Engine runs for a couple minutes, stops hard, no fuel flow

[hanleyclifford]

The quickest way to diagnose the fuel system is to install a fuel pressure gauge right at the carb.

[hanleyclifford]

ABYC and the USCG require an anti-siphon in gas lines if the tank is not entirely below the level of everything else. That's probably why it's there. It can be a check valve, electric, or manual. The check valve was probably the cheapest....

In the Age of Ethanol I cannot imagine anything stupider in a fuel system than a check valve in a pick up tube. FWIW

[joe_db]

You REALLY need a pressure gauge.
Also note my boat has two filters plus the screen in the pump and has no issues with it when everything is working properly. If your filter is clogged, full of water, or leaking air it will be a problem. Leaks on the suction side do not always leak fuel OUT, but they may leak air IN which will disprupt the fuel flow.
I had some odd fuel issues I solved with a pressure gauge and two vacuum gauges, one before and one after the filter. Vacuum after the filter = clogged filter, vacuum before and after = clogged tank inlet or other issue back at the tank. I had my tank fill hose disolving and dropping rubber bits into the tank.

[joe_db]

Agree!!!!
If you are worried about siphons, you can turn the fuel pump off and run the fuel out of the carb to shut down. This is what I do. You can also buy a fuel pump that shuts itself off when it is turned off, get an electrical solenoid valve, or turn a manual valve on and off.

In the Age of Ethanol I cannot imagine anything stupider in a fuel system than a check valve in a pick up tube. FWIW

[JOHN COOKSON]

Bingy
Is your engine a late model A4 and does it have a wire that is co joined at the OPSS with the wire to the electric fuel pump the other end of which runs around the back of the engine and under the distributor to the starter motor?

TRUE GRIT

[Marian Claire]

"Leaks on the suction side do not always leak fuel OUT, but they may leak air IN which will disprupt the fuel flow."

"You REALLY need a pressure gauge."

+1

Dan S/V Marian Claire

[Bingy]

John
Engine is a late model installed on a 1978 C&C 34,with parogon reduction gear and Martec 2 blade folding prop .
Will check wiring in morning and report back.
Please explain why you asked?

[pdecker]

Still shuts down, but after longer runs.

You REALLY need a pressure gauge.
Also note my boat has two filters plus the screen in the pump and has no issues with it when everything is working properly. If your filter is clogged, full of water, or leaking air it will be a problem. Leaks on the suction side do not always leak fuel OUT, but they may leak air IN which will disprupt the fuel flow.
I had some odd fuel issues I solved with a pressure gauge and two vacuum gauges, one before and one after the filter. Vacuum after the filter = clogged filter, vacuum before and after = clogged tank inlet or other issue back at the tank. I had my tank fill hose disolving and dropping rubber bits into the tank.

I thought the fuel problem was fixed, but it's not. I'm going to install a couple vacuum gauges and a fuel pressure gauge as recommended above.

On Saturday, I motored down the ICW to a resort marina for the weekend. It was a three-hour run and I had no problems at all. The fuel tank was down to 1/2 full at the end. Yesterday morning, I put in five gallons of gas from my can which brought it up almost full. The engine ran fine for two hours and then I had another hard shut down. I had spark, but no fuel flow to the carburetor. I could hear the new fuel pump clicking while the engine was cranking, so I don't think the pump or OPSS was an issue. My water separator / filter is less than a year old, but it could still be the culprit. But I still have not replaced the fuel pickup line in the tank since it looked so good when I took it out, but I might just replace that just to be sure there are no leaks. Anything else I should try?

[hanleyclifford]

Your theory from post #11 about heat and vapor lock is sound. Once you have your fuel pressure gauge in place it will be interesting to see if pressure fails suddenly or deteriorates over time. It would also be interesting to know how hot that pump is getting. Next event, check the temp on the pump - be careful; it could be really hot.

[pdecker]

Should I just move the fuel pump to the bulkhead?

Thanks, Hanley! I'll pick up a non-contact pyrometer to check the temperature of the fuel pump. Perhaps the common thread of my problems is that it happens when the engine is at its hottest and it's a really hot day here in S. Florida. Yesterday, it happened at about 3:00 pm. I'm thinking of just moving the fuel pump from the engine to the bulkhead now on the assumption that it's vapor lock from the pump being too hot. But maybe I should wait to get some readings from the gauges to see if it's a clogged water sep / filter. Towboat US is going to get tired of towing me home one of these times.

[Marian Claire]

"The water separator / filter is mounted slightly above the level of the fuel tank." From post # 1.
Man that reminded me of my air leak issue found here http://www.moyermarine.com/forums/showthread.php?t=8205
I believe a small air leak allowed air to collect in the high spot of the system and caused my shutdowns.
Dan S/V Marian Claire

[pdecker]

Thanks, Marian Claire! I double check all the connections on the water sep / filter.

[hanleyclifford]

If at all feasible I would consider moving the filter/separator to a location lower than the fuel tank. As mentioned earlier this is not an extra burden you want to impose on the pump if it can be avoided.

[Mo]

I thought the fuel problem was fixed, but it's not. I'm going to install a couple vacuum gauges and a fuel pressure gauge as recommended above.

On Saturday, I motored down the ICW to a resort marina for the weekend. It was a three-hour run and I had no problems at all. The fuel tank was down to 1/2 full at the end. Yesterday morning, I put in five gallons of gas from my can which brought it up almost full. The engine ran fine for two hours and then I had another hard shut down. I had spark, but no fuel flow to the carburetor. I could hear the new fuel pump clicking while the engine was cranking, so I don't think the pump or OPSS was an issue. My water separator / filter is less than a year old, but it could still be the culprit. But I still have not replaced the fuel pickup line in the tank since it looked so good when I took it out, but I might just replace that just to be sure there are no leaks. Anything else I should try?

I'd be looking at pick up tube. Ran for 3 hrs on 1/2 tank (likely 18 or 20 gallon tank)...experienced no problems. Added 5 gallons and headed back...ran for two hours and shut down....so I figure he was somewhere between 1/4 and 1/2 a tank when it shut down. I think the first holes in the tube will be found there.

[67c&ccorv]

Did you use teflon tape on the new hose barb?