Anyone ever replace the port side cool fuel pump assembly on MPI engines?

Gunn

Gunn

Well-Known Member
TECHNICAL Contributor
Oct 4, 2006
2,335
Potomac River - MD
Boat Info
2003 280DA and 1995 Sea Ray 175
Engines
Twin 4.3l and 3.0l, all w/ AlphaI GenII drives
So I'm an issue keeping my engine from running. The engine shut down on me a couple weeks ago while at idle, docking the boat. Couldn't restart. Dug out the fuel pressure gauge and determined I had no pressure, and then realized I couldn't hear the fuel pump prime when the engine switch was pressed to the 'Run' position. I troubleshooted the issue and found that a 20 Amp fuse that sits on the engine in a bracket near the exhaust manifold had blown. There are three fuses in this holder, next to a couple of relays.

After tracking down an electrical diagram, I found that this 20 Amp fuse went directly to the fuel pump. I replaced the fuse, and the boat started for about 20 seconds...started to idle badly, then died. I checked and sure enough, the fuse was blown again. I checked the harness between there and the fuel pump the best I could and it all looked OK. Replaced the fuse and it ran fine for 5 minutes or so, and then I shut it down. Well today, I went to turn the engine on and didn't hear the fuel pump prime. Sure enough, the fuse had blown. So...I think the fuel pump is somehow loading up on resistance and pulling too many amps and blowing this fuse.

I replaced the fuel pump on the starboard engine two years ago, no problem (that one just outright died, no fuses blown). But I'm worried about getting this one out from under the port side engine. This high pressure electric fuel pump is part of the Mercruiser cool fuel assembly box, consisting of a fuel cooler, fuel regulator and containing box. I'm worried that I won't have enough room to drop it all down and slide it out from under the engine. I had enough clearance on the starboard side as the fuel pump was nearest the keel of the boat. But now on the other engine, it's nearer the outboard side where there is less floor space.

So....has anyone ever done this, DIY or otherwise? Has the engine needed to be raised or removed (please don't tell me that!).

Thanks,
 
Last edited:
Yikes, this is not a good sign!

I may tackle this this weekend and see where I get. I'm hoping that since the bottom of the boat is tapering downward (from port side to keel), that I can actually slide the fuel cooler assembly down and out...we shall see. Hopefully Sea Ray and Mercruiser decided to mount the engine at the height they did just for this purpose...
 
I just replaced my port side Cool Fuel assembly on my 320DA. The delamination issue and the corrosion from the water lines toasted my low pressure pump and it wouldnt start. I have V-Drives to i took out the port side exhaust tubing to get much better access. The water lines are going to be a pain to get off so i simply cut mine at the end of the barb, disconnected the fuel line after turning the sender screw to "by-pass" (so no fuel leaked from the tank), undid the 4 bolts holding the Cool Fuel module on, and it came right out. I replaced my entire unit since the water lines corroded and breached inside to the fuel pumps. If you are just replacing the pumps, make sure you do them carefully. There is a great write-up if you search for "Cool Fuel Replacement" on here. When you have the new pumps in, make sure you fill the canister (about half way) with fuel or the new setup wont prime. I used replacement barbs and connectors from WestMarine to tie back into the water lines i cut to remove the housing. I also used hose clamps instead of the glue and sealant that was originally used. Used Cool Fuel assemblies (with pumps already installed) for for about $300 on Ebay. There is a place in Worcester MA that has them in stock. New ones go for about 1K. Remember to check the valve at the top of the fuel rail after you are done. You should have between 35 and 40 psi at idle. Hope this helps. Let me know if you have any questions. -Mike
 
