Cummins revs randomly ;)

[Taipe]

A vacuum gauge spliced into the fuel supply line at each threaded fitting should spot where air is getting sucked in (e.g. before & after primary filter assembly, 'y' fittings & fuel line valves where another tank feeds the supply, etc.).

[Tomon4winds]

Originally Posted by Taipe

I don't what you mean by "beats like zzz heart". That could mean regular or irregular. Let's drop that analogy. Your title for this thread says "random", some answers to these following questions might clarify whether ongoing fuel injection problems or burned valves/low compression. I'm not familiar with that engine, but assuming it Does not have common rail injection:

Does it have a 2-speed injector pump?

Does it rev up only at operating temperature?

When ideling, does the normal diesel knock occur regularly?

Have you pulled the injectors and had them tested?

I just mean it's not constantly running, just goes bump, bump, bump, not regular with the clock, but kinda regular

I don't think it's 2 speed... not sure how to tell? It's a Lucas CAV Delphi.

Its revving up a few minutes after starting

I'll have a listen for the knock

I have not tested the injectors, it's something I have never done, but I'm keen to do, if necessary

Thanks for your help! Today I will run from a different tank and should be able to eliminate air leaks from the equation...actually I hope it's an air leak

[Tomon4winds]

OK guys, I got it. I changed things around a bit and took fuel from the generator tank, now she runs sweet so it must be air in the line from the main tank. I moved some fuel from that tank to the gen tank and I could see micro bubbles as it went in. I'll crack on with the inspection of that line then! Phew! Thanks for all your advices

[Don C L]

Originally Posted by mvmojo

Had a similar problem. More than likely you've got a small air leak somewhere before the Walbro pump such that it's sucking a little air into the line. Mount the pump as close to your tank(s) as you can so that the fuel to the on-engine fuel pump is pressurized. With the engine turned off, wrap a strip of paper towel around every connection from the pump to the engine and run the pump overnight. You'll probably find one of the paper towel strips damp with diesel the next day.

That's what came to mind for me too. A friend had a similar problem, but with a Volvo, and it turned out to be similar leak.

edit: oops, didn't read your last post. Never mind.

[jimbunyard]

Certainly does not sound from your description like the classic 'hunting' typified by a mal-adjusted Detroit governor...

An air leak or air in the line would be the easiest and most fortunate symptom; that is the cause/cure listed in the operators manual found here

http://www.google.com/url?sa=t&rct=j...5-kptNnPWa7YWJ

Couldn't find a proper service manual (at least from a source I trusted enough to click on).

As the governor is built into the fuel pump, it should have been properly adjusted when the pump was serviced. If you have no luck with bleeding or chasing air leaks, a call to the shop that rebuilt the pump might be your quickest solution.

As an aside, though the classic Detroit hunting might seem to be peculiar to them or those of their type construction, it doesn't have to be. I recently replaced the fuel return lines on an Isuzu/GMC (you have to drain parts of the fuel system to do this) and on start up the engine hunted exactly like an old Detroit. This is a modern, common rail engine, although it has unit injectors just like a Detroit. The hunting worked itself out in a few minutes, likely just air in the system, though it could also have been some electronic gizmo adjusting itself.

Oddly enough, when I fixed the real problem a couple of weeks later (cracked injector body(s) [1900.00 factory reman!!]) the engine started and ran perfectly immediately...

[Diesel Bill]

The hunting on older mechanically injected Detroit Diesels is taken out with a buffer screw on the side of the governor. The screw pushes a small spring against the differential lever to take the slop out of the linkage. After running the rack or racks if a V-series I used to back out the buffer screw and let them hunt for minute because I so loved the sound. I can still hear it in my memory. When I was a kid we went through the Port Authority bus terminal in NYC. I could hear dozens of Grey Hound buses hunting.
Was like music to my ears.