Fergie TEF missfire at idle

[Right-arm fast]

Perhaps the chain slipped whilst you were removing or installing the pump? I'm suprised one tooth made the valve hit the piston though! At least you found the problem, everything's is nice and clean.

 

[MrNoo]

Bit more of an update on the sorry saga!! Exhaust valves were all ok, checked for straightness and blue'd up the seats and they were fine. Put it all back together after re-doing the cam timing while I was at it. It started and ran ok but still with the hunting issue. So I have checked the valve lift with dial gauge and seem to have quite a worn cam on some lobes.
Inlets: .255" .275" .250" .295" and factory spec should be .307"
Exhausts: .310" .250" .300" .310" and factory spec should be .342" so one of the exhaust lobes is giving me .100" less lift than it should be, not sure if that would cause the issue but have managed to source a 2nd hand cam, so will fit that. Unfortunately they dont make repro cams for the TEF but I guess I maybe could get it re-ground but fear it's worn maybe too much.
So the saga continues!!

 

[Right-arm fast]

I think you could get it metal sprayed and ground back to original specs. There used to be a co in Burton on Trent who did it. I have only had the rear crankshaft seal surface done not a cam.

 

[MrNoo]

I think you could get it metal sprayed and ground back to original specs. There used to be a co in Burton on Trent who did it. I have only had the rear crankshaft seal surface done not a cam.

I managed to get a decent 2nd hand cam from Patrick Edwards (just up the road) and having measured, it shows very little sign of any wear so will bang it in this afternoon and see how we go. Did compression test too and all pots came out at 300psi which is a little on the low side but suspect that the new rings have not bedded in yet but I dont think there is anything untoward going on in that department!

 

[Mursal]

Any word ................

 

[MrNoo]

Any word ................

Swan Vesta's…

Chasing my tail, pump went back to be checked over and no change, so will try injectors next (despite them having been done before) had one apart and the tips show blueing but look ok otherwise.
If that does not sort it then the head will come off again, I do have a spare head (that I will try)
Have tried spill timing from 28 degree BTDC up to 38 BTDC and still the same.
And to top it off this afternoon as I was about to load it up for a ploughing match tomorrow, it blew some of the gasket out of the side of the hydraulic pump, so it is now on the naughty step in the shed and will stay there until I can come up with any more ideas, or anyone else does.

It sounds like I am a crap mechanic reading all this!!

 

[Mursal]

Sorry to hear that .................
If you don't mind me asking, is it still knocking, or is it back at the hunting?

 

[MrNoo]

Sorry to hear that .................
If you don't mind me asking, is it still knocking, or is it back at the hunting?

No the "knock" was sorted, it just hunts at idle/low revs and no matter what I do to it I can't stop it, can spray Easy Start all around the venturi etc and engine revs dont change so no air getting in. Changed springs/plungers etc on the pump, no leaks there either, new lift pump/filters. I do have a feeling that maybe a weak injector which in turn leads to almost a misfire (but not quite) and this upsetting the balance between spring on the diaphragm and vacuum and then leading to a uneven hunt/pulse but I will find out soon (I do worry that the ploughing season will be over mind!!)
I did speak to one chap who had the same symptoms on a customer's TEF and he said they never managed to get to the bottom of it, he suspected that skimming the head did not help matters. If the worst comes to the worst I will strip the whole thing down and start again but just build it up in a similar way to how I used to build the race engines as something somewhere is not quite right.

 

[tomlad]

So the fault is only at sort of 6 -800 revs ?

 

[MrNoo]

So the fault is only at sort of 6 -800 revs ?

Yes, I would say more like 600 to 1200, if you adjust the lever on the side of the injector pump it makes no difference to the hunting, just shifts it higher up the rev range. The plunger was originally seized and as such there is a slight bit of pitting but nothing too bad. Compression is good at 300 psi on all pots (new rings maybe not bedded in yet) so one would just start to think about fuel.

 

[Mursal]

Would you not ask for a lend of the injector pump of its mate, then you can eliminate that completely? Running the pump on the bench just mightn't pick up on a problem like that.

