Fuel pump power issue back

[Todd320]

I have 2007 350 MAG MPI horizon engines. Last year, the port engine stopped running. Fuel pump relay burned out. Replaced, ran fine. Next trip, 2 weeks later, engine died again, this time, the harness for the relay was bad. Since then (September-October), no issues. Yesterday, had a great weekend, engines ran great. Put boat on the rack, went to flush it, would not start. Noticed the fuel pump is not making a noise when you put the ignition switch in the on position (like it does on the starboard side).
Replaced the relay, did not fix. I'm thinking the harness again, but also what is the root cause? From what I have gathered by searching this forum, the fuel pump housing is probably "delaminating" and causing high pressure in the fuel system, making the pumps draw too many amps which then are burning up the relay or the harness. Alternatively, I have a short somewhere in the harness that keeps causing this.
Thoughts? I have a call into my tech already, but I have a manorial day trip planned. Not sure he will be able to get to it by then.
As far as diagnosing, if I have a multimeter, what should the pins on the harness read when switch is in the on position? There are 5 pins, if I knew which ones should read 12 volts I could check that and see if I can apply a temp fix to the harness.


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[CliffA]

maybe try to 'wiggle' the wiring harness as someone attempts to start the engines to see if the fuel pump will energize....if it does you have an issue with the harness....if not I would investigate how many amps the fuel pump is pulling to see if there is a partial blockage somewhere....I would also inspect the fuel line all the way back to the tank to insure the line is not kinked causing a restriction....it would not hurt to check the anti-siphon valve at the fuel tank to insure it is not plugged and the ball check valve is free.....

it is possible the fuel pump is going bad....you could run a jumper wire from a 12V source directly to the pump to see if it energizes....but be VERY careful about insuring the ER is free of gas fumes since this will cause a spark....

is the fuel/water separator filter clean?

cliff

 

[Todd320]

I'm going to check to make sure I'm getting voltage to the fuel pump when switch is in on position, if there is no power, the I will backtrack up to the relay to see if power is going into the harness. If voltage is available to the pump, then I'm going to check fuel pressure. No pressure, bad pump. If I have pressure, then it should start.

Now, some easy/dumb questions, assuming I can get the pump to energize, if I want to check the draw, I would need my multimeter to be inline. What's the easiest way to do this? Disconnect the black lead into the fuel pump, and put the meter in between the lead and the pump? I wouldn't crank the engine, I would just put the switch in the on position.

Another dumb one, the tech just serviced this on 4/4, replaced fuel filters. I don't recall seeing any racor-style (with the see through plastic housing and drain) fuel-water separator on my boat. Will my boat definitely have one? Or, will not necessarily look like a racor?


Brown Eyed Girl - 2007 Sea Ray 320 Sundancer, 350 MAG MPI V-drive

 

[Todd320]

Also, I have a new fuel pump housing replaced in 4/2016, so I should not have any issue where the paint on the inside of the housing delaminates. My understanding is the new fuel pump housings corrected this issue.


Brown Eyed Girl - 2007 Sea Ray 320 Sundancer, 350 MAG MPI V-drive

 

[CliffA]

the fuel pumps are also connected to an oil pressure sensor....if there is not enough oil pressure the fuel pump will shut down to save the engine....might want to back track the wiring to that sensor to be sure there are no issues....

definitely check for voltage at the fuel pump as one of the first things to check and if no voltage is present (with key on) back trace the wires until you do find power.........I don't know enough about the wiring of the fuel pump to guide you on checking the amp draw of the fuel pump....someone with more electrical knowledge will hopefully chime in......

I am not sure what type of fuel/water separator filter system your boat has.....mine is the OEM system which has the white filter that looks like an engine oil filter....one thing that is important concerning changing the fuel filter is to be sure the right 'micron' filter is used.....if the filter mesh is too small the flow of fuel will be restricted and force the fuel pump to work harder.....don't 'assume' your mechanic used the correct filter.....your boat will definitely have a fuel/water filter......I doubt it would be a Racor type system unless a previous owner changed it....

 

[skibum]

The water separating filter is inside of the cool fuel module. There might not be one that looks like an oil filter. That's how mine is.

 

[CliffA]

The water separating filter is inside of the cool fuel module. There might not be one that looks like an oil filter. That's how mine is.

OK, thanks.....I don't have the 'cool fuel' module....thank goodness.....

cliff

 

[Todd320]

I need better tools. Found I need a clamp on ammeter which can read amperage without breaking the circuit, not to mention my multimeter can only handle 10 amps. Pretty sure the amps required by the fuel pump will be higher than that.


