choke/starting problem

[alphagalaxy]

The choke is on, but not holding revs. Have to put foot on gas to keep revs going, then choke working as it should, opening up to turn choke off, once warmed up, remains running. Once cold, choke flap down/on position, same problem to start again.

[clartsonly]

what camper do you have? could it be the inlet manifold heater?

[alphagalaxy]

Sorry, I have a 1985 1.9DG Petrol RHD T25.

[alphagalaxy]

Watercooled

[alphagalaxy]

The inlet manifold heater is heating. It burnt my fingers!!

[clartsonly]

is the engine breather blocked? eg pushing oil and gunk back through the carb?

[fairwynds]

Alphagalaxy,

ok, first, lets look at the priciple of these chokes on a DG water cooled engine:

when engine is cold the choke is 'on' (ie the choke flap is closed, giving a richer mixture to start engine)

when the engine is hot the choke should be 'off' (flap completely open allowing lots of lovely fresh air into the carb)

**as the engines warms up from cold the choke should slowly switch off**
**but conversely as the engine cools, when switched off, the choke will slowly switch on**

the carb sits on a set of alloy pipes which deliver the air/fuel mixture to the cylinders via the inlet valves. There is a heating element between these pipes and the base of the carb, which keeps the carb warm and the goes a long way to prevent the carb 'icing' - esp in the cold weather (although its more a question of gas laws and pressure reduction in gases causing the chilling of the mixtures - but thats another story!)
This device, however, is almost certainly (IMHO) NOT your problem.

Now, the important bit for you......

Attached to the side of the carb is the choke unit, an alloy housing which is fed by water from the cooling system AND 12v electrics.

It looks like this:
[IMG:640:480]http://i98.photobucket.com/albums/l261/ ... MG2269.jpg[/img]

There is a metal coiled spring within which heats up and expands (lengthens) thereby opening the choke flap, and staying open because of the hot coolant being pumped through the choke body pipe.
As our vans take several minutes to warm up to temp, this would mean that the choke would stay on for ages until the spring was fully warm....

So now for the clever bit:-
Beneath the coiled spring is a tiny coiled wire 12v heating element which is what the wire in the above pic feeds. Thus, as soon as you turn the key on a cold engine the 12v feed heats up this wire element and this directly heats the coiled spring, long before the warm coolant takes effect. This way the choke operates early and switches off earlier, to avoid high revving, over choking situations. The following pics shows the inside componants of these chokes:
[IMG:640:480]http://i98.photobucket.com/albums/l261/ ... MG2268.jpg[/img]

and:
[IMG:640:480]http://i98.photobucket.com/albums/l261/ ... MG2274.jpg[/img]

BEWARE - THE STAR SHAPED BITS X2 ARE 'CERAMIC' AND FRAGILE!

It is quite common for choke problems to be traced to this tiny 12v heating element. It is very fragile and can break with age, rendering it useless. When this happens, the choke will stay on far too long and play up no end.

All is not lost because (if its broken at either end) it can be repaired. They end of it is crimped into place by VW. This can be removed and a small hole drilled and tapped to take a tint screw and washer, to clamp it back in place. This tiny work (on my choke) was done by a very friendly watch and clock maker intown! (they have incredibly small tools, so to speak!)

This pic shows the tiny screw/repair on mine:
[IMG:640:480]http://i98.photobucket.com/albums/l261/ ... MG2272.jpg[/img]

and the finished article:
[IMG:640:480]http://i98.photobucket.com/albums/l261/ ... MG2275.jpg[/img]

Dont be afraid to take it all apart and recondition it. Yes it can be fiddly but well worth it in the long run. I hope the pics help you to understand whats inside and how it all works....?

Good luck

[kimbobill]

Good article fairwynds is it in the wiki if not it should be

[fairwynds]

Kimbo, thank you. I have no idea how to put it in Wiki! If people want it there, go right ahead....

[alphagalaxy]

Thanks for your reply. Youve taught me something I didnt know. But the problem is, the choke is on the 'on' position, but it is not holding the revs. If I keep my foot on the gas and let it warm up that way, then the choke opens up like it should then it ticks over. I had a Pierburg which was doing this so I changed it for a new Weber and Im getting the same prpoblem. Ive changed the throttle heater, checked the inlet manifold heater, fuel pump Im changing but Im not convinced its that. I did test it and it seemed to work as it should. Im not sure if the engine is building up pressure, would that affect the choke kicking in? Im a bit at a loss now. Not sure what to do!! Appreciate any help or ideas.

[fairwynds]

Mods
as sugested above, could this be put in WIKI for future reference? Sorry but never done that and dont know how!
Cheers... FW