GT-40 Pro Boss Starting Issue after Running

1995 Ski Nautique GT-40 Pro Boss PMC/Ford 351 EFI, 800+ hours

I have had this happen to me 2 times so far this summer. Engine will run fine, multiple starts pulling skiers, etc, no problems. Let sit for a period of time (30-60 minutes) and will turn over but won't start. LP fuel pump seems to be priming. Let it sit for a while, all the time being impatient and trying to restart periodically. Same thing, will turn over but no start. Seems like it wants to start but doesn't. Eventually it will fire and runs fine again, like nothing has happened and will restart multiple times, no issues.

It happened once in late May, ran 30 minutes down river to restaurant/bar, docked the boat, came back after lunch and wouldn't start. Repeated attempts... same thing, I hear LP fuel pump hum, engine turns over, but no start. Eventually after what seems like an eternity, it fires and will have no issues rest of the day.   Same thing this past weekend. Multiple starts pulling skiers, took a break, for a bit, and then no start. Dropped anchor to keep from floating down river, and eventually started, maybe after 30-45 minutes.

I replaced fuel pump and ignition relays and LP fuel pump last year. At that time I wasn't getting any priming. Not the same issue this year. I also replaced the in line fuel filter at the start of this season and should have fresh gas all through the system as I have been out multiple times and have filled the tank several times or more.

I have read through the Poor Man's GT40 Diagnosis forum and spreadsheet, but unless I missed it or an not connecting the dots, I don't see my specific issue listed, unless it is maybe the ignition module / TFI ???

Thoughts / suggestions ?

You need to diagnose the problem when it is actually failing.

Check fuel pressure and spark when it is in the heat soak condition and get back to us.

I think there is a short fuel hose inside the high pressure pump and I believe there are issues with that hose splitting causing similar problems.

Mark no fuel cell on the '95s two separate pumps.
Tim I'll keep you posted. This problem is driving me crazy Seemed to be getting worse, like you it would only happen once in a while know it is happening regularly. I found that if you open the motor box while your taking a break or after the problem arises it will start again. That adds to the mystery of trouble shooting as you don't know if what you found is the problem or if it was just having the motor box open long enough for it to start again.

Yep

39 +/- 3

gun-driver wrote: I found that if you open the motor box while your taking a break or after the problem arises it will start again. That adds to the mystery of trouble shooting as you don't know if what you found is the problem or if it was just having the motor box open long enough for it to start again.

Paul,
Classic heat soak problem. Get the fuel pressure checked first and listen very carefully for the pumps running with ignition on for a few seconds (do they run constant for those few second or seem to start and stop). You can also jumper the pumps so they run all the time as a diagnostic tool while troubleshooting.

lewy2001 wrote: Classic heat soak problem..

It may be related to a heat soak issue, but my question is what changed? Something must have deteriorated, or wore out to cause the issue. I have never had this particular issue before this year. I can hear the fuel pump(s) turn on for several seconds, engine turns over, but no start.

Anyway, I picked up a fuel pressure gauge today. If / when the problem shows itself again, I will check the pressure in the fuel rail.

OK I have a little info on this allusive issue.
After running for a while to get her nice and hot came back to the dock and let her sit for a beer or two, (this is an important piece of the puzzle, you'll see later) Tried to start her back up and two pops then nothing. (as usual) pulled out the meter confirmed power to pumps and they were running (brand new LP). Put on the pressure gauge, no pressure jumped the pumps to make them run continuously still no pressure.
Took one of my empty beer bottles (important part from above) ran the drain hose from pressure gauge to bottle turned on pumps.
Pumped out a bunch of air along with about 3oz of fuel then could hear the pumps catch a prime and bam pressure 40psi motor fires right up.
Before the trip I changed the inline fuel filter and the LP. I used my mighty vac to suck fuel through the line and filter to the intake of the LP pump to prime the line. I could hear the BB in the anti-siphon valve jiggling away so I assume that's good. Started motor at home ran on the bucket checked for leaks everything looks good lets go to the lake and run her.
After the two beer cool down when I ran the pumps at the dock the pumps sounded the same as when I changed the LP (running empty then getting a prime two distinct different sounds)
So some how pumps are loosing a prime. Unless the anti-siphon isn't working as I thought or the fuel is returning to the tank through the crossover hose (stainless hose off the HP) or the fuel regulator is getting stuck open or not closing on shutdown and start fuel is being rerouted to the tank instead of the rail.
This is now the big mystery and the answer to this dreaded hot no start problem. Why are the pumps loosing prime????

Paul I wonder if it is a vapour lock issue???? Remember they did add the FCC to eliminate this problem.

Paul, didn't we already figure this out? '95 (FCC-less) gt40's suffer from heat soak/vapor lock like many other early mpefi marine engines. Not sure where the fuel goes (drain back vs evaporate) but it's definitely heat related- and the closed engine compartment is certainly a contributor. The late 90's mercruiser 502 I had would do exactly as you describe. No fuel pressure if it sat for 15-20 min after running (especially if run hard). Hpp was dry when attempting to restart... I could refill the fuel filter (always noticeably low or nearly empty) and then problem solved. If I kept the box open after running, the symptoms were significantly reduced or eliminated.

The cool-fuel bath that the hpp sits inside (FCC) is the solution. It's the reason only the 95's suffer. Just add one, man!

Paul,if you find a high pressure pump you better grab it,they seem few and far between lately

Kris I just installed a new inline filter along with a low pressure pump before this adventure. I have verified that it's not going backwards, as I trouble shot more it's more like the HPP isn't working 100% and or its overheating and like you said there's a valve in the pump gone bad allowing the fuel to return to the tank instead of pressurizing the rail.
Im almost certain it's just the HPP going bad and the any pressure and fuel I'm getting through the rail is being supplied by the LPP until the HPP cools enough and starts doing its thing.

Tim I can't just throw in an FCC Pete would never forgive me for not keeping it original
Although I could but I'm trying to get this nailed down for the rest of the gang on here, along with the fact that it worked fine for 18 years till now so it should work fine for the next 18 when I solve it.

I finally ran a tank of fuel out of this thing so I'm going to fill up with non ethanol today and test the ethanol evaporation theory.
Lewy spoke with Richard at Skidim yesterday and he said the new HPP's should be in on the 29th he has taken down the listing of the pump on his site but they were listed at $378 I believe verses the $515 + any other fuel line and fittings to retrofit the FCC.
Gary linked me to a similar problem on his Shamrock forum and there was discussion about a stuck open injector causing air in the rail and rough idle. I don't think this could be the problem as I think that would cause a hard start with a raw fuel smell on start up which I have neither. Plus once I bleed the rail it's solid fuel and runs and idles perfect except for a very slight off idle stumble which its had for a while. Thoughts on that??

Gary

Why can't you use an automotive version?