Ford Lehman 2715E Air In Fuel @ Last Bleed Screw

[CaptainBob]

I've been trying to solve my air in fuel issue for ages now - getting despondent. Tried everything.

Symptoms only appear if the engine hasn't been run for 24 hours plus. Once it starts, it's fine. No hunting or revs fluctuation. So it's a tiny leak.

I also note that after a 24 hour wait, if I then bleed the cold engine, I find air immediately, but only at the final bleed screw on the injector pump - nowhere else. If I bleed that air, the engine fires up perfectly.

The final section of fuel hose goes down hill from the last fuel filter before then rising up to the injector pump - a big 'U'. Am I right therefore in thinking that as air is only found at the injector pump, it _must_ be getting in at the final hose connection (where it enters the injector pump), or even at one of the bleed screws on the pump itself?

Having re-done the final connector repeatedly, and applied Loctite gunk to it and the lower of the two bleed screws, I'm starting to wonder if there might be some leak in the injector pump itself. Is that possible?

 

[pvb]

The final section of fuel hose goes down hill from the last fuel filter before then rising up to the injector pump - a big 'U'. Am I right therefore in thinking that as air is only found at the injector pump, it _must_ be getting in at the final hose connection (where it enters the injector pump), or even at one of the bleed screws on the pump itself?

Yes.

Having re-done the final connector repeatedly, and applied Loctite gunk to it and the lower of the two bleed screws, I'm starting to wonder if there might be some leak in the injector pump itself. Is that possible?

I imagine it could be possible. What about the final bleed screw - have you tried putting a new washer on it?

 

[pampas]

DPA pump or inline? if DPA the return line should go to a return to the last filter. If so does it go to a Banjo with the bleed screw?

again if to a Banjo remove and clean the tiny hole in the wall about 40thou, this can get blocked and cause many problems , one of which you seen to have.

When bleeding the pump again only bleed, useing the lower point as air trapped in the top acts as a partial damping in the govenor section.
Worth checking as this tiny hole is often forgotten, trust this helps, and my comments only apply for a DPA pump.

 

[CaptainBob]

No return line to last filter.It's minimec pump. Return line is under engine cover then out and back direct to tank.

Ta for confirmations.

 

[essexboy]

The injector drain pipe can be a problem on these engines, usually leaks fuel into the sump, and shows up with increasing oil level !
The connector to the outside of the cylinder head was a bit " iffy" we used to pressurise the to test.

 

[MYStargazer]

If you haven't got them already, these manuals may help.

http://bf494.co.uk/blog1.php/2009/02/21/ford-lehman-marine-diesel-engine-stuff

 

[fisherman]

A long shot, I had problems for ages, turned out the last bleeder on top of the filter the seat was scored slightly, would cause trouble only when the filter became partially blocked. In your case it does seem unlikely the bubbles would follow the drop in the delivery hose, but I wouldn't rule it out if the bubbles are small and the flow sufficient. When you stop they collect at the top. Can you refit the last hose to go up then down? If so the air would collect at the top of the loop and cause trouble a few moments after starting.

 

[CaptainBob]

Thanks for all replies!

The injector drain pipe can be a problem on these engines, usually leaks fuel into the sump, and shows up with increasing oil level !
The connector to the outside of the cylinder head was a bit " iffy" we used to pressurise the to test.

Hehe yeah we've had the rising oil level issue. Did find the final banjo and some of the others along the line were a little less than fully nipped up. I nipped them up. Yet to see if the problem has resolved itself. Is there an easy (without pressurisation) way to do so other than by simply monitoring oil level? Can the engine be run with the cover off? Presume that will that make a mess!

I imagine it could be possible. What about the final bleed screw - have you tried putting a new washer on it?

I can't believe it - that was the problem! No spare copper washers to hand so I just applied some Loctite 572 on the mating surface as a quick/bodge/fix test. 24 hours later engine fired up without any hint of hesitation. First time that's happened since this all started.

Hadn't crossed my mind that would be it - that last bleed screw looked fine!

Thank you!