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Low fuel pressure 5.0MPI

L

last_dollar

Member
My 2003 Mercruiser Alpha 5.0 serial number Om626769 has me stumped. I replaced the fuel pump with a Quantum E11004 recommended by one poster on this forum. I also replaced the fuel pressure regulator inside the Cool Fuel 2 module plus the one on top of the rail. Two fuel pump regulators? Oh well, it was in the parts diagram. I have replaced the fuel filter plus I have ran a hose from a separate tank directly into the inlet port on the filter thinking that the fuel cut off solenoid was somehow plugged up. When the key is turned on the pump runs for a few seconds and the pressure at the rail is 29 lbs. When the engine starts the pressure drops to about 25 lbs. The needle of the pressure gauge jumps around some. Stated pressure in the manual I have says it should be around 40 lbs. Although I have not ran the boat on open water (it's on the trailer) It seems to run and start very well. I'm thinking that under load the engine will not produce much power considering how different the pressure is from the stated required pressure in the book. I even tried a different pressure gauge thinking my old gauge was giving false readings....it was not. If I remove the vacuum hose from the pressure regulator the reading goes up about 5 lbs and from what I've read this is good, the regulator must be working. The only thing I can think of now is the new pump must be at fault and not able to put out the correct pressure. This Cool Fuel 2 module is practically impossible to remove and install. It takes literally hours to get it back in.....back breaking work in this heat. Would appreciate anyone who could think of something else before I go taking this pump out again.
 
Have you checked the voltage at the connector for the fuel pump??
Sometimes the relay will corroded causing a drp...
 
What was the psi before changing all the parts mentioned?
Did you replace the small screen found under the regulator down at the fuel pump?

Was the regulator OEM or aftermarket?
 
The regulator was Seirra brand. Not OEM but I've always had good luck with Seirra parts. The small screen under the regulator was replaced, it came with the regulator.
 
last_dollar said:
I may have used the wrong part ! Trying to cross reference the OEM to Sierra and it does not compute. Will call Sierra support today!!
Click to expand...
type your serial number in the merc parts section on this site - in upper left of this page 'Boat Engine Parts'=>sterndrive parts=> mercruiser parts

takes you to a splash page where you can put your serial number in-

MerCruiser Motor Parts at MarineEngine.com

Buy from the largest online inventory of genuine MerCruiser stern drive parts including discount aftermarket parts. New and vintage parts available at MarineEngine.com.
www.marineengine.com www.marineengine.com

Can also click all engine and drive models on RH side

What I like about this site it will list both OEM and aftermarket like sierra easy to cross check fitment- if you have the sierra part number you used it you can cross it to the OEM part. Also when you click on a part number detail at bottom of the page usually gives fitment and part number cross reference including merc superseded p[art numbers
 
Fuel pressure problem solved thanks to your response !!!

Yes, I installed the wrong pressure regulator. The regulator I ordered was Sierra 18-33207. This part number cross referenced to 807952A1 Quicksilver OEM. I thought it crossed to Quicksilver 861126A1. The 5.0 Mercruiser EFI engine uses the 807952A1 (Sierra 18-33207) and my 5.0 MPI uses 861126A1 with no Sierra aftermarket made. Apparently the EFI engine requires less pressure than an MPI engine. I have ordered the OEM 861126A1 and need my ass kicked for substituting aftermarket part numbers. Sometimes it works and sometimes it does not. Now it will take me several hours to pull the Cool Fuel 2 module out and reinstall it with the correct regulator.

I'm very grateful for your help!!!!! Many thanks!!!!!
 
last_dollar said:
Fuel pressure problem solved thanks to your response !!!

Yes, I installed the wrong pressure regulator. The regulator I ordered was Sierra 18-33207. This part number cross referenced to 807952A1 Quicksilver OEM. I thought it crossed to Quicksilver 861126A1. The 5.0 Mercruiser EFI engine uses the 807952A1 (Sierra 18-33207) and my 5.0 MPI uses 861126A1 with no Sierra aftermarket made. Apparently the EFI engine requires less pressure than an MPI engine. I have ordered the OEM 861126A1 and need my ass kicked for substituting aftermarket part numbers. Sometimes it works and sometimes it does not. Now it will take me several hours to pull the Cool Fuel 2 module out and reinstall it with the correct regulator.

