Boat seems to starve for fuel

[paulwolfe]

I have a 06 21I. It seems to be starving for either air or fuel. I pulled the water separator off yesterday and noticed no water in fuel when I let it settle. Fuel was clean. I changed the fuel filter although it was very clean as well. This is the 340 HP Marine Power 5.7. It has the electric carter fuel pump on the starboard side. This may be the root. In the posts I've read quite a bit about the fuel regulator? Has anyone had issues with that? What are the symptoms? My boat doesn't seem to have access to the valve at the tank that I've heard some have had issues with. The last time I had the boat out, it ran fine until I was bringing it in - started to sputter. When I was working on it yesterday I noticed some black carbon looking exhaust. Makes me think it's an air thing? Any ideas men?

[ajholt7]

Had you sat for a while before heading in? If I sit for a while when the engine is warm I sometimes get vapor lock. I just leave the hatch open for a little while and all is good.

[chpthril]

Have you ever cleaned the spark arrestor?

Is the engine reaching normal operating temps? 'bout 170*.

How fresh is the fuel?

Was it run then stored with a fuel stabilizer in the tank?

[paulwolfe]

Have never cleaned spark arrestor. Yesterday when I was working on the boat the engine was just getting warm, however as the day progressed it wanted to stay running for a shorter and shorter amount of time. I don't think it is bad fuel. Yes it had stabil in it, However, I just gassed it a month or so ago. About 1/2 tank. I will find a way to check fuel pressure today. I don't have a gauge. When I depress the valve on the fuel crossover tube the fuel is there but very low pressure or so it seems. I pulled the regulator and could not get any air to go through the center tube of it. This may be normal. What is on top of my fuel water separator that is electric? Is that a secondary pump? I thought I saw that you posted something about a diaphram in the regulator on the top of F/W separator? May be an older motor. Thanks for the help.

[paulwolfe]

No, just a constant first of the season run. It was cold that day too. I know these things will vapor lock - mostly because of design. There is very little air going in to the engine compt. Thanks tho.

[chpthril]

Actually, the Marine Power fuel system has a cooler, so Vapor-lock is hardly ever an issue. When it is, it's noticed on start-up (hard to start) then clears out once cooler fuel from the tank reaches the fuel rail. Now, any fuel injected engine can vapor-lock if pressure is lower then normal.

[paulwolfe]

Okay Chpthril,

So I plugged in to the injector rail with a injector pressure gauge. It looks like this: Turn key, pumps turn on PSI jumps tp 60 psi. 20 seconds, pumps turn off and pressure disipates to about 5. So in other words, the lines is not holding pressure. Doesn't this mean I have a faulty fuel regulator valve? Engine will also not start. It tries to fire - but will not go. Any ideas?

[chpthril]

Okay Chpthril,

So I plugged in to the injector rail with a injector pressure gauge. It looks like this: Turn key, pumps turn on PSI jumps tp 60 psi. 20 seconds, pumps turn off and pressure disipates to about 5. So in other words, the lines is not holding pressure. Doesn't this mean I have a faulty fuel regulator valve? Engine will also not start. It tries to fire - but will not go. Any ideas?

Could be, but could also be the pump itself bleeding back. This will make for hard starting, but if the pressure is within spec, the engine will run normal. Once the engine is shut off, the drop in fuel pressure can lead to vapor lock.

Run the test again, but once you see 60 psi, pinch off the return line. If the pressure holds, its the regulator, it the pressure drop, it's either a leaking injector or fuel pump. Run the pressure test one more time, but this time pinch off the supply line. if pressure holds, it's pump, if it still drops, it's an injector or 2. This can lead to hard start, vapor lock and a rough running engine.

[paulwolfe]

Chpthril -

Both tests came back disipating pressure. Would I pull plugs and look for something soaked at this point? Is the press. regulator still a possibility? I then squeezed off both return and feed line and still it bleed off. That sort of rules it to an injector in my book?

[River Runner]

Remove the vacuum line to the pressure regulator. Block the vacuum source. Start engine. If fuel is coming from vacuum port on pressure regulator it is bad.

When blocking the return line on fuel pressure test the pressure should INCREASE.(engine running) If not regulator is bad.

Very rare for regulator to fail but it does happen. Most likely one way check valve in fuel pump failed.

[paulwolfe]

River Runner =

Wouldn't you think it's an injector? I tried pinching both supply and return fuel lines together and it still would bleed off.
I'm also getting some black out the exhaust = running very rich - will barely idle.

[River Runner]

River Runner =

Wouldn't you think it's an injector? I tried pinching both supply and return fuel lines together and it still would bleed off.
I'm also getting some black out the exhaust = running very rich - will barely idle.

If both were pinched at the same time and you still lost pressure(assuming both lines were COMPLETELY blocked off) then yes an injector could be bleeding down.

If so you need to remove the injectors and fuel rail and while still hooked up, energize fuel pump with key on engine off and you will find the leaking injector. No smoking allowed while performing this test!!!

[jsz]

Have you thought about a bad anti siphon valve at the gas tank? Mine was having the same problem and it now runs fine after the dealer replaced the valve. I looked at the old one and even though it seemed to function (spring loaded ball was not stuck) they said it was making the fuel pump work too hard to draw fuel causing it to starve.

[paulwolfe]

This is a mystery boat. I pulled the injectors out. keyed on the power, pumps ran pumped up to 60psi. Not a single drip. I put it all back together screwed in new plugs and fired it back up. It cranked right up, but wont idle for long. Then I noticed the throttle wasn't working along with the rest of the accessories. So, I spent this evening looking for a bad ground. Battery has plenty of juice. Good ground on the back of engine. Looked uder dash - the ground block up there looked good no corosion and snug. So I noticed too my radio remote was flickering on the dash, I turned the heater on - flickering stopped. Good lord. Need to get the meter out and start process of elimination. ANy ideas would be appreciated.

[paulwolfe]

I think I better find that ball valve and take a look at it. Took care of my electrical issues. Engine runs but still choppy. The fuel pressure hangs right at 50psi. I'm down to just fuel regulator and ball valve at tank for the fuel system