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Fuel pump

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Dream Catcher

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I have a 2004 Maxum 2700SE with a 6.2 mercruiser MPI. Been having a problem all season, got towed in twice. problem.... when I turn on the ignition key i am supposed to here the fuel pump power up, but it doesn't. so far the boat has had a tune up, fuel pump, fuel pump relay new fuses for fuel pump. during the year it would not power up, i would move wires by the relay and it would start. did that twice and now moving anything it still wont power up. my mechanic hot wired the fuel pump and the boat started right up. he seems to think its the computer but cant find one to plug in and try and cant return electronic parts and they are expensive . any other suggestions...
 
The most likely cause is a wire losing it's connection someplace more probable due to either corrosion to a wiring pin or connector harness or a wire pin is backing out of a harness connector should you not be able to find a chaffed wire to either the fuel pump circuits power or ground sides or Key On Ignition side circuits.

You may want to try continuing with inspecting and multimeter testing each wire circuit individually that has some sort of partnership to the fuel pump and key on 12v power and ground circuitry including the relay wires and ECM wirings for each circuit... For guidance, the wiring circuits can be found online inside Mercruiser service manual number 36.

The following link is just meant to be one example of many to use to help get an idea of what you might be looking for as to possibly having a corrosion issue someplace within a wiring circuit or wiring harness connector either at the cannon plug, a sensor connector, fuse holder or relay harness connector, etc., http://www.marineengine.com/boat-fo...Mercruiser-350-Mag-Starter-Continually-Cranks

While it could be an internal ECM issue, you may be better off trying to first eliminate the wiring system as that is typically the first to fail under normal circumstances meaning nothing known has compromised the ECM such as water ingestion, battery cables connected backwards, lightning strikes to the boat, etc. etc.

If you still suspect a bad ECM then there is a repair facility in Fresno, CA that you could send in your design model 555 ECM for testing and possibly have it repaired depending on damage before having to decide on buying a new ECM. https://whipplesuperchargers.com/index.php?dispatch=products.view&product_id=73

Though it seems the repair cost went up $100.00 to now $600.00 the last price I've heard for testing the ECM to ensure it's "good"/diagnose was $100.00 but not sure now. It's best to call them first.

Since you were able to wiggle things around and it seemed to work at some points, stay on the wiring connections before buying an new ECM as something would appear from your description of being overlooked.

Let us know, good luck.
 
IDK is it like a car where the fuel pump comes on when to turn the key for a few seconds to prime the system then turns off. And then once the engine has started the fuel pump then runs as long as the engine is running? I believe it uses the signal from the oil pressure senser (the one with two wires) to keep the pump running?
 
kimcrwbr1 said:
IDK is it like a car where the fuel pump comes on when to turn the key for a few seconds to prime the system then turns off. And then once the engine has started the fuel pump then runs as long as the engine is running? I believe it uses the signal from the oil pressure senser (the one with two wires) to keep the pump running?
Click to expand...
Per se on Merc marine MPI engines.. The fuel pump doesn't utilize the oil pressure sensor to keep the fuel pump running power wise. It's only used on their carbureted engines which uses a similar looking sensor which is actually a oil pressure switch to help take over the power to the fuel pump.

On MPI's, the ECM sends a signal to activate the fuel pump relay first at key on/up for two seconds then once the ECM reads an RPM signal starting from the Crankshaft Sensor on this particular engine model, it keeps the fuel pump energized until the engine dies/no more RPM signal.
 
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