I'm very grateful for your help!!!!! Many thanks!!!!!
Click to expand...
Shouldn't really need to pull the hole unit out to change the regulator... Remove the 2 nuts from the motor mount studs, slide the CF unit bracket off and let it hang a bit low, depending on room and ease of access to the regulator return hose at the unit, you could try disconnecting the other end at the fuel filter housing on the other side and route the hose and regulator together as needed... Then remove the 2 small bolts to the regulator once you figure out what side of the hose you want to disconnect from and reconnect to when more out in the open of putting it back together with the new regulator.

Hose numbers 12 and 28 are the same for regulator,
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Mercruiser (5.0l Mpi 350 Mag Mpi Mx 6.2l Mpi Sterndrive) Engine Components

www.marineengine.com www.marineengine.com
 
Dieter said:
type your serial number in the merc parts section on this site - in upper left of this page 'Boat Engine Parts'=>sterndrive parts=> mercruiser parts

takes you to a splash page where you can put your serial number in-

MerCruiser Motor Parts at MarineEngine.com

Buy from the largest online inventory of genuine MerCruiser stern drive parts including discount aftermarket parts. New and vintage parts available at MarineEngine.com.
www.marineengine.com www.marineengine.com

Can also click all engine and drive models on RH side

What I like about this site it will list both OEM and aftermarket like sierra easy to cross check fitment- if you have the sierra part number you used it you can cross it to the OEM part. Also when you click on a part number detail at bottom of the page usually gives fitment and part number cross reference including merc superseded p[art numbers
Click to expand...
Yes, I believe that this is one of the only websites that offers aftermarket cross reference which really makes it nice to see what other parts might fit for reassurance. :cool: (y) :) Marine engine is a trustworthy site for looking up parts and other things boat related.
 
last_dollar said:
Fuel pressure problem solved thanks to your response !!!

Yes, I installed the wrong pressure regulator. The regulator I ordered was Sierra 18-33207. This part number cross referenced to 807952A1 Quicksilver OEM. I thought it crossed to Quicksilver 861126A1. The 5.0 Mercruiser EFI engine uses the 807952A1 (Sierra 18-33207) and my 5.0 MPI uses 861126A1 with no Sierra aftermarket made. Apparently the EFI engine requires less pressure than an MPI engine. I have ordered the OEM 861126A1 and need my ass kicked for substituting aftermarket part numbers. Sometimes it works and sometimes it does not. Now it will take me several hours to pull the Cool Fuel 2 module out and reinstall it with the correct regulator.

I'm very grateful for your help!!!!! Many thanks!!!!!
Click to expand...
Anytime. That is why I love this site! Yes EFI is lower pressure for throttle body injection vs multiport. If you order by serial number here you will always get the correct part.
Fun Times said:
Yes, I believe that this is one of the only websites that offers aftermarket cross reference which really makes it nice to see what other parts might fit for reassurance. :cool: (y) :) Marine engine is a trustworthy site for looking up parts and other things boat related.
Click to expand...
Absolutely they have been my go to for years. I assume you are the same Fun Times as on Iboats forum? I cant understand why they don't do something similar...

When I did my repower in 2015/16 I did a 4.3 => 5.0 swap and used these parts lists extensively to see what I could use off the old engine vs buying a complete bobtail. Saved me about $1500 back then .
 
I simply have no room on my 2003 Sea Ray 225WE to gain access to the cool fuel 2. I just pull it out the front by disconnecting all the hoses. Going back in is the problem, requires two people. I'm glad I did pull it out though because I seemed to have a damp connection on the return line at item 17 in the diagram! Must have been a very small leak but any leak with gasoline is dangerous! To be cautious I have ordered item 17 and 18. Didn't like the way the inside of item 17 looked and was afraid it would not seal. Looks like I'm down for another weekend!! Thanks again for your sharing of knowledge.
 
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