5.0 mercruiser mpi fuel pressure

[Jerry230Atlantic]

I have a 2007 Rinker with 5.0 MPI engine, ser #0W381650. She has 75 hours on the engine. My only problems are cold start RPMs stay at about 650 slightly rough RPMs. I ran a lot of fresh fuel through it and I'm using Mercruiser quick clean additive. I replaced the IAC filter and checked that it functioned. My other issue is hot restart. I have to advance the throttle a little acting like it has too much fuel. So the other day I put a fuel pressure gauge on the fuel rail and with cold start it was at 90 PSI until I Advance the throttle a little then it dropped down to 60 PSI. I checked the fuel gauge compared to air pressure and it is accurate. Before I buy a fuel pressure regulator is there any test that I should do? I believe the fuel pressure supposed to be 45 PSI? I don't want to buy the wrong part. I don't want to lose my man card and go to the dealer! Thank you

 

[alldodge]

Your regulator is either stuck closed or plugged up, and your pressure should be 43 psi.
Remove the regulator and look at item 14 the filter screen. They get clogged up some times. Also check the hose going from the regulator back to the filter. If after cleaning and your still getting high pressure then you need a regulator

http://www.mercruiserparts.com/bam/subassembly/31848/7585/50

 

[Jerry230Atlantic]

Thanks . Very easy to pull regulator out and my screen is perfectly clean. I have been researching a new one it seems as though 60 PSI might be right for that one?

 

[alldodge]

Thanks . Very easy to pull regulator out and my screen is perfectly clean. I have been researching a new one it seems as though 60 PSI might be right for that one?

Your motor runs at 43 psi, the regulator max pressure is at 60 psi and above that can damage it

 

[Jerry230Atlantic]

Thanks. It is stamped 4 bar on my regulator and that means the 60 psi makes sense? It is the factory one and I am at 75 hours. I don't have the specs though. Is the 45 psi from the manuel? If the 60 is right my big question would be is it right for it to be at 90 PSI until I bump up the throttle ? It does go to the 60 as soon as I hit 1000 rpms and stays at 60 psi at 650 rpms after the short bump up in rpm

 

[alldodge]

You are correct about the MAP/T being 3 bar, but this has no effect on fuel pressure, it measures air pressure and temperature
Merc 885165. Bosch 0261230075, GM 12568929

The fuel pressure comes from Merc manual 31
You have to much pressure

 

[Jerry230Atlantic]

Prior to last night I was only working on the upper regulator, I had no idea there are two regulators in this sytem. My problem regulator is at the Gen 3 cool fuel module. When attempting to clean paint out of modual I dropped the spray nozzle tube from carb clean into the module so I ended up pulling the module off. I had read about being careful on the cooling lines and didn't hurt them. The only line I couldn't undo was the high pressure push pull line held in place with a pin. I sure tryed to pull with pin out. I couldn't find my spring relise tool to see if its held in place like that. What is the trick to getting the high pressure fuel line off? I do have everything back together now and it's running fine but I know I'll be addressing this again. There was no paint flaking from inside the module only the lid I'll probably end up buying a new lid offseason. Thanks

 

[alldodge]

Your fuel pump is first Gen cool fuel with boost pump and does not have any paint in it and it never has. The paint was found only in the first years of the Gen 3 cool fuel like the one below

When the pin is removed the line is being held in place by its O rings only. They are just stuck and since there is no issue with fuel supply I would not remove it. If it is removed you will need to replace the O rings. Places to concentrate for over pressure is the regulators and the line going from regulator back to filter canister.

 

[Jerry230Atlantic]

That picture is what mine looks like. I had to be careful with the plastic fittings for the cooling lines. When I took it apart it look like half the tank was painted inside it was a clear line showing paint and not painted. None of the paint inside the tank was loose. The paint that was loose in huge chunks was in the lid right next to the pressure regulator and stuck on the regulator. I'm surprised I wasn't able to pull the fuel line now with it just being the O-rings. Hope to do sea trial tonight but it sure did good with the flusher test on land. All starting issues resolved and normal fuel pressure. I'm happy to do the work myself . if I was ever out on a trip somewhere or in some situation at least I'll have a better chance to get my boat running. I believe depending on the mechanic that would have worked on this they might have just cleaned it before me and been reasonable or had me buying the fuel modual amd more!

 

[alldodge]

OK my bad, you have a bravo drive