GT 40 Fuel Pressure and Engine Question (2001 SAN)

[hrwboarder]

Hey guys, we were out two weekends ago and the boat (2001 SAN Fuel Injected GT-40) was fine but began to hesitate right when you would get on the throttle to just take up or pull someone up. We thought it was probably just a little bad fuel and used some fuel injector cleaner to run through with the next tank (Lucas Oil Brand). So the next day we went out and boat seemed to be a little better. It would hesitate at the bottom end (the boat shakes as if it is not getting fuel) and then kind of jump up out of the water after a few seconds like it was fine. But as the day went on it kept getting worse. The next day we went out (long weekend) the boat was about the same and we figured we needed to change the fuel filter. We went out this past weekend and the boat would hardly go at all. Pretty much not plane out with a load of people in the boat and has absolutely no throttle response. So we took the boat home, changed the fuel filter and distributor cap. This seemed to help right after we did it and then we were back to square one. Right this moment we are checking the fuel pressure and are wondering what exactly our specifications on PSI should be. When we give the boat some throttle the fuel pressure drops and we were wondering what exactly should be happening? Also what other things may we want to look into? Plugs and wire? The boat just really seems not to be getting enough fuel.

[BT]

RE: GT 40 Fuel Pressure and Engine Question (2001 SAN)

i think the fuel pressure should be around 35-40 psi. maybe as much as 45.

[hrwboarder]

Our fuel pressure is at about 34 PSI when the boat is idling. But should the fuel pressure actually drop as the RPMs increase? Because as the throttle is increased the pressure gradually decreases.

[RJP56]

Ford GT 40 Problems

We own a 2001 Sport Nautique/Air Package with the same problem. Not a nice feeling knowing whether your going to need to paddle home!

[DanielC]

RE: Ford GT 40 Problems

Fuel pressure check, GT-40
http://www.planetnautique.com/index....=fuel+pressure
This is the fuel pressure with the engine not running, and the connection made. when you start the engine, the fuel pressure will drop, unless the vacuum hose to the fuel pressure regulator is disconnected and plugged.
The fuel pressure should be 39 +- 3 psi.
How many hours on the engine? Are the original spark plugs in the engine?

[hrwboarder]

There are only about 170 hours on the engine and I am sure that the original spark plugs are still in there. Our fuel pressure actually drops to about 30 PSI and seems that it will keep dropping. Even with the vacuum hose not disconnected and plugged is that normal? I just talked to Tommy at White Lake and he said that he felt sure that it was probably a fuel pump problem or the hose inside the control cell. So we will look into checking the supply pump first and then move onto the control cell. Thanks for the help. Any input is appreciated!

[DanielC]

The fuel pressure should drop when the engine is at high vacuum, at an idle. Engine idling, low fuel demand, higher fuel pressure not needed. At wide open throttle, high fuel demand, higher fuel pressure needed. The mechanical fuel pressure regulator controls this, provided there is enough fuel flow, at the pressure required, that that the pressure regulator can bypass excess fuel back into the FCC.

With only 170 hours, the spark plugs, and the rest of the ignition system should be OK.
Ignition system test:
http://www.planetnautique.com/index....=ignition+test
If you do get a strong steady spark with the tester, I would assume the ignition system is OK.

There is a possibility that the fuel filter inside the FCC is plugged. Is this the one you changed? It is inside the FCC, mounted around the high pressure fuel pump. There is also a rubber hose inside the FCC, that connects the high pressure pump to the outlet fitting in the FCC. There have been a few cases of this hose being defective. If this hose leaks, the fuel pressure will leak off inside the FCC.
On a running engine, the fuel pressure should be lower at an idle, and it should get higher as the throttle is opened.
I have had a low pressure pump fail on my boat. It shut the engine down completely. No idle, crank forever, no start, not even one cylinder firing occasionally. The low pressure pump should have 5 to 6 psi, but more importantly, it has to have a good flow, I believe it is rated to flow about 70 gallons of fuel per hour. More than a gallon a minute, or a quart in 15 seconds.

[hrwboarder]

Thanks for all the info. We will try the ignition system test and see what we get there. That hose inside the FCC is what Tommy also told us to check. We changed the fuel filter inside the FCC yes. Hopefully tonight or tomorrow we can get a check on the supply pump. We will do a little more testing and I will keep an update on what happens. Thanks for the help.

[hrwboarder]

Okay, so here is an update.
We began trying to find our problem by checking the supply pump. We did not have a very steady flow of gas and it took about 8 primes using the start switch to fill up a 16 ounce bottle. So we then took off the fuel hose from the pick up valve and placed it in a gas can and it took about half the amount of times to prime it and we had a very strong stream. We opened the gas cap in hopes that this would prove that the vent to the tank was not stopped up and we had no change. So we believe that the fuel pick up is stopped up.

So now to the question. What is the best way to go about cleaning out the pick up line? Is there a general method to use or do you guys have any input from past experience?

As always thanks for all the info.

[eseybold]

I have a 2000SNOB with a GT40 witht same exact problem. My pressure was only 30 psi - so I changed both high and low fuel pressure pumps and the filter and the cap and rotor and the plugs. Boat runs a little better and my pressure is now 34 at idle but drops when I give it throttle. I am about to take out my fuel pick up lines and look for clogged lines. Any other suggestions ? My timing is fine - I checked that too.

[DanielC]

There is a screen on the fuel pickup, inside the tank. There is also an anti siphon valve on the top of the gas tank. I am not sure about an anti siphon valve on Super Airs.
Remove the hose from the gas tank, that feeds the fuel pump. Make sure you are not on the return line.
The two hoses look the same, but one has a piece of red tape wrapped around both ends. The hose connected to the fuel pump at the engine end is the fuel supply line. The hose connected to the FCC at the engine end is the return line.
Remove the anti siphon valve, if you have one.
Blow air backwards through the fitting, into the tank. That will dislodge crud around the fuel pick up inside the tank.
Put everything back together, and recheck the flow from the low pressure pump.
If the flow is now good, the screen was clogged.
You will also have to clean out the gas tank to prevent the problem from happening again.
Super Airs may not have an anti siphon valve, or they might.

[eseybold]

thank you for that tip - I will do that. It makes sense.

[nms1991]

Do not try to blow back through the anti siphon valve as it will block thr pressure from going into the tank. You have to remove the hose off of the anti siphon valve then remove the pickup from the tank and look at the bottom of the pickup and check the screen and check to see if they put the screen behind the anti siphon valve in the pickup.