this is odd

[rbodell]

Every once and a while my engine misses firing 3 to 5 in a row. Sometimes it slows down enouugh that you think it won't recover but it does. Once and a while it actually does shut down but starts rite back up.

At first I thought it was a fuel filter so I changed both of them. Then I thought it might be combination of the cold and dust in the oil in the linkage so i got some diesel fuel out and cleaned all the linkage. I have also checked valve clearance. I also run a constant load on it with an alternator charging batteries.

There is no rhyme or reason for when it does it. Mostly about 4 to 6 times an hour. I can not duplicate it either, just whenever it feels like doing it.

[rbodell]

Could it be low compression not allowing the fuel to ignite ? Could it be something amiss in the injector pump ? Maybe a stuck output valve (forgot the technical term  - the thing that you encounter when you take the fuel line off the to of the IP).

Just some thoughts ....
If it was me, I have a spare IP and I would install that and see what happens.

Jens

I was not aware that there was an output valve in an injector pump, I don't know anything about them. The only injector problems I have had on any other diesels was smoke and that was the injector itself.

I been thinking about getting a spair injector pump and injector, Maybe it's time to quit stalling and do it.

I think the compression is ok because when it is not missing it runs perfect. Also when I try to start it by hand, it is still a bear. I can barely turn it over by hand with the flywheel. I have to wait and let the compression bleed off and move it a little farther several times to get it past TDC.

[biobill]

Bob,
  I've got the same problem. I was thinking a governor glitch but it seems to be responding to it rather than causing it. Sounds like it starves for fuel or sucks a bubble for an instant. Some guys have found out of round cam followers on their IPs but it seems too intermittent for that.
  I had chalked it up to fuel. I'm running mine on biodiesel that got too old to pour into something not easily rebuildable , but you're running on WMO if I recall correctly. I dunno? Any other ideas?   
     Bill

[Curtis Shipp]

Could it be small drops of water building up in the pump or injector from the used oil.

[dieseldave]

   Or a vapour lock,due to a'light end' boiling off.

[biobill]

  I'll grab a few gallons of petrodiesel next time I head out to the bright lights. A long trip, not available locally. The stuff scares me though - don't they make it out of the same stuff that they pave roads with?
  Vapor locks and contaminants sound right but I can't quite wrap my mind around it. The only part of the system that gets hot is the injector itself. Could something be vaporizing in there? Under pressure? Does the pressure return to atmospheric (or less) between firings? With my hand on the HP line I can't detect any interuption in the firing beat when it misses.
    Bill

[lendusaquid]

Could air be getting into the low pressure fuel line ?.Try tightening your nuts up.Maybe clean the injector.

[rbodell]

Could air be getting into the low pressure fuel line ?.Try tightening your nuts up.Maybe clean the injector.

I bled the fuel lines several times, no air. Also cleaned the injector and the chamber it fires into when I changed the head gasket about 30 hours before this started.

[rbodell]

The injector assembly has bits and pieces in it so you could have an issue in there if you feel you have a proper IP pulse even when it misses.
Things could have gotten sticky from using veggy oil maybe ? Again, I would run some regular diesel through it and maybe that takes care of the issue (cleans things up). It might be something that you have to do on a regular interval just like changing oil ? If you are using BioDiesel, it could be that you have issues with your process and things gum up.

Jens

I will be needing fuel in another day or two so I will try some straight diesel. I run wmo and diesel, no wvo.

[lendusaquid]

Um ,could a valve be sticking open a fraction?. Ill keep thinking.

[rbodell]

The injector assembly has bits and pieces in it so you could have an issue in there if you feel you have a proper IP pulse even when it misses.
Things could have gotten sticky from using veggy oil maybe ? Again, I would run some regular diesel through it and maybe that takes care of the issue (cleans things up). It might be something that you have to do on a regular interval just like changing oil ? If you are using BioDiesel, it could be that you have issues with your process and things gum up.

Jens

I will be needing fuel in another day or two so I will try some straight diesel. I run wmo and diesel, no wvo.

How would you check the pulses? It doesn't sound any different when it doesn't fire other than not firing.
I don't hear the noise from the fuel pump like when you are cranking it before you throw the compression release, but I don't hear it when I shut down normally either either. That might be just engine noise though.

[rbodell]

Um ,could a valve be sticking open a fraction?. Ill keep thinking.

What would I look for to check that?

[lendusaquid]

Since i have not had this problem i can only guess.I would look for a cloud of unburnt fuel coming out of the exhaust.And next time i had the head off i would check the valves.

[Tom]

I agree (for what ever that is worth) a white puff of smoke would be a misfire and possibly water or other contaminants in the fuel. Nothing may indicate a lack of fuel or air bubble. I know when I've done an inadequate job of bleeding the injector it will  run for a bit, then coast, then catch and run again until the last bit of air has cleared. 

[dieseldave]

Come to think of it,I'll put my money on a valve sticking open a fraction,due to a guide being gummed up. Shot of WD-40?