But if you don't want to ruffle any feathers
Would the governor spring behind the diaphragm be a little on the weak side?
Vacuum gauge T'ed into the vacuum pipe, see if it changes in sympathy with the hunting?

Might be worth allowing a small amount of vacuum to be lost, either crack open a fitting ever so slightly or fit a tap so you can control the opening to let a small bit of air in.
But proceed with caution as I think the vacuum is the only control it has over maximum rev's.

 

[MrNoo]

Yes vacuum is the only control over revs, I have already tried "bleeding" vacuum off with no difference, the main spring I have changed with another. I am sure the vacuum changes in sympathy with the hunting as I can watch the rack move in the same rhythmic fashion as the hunting.
I would agree re the pump, only I am loath to take the one off our other TEF as it runs like a little sewing machine, I used a local company for both the injectors/pump but not one I have used before, we normally use one from up North.
I have not done a leak down test but did a compression test, pistons were not marked re "front" but instead had "Bepco" stamped on the top so put them in all the same way, rods too, although I dont think they are offset so it wouldn't be an issue.

 

[Mursal]

And you are happy with the engine and the way it runs, only its hunting?
If so, I would think its pump/governor control rather than engine.
The air filter on or off makes no difference?

Did you try opening the fuel line to the pump just in case the pressure control on the lift pump isn't working, or set to high?

 

[Right-arm fast]

might be worth restricting the vacuum with a small tap in the airline near the governor housing which you can slowly close to even out and maintain a constant vacuum in the diaphragm chamber rather than it being pulsed when the inl. valves open. Am assuming the fuel pump has been checked properly and there isn't a damper missing or play in any of the linkages which would let the rack move or the plungers rotate.

 

[tomlad]

Or if were thinking bedding in ect give some pain for an hour under nice load.??

 

[tomlad]

Is the link and rod thingy fitted @MrNoo r/h side of diaphragm -back to throttle linkage?
Ive a memory of something in there that tried to balance out hunting at the idle /low vacuum pull .?? Adjustable ? Plunger inside if free

 

[MrNoo]

And you are happy with the engine and the way it runs, only its hunting?
If so, I would think its pump/governor control rather than engine.
The air filter on or off makes no difference?

Did you try opening the fuel line to the pump just in case the pressure control on the lift pump isn't working, or set to high?

Yes, it runs ok but I need good low end throttle control for match ploughing, as we like to go slow!!! Filter disconnected makes no difference. I have tried opening the fuel line bleed whilst running and again makes no difference, wasn't aware there was any pressure control on the actual lift pump, just 2 one way valves and then a restrictor on top of one of the fuel filter bowels going back to tank via injector overflow ports.

 

[MrNoo]

might be worth restricting the vacuum with a small tap in the airline near the governor housing which you can slowly close to even out and maintain a constant vacuum in the diaphragm chamber rather than it being pulsed when the inl. valves open. Am assuming the fuel pump has been checked properly and there isn't a damper missing or play in any of the linkages which would let the rack move or the plungers rotate.

No play in any of the linkages, made sure it was all done properly and slop free. I could assume that there should be a vacuum pipe damper which would do as you say and stop the hunting but I am not aware of any on any of the engines I have worked on. Pump was gone through having new elements fitted, calibrated and phased and then checked over again last week.

 

[MrNoo]

Is the link and rod thingy fitted @MrNoo r/h side of diaphragm -back to throttle linkage?
Ive a memory of something in there that tried to balance out hunting at the idle /low vacuum pull .?? Adjustable ? Plunger inside if free

Yes Tom, it is all connected and if you disconnect it and move by hand all it does is move the surging up the rev range, plunger is free and you can feel when it comes into contact with the diaphragm.
I thought the same so stuck a cultivator on the back of it and gave it some stick for an hour but still no better.

 

[tomlad]

put the reduction box on it so u can rev faster

mine did basically the same b4 I stripped it , but mines still in bits id been blaming the slop in linkage and the diaphragm
I've a memory of reading about adjusting summin to counteract the hunt BUT I may be taking shite and wrong machine altogether captain .