MAKC said:
I just replaced my port side Cool Fuel assembly on my 320DA. The delamination issue and the corrosion from the water lines toasted my low pressure pump and it wouldnt start. I have V-Drives to i took out the port side exhaust tubing to get much better access. The water lines are going to be a pain to get off so i simply cut mine at the end of the barb, disconnected the fuel line after turning the sender screw to "by-pass" (so no fuel leaked from the tank), undid the 4 bolts holding the Cool Fuel module on, and it came right out. I replaced my entire unit since the water lines corroded and breached inside to the fuel pumps. If you are just replacing the pumps, make sure you do them carefully. There is a great write-up if you search for "Cool Fuel Replacement" on here. When you have the new pumps in, make sure you fill the canister (about half way) with fuel or the new setup wont prime. I used replacement barbs and connectors from WestMarine to tie back into the water lines i cut to remove the housing. I also used hose clamps instead of the glue and sealant that was originally used. Used Cool Fuel assemblies (with pumps already installed) for for about $300 on Ebay. There is a place in Worcester MA that has them in stock. New ones go for about 1K. Remember to check the valve at the top of the fuel rail after you are done. You should have between 35 and 40 psi at idle. Hope this helps. Let me know if you have any questions. -Mike
Click to expand...

You have cool fuel III - his is different
 
Just a question - if I have the modules with what appears as black ends and hoses with hose clamps on them, I'm assuming they were replaced previously under warranty. T
 
Hose clamps and a blue drain plug (like a wing nut) indicate cool fuel 4. So yes, your CF3s are replaced by CF4.
 
Great! Now if I can only figure out how to replace the fuel filters without the gas pouring out. Going to try and turn the electric fuel valves manually. I've done everything according to the instructions, but literally a half gallon of fuel had poured into the bilge before I had to just reseal the top three bolts. That was fun to clean up :)
 
MancaveII said:
Great! Now if I can only figure out how to replace the fuel filters without the gas pouring out. Going to try and turn the electric fuel valves manually. I've done everything according to the instructions, but literally a half gallon of fuel had poured into the bilge before I had to just reseal the top three bolts. That was fun to clean up :)
Click to expand...
You got a problem there, not normal
 
Well I'll assume it's an open anti-siphon valve...either the valve is defective or stuck open, in either case I'll manually close it and find a replacement. I can't think of any other reason you would get fuel coming into the module...gravity is feeding the fuel as there is no pressure, just flow.
 
Interesting point as to what controls the fuel depth in the module. The valve your referring to just opens and closes electrically, doesn't know if the engine just has the key on or WOT. There's also a spring loaded check valve on the side of the module that I have no clue to its function
 
I would think the issue has to be related to the shut off valve or maybe there is valve of some type where the fuel feeds the module. I'll have to go look at a diagram and research that one as I would think that is a logical place for a check valve of some type. I can't imagine there is that much fuel in the lines from the pumps to the injectors that would flow back into the module and pour out the amount of gas I was dealing with. This is one is likely to be handled by the shop unless I can research a logical reason why that much fuel would be coming out the filter area.

I guess I should ask when you remove the fuel line to the module, there would obviously be a fair amount of gas in the line itself, is there something special to do? I have to believe the anti-siphon valve plays a part in closing this off.
 
I've never had a problem with messing with these coolers. Not when Removing the fuel line that feed the CF, nor when pullling the line that sends fuel to the rail, nor when changing the filters. Strange.
 
So when you've removed the fuel line, did you do anything like manuallly shut off the siphon valve? or did the hose have something on the end that shut off automatically when not in the module. This is really strange now.
 
Starting to think that check valve in the module may be key. I guess I could try just remove the fuel line coming into the module.
 
If you remove the fuel line your module will still be full of fuel. Run this question by Merc. they're vey helpful 920-929-5040
 
The module would be full, as it should be, I have to figure out why there's continued flow of fuel...it can only come from the fuel line that's why I'm asking if I remove the fuel line, I assume there's some fuel in the line, but it should stop flowing fuel...correct? If not, the anti-siphon valve is clearly not working.
 
Trace the fuel line back to the tank. You should come to a fuel solenoid. With the ignition OFF that solenoid should be CLOSED. When the ignition is on the solenoid will open and allow fuel to flow to the CF. Maybe it's stuck in the open position??
 
So the fuel line coming into the module does not directly pout fuel into that cavity? I guess this is where the check valve comes into play. I'm assuming, without seeing the module taking apart, that the fuel runs into the module through a channel/cavity and the check valve is between that inlet and the cavity for the filter cartridge assembly. I would love to have one of these on the bench right now to see if the whole thing.

Seems it's between the fuel cut off siphon valve and a check valve...easy enough to figure out next weekend.
 
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