Thread: Rough running at high power

I agree it sounds like insufficient fuel. Apart from the filter, it could be the almost inaccessible strainer on the bottom of the fuel pump, where the fuel line attaches, or an air leak anywhere on the suction side, or a blocked or partly blocked fuel tank breather.

Less likely is something like an exhaust valve sticking when it gets hot, or an injector malfunctioning when hot, or something along those lines.

John

That is the exact symptom mine gave when the tiny gauze filter blocked up. The problem I then had was that the lift ( primer) pump gave up the ghost at the same time.
That was fun.

Both mine have done the same..... Never fixed it though

JDNSW/Deejay - I actually removed the gauze filter before I installed the engine (since its such a PITA to get at) and fitted the inline filter to do the same job, so sounds like its that filter as I thought.

Best I just get off my butt and fit the CAV filter/sedimenter thats sitting on my workbench

Rovercare - I'm assuming the engine/s you had the problem with aren't the one you are running now? Doesn't sound like that would go as well with a fuel restriction

Steve

Yea, the one in there now, it's a small hesitation, same revs, heavy load, the reco engine in my rr was the same, this one was fine at 300k till upping the fuel, I'm guessing it's to do with the pump

Originally Posted by rovercare

Yea, the one in there now, it's a small hesitation, same revs, heavy load, the reco engine in my rr was the same, this one was fine at 300k till upping the fuel, I'm guessing it's to do with the pump

I also get a slight hiccup/hesitation occasionally when I give it a bootful around the same revs but lighter load. Like a bad accellerator pump on a carby motor, but not enough to worry about.

This roughness under heavy load will continue for a few seconds before I either lighten off or change up a gear. Would probably continue the same if I let it but I dont like the feeling ...

Steve

Originally Posted by steveG

I also get a slight hiccup/hesitation occasionally when I give it a bootful around the same revs but lighter load. Like a bad accellerator pump on a carby motor, but not enough to worry about.

This roughness under heavy load will continue for a few seconds before I either lighten off or change up a gear. Would probably continue the same if I let it but I dont like the feeling ...

Steve

Ok mine aren't that bad

I agree fuel.

The filter seems unlikely but replacing it is a quick and easy way to check. Being a stage 1 and so a bit older I'm thinking lift pump. Mine died and the 2nd one was a dud. The current lift pump is a Bosch and has a roller bearing on the end of the cam lifter instead of just a flat surface - very flash.

As a last resort I would check the fuel line joins disconnected as part of the engine fit for air leaks and check the fuel tank pick up for blockage.