Mercruiser 4.3 MPI will not start (No beep noise and ....no power going to fuel pump)

[diver94]

Hello,

I recently bought 2003 Regal w twin Mercruisers (2002) 4.3 MPI and bravo III. Sometimes, I have a problem with the port engine (again?sometimes it wont start). When I turn the key, the gauges move and the engine hours show on the tach gauge, but I don?t hear the Beep? noise and I don?t hear the fuel pump priming noise. When I turn the key, the engine turns and turns but does not start.

Then, I just wait for 1 hour and magically when I turn the key, I hear the beep, fuel pump priming noise and the engine starts right up!

I don?t think it?s the switch, because when it starts, I can try 20 times and the beep always comes on.

I don?t think it?s a bad fuel pump either?again, when it starts it work perfect.

I think it could be a lose ground or cable that goes to the fuel pump. Or some safety sensor (kill switch) that is killing the power to the fuel pump.
Please let me have your thoughts.
Thanks!
Lui

 

[alldodge]

I'm thinking you have a bad main power relay. There are two of them side by side next to the ECM, small square plastic. One is the main power and the other is the fuel pump. They can be swapped with one another. Could also be the power connector which goes from the engine harness to MPI harness (look for a flat connector near the back). After that the ECM connectors

 

[bman440440]

No Title

here is pic of (relay's) where they are in a 2009 5.7 MPI... should be similar

 

[diver94]

Got it..THANKS!
Just to confirm, Im uploading a cpl of pics. I hope they are not hard to remove. I will try to switch them with the starboard engine (to eliminate the relays) and I will also check all the connections. Please let me know if you have any other words of advice (I read something about an oil pressure switch)

Thanks!
Luis

 

[bman440440]

yes that's them... they are easy to remove

 

[diver94]

Thanks!

 

[Fun Times]

(I read something about an oil pressure switch)

Being an MPI engine model, the oil pressure switch will not have any affect on this situation as it doesn't control the fuel pump circuit..That is for carbureted engines only.

Also try checking for loose/bad connection at the engine fuses located near the relays that look like the photo below but will have a cover over them.

With the ignition key on / engine off, carefully wiggle all the wires you can locate starting with the main wiring harness cannon plug found on the engine running back to the helm. http://www.bing.com/images/search?q=mercruiser+cannon+plug&FORM=HDRSC2