1997 PCM GT-40 Low Fuel Pressure/won't run

[Rideaneversummer]

I have a 1997 PCM Fuel Injected GT-40 in my Hydrodyne Nexstar. last week I did a tuneup, replaced dist cap, rotor, plugs, wires, and fuel filter. Took it out over the weekend and it ran great for an hour. We then went and tied up with some other boats for an hour or so. Started it up to drive back to the dock, a couple hundred yards from the dock the engine stuttered, choked then kept running for a few seconds, then stuttered again and died. It would not re-start (sounds like a fuel issue). I got it home and put on the faka a lake yesterday and it started, then stuttered and died, and I couldn't get it re-started. So I got out the fuel pressure gauge and it only has 10 psi on the fuel rail.

When I replaced the fuel filter, I could see that the little clear tube in the FCC had been replaced with a black hose segment so I didn't replace that (I know that is a common problem)

Fuel relay-when I turn the key I hear the fuel pump charging up the rail, this wouldn't happen if it was a bad fuel relay right?

Is there a way to test the high and low pressure fuel pumps individually? or since I'm getting 10 psi at the rail can I assume it's the high pressure pump?

Any other suggestions on things I should look for?

Thanks,

[Rideaneversummer]

Update, I went out there tonight to see what else I could learn. I was going to take the FCC canister off and check the short hose inside. When I removed the drain plug only a little bit of fuel came out. So the FCC is not getting fuel. To double check that, I pulled off the hose from the LP pump to the FCC and turned the key several times and sure enough, no fuel came out. So I know that the LP pump is not doing it's job.

Before I go out and buy a new LP pump, is there any other reason the LP pump would not be pumping fuel? Is it possible it lost it's prime and I need to do something to prime it? Anything else I could be missing? Yes there is plenty of gas in the tank.

[s_kelley2000]

Is the pump making any noise and just not pumping much fuel? If it's totally dead it could be the relay or wiring but in your original post you said you can hear it? It could be the anti-siphon valve is gummed up preventing fuel from being pulled. This is a check valve on the gas tank connected to the fuel supply line. If it's not that then it's probably that your pump is on it's last leg.

[MTRBTR]

Those LP pumps are pretty cheap

[DanielC]

The low pressure pump has one job. Keep the FCC full of fuel.
This is what the inside of the LP pump looks like.


Notice the screen wrapped around the central body of the pump rotor housing. It can get clogged.

This is the order that parts go back on the pump, top first, the screen, the metal disk on top of the rotor, the gasket, and then the pump cover.


Screen and rotor disk,


Gasket,


and then the top cover. sorry, no picture.


Go to this thread.
http://www.planetnautique.com/vb3/sh...=fuel+pressure

The thread shows you how to use the test port of the engine's computer, to turn the fuel pumps on. you can also turn the fuel pumps on by jumping pin 30 to pin 87 on the fuel pump relay socket.

The low pressure fuel pump should put out about 5 to 6 PSI, and flow around a quart of gas every 15 seconds.

Be careful of spilling any gasoline in your boat. If you take the low pressure pump apart, make sure there is no fuel leakage after you put it back together.

[Rideaneversummer]

Is the pump making any noise and just not pumping much fuel?.

Yes, the pump is running. I ran the pumps by grounding the STO. I put my hand on both pumps and you can feel a slight vibration on both, indicating that the pumps are running. After doing that last night I did some more reading, and the anti-siphon valve came up but I didn't have time last night. I plan to check that tonight. I plan to pull the anti-siphon valve off and check it, then put a hose in a can of gas and run the pump to see if the pump will pump fuel that way. If it's still not working I will replace the pump.

MTRBTR, you are right $126 is relatively cheap, but I've never been a fan of throwing money at parts without being sure that's the problem. I would rather fully diagnose a problem first, then replace the parts that I know need replacing.

DanialC, thanks for the great pictures. If the anti-siphon valve looks good, and the pump still won't pump fuel even from a different can I think I will pull the pump apart and check that screen. What can it hurt, that would be my last option before just replacing the whole pump.

Thanks everyone for all the replies.

[MTRBTR]

$126 seems really high. Don't blame you for figuring it out for sure. Seems like I paid less than $50 for mine.

