumps per each engine)
sometimes you can turn the key on and the fuel pumps run for two seconds and turn off engine starts and runs
sometimes you can turn the key on and the fuel pumps DO NOT run for two seconds engine fails to run.
The power failure of the fuel pumps are intermittent, could run engine for 30 mins on and off throttle and while returning to dock fuel pump fails, could leave dock going out fuel pump fails. power is lost to both fuel pumps. there is one black and one gray wire that splits (looks like a factory split) and becomes two black and two gray one set going to each fuel pump.
because i have an unlimited parts supply called a starboard engine here are the parts i have swapped.
key switch
kill switch
ecu
fuelpump relay
ignition/system relay
engine coolant sensor
15 amp fuse
replaced fuel filter
replaced water / fuel separator
cleaned cannon plug
so my question is what communicates and allows power to the fuel pump.
turn on key switch and how many sensors have to make connection to allow this?
or what could be failing and not allowing power to continue. remember that list of parts I’ve swapped the starboard engine in running fine.
thanks for your help in advance and I will look for a sharp object to poke my eye because it is be less painful than this.
Thanks Randy

My WAG - landyard ie: kill switch ? Do you have one for each motor or one for both ?

Are you totally sure it's just the fuel pump that stops receiving power ?

Anyway - here are a bunch of electrical diagrams for many Mercruisers:
http://www.boatfix.com/merc/Servmanl/16/16F4R2.PDF

Start looking for the simple things, I don't think any of your parts are the problem.....Look at all the connections real close,check the ground wires closely to see if one is making a intermittent contact; check all the plugs to see if one of the contacts is broken where they plug together and last but not least look to see if a wire is bent over or has a sharp kink in it where someone has stepped on it between the motor and a foot .........if that does not find anything dig out the tester and start checking the wires to the fuel system. Just guessing right now --------- Good luck .


Jim

One per engine and replaced both

Yes you can here something along the fuelrail click power up and off when the fuel pump doesn't come on. Also I had a fuel pressure gage hooked up when the power cut off and the engine ran until fuel pressure dropped off

Jim I have, the problem is what to check when no power condition exist. number 3 on cannon plug, number 30 or 86 on the on the fuel relay. Black/green wire to ecm ect. The repair manual I'm using referenced all the wiring diagrams but mine. So the trouble shoot guide was not 100% correct. My fuel pump relay has two pink one black w green and one gray wire. Engine booklet is July of 1999

Could the pump relay be getting tired/sticky. Thougn not on a boat, I had one internitently working on a ford explorer. next time it doesnt work try tapping on the relay a couple times.

Swapped relays to starboard engine and swapped between ignition relay

Get on the phone Monday morning and call Sunsation for a copy of the wiring diagram for your boat-----You cant fix some thing if you don't have the right wiring diagram---- of course if Sunsation would have stuck with the Merc diagram maybe you would be able to see whats going on.


Jim