xlint89

Well, what a bust. Literally.

Yanked the cool fuel from the engine. Looked at the O ring I was wondering about and it seats right into the recess of the pump. (DAM.......I was hoping it was something stupid)

While it was out I decided to verify all connections are good. Puyt a wrench on the fitting between the regulator and the return hose, tightened it down, and...... SNAP. Brass fitting broke the threads right off inside the regulator.

So now I'm dead in the water until I can get my hands on that part.

While it was all out and I'm curious about that O ring, I put my vacuum pump on the port of the cooler that supplies the fuel rail hose. Put my finger over the pressure regulator hole and the end of the hose going back to the fuel filter. Pumped it up to around 10" of vacuum and it held. No air leak between fuel filter to fuel rail supply hose. .

gdawson1970

Been there, done that...had to order the Merc only brass fitting for $23.....I'm also suffering from a fuel delivery issue so I am following this thread. ( 502 mag mpi so it's basically the same engine as yours )
I have the Service manual #23 on PDF I can send you if you send me your e-mail address?

xlint89

Thank you for the offer. I finally got a copy of the manual shipped to me on Monday. Now i got some trouble shoot tables i can try out.

This thing's been fighting me from the get go. Got the boat shipped here in May and haven't been on the water yet.....

Ordered the brass fitting off Ebay. 2 days later I get an email saying it's unavailable and the order has been canceled.

Ordered another one Tues night after getting the notice. Tracking number says it was delivered the next day. Shipped from some city in CT and was delivered to the same city in CT. WTF????

This boat is possessed.

xlint89

All the parts finally showed up this week and got installed. I have mixed feelings about the results.

1. Vacuum tested the system by inserting a hose into the cooler where the supply hose feeds the rail. Capped off the fuel inlet fitting at the water seperator/filter. It held 15" of vacuum with no drop in reading.

2. Blew into the fuel supply hose from the tank to the filter. No air leaks and anti siphon valve holding.

3. Used pipe sealant on ALL hose fittings.

4. Used the vacuum pump hooked up to the cooler to prime the fuel lines and new fuel filter. Drew 4" of vacuum, but would drop down to 2" when I would stop pumping

5. Replaced the pressure regulator mounted to the fuel rail.

6. Checked screens/filters, hoses, and fuel filter housing for obstructions. No problems found.

Key on a couple times to prime the pump. Holding 32 PSI still. The manual says i should be taking reading while the pump is running/priming for those 2 seconds. When that is done, I'm seeing 38 PSI. (same as when you remove the vacuum hose from the manifold)

Fired up the boat and the fuel pump whine was less noticeable. Thinking maybe this is normal volume?

Held the pressure release button on the fuel gauge to view the fuel flow from the rail. Lots of bubbles at first, which makes sense since the system was open. After about 15-20 seconds of holding the button open, it pretty much stooped . Very few and very small bubbles would escape after the initial bleed.

So according to the repair manual, I'm good to go.because I'm only losing 6 PSI from the 38 PSi at prime to 32 PSI when idling.

There's nothing else I can do other than drive the boat and see what it does at this point.



.

AllDodge

iTrader: (1)

I see an issue with these numbers, I would like to see no more then 1 hg

gdawson1970

I'm fighting mine too man.....runs great on the hose at the house....put it in the water and an hour down the water it starts surging, fuel pressure starts dropping down to 20 back to 40 then back to 20.....it's about to get a nice Holley 4 barrel and Victor Jr intake and be done with the EFI

xlint89

That was pulling the fuel from the tank, through the anti-siphon valve,fuel filter, fuel pump, and out the cooler..

Do you still think I should only have 1" going through all that?

I wonder what it would have been if I installed the vacuum pump before the fuel pump inlet.

Thank you.

xlint89

Yours may be the fuel pump getting hot (starting to fail) after an hour?

Do you have the VST gen I cool fuel system? I've read installing a return fitting eliminates a lot of the fuel problems with that system.

AllDodge

iTrader: (1)

Once everything is full of fuel, then it should be the same as drawing straight from the tank. The electric pump doesn't suck much at all, not like the mechanical pump.

xlint89

Thank you. Will be looking into this further.