[Rideaneversummer]

Update,

I went out last night for some more trouble shooting. I pulled off the anti-siphon valve and it looked good. The ball moved freely and it was not gummed up. I then took the LP pump feed hose without the anti-siphon valve and put it in a can of gas and ran the LP pump. It started pumping gas. I hooked the LP back to the FCC and ran the pump. Psi on the fuel rail went right to 40 psi!. Since the anti-siphon valve seamed good I thought maybe it was the fuel pickup in the tank so I pulled that out. It was a poly hose with a screen on the pickup end. Screen was clear, hose looked good. Put it back in the tank, hooked up the anti-siphon valve, hooked up fuel hose, removed the LP to FCC hose and ran the pump. Sure enough, it started pumping gas out of the tank. Re-attached LP to FCC hose and ran the pumps. Psi on the fuel rail went right to 40 psi. It seamed like everything was working properly so I turned on the fake-a-lake and started the engine. It started right up and ran great. Psi at the fuel rail stayed right at 35 psi.

So what was the problem? I'm not exactly sure. I know the LP pump was not pumping fuel out of the tank, but I don't know why? The anti-siphon valve and the fuel pickup both seamed to be working ok. I don't know if there was some air trapped somewhere that wouldn't let the pump prime or what. It's pretty baffling but it's working for now so we'll see how it does on the lake this weekend.

[DanielC]

In my post look at the first picture, the one with the fuel pump rotor exposed. The vanes in the pump are not spring loaded, you will notice one is retracted.
My theory, a bit of dirt, or some gasoline residue can make the vanes not extend out to the inside of the pump body. Then the pump does not move gasoline, even though it is spinning.

[Rideaneversummer]

Daniel C, that sounds like a good theory. Would 1 stuck vane out of 4 cause the pump to completely stop pumping? I really don't know?

I didn't pull the pump apart because it started working before I got to that step, but if it was one or more stuck vanes in the pump that would still be odd that they would just start working all of a sudden. I'll just have to see what happens when I get on the lake this weekend and romp on it. I will report back next week.

[jonsquatch]

How long a hose was on it when you ran it out of the can of gas compared to the normal run. If it was sticking enough that it couldn't get a good enough prime to pull the fuel from the tank maybe that change was just enough to get it to prime and and then it was able to free up the vanes?

[skiflyer45]

Have you checked the in-line fuel filter? $10 at autozone....It's a cheap and quick. It sits on the passenger side under the rear floor board. Take off the motor cover and lift the floorboard and you will see it. Not a common issue but you never know.

[DanielC]

"Have you checked the in-line fuel filter? "
I am pretty sure the 1997 boats did not have this filter. Later models did.

[Super_sport]

SO my 1995 Super Sport was having similar issues but I was getting a really loud WHINE from the High Pressure Pump (Non FCC).. it is located right after the low pressure pump at the motor. No power off idle! Took my low pressure pump apart too.. looks just like yours. replaced the fuel filter with a clear Atwood model... so I can see the fuel flowing.. which is nice.. if the pump primes, its not the breaker or relay. I had to Replaced the High Pressure pump (Nautique Parts thank you!)... hard to come by.. and $285! the low pressure pump is about $120.. Is it possible for the low pressure pump to sound like its working, but not pump enough fuel and burn out the High pressure pump? Does your Hi pressure pump whine at all? Wheep - Wheep - Wheep pulsing noise while its running ? After replacing the high pressure pump, it runs like a champ.. until yesterday, when I started to hear the pump do its whine again... maybe its the low pressure pump starving the hi pressure pump...?

[Rideaneversummer]

jonsquatch: the hose was the same length, I just took the anti-siphon valve off the end of the hose and put it in a can of gas

Daniel C: you are correct, my 1997 Hydrodyne does not have an inline fuel filter, although that might be a good thing to add.

Super_sport: You should check your fuel pressure at the rail and make sure you are getting enough fuel. Second you should lest the flow of the LP pump. Do that by unhooking the line from the LP to HP pump and jumping the pumps as described above. It should flow about a quart of gas every 15 seconds (or 1 gpm). The LP pump can sound like it's working, but not pump fuel.


I had my boat out for several hours on Sunday and it worked perfect. My best working theory on what happened is that the engine bay got hot and I didn't properly cool it down (run blower for long enough, open engine bay) before starting and driving the boat back to the dock. This must have caused some sort of vapor lock or fuel starvation problem that caused the LP pump to loose prime, and it seams like the LP pump was not able to gain the prime back with the anti siphon valve in line. Once the anti siphon valve was removed it was able to prime. Once the pump was primed it worked fine. That's my best guess so far.