Injector pump rack

[Mukiwa]

I have been having problems with wildly varying idle speeds.

An engineer came out yesterday and diagnosed a sticking rack in the injector pump. I have no idea what that might be.

He recommends having the pump reconditioned which will cost about £200/£300.

Is this better than sourcing a new one?

[Timleech]

I have been having problems with wildly varying idle speeds.

An engineer came out yesterday and diagnosed a sticking rack in the injector pump. I have no idea what that might be.

He recommends having the pump reconditioned which will cost about £200/£300.

Is this better than sourcing a new one?

 

What is the engine?

[Mukiwa]

It's a Nanni 3 cylinder, 29 hp engine with Hurth gearbox ZF 100.

[Geoff Taylor]

Hi, I would first of all guess that the engine has not been run for a while and was this problem beginning to happen the last time it was used?, the first thing to do would be to change the fuel filter/ water trap etc and run the engine up to operating temperature as these symptoms can be a sign of fuel related problems before jumping to expensive conclusions, the rack could be sticking but unlikely on that particular inline injector pump.

Try opening and shutting the throttle quite a few times and make sure that you can block off your air intake with a piece of solid material (not rag) should the engine stick flat out in order to stop it. Hope this may help

[Mukiwa]

Hi Geoff. The problem first became apparent a couple of years ago and over time has become steadily worse.

It only happens at lower revs ie idle can vary between 950 and 1250 revs. Another symptom is that is does not increase speed smoothly. All the symptoms are worse when the engine is up to full operating temperature.

[Geoff Taylor]

Hi, As it has happened over time, it could be wear and tear and need a recon (much cheaper than new) which will basically be a new pump again. There should be a rack adjusting screw and locknut on the front casing with either a lead seal or alloy top hat on it.

I would proceed with caution but should you wish to have a play, mark it and screw in quarter turn at a time to see if any different, screwing out will overfuel and may get worse results. There are no other adjustments that I can recall externally.

The only other thought I have would be a lot of play in the throttle linkage that could be helped by attaching a spring on the throttle arm to pull against the morse cable temporarily to see if it helps. (I have come up against that problem with a different engine).

[Loafer]

If you have a small lift pump, with a little bolt on the top, try seeing if that is free from grunge. It might have a blocked gauze filter in it. You just need to unbolt it and have a look, then possibly re-bleed the fuel system. Worked for me, after refuelling at a place wot 'ad grotty diesel.

[by'eck]

If you have a small lift pump, with a little bolt on the top, try seeing if that is free from grunge. It might have a blocked gauze filter in it. You just need to unbolt it and have a look, then possibly re-bleed the fuel system. Worked for me, after refuelling at a place wot 'ad grotty diesel.

 

I think Loafer may have it. If the lift pump action is compromised by partial blockage within on filter before it, at low engine speed it may not pull enough fuel through whereas higher revs mask the problem.

[RLWP]

 

I think Loafer may have it. If the lift pump action is compromised by partial blockage within on filter before it, at low engine speed it may not pull enough fuel through whereas higher revs mask the problem.

 

I have seen one of these pumps with a faulty valve too, idling was terrible!

 

Richard

[by'eck]

 

I have seen one of these pumps with a faulty valve too, idling was terrible!

 

Richard

 

My experience was with a Volvo TMD31B. It had intermittent fuel starvation dragging air into the system for several months. Although temporarily cured by cleaning filters, polishing fuel etc., it was eventually traced to a cm2 lump of massed grunge in the lift pump. Note this had been removed earlier and appeared to be sucking and blowing quite well when operated by hand, so was not initially suspect.

[Tony Brooks]

Ditto on a 4 cyl. Beta with the circular disk shaped lift pump with six screws holding it all together. I found the valves clogged with what I think was bug residue. These pumps are easy to strip to get at the valves and a short while with some solvent, artist's brush and maybe a cocktail stick clear it. Just mark the cover and body so the parts are correctly aligned to each other, otherwise a land (bar) across separating two pumping chambers will not line up and it definitely will not pump.

[RLWP]

Yes, it was one of those pumps I found the problem with. From memory, the valves are a plastic disk covering both inlet and delivery. The one I stripped had a broken valve disk

 

Richard

[Mukiwa]

Thanks for all the suggestions.

It is not caused by the cabling as when this was disconnected the problem still occurred.

I like the idea about the filter in the lift pump. A couple of years ago I did have dirty fuel and when it was cleaned a lot of grunge came out. I will try that before I go any further.

I get the impression that if needs be it would make sense to have the injector pump reconditioned rather than buy a new one.

[RLWP]

Sorry, yes. If it comes to it, get your pump reconditioned rather than buy a new one

 

Richard

[Mukiwa]

A few hundred pound later, a reconditioned injector pump fitted, new fuel pipes, governor checked and lift pump removed and I am back where I started. The engineers are tearing there hair out. They have been in touch with Kubota and they can offer no further suggestions. As you can imagine I am extremely frustrated and to make matters worse it is now beginning to vary it's revs at cruising speed (1600). Not by much but within a range of 100 rpm.

It's difficult to know where to turn next.

[RLWP]

Lift pump replaced?

 

Richard

[Mukiwa]

Lift pump replaced?

 

No. I understand it was just removed and examined.

[RLWP]

Examined is OK assuming they dismantled it.

 

Richard

[Mukiwa]

I don't know Richard. I'll ask the question although at the back of mind I seem to recall someone mentioning that they are sealed units on this engine.

 

Mike

[Geoff Taylor]

A few hundred pound later, a reconditioned injector pump fitted, new fuel pipes, governor checked and lift pump removed and I am back where I started. The engineers are tearing there hair out. They have been in touch with Kubota and they can offer no further suggestions. As you can imagine I am extremely frustrated and to make matters worse it is now beginning to vary it's revs at cruising speed (1600). Not by much but within a range of 100 rpm.

It's difficult to know where to turn next.

 

Did the diesel reconditioner report anything wrong with the injector pump and were the injectors also serviced/replaced ? , if all of this was done then my guess is that something was overlooked inside the injector pump or it was recalibrated incorrectly (it does Happen!) . I am not sure about the Kubota but quite a few engines have a centrifugal advance/retard device built into the pump timing gear and this can definately cause exactly the same problems if the springs weaken or break.

[bizzard]

Could be a blocked or partially blocked fuel tank breather. You could try running it with the filler cap off, but put a cloth over the filler in case dirt or leaves blow into the tank. And is the spill back dribbling ok?

[Mukiwa]

Thank you Geoff I'll ask the reconditioner about that.

 

Hi Bizzard we did try running with the fuel cap off but it made no difference. Thanks for the idea though.

[by'eck]

Lift pump replaced?

 

No. I understand it was just removed and examined.

 

See post #10 - I examined mine after removal but foolishly didn't strip it as it appeared to work okay.

[Mukiwa]

An update. Three springs have been replaced in the governor. The slight variation in revs at cruising speed has been cured but the basic problem of revs at idle still persists. When the engine is cold or freshly started it will idle at 950 rpm. As soon as it is warm it will not drop below 1250 rpm. I guess I will have to live with it as I'm not prepared to spend any more money on this engine.

[Geoff Taylor]

Hi, that is good news on the constant revs front, as for the idle I would set the RPM with the engine warm as that is the norm of setting any engine that is not ecu controlled or has a cold idle device fitted.