Fuel problem

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Patrick Lombard

Patrick Lombard

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Dec 23, 2003
268
Hunter H31 83-87 Captain's Cove Bridgeport, CT
Here's the problem: Yanmar 2GM20. Last week out motoring back in motor dies. Had fuel but the small filter on engine was empty. Changed out all 3 filters on the system. Primed the system and got motor started and motor in. Next day changed out all fuel line and checked tank vent, OK. I changed out the lift pump 2 seasons ago. I went out today and after 20 mins of motoring it die again. Same problem no fuel in the small motor filter. Hand primed the system. Started motor and returned to dock. I don't understand what could be the cause. New filters, new lines, 2 year old lift pump that seems to works. I can hand pump it OK. The fuel tank was removed 4 years ago and cleaned out when I installed a fuel guage.
 
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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Patrick: Have you removed the fuel pick up from the tank yet? It had a screen on it when they were new. This may be partially blocked. When you are not under load the engine uses very little fuel and there is probably enough fuel passing through the screen.
 
Patrick Lombard

Patrick Lombard

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Dec 23, 2003
268
Hunter H31 83-87 Captain's Cove Bridgeport, CT
Steve haven't talk with you for a while, how are you?

When I replaced the fuel lines I was able to blow back with ease into the tank and hear bubbles. Plus like I said I clean out the tank 4 years ago.
 
Patrick Lombard

Patrick Lombard

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Dec 23, 2003
268
Hunter H31 83-87 Captain's Cove Bridgeport, CT
If it was anybody else with this problem I tell them, Its your lift pump.
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,353
Catalina 34 224 Maple Bay, BC, Canada
Analyze, don't assume

The deal: "new filters, new lines, 2 year old lift pump that seems to works. I can hand pump it OK"

Once had a friend who put new filter on , ran engine, later died. After weeks of messing and worrying? Took the "new" filter off, found the O ring banked in slot or groove, and a small bump in the new canister edge which had prevented a positive air seal, bloowie to his fuel system. Replaced the "new" but broken canister, issue fixed but months later. This is why they say assumptions are the mother of f-ups.

If the lift pump is before the filter and between the tank and filter, it's in the wrong place, should be after the filter. If pump has filter on bottom could be jammed. No filter could be clogged pump with no filter upstream.

Forget what you did new, pretend it's old or someone elses work. What would YOU do as a detective?

Start all over again assume nothing.
 
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Dan Johnson

Dan Johnson

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Oct 14, 2005
2,191
1983 Hunter H34 North East, MD
Patrick...

I suspect an air leak is causing you to have to reprime the pump each time the engine dies. Did you replace the copper washers at each fuel banjoe as a part of your rebuild? If you didn't, try replacing them. Follow Stu's advice--assume nothing!
 
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Benny

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Sep 27, 2008
1,149
Hunter 320 Tampa, FL
Second the suggestion of an air leak. The bleed screw on the secondary filter housing is prone to thread stripping allowing air in; I would check it first. The leak is pretty large if in 20 minutes the engine dies so look for a fuel leak as well. The diaphragm on the lift pump would be suspect if there was fuel coming out the bottom. Replacing all the copper seals would be a sensible measure. Sometimes performing inexpensive cures correct problems trumping cumbersome diagnostics.
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,353
Catalina 34 224 Maple Bay, BC, Canada
Benny said:
Sometimes performing inexpensive cures correct problems trumping cumbersome diagnostics.
Click to expand
Benny, with all due respect, I couldn't disagree more. Any diagnostics requires a complete analytical approach, much as I suggested in my earlier post. Throwing effort at a few things hoping they work may not resolve an underlying larger issue and may be a bandaid when surgery is indicated, or vice versa. Without a complete, systematic plan, the effort is doomed to a 50/50 chance of success, which in my book is an unacceptable prognosis, and a waste of effort, too.

Cumbersome diagnostics? There's a new oxymoron, thanks for that one!:)
 
Cpt. Jon

Cpt. Jon

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Dec 9, 2008
426
1980 Hunter 30 "Denali" Seaford, VA
Benny said:
The bleed screw on the secondary filter housing is prone to thread stripping allowing air in; I would check it first.
Click to expand
I was cursed with this problem on my old boat with a 1GM. Had to replace the filter housing, but I never had a problem since then.
 
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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Patrick: I would have to agree with Stu. You really need to start at the beginning of the system and inspect everything. You may have a loose hose clamp, bad banjo fitting, cracked hose, etc. Obviously you have check for leaks, but you are probably sucking air for the secondary filter to be dry.

Good luck and let us know what you find.
 
Patrick Lombard

Patrick Lombard

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Dec 23, 2003
268
Hunter H31 83-87 Captain's Cove Bridgeport, CT
First let me thank you all for your replys and tips. I think I found the problem. I checked the primary fuel system today using a hand vac pump, the kind you use for bleeding brakes. It was the 1/4 turn fuel shutoff petcock packing gland on the tank. Tighten packing nut and till it held a vac about 3/4 of a turn. Ran motor at dock for 3 1/2 hrs at different speeds in and out of gear. Never died. Thanks again to you all.
 
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Deadline2

To rule out bad fuel...

Buy a portable red gas tank as found with gasoline outboards and cut the forward hose to fit the intake at the first fuel filter. Prime it with the pump on the hose and see how she runs.

Worst case, problem still recurs. But at least you know it's not fuel. And now you have an emergency fuel tank in case something does contaminate the fuel tank.
 
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