Low fuel pressure getting desperate for an answer.. please grlp

[DarrenC]

Any help is very appreciated. I have a 2001 C Ray Sundancer with dual MerCruiser Horizon 350 MPI‘s. Having a serious problem with low fuel pressure on port motor. We replaced today the fuel pump the fuel cooler the fuel regulator. pressure still at 20 psi and drops to zero doesn’t hold. Can anyone offer any suggestions as to what it may be.. engine only go up to 3,000 rpm half throttle and no increase in power after half throttle. Thank you.

 

[Espos4]

Some of these motors have 2 fuel pressure regulators. The "real one" is on the pump assembly on my Cool Fuel 3 set-up. Not sure what type of fuel cooler you have, possibly cool fuel 2?

There is also a dummy regulator up on the fuel rail, but since this isn't a return type system, that regulator doesn't control pressure. I believe its there because they use parts from the automotive set-up

 

[DarrenC]

We replaced the fuel filter, fuel cooler and regulator all inside the same box down below today. Did not make a difference except my pockets are getting shallow lol

 

[scoflaw]

More than likely a restriction from the tank to the pump. Check your lines, anti syphon valve/ electric cellonoid and everything else between the 2. Fuel rail clean ?

 

[Zim]

Check the lines for blockage all the way to tank. Also check lines for cracks.

 

[DarrenC]

More than likely a restriction from the tank to the pump. Check your lines, anti syphon valve/ electric cellonoid and everything else between the 2. Fuel rail clean ?

 

[DarrenC]

Can you explain what you mean by fuel rail clean?

 

[DarrenC]

Check the lines for blockage all the way to tank. Also check lines for cracks.

 

[DarrenC]

Do you mean fuel line from tank to fuel filter? Should I take this line off and blow it out? Trying everything!!!

 

[DarrenC]

More than likely a restriction from the tank to the pump. Check your lines, anti syphon valve/ electric cellonoid and everything else between the 2. Fuel rail clean ?

We changed the fuel filter.. should I remove the line and blow it out? It goes up to 28 psi at switch but then doesn’t hold it drops to zero.. however the first time I turn pump on it holds but as soon as we try again it drops to zero

 

[scoflaw]

Try rigging a line of the same diameter from a gas container plumbed to the fuel filter. Assuming you have a CF2, make sure the fuel line from the filter to the fuel pump is clear. E10 can raise hell with the innards of rubber fuel lines. You are going to have to verify that every inch of the fuel system is clear.

 

[DarrenC]

Try rigging a line of the same diameter from a gas container plumbed to the fuel filter. Assuming you have a CF2, make sure the fuel line from the filter to the fuel pump is clear. E10 can raise hell with the innards of rubber fuel lines. You are going to have to verify that every inch of the fuel system is clear.

 

[Zim]

Do you mean fuel line from tank to fuel filter? Should I take this line off and blow it out? Trying everything!!!

Yes. Lines should be removed and inspected.

 

[PlayDate]

Unfortunately, this isn't making a lot of sense.

If you could post the serial number of one of your engines....it would help sort out where to look. For the sake of discussion, I believe your tank line goes to a water separator then to a tank selection valve then down to the fuel pump assembly. You have replaced the fuel pump assembly and it really would be unusual to have a failure in the water separator or tank selection or crossover valves. You can eliminate a tank/tank line/water separator problem by switching to the other tank for the port engine.

If you have done that, then the line from the valve to the fuel pump assembly is next. Look for kinks and make sure the fittings are tight. If air is getting in the line....pressure will be a problem. Again....that would be unusual.

What is left is the fuel pump assembly and the line to the injectors. Where did the new assembly come from? To eliminate the fuel pump assembly.....I would pull the one off the Starboard motor and see if it works on the Port motor. If it does....problem solved. If it doesn't you know you have a pressure side blockage.

There was a retrofit check valve that some people installed to stop vapor lock on the pressure side. If that is stuck or partially stuck.....that could create the problem you have.

 

[Quint4]

Did you replace or clean this particular filter?

 

[cfd95]

just went thru the same problem on my starboard motor.
Replaced pump /cooler/regualtor.
Still no change 20 psi
Did a compression test 2 cylinders had 30 PSI compression.
Had bad valves and and seats.
With 2 dead cylinders there isn't enough vacuum to open the pressure regulator.
Before you start going further do a compression test.

 

[DarrenC]

Serial# OL 670519...OL 671965

 

[DarrenC]

I did a compression test on each cylinder last week and each read 185 to 190 all cylinders.

 

[DarrenC]

Did you replace or clean this particular filter? View attachment 57881 View attachment 57882

Yes I put a new regulator and screen in from Kellogg. New fuel pump and cooler from Kellogg.

 

[Espos4]

just went thru the same problem on my starboard motor.
Replaced pump /cooler/regualtor.
Still no change 20 psi
Did a compression test 2 cylinders had 30 PSI compression.
Had bad valves and and seats.
With 2 dead cylinders there isn't enough vacuum to open the pressure regulator.
Before you start going further do a compression test.

Vacuum applied to the regulator will lower the fuel pressure slightly, it doesn’t stop or start the fuel flow.

Under a heavy load or wide open throttle, the engine produces very little vacuum and this will raise fuel pressure to help compensate for the increased injector pulse width and high fuel flow rate.