Universal M-25XPBC stalling

[dhandzy]

Hi -- I can start the engine on my Catalina 310 but it behaves as if starved of fuel and stalls at throttle up. Even at idle, it revs up and down oddly. I've replaced the air filter and both primary and secondary fuel filters, ensuring to put enough diesel on all o-rings/gaskets. Next, I plan on removing all fuel line connections to check if the hose liners are clogging the fuel line.

What should I try next? Thanks for your advice!

 

[Don S/V ILLusion]

the first guess/explanation would be a clogged tank pick-up screen. Next guess - assuming fuel is getting thru the primary bowl, have the injectors tested.

 

[Hayden Watson]

The changing revs with no change in throttle position is indicative of air in the fuel line. I would suggest bleeding the fuel lines with the lift pump and bleeder screw first. If that does not work, bleed the fuel lines to each injector. You should also check all of the fuel lines from the tank to the lift pump because that is the suction side and a tiny leak in any of those lines or fittings will cause your symptoms.

 

[Stu Jackson]

Good advice, and there's this, too:
Fuel Starvation and The Obscure Check Ball Valve

Fuel Starvation and The Obscure Ball Check Valve


Please don't post the same question in two forums. They will appear in a review of new posts anyway.

 

[dhandzy]

Thanks, Stu. I replaced my racor last year so the check valve ball should be good. Next I'm bleeding the line at the injectors per the manual's instructions. I'll see if I can delete the duplicate post -- good point about both being picked up in the new posts section.

 

[dhandzy]

Thanks everyone for your help. Turns out it was a faulty power connection from the lift-pump solenoid. I could hear the solenoid engaging when I turned the key, but I didn't hear the distinctive lift-pump high-frequency (40 Hz?) clicking. I was ready to go buy a replacement pump but a friend suggested it might just have a corroded voltage connection, and sure enough, that's what it was. Engine now fixed and purring at all throttle speeds and under load.

 

[jviss]

Thanks for getting back with the update. Funny, my M25 in a Catalina 36 would happily run without the electric pump. I guess it's where the tank is located, etc.

 

[dhandzy]

@jviss - yes, I was also surprised because my tank is above the engine and lift pump, so I expected gravity to do the trick. Without the lift pump operating, the engine gets enough fuel to sputter and operate at low throttle but not enough to fire properly and certainly not enough to operate above about 1,500 RMP. That might indicate a clog somewhere or too fine a filtering element somewhere in the line b/c I really do need that lift pump to operate for the engine to not be starved. NB: My tank is nearly full so it's not lack of gravity on the volume of fuel.

 

[jviss]

Yes, maybe a dirty screen somewhere.