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

You will get very little info from that year ECM. It will tell you nothing about the fuel side of your engine.
 
Had a friend go through something somewhat similar this year on a 2010 310 dancer with 350s. He had a fuel pump burn out due to a crack in an elbow where the fuel line meets that tank. The crack allowed the pump to suck air and would lose fuel pressure. I don't know any more details than that, but might support checking the lines thoroughly to ensure you have no leaks/cracks.
 
Darren,

Thanks for the serial numbers.....it makes it easier to sort out the components.

I assume you are reading fuel pressure at the Schrader valve located on the fuel rail. What doesn't make any sense is that engine should not start or run with 20 psi at the fuel rail which leads me to believe your gauge is wrong or the Schrader valve has a bunch of debris behind it. The injectors require 38-40 psi just to fire anything less and the starter just spins. You can unscrew the Schrader valve with a tire stem core tool and check it.

If it is the gauge....it will read the same on the good engine. I'm curious what that engine reads for fuel pressure.

There is a point in diagnostics that you just have to start over. You have done a lot of replacement and still have the same problem. If it was my boat, and the gauge and Schrader valve check out.....I would swap the parts from the good engine one at a time until the problem went away. It is something simple but it isn't obvious.
 
If the correct pumps were installed and wired correctly you need about 42 psi to even run correctly. So either the fuel lines are severly restricted, the pump is bad, or the injectors are leaking
Run a remote outboard tank at the fuel sep.to prove the fuel lines
 
If the correct pumps were installed and wired correctly you need about 42 psi to even run correctly. So either the fuel lines are severly restricted, the pump is bad, or the injectors are leaking
Run a remote outboard tank at the fuel sep.to prove the fuel lines
We did that off the start and was only getting 22 psi.. and not holding. Someone ran another diagnostic today and getting around 30 psi.. it was doing same with desperate tank
 
Did you get this figured out? What do plugs look like? I may have similar issue and leaning toward fuel pressure regulator.
 
Start with the simple stuff first. Is the tank vent Ok? Loosen or remove fuel fill cap and See if issue resolves. If not, check the anti siphon valve with a new one or straight elbow temporarily. An internally collapsed fuel line can suck shut reducing pressure as well.
 
Any update on this thread?
 
Can anyone tell me where to find the anti-syphon valve? Right engine (7.4 454 ) quit while running about 3100 rpm. Limped in on left engine. Right one won't start, now. Appears not to be getting fuel.
 
Can anyone tell me where to find the anti-syphon valve? Right engine (7.4 454 ) quit while running about 3100 rpm. Limped in on left engine. Right one won't start, now. Appears not to be getting fuel.


Hey Ron,

Welcome to CSR!

Unless you have different engines in your 1993....I presume you have carbs instead of EFI? Does it crank and not start? If you do have carbs then the fuel pump is probably mechanical and may be the problem.

In regards to anti-syphon valve.....I'm not sure what you are referring to on your engines.
 
Any update on this thread?
Good afternoon, just letting everyone know the update and fix to my problem. After much research and replacement of different parts. The problem was the fuel injectors. It would not get the proper horsepower under load in high pressure. I changed all the injectors and the motor runs beautiful, everything including RPM just as it should be. Thank you everyone and thanking god for helping me resolve the issue.
 
Hey Ron,

Welcome to CSR!

Unless you have different engines in your 1993....I presume you have carbs instead of EFI? Does it crank and not start? If you do have carbs then the fuel pump is probably mechanical and may be the problem.

In regards to anti-syphon valve.....I'm not sure what you are referring to on your engines.
Hi John, and thanks for the welcome and the reply. Yes to carbs. Starboard engine died on me when cruising about 3100 rpm, about 25 Kts. Luckily, I was only about 3 miles or so from home docks after being out in the ocean for some fishing. Limped back in on port engine, and parked on the "alongside" outside dock rather than trying to maneuver single engine into my usual back in tight spot. Not getting any fuel to carb. I had seen mention to anti-syphon valve earlier in this thread, ergo the question. Son and law and I are going to remove the mechanical fuel pump this morning, and probably order a new replacement this afternoon after confirming the P/N. Probably looking at this one: https://www.amazon.com/MerCruiser-M....4l+sea+water+fuel+pump&qid=1572861944&sr=8-1
Will see how it goes. Again, thanks for the reply, and have a great boating day.
 
That should work fine. It is a pain on the Starboard motor.....hopefully your son in law is small in stature or has really long arms! :)

I believe your pump is integrated with the raw water cooling pump so you might want to pull the whole assembly and replace the impeller at the same time.

We had a thread with pictures at one point but the pictures seem to have disappeared.

http://www.clubsearay.com/index.php?threads/7-4l-combo-sea-water-fuel-pump-maintenance.918/
 

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