High Fuel Pressure

[badrano]

I've been running rich and did a pressure check and I'm running about 70psi at idle.
Trying to get a couple questions answered so I can just hop from one thing to another to get me through the diagnostics.

Last season I got the fuel injectors cleaned which apparently they needed it. 2 of the 8 had a poor spray pattern. At the time I had checked fuel pressure and it seemed ok but never to did get out to check it with the engine under load. For the rest of last season, everything seemed ok.

I've only used the boat about 4-5 times since May this year and the rich condition became more noticeable yesterday as it almost stalled out on me at idle and my fuel usage for the trip I took seem unusually high. When I got back to the ramp, she was smoking pretty good.

My next step is to check vacuum. If that's is ok, I'm going to assume I have a pressure regulator issue. I realized I have 2 regulators.... one on the rail and one on the cool fuel 3 module. How do you determine which regulator is the issue? Should I just replace both? This is a 20 year old boat.
Looking closer at the fuel module, it looks like I could get the regulator off using a wrench (no real room for a socket, especially for the bolt that's right under the edge of the exh manifold). But then how can I make sure I've torqued the bolts back down afterwards? Do I have to consider pulling the fuel module off?
I understand that my serial number falls into the range of the service bulletin for the paint issue on the cool fuel 3 modules.

Any other advice/guidance to resolve the high fuel pressure?

 

[alldodge]

The Reg on the rail does not actually regulate pressure, it's there as a damper, it try's to reduce the pulses coming from the fuel pump.

Make sure the Reg on the fuel module is not clogged up. It needs to be able to return over pressure back to low side of pump module. Needs a good cleaning

 

[badrano]

The Reg on the rail does not actually regulate pressure, it's there as a damper, it try's to reduce the pulses coming from the fuel pump.

Make sure the Reg on the fuel module is not clogged up. It needs to be able to return over pressure back to low side of pump module. Needs a good cleaning

You just answered the general knowledge question I had.....How does a clogged regulator cause high pressure.

What you say about a clogged regulator is something I was wondering based other stuff I've read plus the fact I have the original fuel module.

 

[badrano]

Pulled the regulator off the fuel module. I don't have anything to compare to it to say whether or not it's significantly dirty or just a little dirty but there is definitely some grime on the screen.
Also, when I did pull it out, there was a string of paint hanging off the center part and across the screen....hard to tell if that was just from pulling it out or if the paint was truly blocking the screen.
Looking inside of the housing, looks like more paint might want to come off. The big question is do I try to scrape the paint out with a pick tool with the module still on the engine or should I pull the module off to really get a good working vantage point.
Or I see what looks like some type of repair kit - 8M0130861.

 

[alldodge]

I would remove to get a real close look at everything. Clean the entire unit and see if any other parts need to be replaced.

Did a search on the Regulator 892681 and was able to find for $107 and says it's OEM

Fuel pump

 

[badrano]

I would remove to get a real close look at everything. Clean the entire unit and see if any other parts need to be replaced.

Did a search on the Regulator 892681 and was able to find for $107 and says it's OEM

Fuel pump

Any thoughts on replacing the fuel module housing (8M0178981 / 892677) with the redesigned one so paint delamination will no longer be an issue?

 

[alldodge]

Any thoughts on replacing the fuel module housing (8M0178981 / 892677) with the redesigned one so paint delamination will no longer be an issue?

Depends on how well it can be cleaned

 

[Lpgc]

Just a side note, to compare how much fuel will flow through an injector at a certain pressure versus a different pressure compare the square roots of both pressures. E.g. If it's supposed to be 40psi but it's getting 70psi, square root of 40 is 6.32, square root of 70 is 8.37, 8.37 / 6.32 is 1.32 so the mixture will be 32% richer at the higher pressure.

 

[kd4pbs]

If the Mercruiser cooler is made of aluminum, I'd just de-paint it and use Alodine on all the exposed aluminum.

 

[badrano]

Just a side note, to compare how much fuel will flow through an injector at a certain pressure versus a different pressure compare the square roots of both pressures. E.g. If it's supposed to be 40psi but it's getting 70psi, square root of 40 is 6.32, square root of 70 is 8.37, 8.37 / 6.32 is 1.32 so the mixture will be 32% richer at the higher pressure.

Interesting analysis. I know my wallet felt that 32% richer mixture.

 

[Fun Times]

Now you have to be careful that the paint didn't make its way to the injector....Again?... Also you may have to clean the inner fuel rail and the fuel damper on the rail (that's similar to a regulator) as you wouldn't want to lose it's needed performance... I believe you can open the one up on the rail and clean it without buying an over priced one from Merc or search out a similar GM auto one or search the Merc part number for a good quality equivalent match number wise online or eBay to find hopefully an AC-Delco or just as good… be careful of the $10.00 ones you’ll probably see in a deep search.

Up to you but probably better to try and remove the module to see if you can get a good cleaning out of it as even if you think you can’t get it all, then you’ll have to remove it to get a new one installed anyway.

The top cover “bottom side” and passages needs inspection and possibly cleaning as well if you give it try…. Regulator areas….

I could see a partially blocked regulator keeping the pressure around 70 as there’s been reports over the years of being as high as 100psi when fully blocked.

 

[badrano]

Now you have to be careful that the paint didn't make its way to the injector....Again?... Also you may have to clean the inner fuel rail and the fuel damper on the rail (that's similar to a regulator) as you wouldn't want to lose it's needed performance... I believe you can open the one up on the rail and clean it without buying an over priced one from Merc or search out a similar GM auto one or search the Merc part number for a good quality equivalent match number wise online or eBay to find hopefully an AC-Delco or just as good… be careful of the $10.00 ones you’ll probably see in a deep search.

Up to you but probably better to try and remove the module to see if you can get a good cleaning out of it as even if you think you can’t get it all, then you’ll have to remove it to get a new one installed anyway.

The top cover “bottom side” and passages needs inspection and possibly cleaning as well if you give it try…. Regulator areas….

I could see a partially blocked regulator keeping the pressure around 70 as there’s been reports over the years of being as high as 100psi when fully blocked.

I popped the regulator off the rail, it was clean.

 

[badrano]

I guess I will figure out, but is it best to remove the fuel module by unbolting the brackets from the engine block or unbolting the module from the brackets. The side bolts are simple to get to, just not sure yet about the bolts on the back of the module.