Fuel Pump or ? on Excalibur that stops running randomly

[SkiLunautique]

Have an 05' Excalibur SBC 350 (206 SNOB) that is having intermittent problems of simply dying out typically in gear at idle or just coming up off idle. Each time it occurs the next day or adding fuel (thought bad gas was the culprit initially) seems to resolve the problem and it fires up again, runs fine until the next event. It currently is running, at the moment.

Boat runs perfect otherwise so ruled out tune-up, etc., have bypassed the lanyard to rule it out, the FCC filter was new as of last fall, fuel is fresh and contains no ethanol.

Have heard there may be another in-line filter before the LPP (low pressure pump) however I cannot locate it, anybody know where it might be?

When the ignition is cycled on, by touch both the HPP (high pressure fuel pump) and the LPP are cycling on normally, which should rule out the fuel pump relay or fuse.

I am leaning towards the LPP being bad however before I replace a $150 pump I wanted to see if any of you have a known way to determine otherwise or if the problem lies elsewhere.

Have not put a fuel pressure gauge on the schrader valve (60psi is norm)cause that requires a trip to the mechanic, and even if that is low which pump would be the cause?

Thanks in advance for your time and thoughts!

[AirTool]

There was a recall from PCM on the LPP for some serial numbers in that era. But they failed on the first trip or so. I don't see how you could have made it this far with the bad pump. Check the PCM website for the serial numbers. If you are in the window, Post the color of the plastic plug on the pump and I'll tell you if it has been changed.

I've posted a pic of the coarse filter. Very few years have them.

[SkiLunautique]

Thanks Tool, original owner and pump never changed to my knowledge. If you are referring to the electrical connection plug color - grey to another grey. Pump is black everywhere else, you can even see paint on the power/ground wires at the base, which would lead me to believe it is original.

Checked PCM's site and did not locate any recall notices, most info is 07' and newer. I will email them in the AM.

One surprise I did find was the fuel supply line from the LPP, ran forward then down and aft, it was bent to the point of almost kinked where it returned back to aft. Had to cut out the factory wire ties and adjust things so it was positioned better. Ran before and after so not the issue, more a wt.....

[AirTool]

The link is dead. I've attached the letter and pasted below text from PCM. Here are the SN number range

Model Year 2006 PCM Owners Serial #’s 460000-461457

I see now it is 2006 only but check your S/N - it is probably a 45 number.

PCM: "If your pump has a black dot on the wiring harness, it needs to be replaced. If it has a white dot on it, then it has been replaced."

I was thinking it was the plug color but it is the dot color. I had the white dot so PO had it changed.

[DanielC]

I know more about the GT-40 Ford engine than the GM engines, but some things are similar, or the even the same.
Here is a picture of the low pressure pump on the GT-40.

It has a screen in it, that can get dirty. The screen is hard to see, here is the same pump without it.


Here is how to check the fuel pressure on a GT-40. You may think it does not apply to you because you have a GM engine, but there is some information on the specs on the low pressure fuel pump. I believe it is the same on the GM engines. go to post #8 in that thread.
http://www.planetnautique.com/vb3/sh...=fuel+pressure

Here is brief explanation on how the fuel system works.
The low pressure pump draws (sucks) gas out of the fuel tank, and fills the FCC. The FCC has a second return hose that goes back to the fuel tank, located at the top of the FCC. The low pressure pump has one job, keep the FCC full of gas.
The high pressure pump in inside the FCC, inside a filter. The high pressure pump supplies more than enough gas to the fuel rails for the injectors to satisfy engine demands. There is a pressure regulator that bleeds gas back into the FCC to maintain a constant fuel pressure in the fuel rails.

My boat is a 1997 Ski Nautique. Sometime after my boat was made, they added a second fuel filter between the gas tank and the low pressure fuel pump. If your boat has this, it should catch any crud before it reaches the low pressure pump screen. I do not know if your boat has the second filter, you will have to find this out.

I do not know about the GM engines, but the Ford engines have no feedback to the engines computer on the actual fuel pressure. The computer just assumes the fuel pressure is correct. Because of that, you have to know what the fuel pressure is WHEN YOU ARE HAVING PROBLEMS. This requires you get a fuel pressure gauge, and know how to hook it up safely, and drive the boat with it attached, and be able to do it without having any gasoline leaks.

