Cooling Problem

[dogbert]

I'm not sure. However, there is an alarm for it. I'll find out when I get my boat back (hopefully Tuesday).

[dogbert]

dogbert - what was the problem? What does the engine monitoring system monitor besides oil pressure and water temp? If it's fuel pressure do you know where the sensor is?

Ok, so here's what I found out. It was the fuel pressure regulator and it sits on top of the fuel cooler. In order to remove it, they had to remove the muffler. Sounds like it was a real PITA. The fuel cooler is just a pipe where the fuel goes around the pipe through an outer enclosure. It looks to be made of copper. The fuel comes in from underneath and exits on top through the fuel pressure regulator. Mercruiser made engines that would alarm for low fuel pressure or wildly fluctuating fuel pressure for about 3-4 years starting in my model year. The regulator has a diaphram that basically disintegrates after 7-8 years. If you own a Mercruiser, you will have this problem. Marine Power has no such part.

Now for the scary part. When they put it all back together again, apparently the mechanic forgot to check the inbound fuel line. We were out boarding and I started to smell fuel. I opened up the bilge and almost fell over from the fumes. After much rinsing (using ballast pumps and my bilge pump), I was able to make it back to my dock without turning into a crispy critter. It turns out the line into the cooler is a compression fitting with 4 o-rings. One of them got pinched when they put it back on. My service manager felt awful about what happened and made it right. I told him I was pretty torqued about it, but kept things cool so he would continue talking to me. In the end, it was just 6 lost hours without the boat. Probably saved me $100 in gas.

This type of repair is probably not a DIY for most folks.

But, I did learn that there's no way that the fuel cooler would ever get blocked by impeller debris...it's just a straight tube with no obstructions.

[R&T Babich]

I'm assuming when you say they had to remove the "muffler" it was the "exhaust manifold" they took off and that would be a real PTIA. I've been wondering if you can get to the fuel pump without taking that off. My first thought was to take out the alternator.

Good info on the regulator. Our boat is 7 years old and even though it doesn't have a lot of hours the regulator is in constant contact with fuel, running or not. I'll start looking for the best price on a regulator.

I think I'm going to install a fuel pressure gauge. I could then see the pressure come up just before starting, see the lower pressure at idle and higher pressure when cruising.

If you don't mind, what is your engine serial no.? I still can't find a fuel pressure sensor for our engine in the Merc Parts Express drawings. The engine monitoring system would need some kind of sensor.

[TeamAllen]

Add a gauge like this?

[dogbert]

Teamallen, you need to come visit me and help me work on my boat

[R&T Babich]

Teamallen - I added a fuel pressure gauge similar to yours. I moved the test valve to the other rail. When I turn the ignition switch to RUN the fuel pump pressurizes and the gauge reads 30 psi. After the pump stops the pressure drops back to around 22-24 psi. Does yours work about the same? It seems ok. I'll take the boat out in 2 weeks and see how it works with the engine running.

[R&T Babich]

Mercruiser made engines that would alarm for low fuel pressure or wildly fluctuating fuel pressure for about 3-4 years starting in my model year.

Dogbert - I think I found the fuel pressure sender. It was hiding under the starter slave relay.

[R&T Babich]

I think that is a fuel pressure sender. When I took it off fuel came pouring out. Thing is it is not listed in any of the parts drawings on Merc Parts Express, the customer service guy at Mercury didn't know what it was, a couple of parts suppliers don't list it and the Chevy parts guy couldn't find any application with square fuel rails and a sender. The sender has 3 wires and they appear to head off thru the harness to the ECM. It has the number 007399 stamped in the shell. Does anyone know what it is, does & where to get one if it goes bad? Maybe it's mentioned in a specific 350 Mag MPI manual. Is there a good manual to get for the Mag MPI?

I was talking about the Mag MPI in general with the parts guy at Go2Marine. He thought there were several conditions, not just water temp, oil pressure and (apparently) fuel pressure that will trigger the engine monitor alarm.

Also, there is not a replacement part available for the ECM and it is discontinued from Merc. He said there are quite a few boats just sitting out there that have a bad ECM, not just Mercs, because the manufacturers discontinue the part and the aftermarket has not found it profitable to tool up. Some people are ripping off the FI and going back to carbs.

[chpthril]

I think that is a fuel pressure sender. When I took it off fuel came pouring out. Thing is it is not listed in any of the parts drawings on Merc Parts Express, the customer service guy at Mercury didn't know what it was, a couple of parts suppliers don't list it and the Chevy parts guy couldn't find any application with square fuel rails and a sender. The sender has 3 wires and they appear to head off thru the harness to the ECM. It has the number 007399 stamped in the shell. Does anyone know what it is, does & where to get one if it goes bad? Maybe it's mentioned in a specific 350 Mag MPI manual. Is there a good manual to get for the Mag MPI?

I was talking about the Mag MPI in general with the parts guy at Go2Marine. He thought there were several conditions, not just water temp, oil pressure and (apparently) fuel pressure that will trigger the engine monitor alarm.

Also, there is not a replacement part available for the ECM and it is discontinued from Merc. He said there are quite a few boats just sitting out there that have a bad ECM, not just Mercs, because the manufacturers discontinue the part and the aftermarket has not found it profitable to tool up. Some people are ripping off the FI and going back to carbs.

Just a wild thought, but that looks a whole lot like GM's A/C high pressure cut-out.

1) ground
2) 5 v ref
3) signal return

[spooner]

Also looks similar to Chryslers a/c transducer. but I bet the threads are not the same it looks bigger. The thread size looks like a ICP or EBP(the revised ones) for a Ford 6.0L.

[R&T Babich]

I think that is a fuel pressure sender...... the customer service guy at Mercury didn't know what it was, a couple of parts suppliers don't list it.

Also, there is not a replacement part available for the ECM and it is discontinued from Merc.

Update: After additional research and talking to another Merc tech guy there is a fuel pressure switch on the GM Marine EFI 3 series engines - Merc part no. 710-881879A 8.
GM made a series of Marine EFI engines - MEFI-1 1993, MEFI-2 1996, MEFI-3 1998 and MEFI-4 2001. One chart I saw indicated only MEFI-1 and MEFI-3 systems were used by Mercruiser. The MEFI-1 controller would have a GM part no. 16234539 on the bottom and the MEFI-3 would be 16236999. The fuel pressure switch was used on the MEFI-3 & 4 versions and would generate error codes 61 - fuel pressure high and 62 - fuel pressure low. GM no longer makes the MEFI controllers so Merc can't supply them, either. An MEFI-3 system can be upgraded to an MEFI-4 with connector/wiring changes.

[teachercop]

This type of repair is probably not a DIY for most folks.

But, I did learn that there's no way that the fuel cooler would ever get blocked by impeller debris...it's just a straight tube with no obstructions.[/QUOTE]

If my memory serves from this past July at Powell, doesn't the cooler have mini vanes the drop down 90 degrees off of the tube? I think that is what is referred to when it is believed the cooler loses its effectiveness of fuel cooling capacity.

Is it believed the fuel sender is sending erroneous messages/signals to the ECM?

[dogbert]

If my memory serves from this past July at Powell, doesn't the cooler have mini vanes the drop down 90 degrees off of the tube? I think that is what is referred to when it is believed the cooler loses its effectiveness of fuel cooling capacity.

Is it believed the fuel sender is sending erroneous messages/signals to the ECM?

No, there are no vanes, it's just a straight pipe that's got an outer sleeve.

No, the fuel sender was not sending erroneous messages. There's a diaphragm inside the fuel pressure unit that wears out after 7 or 8 years.

R&T Babich, great info! Thanks for doing the research!