PCM GT40 backfires

I have a 1997 SkiNautique 176 with a PCM 351 GT40 engine. It has about 600 HRS on the clock. It has not run much over the last two years (about 5 HRS run time). Anyway, I just pulled it out of the garage, changed the oil, drained the fuel out of the FCC and chenged tge fuel filter. The old filter was a little dirty bit nothing major and the fuel looked and smelled OK. Anyway, took it out and it ran it for 15 - 20 minutes without any issues. Parked it at camp for about 1.5 hours, and afterwards, it would barely run. Idled poorly and would backfire and die at anything above idle. Changed plugs (looked good), plug wires and coil wire, distributor cap and rotor with no help. It sounds like both pumps are turning on OK when you turn key. Any ideas would be appreciated.

Thanks,
Bruce

Bruce how old is the gas? New fuels don't last very long before it seperates.I'd get it out of the tank,drain the filter and throw in a can of seafoam and refill with fresh fuel and go from there.

I believe that I had about 1/2 to 3/4 tank most likely from last summer.
My plan is to drain the FCC again, remove canister and look for anything obvious. Thank you for your advise.

Bruce,

I have a '97 Ski Nautique and I had a similar problem. Mine ran fine and then after turning it off for a while and then when I went to start it back up it would not run past idle speed and backfired when you gave it throttle as you indicated. What it turned out to be was a crack in the clear fuel line that is inside the FCC. When you take the FCC back off you will see the fuel line and I would bet you will find it has a crack in it which is not allowing it to pump at the right pressure. This line was later changed to a more durable one and it can be purchased from Discount Inboard Marine. Vince at Discount Inboard Marine diagnosed my problem and it turned out to be exactly what I have described above. Hope this helps. Kevin

Kevin,

You were exactly right. I took apart the FCC and found a crack in the fuel line that connects to the high pressure fuel pump. After replacing the bad chunk of fuel line, the boat ran fine in the yard. As always, the true test is on the water. Thanks for the tip!

Bruce

Bruce,

I'm glad I could help. It appears that this is a common problem on '97s with GT40s and if not diagnosed correctly a person could spend a lot of money trying to fix it. Thanks to Vince at Discount Inboard Marine for diagnosing the problem when I had it since it is an inexpensive fix. I have offered this tip previously and it fixed the problem for another Correct Craft Fan member. Thanks to Keith for giving us the Forum to talk about our boats.

Kevin

WOW! Kevin, you da man. I was going to go to the auto parts store and invest $58 in a pressure gauge tonight to test the high pressure pump. That would have let to a low reading I bet, and then I would have ordered a $140 fuel pump. I just went outside and pulled the FCC again and removed the pump and hose. At first it looked ok, but then....I found a tiny crack, you almost have to squeeze the hose for it to open up to where you can see it. I was floored. Based on it being exactly your problem, and the other guy on this thread...I am optimistic! No just have to wait 3 days for my parts to get here! THANKS THANKS THANKS.

I think I found it http://www.nautiqueparts.com/internalfuelhoseforfcc.aspx

ricofrancois wrote: I think I found it http://www.nautiqueparts.com/internalfuelhoseforfcc.aspx

For the convenience of all, here's a proper link.

The FCC is on the front of the engine, passenger side. Google "GT40 FCC" to see a pic.

Here are complete instructions I posted a couple years ago somewhere here.


The FCC and bowl is the black cylinder on the port (passenger) side of the engine (should be) on the front. Has hoses going in and out of the top. To check the suspect internal hose:

1. Drain gas (and separated water) from FCC bowl. Do this by removing the valve on the bottom of the cylinder, have a quart plastic bowl under it to catch the fuel (and water and probably some gunk) that will come out. Drain it completely. Replace the valve, using some gas-rated thread tape, and tighten firmly.

2. Unscrew the FCC bowl from the top part like you would an oil filter. I used an oil filter wrench that was a bit too loose of a fit, so I put a small wrench under the filter strap, which firmed it up so it wouldn't slip. Put filter wrench near top of cylinder. If you're lucky like I was, it'll unscrew fairly easily and you can remove it. If not...search this forum for "FCC removal" and you'll read of the different ways others got it loose if it was really stuck. It can really be tough to get loose it seems. Be careful not to damage it!

3. Once loosened, unscrew and remove FCC bowl; what you should see remaining is the high pressure fuel pump hanging from the suspect hose, and the power wires, with the fuel filter on the pump. OR the fuel filter might be stuck in the bottom of the FCC bowl. Remove the filter from the pump by sliding it off (or if it's in the bottom of the bowl, use some tools to get it pried out.)

4. Remove the fuel pump and hose, you will destroy the crimped clamps while doing so. That's OK.

5. Inspect the hose carefully. Squeeze it all around...you will see a little crack in the hose if it's damaged. Assuming it is.....(or even if not, replace it anyway)

6. Call Skidim and ask for a repair kit. It's a dollar. While you are at it, order a new fuel filter as well. The hose will come with new clamps and a new o-ring for the top of the FCC; there will also be one in the new filter, keep this as a spare.

7. Carefully remove the old o-ring from the top of the FCC where the bowl screws in. You need to look up from underneath to see it. DO NOT score or damage the top of the FCC while prying this o-ring out. Put the new o-ring in place, I used a bit of oil to lubricate it, just like you should with an oil filter.

8. Install the new hose on the fuel pump, then to the top of the FCC outlet, using the new crimp clamps. Reconnect the wires to the fuel pump.

9. Slide the new fuel filter onto the fuel pump until it's seated.

10. Feel with a finger to make sure the new o-ring is still in place at top of FCC. Slide the FCC bowl over the fuel pump/filter, and screw it back in. Lubricate the threads with some oil or grease first. Hand-tighten, then finish tightening with oil filter wrench. Don't overdo it!

11. Turn the key one click, and off again, repeating several times. You should hear the fuel pumps kick on for two seconds each time. After 3 or four times, the FCC bowl should have plenty of fuel in it again.

12. Making sure you have water supplied to the freshwater intake, start the engine and see how she runs. Hopefully, your problem is solved at this point.

Good luck.

The 1995 GT 40 does not have the FCC, so don't think you will find the same issue if I have learned this correctly from reading the Poor Man's GT-40 Troubleshooting Guide and reading just about everything Lewy has to contribute.

When you say won't plane what RPM is it getting to?

Is the Profile Ignition Pickup(PiP) sensor loose in the distributor? Does the PiP have any flakes of metal on it that could be interfering with the cylinder 1 detection? Do you have the bonnet on the distributor that prevents cross talk between the distributor and the Thick Film Ignition Module(TFI-IV)?

To check the fuel pressure simply put a fuel pressure gauge onto the schrader valve located on the bow section of the starboard side fuel rail.