Brown Eyed Girl - 2007 Sea Ray 320 Sundancer, 350 MAG MPI V-drive

 

[Bt Doctur]

I don't recall seeing any racor-style (with the see through plastic housing and drain) fuel-water separator on my boat.

Unless you have an outboard you never will see those filters. You can have a Racor with the base that drains but it will be a melal one

 

[Todd320]

FIXED! The harness the relay plugs into was shot, so I cut it off, went to autozone, picked up a $6 30A 4 prong relay, a pack of female quick disconnects, and heat shrink tubing. Connected it up according to the wiring diagram, and engine started right up. I also ordered a Mercruiser replacement kit (879346A48, 15$) complete with butt connectors and a shrouded harness, but that will not get here until next week. Needed boat fixed for Memorial Day weekend!


Brown Eyed Girl - 2007 Sea Ray 320 Sundancer, 350 MAG MPI V-drive

 

[scoflaw]

It will probably happen to you again. Not normal for a harness to fail in a boat that age. Probably cooked it from too much resistance. Check your fuel pressure

 

[Smokeio]

So how many wiring harnesses did you replace? Your first post stated you replaced the harness. Did that include the relay socket?

This is a recurring theme with these motors. I'll bet if you look closely at the original relay socket you'll see a burnt connector. I had the same issue and if you search through this board you'll see many more. It doesn't make sense that the pump would over amp and burn out the connector before the fuse blows. My connector looked like it had opened up like someone stuck a meter probe in there to test the voltage. It's odd that so many people have the same issue.

 

[scoflaw]

So how many wiring harnesses did you replace? Your first post stated you replaced the harness. Did that include the relay socket?

This is a recurring theme with these motors. I'll bet if you look closely at the original relay socket you'll see a burnt connector. I had the same issue and if you search through this board you'll see many more. It doesn't make sense that the pump would over amp and burn out the connector before the fuse blows. My connector looked like it had opened up like someone stuck a meter probe in there to test the voltage. It's odd that so many people have the same issue.

Not odd at all... the paint chip problem which causes the fuel pressure to spike puts an excessive load on the fuel pump. Monitor your pressure.

 

[Todd320]

So how many wiring harnesses did you replace? Your first post stated you replaced the harness. Did that include the relay socket?
.

My previous tech was supposed to have replaced the harness. When I replaced it, there was no evidence of this. No butt connectors, part did not look new, nothing. He must have cleaned it back in November and it's worked until now.



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[Todd320]

Not odd at all... the paint chip problem which causes the fuel pressure to spike puts an excessive load on the fuel pump. Monitor your pressure.

I should not have the paint chip problem, since I have a new fuel pump housing (but not new fuel pumps).
Possible the previous housing had the issue and maybe paint remaining is causing an issue?

Regardless, I should check the pressure. But, slightly out of my comfort zone. Fuel scares the crap out of me. I did buy a new pressure gauge.

I should also check the amperage being drawn too(heard fuel pumps in general will draw too many amps when they start to fail), which my previous tech said he did, but now I believe he probably did not do.

The new relay/harness coming from MerCruiser uses thicker/wider contacts than the ones previously installed. I'm hopeful that this results in a final solution, but I'm betting new fuel pumps are on the horizon (get it, I have Horizon MPI engines! Hah, I made a funny).



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[Todd320]

NOT FIXED: the auto parts relay I used (30A/12V) stopped working after 20 minutes, the 85 or 86 prong just came right out of the relay (85-86 is just supplying voltage to the relay, not the fuel pump).
FIXED: Replaced with a larger 12v/14v 40A relay, made it the rest of the way to Caladesi Island (4 hour drive total, 45 miles). I have one more backup relay!


Brown Eyed Girl - 2007 Sea Ray 320 Sundancer, 350 MAG MPI V-drive

 

[JeffMac]

I had this same issue for almost a year where I would burn through relays and wasn’t sure if the cause was a loose connection, a bad fuel pump , etc. It was definitely the high pressure fuel pump. My mechanic said he has seen a bunch of these and once he swapped it out I haven’t had an issue. Btw, my engine has the Gen 2 fuel pump system which does not suffer from the paint delamination issue that I have read a lot about on here. Anyway, can’t believe it took so long for me to bring it in and get it diagnosed by a pro, but I’m glad I did.