Diesel fuel system problem

[gettinthere]

I've discussed earlier on SBO a stalling at idle problem. Eliminated the alt and started looking at fuel delivery.

The engine, perkins 4.154-200 (japanese) can stall on warm up or at idle speed, intermittently. No issues at cruise speeds.

I ran the fuel primer pump and cracked open the bleed screw and it took quite a while for fuel to come out the bleed screw. This bleed screw is at the top of the secondary filter, a screw on canister.

So I first changed both primary and secondary filters. I've been motoring ICW about 4 to 8 hours a day since then and still have the issue. Every morning I crack the bleed screw and run the primer pump for a minute or two before seeing fuel at the bleed screw.

When I crack the bleed screw I can hear a slight hiss so there is some vacuum there in the filter.

There could be any hundreds of possible places anywhere in the system where the problem is. Any suggestions on how to shrink this wild goose chase?

 

[woodster]

the only thing i can think of is to start bleeding from the first point closest to the pump and work your way forward untill you get all of the connections eliminated ...when was the last time you cleaned your injectors

 

[kloudie1]

Air leak is somewhere between the tip of the pickup tube in the tank and the suction of the lift pump. Things like the valve packing on the fuel shutoff at the tank aren't obvious, nor are little things like a crack in the pickup tube inside the tank above the fuel level. Any point of the line above the fuel level in the tank and the suction of the primer pump can leak air in without leaking fuel out.. past the primer pump, I would expect to see fuel weeping when the pump was running.

 

[Maine Sail]

If you have a Racor 500/900 etc.make sure the square black lid gasket is not twisted and that the little red t-handle gasket is in good shape....

 

[gettinthere]

The primer pump I use to bleed the system does not run during operation.

I would HOPE that replacing the racor filter and its gaskets would have eliminated an air leak there...but cant assume anything!

Keep em coming

 

[kloudie1]

I understood that you don't run the primer pump constantly. My point was that if there was an air leak downstream of the discharge of the primer pump, I would expect it to weep very slightly during the time that the primer pump is running.. I am assuming that the lift pump is downstream of the primer pump? if so, and you see no weeping, when the primer pump is on, then the small air leak is most likely between the suction of the primer pump and the surface of the fuel inside the tank.
Happy hunting !

 

[Stu Jackson]

Keep em coming

There's really nothing left. The guys have told you about all the usual suspects. Only YOU can get to each one of them and check them out. A systematic approach is required. Air introduction in the lines is harder to find on the suction side, so try back blowing through those lines. You may need a second helper to see stuff. Good luck.

 

[gettinthere]

Klowdie

Wasnt doubting your idea, just clarifyin.

Thnx much

 

[Ralph Johnstone]

Air introduction in the lines is harder to find on the suction side, so try back blowing through those lines.

At this stage in the game, Stu's idea is the only way you're about to find the leak. Try installing a hand operated OB engine primer bulb as close to the fuel tank as possible and then pressurize and go through with a wiping rag checking for leaking fuel.

Still no leaks ? ? ? ..................... it's got to be inside the fuel tank.

 

[Slow lane]

Air in system after engine is stopped is often the seal on the injection pump shaft. They only leak air in not fuel out. You may want to try a back check valve. John deer uses them on some of their engines if I remember right the one they use on 6415 tractor is cheap under 20$ and can easily installed just before your filters. I've used this fix on several ind and marine engines.

 

[jibes138]

Check your hoses, I've seen old hoses split from age and leak fuel, they could just as easily leak air into the system.