5.7 Crusader Engine Problems

[Comogene]

Typically, pick-up tubes are welded to a pipe fitting which then screws into the top of the fuel tank. An anti-siphon valve screws into the fitting which in turn connects to the fuel line. The fuel pump's suction action is sufficient to pull open the anti-siphon valve and allow fuel to flow out. You should be able to unscrew both the fuel line fitting into the anti-siphon and the pick-up tube into the tank to examine.


I had debris in the tank that would be sucked into the pick-up tube and restrict the flow of fuel. Once I slowed down, the debris would "fall" away from the pick-up and the motor would run normally for a while.


Your symptoms seemingly indicate a restricted flow of fuel. Could be debris in the tank at the pick-up, debris in the anti-siphon or even a collapsed fuel hose that may have been softened by E-10. All of these would appear to recover and then repeat. The best test would be a fuel pressure gauge mounted before the fuel pump. If there is a clog between the tank and the pump, this instrument would show it. Should the pressure remain steady in spite of a drop in RPM, then the problem is from the pump aft.


Gene

[g.ross]

The yacht mfg standards require the installation of an anti-siphon valve on the feed line at every tank..on gas powered vessels only. This valve is usually aluminum containing a disc held on a seat by a weak spring with just enough tension to prevent fuel siphoning from the tank unimpeded if there if a break in the fuel line or some other such problem. My experience with a similar problem was that a small amount of debris (insect parts) would accumulate in the valve and gradually force it to close. When the engine died the fuel pump vacuum stopped & the debris would settle back down the inlet tube, free the valve only to repeat the problem over & over. Once I clued in the fix was easy I removed the valve, cleaned it. And then using an outboard type fuel primer squeeze bulb removed fuel from the pickup tube and the bug bits with it.

[seabreez]

Originally Posted by a64pilot

Pressure gauge would confirm fuel delivery, pressure woudl go to zero or close to it just before it died.
Just a temporary one, I have never seen a check valve in a fuel line, .

There is a check valve at the tank fitting. It usually has an arrow in the direction of the engine. I think it is a requirement for Canadian boats. It is a spring loaded ball valve and works with vacuum from the pump and it will let some dirt go through but not much... A pressure check will determine if enough fuel does go through... I usually take the hose off and the valve and look into it to check. Then blow in it to see if it comes off the seat.

[Cheechako]

Originally Posted by seabreez

There is a check valve at the tank fitting. It usually has an arrow in the direction of the engine. I think it is a requirement for Canadian boats. It is a spring loaded ball valve and works with vacuum from the pump and it will let some dirt go through but not much... A pressure check will determine if enough fuel does go through... I usually take the hose off and the valve and look into it to check. Then blow in it to see if it comes off the seat.

Good point on the check valve in gas powerboats.

[Porch Swing]

Good Morning,
Just wanted to let everyone know that i appreciated your ideas and solutions to repairing my engine troubles. I attached a outboard motor tank to the engine and boat ran fine. Working back from fuel filter, found a ball of lint and other debris in elbow coming out of the tank. That fixed it. thanks. again.

[Cheechako]

Nice to get an update, thanks!

[seabreez]

Originally Posted by Porch Swing

Good Morning,
Just wanted to let everyone know that i appreciated your ideas and solutions to repairing my engine troubles. I attached a outboard motor tank to the engine and boat ran fine. Working back from fuel filter, found a ball of lint and other debris in elbow coming out of the tank. That fixed it. thanks. again.

Did you see the spring loaded check valve at that elbow?

[Cheechako]

IIRC, the spring loaded check valve is a requirement depending on the engine height in relation to the fuel tank.


something like this: "If your gas tank is above your fuel pump, in overall height, then yes there should be an anti siphon valve (check valve)
If the fuel tank is below your fuel pump, then an anti siphon (check valve) is not required by law, but may still have one in it."