Ford Lehman diesel fuel starvation?

I am a new owner of a 42' Grand Banks with twin Ford Lemans. Currently running boat from FL to TX. Most of way and now been dealing with starboard engine stopping cause of loss of fuel. After I open bleed bolt on injector manifold and hand pump to prime supply line, engine starts right up and we go another 2-4 hrs and same thing happens again. I replaced primary Racors and cleaned the bowl. I also cleaned a debug inline device upstream of Racors. Only things I can think of are: replace fuel pump, blow out fuel line with compressed air and remove debug device entirely. Anyone know what is most likely reason? Tanks are full and no leaks in fuel system. Bilge is clean.

On-engine filters been changed?
Lift pump. They are cheap from a tractor dealer and do fail. Change it out with a new gasket as they are also the number one cause of oil leaks. Keep the old one as a spare.
Check that the bleed screws on the Simms pump have good copper washers. I chased an air leak for months and it turned out to be a tiny copper washer under a screw on the pump. It took a couple of hours of running to finally get enough air in the Simms to stop the engine.

Things I would do to a new-to-me Lehman:
Change the oil and filter
Change the Simms oil
Change the on-engine fuel filters
Change the Racors if you have them
Buy another lift pump and keep the old one for a spare
Unless otherwise documented, change the 2 heat exchangers and service and keep the oldies for spares - water in the oil = many boat dollars
Change the raw water impeller
Check the belts and hoses and make sure the raw water system has double clamps
Exhaust system good?

Sooner rather than later, take off the valve cover and check the injector lines for leakage, it's easy to replace the copper washers. If they leak they will dilute your oil. If there is no documented servicing of the injectors and it smokes too much and puts a lot of fuel in the water, bearing in mind they all smoke and put a lot of fuel in the water(!), service them.
Check/set the valves
Retorque the cylinder head bolts - I know the manual only says to do the turbo engine but....
ASAP get Bob Smith's coolant tank
Do the Simms mod (drill the filler cap if no hole there already, remove and block the drain pipe, never again remove, or permanently plug, the level hole; change the drain plug for a small valve). You will have to measure the Simms oil forever after (big deal).

That's all I can remember, except to write it all down.

You may be sucking air somewhere. If repriming solves issue that is the likely cause. Then find out from where.

Ford Lehman fuel starvation?

Thanks to both of you for suggestions! I finally got hold of mechanic who did work before leaving FL. All filters were replaced. He says could be small air leak between Racor and fuel pump or could be dirt/grit in Racor check valve. When we get to next marina on our trip, I'll check all fittings are tightened and remove Racor bowl and clean out the ball valve above plastic skirt.

Greetings,
Mr. 49. Experienced the very same thing last year. Replaced the fuel line between the tank and the Racor. Problem solved. Turns out the inner lining of the fuel hose had delaminated from the outer and was being sucked mostly shut by the fuel lift pump over time. Would run on the fuel left in the Racor then die. Wasn't 2-4 hrs. though. More like 40 minutes regular like clockwork. Blowing through the line wouldn't have done much.

Another thing that fits the symptoms is a plugged fuel tank vent.

Just like forgetting to open the vent on an OB tank.

I've had the same problem with decaying rpm and finally shutdown when fuel falls below about 1/3 in all 3 of my tanks. I think it's an air leak and will test by seeing how long my fuel system will hold a vacuum.

RT Firefly said:

Greetings,
Mr. 49. Experienced the very same thing last year. Replaced the fuel line between the tank and the Racor. Problem solved. Turns out the inner lining of the fuel hose had delaminated from the outer and was being sucked mostly shut by the fuel lift pump over time. Would run on the fuel left in the Racor then die. Wasn't 2-4 hrs. though. More like 40 minutes regular like clockwork. Blowing through the line wouldn't have done much.

Click to expand...

+1 for checking that. A collapsed fuel line shut down my single engine once.

can you switch the starboard engine over to the port tank and see what happens??? that would give you a better idea whats going on?

When you change the engine mounted fuel filters be sure to get the old o ring type gasket out of the recess before putting in the new one. I fought with issues similar to yours for several hours before finding my error.

Enough gunk in the fuel tank can slowly plug the fuel pickup.

Shutting down relieves the suction , so the gropsh falls away for a while.

Try a shut down at a set period of time , wait 5 min or so ane restart.

If it runs with no forced shutdown between timed periods , you may have found the cause.

RT Firefly said:

Greetings,
Mr. 49. Experienced the very same thing last year. Replaced the fuel line between the tank and the Racor. Problem solved. Turns out the inner lining of the fuel hose had delaminated from the outer and was being sucked mostly shut by the fuel lift pump over time. Would run on the fuel left in the Racor then die. Wasn't 2-4 hrs. though. More like 40 minutes regular like clockwork. Blowing through the line wouldn't have done much.

Click to expand...

Sounds also like what happened to mine...I was getting 6 to 8 hours then it would die.
ADC has a flex line kit for cheap.

Ford Lehman diesel fuel starvation

If you have a Racor turbine filter, you may consider rebuilding it. Inside the filter (turbine series) is a floating "ball" that floats to the top of the chamber to prevent loss of vacuum when the engine is shut down. With age, the "ball" may lose it's ability to float. You can buy a Racor repair kit for this item. I did this on my older Racor 1000 and it seems to have solved the problem of my engine losing its prime.
If you examine an exploded view of your Racor, you can see the "ball".

Ford Lehman diesel fuel starvation

Referring to link above, after I rebuilt the Racor 1000 I put a "glop" of heavy grease on top of the nuts/washers on top of the engine mounted twin fuel filters. If there was a minor air leak at the fittings, it solved the problem. Not professional, but it worked. I had the loss of prime problem about four years ago and am not sure whether the Racor rebuild or the glop of grease on the secondary fuel filter fittings solved the problem, but I haven't lost the prime since.