Just because the fuel pump relay cycles the pumps on does not mean it is good. It could be intermittent, and even though the contacts in the relay are being pulled closed, they may not actually be making a good contact all the time. As much as I hate to diagnose problems by just replacing random parts, the relays are pretty cheap to get. One way to bypass a relay is to jump pin 30 on the relay socket to pin 87.

If you do not know the pin connections on the cube relays, this thread has the information. Again, the thread is more focused on Ford engines, but there is still some useful information for you "off brand chevy" engine owners. Sorry, Ford VS Chevy rivalry exists on boat forums too.

[AirTool]

I do not know about the GM engines, but the Ford engines have no feedback to the engines computer on the actual fuel pressure.

No feedback on GM either. There is a regulator that keeps the proper pressure (limits) and as you say, the pump has to be delivering the pressure (and flow) or there is not enough fuel.

[TRBenj]

When the ignition is cycled on, by touch both the HPP (high pressure fuel pump) and the LPP are cycling on normally, which should rule out the fuel pump relay or fuse.

Just because the fuel pump relay cycles the pumps on does not mean it is good. It could be intermittent, and even though the contacts in the relay are being pulled closed, they may not actually be making a good contact all the time. As much as I hate to diagnose problems by just replacing random parts, the relays are pretty cheap to get. One way to bypass a relay is to jump pin 30 on the relay socket to pin 87.

One would assume that based on Lu's description, both pumps are being turned on properly when the non-running/starting symptoms are present. Otherwise, that piece of information is useless, as it doesnt rule out something failing intermittently.

[DanielC]

TR, I am going to respectfully disagree with you. It is entirely possible for a relay to make an "adequate" connection, but as electrical current flows through the poor connection, the connection heats up, resistance at the connection goes up, and because of the heating, the connection no longer passes enough current to supply the fuel pumps.

Almost all switches have a tiny arc when they open, and close. This happens more with inductive loads. This tiny arc slowly degrades the contacts.

I was having similar problems with the engine on my boat. (1997 Ski Nautique 2399 hours) so far, replacing both the relays for the fuel pump, and the engine's computer seem to have fixed the problem, but I have not put enough time on it after the relay replacement to be sure.
Both used relays bench test good. I did notice an occasional variation in the resistance of the closed contacts, occasionally, but the resistance shown is right at the lower limit of the resolution on my Fluke 177 meter.

[TRBenj]

Yes, the relays can be an issue- intermittent connections at the relay (either due to the relay itself or the harness/plug) can certainly be the culprit... Ive seen it happen.

However, in this case, whether clearly communicated or not, he has been able to reproduce the fault for an extended duration. The boat will not start. During this time, he has confirmed that both fuel pumps cycle on and run. I agree with him when he stated that by doing this, we can eliminate the relays and their connections as the cause.

[SkiLunautique]

Tool, yes 45xxx no., so not in that recall, thanks though!!

My GM bud is stopping by tonight with his tools, says they will determine if a pump is bad.

Will also ask his thoughts on the relay, thanks for the info on jumpin and the screen Daniel, should that be necessary.

[DanielC]

Tell your GM buddy that the engine does have an Assembly Line Diagnostic Link (ALDL) connector on it.
If my memory serves me correctly, you can take a low amp test light, and hook it up to the "E" and "F" connections on the link, and jump the "A" and "B" connections together, and the test light will then flash any codes stored in the computer. This is similar to using a jumper to flash codes on a pre 1996 OBDI GM car

[AirTool]

There is also a bulletin on camshaft retard. I'll see if I can find it.

But I don't think the symptom is intermittent.

[AirTool]

There is also a bulletin on camshaft retard. I'll see if I can find it.

But I don't think the symptom is intermittent.

Here it is, but I think you are safe again.

http://www.planetnautique.com/Correc...SUP2003-06.pdf

[SkiLunautique]

Will need to bring it over to his shop to get everything tested, Sat AM hopefully. While looking it over he commented of seeing issues with the dist cap I have (in the automotive world) and is going to take it off and inspect it. Said it looked identical to the Automotive version, do you guys know if it is the same or is there a "marine" mod for this application??

Thanks again for your thoughts

[bryn1770]

Had the same problem with our 05 206, couldnt figure it out unitl I noticed that every once in a while the fuel pump would not cycle while messing with the boat in the driveway. Replaced the relay (Part# R130011A) and have not had the problem since. You may have a relay that is just on the verge of quitting on you.