2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

[bigcheesecake]

I just bought a boat w/ mercruiser 350 MPI that has 30 hrs of runtime. Boat sat for 3 years with 1/4 tank of gas and appears that engine was not winterized other than water cooling plugs removed. Engine has been giving an inconsistant audible alarm, 2 beeps every 60 seconds and does not happen every outing on the lake. I purchased a scan tool and have read the engine codes several times. At first, the engine would beep and I would turn off engine before hooking up scan tool. This would erase the code that triggered the beeping because I did this several times and would only get the codes for accessories not installed on this engine (Sea Temp, Pitot Tube, Fuel Level, Triml, etc.).

The last three trips out I've hooked up scan tool before starting engine and when engine beeps, usually after 0.25-2hrs, I get a new code: Fault Code 151 Fuel Pump Relay. The engine has also started to hesitate slightly while cruising as if the fuel pump is going bad. Beeping will go away if I turn off ignition and restart engine.

Another issue I've noticed is there seems to be some sort of short circuit with the electical system. All of the gauges on the dash will "pulse" at the same time and if gauge lights are on all will dim at same time. The scan tool shows that the engine voltage stays at a steady 14-14.4 volts even though the gauge on the dash reads 10 volts. Same thing with the water temp. The scan tool shows 140-160 engine temp but dash gauge reads 200-225.

Please help. I'm pretty mechanically inclined but do not have the service manual for this engine yet.

 

[Don S]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

What's your engine serial number?

here is the manual for the 555 ECM
http://www.4shared.com/document/FWwx1Vs7/Service_Manual_36_Rev_1_SBC.html

 

[dingdongs]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

two gauges showing above temp readings and below voltage readings.have you changed impellor and checked grounds on battery yet.also do the manifolds feel too hot to touch at these temps?

 

[BigBoreLynn]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

Have you checked the fuel water seperator,fuel filter,fuel pickup?
You may also want to make sure the fuel tank vent is not clogged, causing a vapor lock.
Last but not least look for collapesed or pinched lines!

 

[Pete104]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

I'm just curious about what kind of scan tool?

 

[burp]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

bigCheesecake,

My 2003 496Mag was giving an intermittent fuel pump relay error. The audible alarm (2 beeps/min) could be reset by stopping and restarting the engine. The fuel pump relay was reseated and later replaced but the intermittent fuel pump relay error/alarm remained. The intermittent error was finally resolved when the CAN bus connectors on the engine wiring harness was reseated.... that was several years ago and the problem has not returned.
On the 496Mag engine there are 3 identical relays near the ECM/PCM module, one of which is the fuel pump relay. Since the 3 relays are the same, they can be swapped around for troubleshooting purposes. I suspect the arrangement on the 350Mag engine is similar.

 

[bigcheesecake]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

Thanks for the tips. I've swapped the relays and reseated the CAN plug and will see if this resolves the problem. Just to be safe I also ordered a new relay and fuel filter.

 

[bigcheesecake]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

So I've replaced the fuel filter and fuel pump relay but still getting beeps and fault code 151:fuel pump rly. Not sure what else could trigger this code or exactly what the computer monitors in this system.

 

[Pete104]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

The failure codes have to be cleared from the ECM.

 

[muc]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

The failure codes have to be cleared from the ECM.

Why?

 

[Pete104]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

Because the way the ECM is set up, says so.

 

[muc]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

Because the way the ECM is set up, says so.

Oh --- can you help me find that in the service manual?

 

[muc]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

Sorry Pete ? just messin with ya --- if this engine is a 350 cid MPI MerCruiser you don?t need to clear faults to make the horn stop sounding, you just need to fix the problem.

Welcome to iboats BigCheese. We really need a serial number to help you because MerCruiser doesn?t have a fault code 151 and fuel pump relays don?t set a fault code.

 

[burp]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

....and fuel pump relays don?t set a fault code.

muc, If you look at the published list of PCM/ECM 555 errors, I'd agree with you....but after experiencing the alarm problem intermittently myself on a trip across the Chesapeake Bay, having the error read out by the shop on the water immediately after coming back to the dock, swapping the relays around by the shop, and followed by a 30-45 minute on water run with the Merc laptop/software connected to the engine....I questioned the validity of the error being read out as well. I purchased a spare fuel pump relay "just in case" and (weeks) later installed it in an attempt to rectify the intermittent alarm. The intermittent errors continued and I noted the engine hours each time the alarm sounded. If you stopped and restarted the engine, the alarm condition would reset. Minutes and sometimes hours later the alarm would sound. Finally after a couple of months dealing with the intermittent alarms, I took the boat back to the same shop (a 4 hour one way tow). The mechanic compared the alarm times read out of the PCM555 with the alarm times that I noted from the hour meter on the boat, all the alarms were the fuel pump relay error. I had doubted the fuel pump error as one would expect engine performance problems to be encountered if the fuel pump relay had a problem, yet the engine was able to run at WOT. After two weeks time, the shop going over the connections on the engine wiring harness, on water runs and $400 for labor cost's later...the problem was resolved. It was one of the CAN bus connections on the engine wiring harness. Discussing the problem resolution with the mechanic, it became apparent that the mechanic had also involved the Merc factory for the resolution.

 

[bigcheesecake]

Re: 2003 Mercruiser 350 MPI Fault Code 151: Fuel Pump Relay

Engine #OM 641557
MCM 350 MAG MPI
ECM-555

The engine is a Mercruiser and everytime the 2 beeps/minute sounds and I plug up the scan tool the only new code is Fault Code 151: Fuel Pump Rly. As soon as I turn off the ignition this code is erased and the beeping stops for the moment. Usually triggers again after engine has warmed up for a hr or so and when pulling someone up on wakeboard at full throttle. The last time I went out the engine actually shut itself off twice and the only code stored was 151.

 

[02809Bristol]

Any idea where you can look for CAN BUS CONNECTION that would be bad ??? Is there a certain one

 

[GA_Boater]

Any idea where you can look for CAN BUS CONNECTION that would be bad ??? Is there a certain one

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