High reving TIckover on a DG 1.9 Petrol

[melvin]

Hi All,
Just wondering if anyone has had the same problem/solution to the following problem. I can't complain too much as the old bus starts on the button and drives quite well but my tick over when warm is around the 1500 mark, I have adjusted the tickover screw right back so it is no longer even touching the throttle, the fast idle cam/choke is operating as it should and the timing is at 5deg as per the marker. If you disconect the vacuum advance the tickover goes down to about 900/1000rpm.
If I push on the throttle cam to close the butterfly I can get the tickover to be about 1100rpm, so if I were to bodge it and fit an extra spring to the throttle linkage it would almost solve the problem, but that would be a bodge, and only masking the problem.
When cold the tickover is about 1300rpm.
I think I have mentioned everything, any ideas anyone??

Cheers

M

[Ian Hulley]

Ours has had a spring holding the butterfly shut for years, cable tied to the petrol pump. I only realised it was there when I swapped the engine.

Ian.

[kevtherev]

Hi All,
Just wondering if anyone has had the same problem/solution to the following problem. I can't complain too much as the old bus starts on the button and drives quite well but my tick over when warm is around the 1500 mark, I have adjusted the tickover screw right back so it is no longer even touching the throttle, the fast idle cam/choke is operating as it should and the timing is at 5deg as per the marker. If you disconect the vacuum advance the tickover goes down to about 900/1000rpm.
If I push on the throttle cam to close the butterfly I can get the tickover to be about 1100rpm, so if I were to bodge it and fit an extra spring to the throttle linkage it would almost solve the problem, but that would be a bodge, and only masking the problem.
When cold the tickover is about 1300rpm.
I think I have mentioned everything, any ideas anyone??

Cheers

M

when cold depress the acc. once and remove your foot. Start the engine with out touching the pedal, it should start and run at 2000 rpm
touching the acc. will drop it to 1500 then as the engine warms eventually to 900

If the butterfly isn't closing then there must be a reason for it

[melvin]

Tried what you said, On Startup the idle is around 1300 but with a blip of the throttle this seems not to change? Until the engine is warmed up then it goes higher again!
I have pre-booked (with the wife ) some time in the garage on Wednesday night so I'll take a good look at the fast idle adjustment to make sure thats set right.

Cheers
M

[kevtherev]

are you guessing the rpm?

[melvin]

No, I only say 'around 1300 rpm' as my aftermarket gauge was a small cheapy one from ebay so I don't know for sure how accurate it is. but I beleve its fairly accurate.

Cheers
M

[kevtherev]

For adjustments to this part of the carb it must be removed, along with the bi metal spring and housing

1/. Adjustment of fast idle cam must be done using a vacuum pump mechanism to the 2nd stage choke and create a vacuum around 300 Millibar
2/. Open the throttle , to freely move the cam.
3/. Gently move the lever (c) or the dog in the bi metal spring housing, clockwise and then release the throttle valve.
4/. Check the distance (x). It should be 0.2 - 0.8 mm.
Adjust the value using distance lever (d)



With carburettor off "set" choke as normal (manually) the throttle stop screw A should sit on top of cam lobe 1, once the throttle shaft is moved it should drop to cam lobe 2.... then when the carb is on the engine the coolant temp will move it down the cam progressively .

Further refinement can be found using screw A when engine is HOT and at working temp adjust screw A to final cam lobe 4 to just touch the surface of lobe.

[melvin]

I'm not going to lie, most of this has gone over my head (parts 1 to 4) Pierburg carbs are not my thing really
Although this morning I thought I'd try the cold start method you suggested again.
Depressed the pedal then let go, started up and we were on about 2500rpm, I waited a few seconds then depressed the pedal again and this time it went down to 1100rpm!
Once warm we were back up to around 1300-1400rpm, until I give the throttle linkage a poke with my finger, then were back to 1100rpm
I think I'm going to leave the fast idle alone for now as it seems to be functioning semi right (if it ain't broke don't fix it kinda thing).
Just need to look at why the throttle is sticking at idle, plenty of lube on all the joints I think is the next port of call...
Thanks
for your help! I'll let you know how I get on.

M

[kevtherev]

Depressed the pedal then let go, started up and we were on about 2500rpm, I waited a few seconds then depressed the pedal again and this time it went down to 1100rpm!
Once warm we were back up to around 1300-1400rpm, until I give the throttle linkage a poke with my finger, then were back to 1100rpm

by the sound of it if you adjust screw A out you will achieve a lower tickover

[Whitevanman]

Also check the throttle cable is not sticking. You can easily check this by disconnecting it temporarily to see idle speed changes. I had this problem and a new cable sorted it.

Mark

[alanf_uk2002]

Hello folks, not that this is going to help you too much but my van does exactly what you have said (running at 2500rpm then drops down etc). I have completely rebuilt my carb at the weekend (not for this reason) and on refitting/running I noticed that the throttle did stick a bit near the throttle stop and touching the cable would, as you say, drop the revs back down. I think it's just crap in the throttle springs or in the spindles due to wear and tear; I gave mine a good clean and lubricated it but it still does it. Maybe fitting a secondary spring to the throttle might help?

I'm just happy mine runs better so I can live with the "characteristics" of the carb...for now anyway.

Regards
Alan

[getunder]

My engine speed suddenly became a bit faster than I wanted. After all sorts of pavlova found that the cable adjustment under the van under the throttle pedal needed adjusting. Fine ever since. Not a lot of people know its there. Not in Haynes .