3tne88 intermittent misfire

dougdanger · Jul 27, 2014

Hey guys, my engine develops a misfire when the revs are mid/high .. Not all the time , comes and goes but its enough to stall the engine.
If I back it off to idle it clears after a while or if I turn it off and let it sit for a while it comes good again..
As soon as I give it full load again it begins to stumble again ... Seems to get worse the longer I run it !
Filters are clan and can't see any water in the fuel ..

Any ideas ??

Cheers, Doug ..

winston1 · Jul 27, 2014

Your problem sure sounds like starvation of fuel. Just browsing the service manual on that model would indicate it has a fuel feed/priming pump attached to the injector pump. If that is so, have you checked it out making sure it is functioning properly?

dougdanger · Jul 27, 2014

winston1 said:
Your problem sure sounds like starvation of fuel. Just browsing the service manual on that model would indicate it has a fuel feed/priming pump attached to the injector pump. If that is so, have you checked it out making sure it is functioning properly?

Yeah, my thoughts were fuel starvation .. All fuel bowls are full and the electric pump seems to be operating OK ...
Is there another lift pump ?

winston1 · Jul 27, 2014

dougdanger said:
Yeah, my thoughts were fuel starvation .. All fuel bowls are full and the electric pump seems to be operating OK ...
Is there another lift pump ?

I don't know, can only comment on what I saw in the manual. It showed a priming pump with a little hand priming lever but I also think it might run off the camshaft. That type pump serves as a priming pump but also as a feed pump. Your must be completely different if it is electric.

normde2001 · Jul 27, 2014

I would start by replacing fuel filter(s) and bleeding fuel system. If you have SEAFOAM, use in fuel.
( Actually, first try loosening fuel cap).

alorio1 · Jul 31, 2014

normde2001 said:
I would start by replacing fuel filter(s) and bleeding fuel system. If you have SEAFOAM, use in fuel.
( Actually, first try loosening fuel cap).

Yes check the vent off line coming from the tank for blockage and all the filters. If the vent off line gets plugged the fuel pump will be in a bind trying to get fuel from a tank that has a vacuum pull instead of a free flowing gravity fed pump.