3GM30F Fuel pump leak ?

[walmsleyc]

I have a fuel leak that occurs whether the engine is running or not. I have not 100% located the source, but - I believe that it is on or near the lift pump.- The leak is only a few ounces over a few days- It leaks with the engine off, and to some degree with the engine on (not sure if it's more or less than when off)- When inspecting (after previously wiping all fuel away), the pump will be wet, as will the braided covered line between the pump and filter, and the bottom of the filter as well will be wet.- Activating the lift pump (via the lever) appears to cause new fuel to  be force out (leak) somewhere near the back side of the lift pump.I will need to get some better lighting and a mirror on a stick to better see what going on. Right now, I use a flash light, and mostly feel by hand and check my fingers for fuel (not very accurate).I've ensured that the various bolts, connections, bleed screws, etc are snug. Does anyone have any suggestion on what to check for and what is likely to be the problem?Chris

 

[RichH]

Be careful ...

If the diaphragm on the lift pump ruptures/splits the fuel oil can be sent into the crankcase. Check your crankcase oil level to be sure that you're not diluting the crankcase lube oil with fuel oil. There should be a 'weep hole' in the casting of the lift pump to dribble fuel to the 'outside' of the engine once the diaphragm begins to 'go' .... but may be painted shut. Check the crankcase level !!!!!!!!!!!!

 

[walmsleyc]

Will check again ...

I have checked the oil fairly recently, and there wasn't a change, but I'll absolutly check again. The weep hole sounds like a possibility and if the diaphram was "going", I suppose it might leak a little all of the time.Any chance someone can describe where the weep hole is?Chris

 

[Clark]

Chris, isn't your filter and braided line above

the lift pump? They are on mine and if yours are arranged that way too, the fuel would have a hard time traveling UPWARD from the pump to the lines and filter. I had a seepage on mine and it turned out to be the washer under the hi-pressure bleed screw. A little bit of fuel would seep out from it, dampen the filter and eventually find its way down the line to the lift pump.Just a thought and good luck.

 

[walmsleyc]

Sequence of things ...

I believe that things flow (from upstream to down):- from tank- to primary Racor filter- to lift pump on engine- to secondary filter (through the braided line)- to injector pump- to injectors- back to tank through return lineMy tank (Legend 35, 1987) is above most, if not all, of the filters and pumps, so any leak could be subject to the static pressure of the fuel in the tank.It is the secondary filter (on the engine) that is also wet. It does seem strange that the pump and the secondary filter are both wet because the braided line between the two loops downwards, and one wouldn't think fuel travel back uphill (except for capillary action). Maybe I have two leaks? The pump seems to really get wet when I activate it, but maybe the bleed screw of the secondary filter leaks too? Chris

 

[walmsleyc]

More info ...

Well, I think I have two leaks.1) the "other" bolt on the top of the secondary filter (what's that for anyway?) was leaking. Tightening that solved that problem. That's why that area was always wet with fuel.2) The fuel pump, is/was the other problem. The 4 screws that how the diaphram cover on were somewhat lose. Tightening them seem's to improve the problem, but not eliminate it. It's very hard to tighten those while the pump in on the engine, so it could be that there were not all tight enough. When the pump runs (engine running, or manually operating the pump level), the pump becomes damp with fuel at the aft end, just under the inlet port. I suppose that I'll need to remove it and examine/test it to determine if the diaphram has a hole/leak, or if cover is still the problem.Chris

 

[Dan Johnson]

Chris...

Replace the plastic washer under the bleed screw on top of the Yanmar filter first, along with the brass one under the other bolt on top. Still leaking, next step is to replace the O-ring on the filter canister if the canister continues to get wet (the original one is quite skinny--go to a well stocked hardware store and get a couple of the same inside diameter but of a thicker cross section--they'll seal better). Still leaking, next is to replace all the brass washers on all the fuel line banjoes between the tank connection to the lift pump and the ones under the connections to the high pressure pump. You can only tighten these bolted connections once solidly before they no longer seal if you try to remove and tighten them again.