Club 80-90 Forums

Hi All

Ok a few details first

2 litre Air Cooled
CU Engine
Electronic Ignition
98k

After 10 years of very reliable driving the van has developed an annoying intermitent fault.

Whilst driving the engine has a tendancy to cut out to what seems to be about 2 cylinders. I can free wheel to the roadside and the engine has no power but still ticks over. Try to rev but no pick hence the thought of only 2 cylinders.

Switch the engine off once or twice and then it will start and be ok once again.

I've done a couple of 100+ mile journeys recently and this tends to happen during the first 10 miles but as I said can happen anytime.

Tried changing plugs, dist. cap, rotor arm, ig. leads and fuel filter and have run 2 lots of Redex through. Can't find any air leaks or hear any hissing.

I can't recreate the problem at home on the driveway to try and work out what it is. Also get the occasional backfire going downhill in 2nd.

Can run ok for miles but now worried it's going to catch me out sooner or later.

Any help much appreciated.

Dale

disconnect the 2 leads from the idle stabiliser box (black box next to the igition module) and connect them together... if this hasnt already been done!

these can affect the running, dont bother replacing it...

Thanks

I will give that a go. I didn't realise it could affect the van while actually driving and not idling.

I'm really just trying to try all the obvious and inexpensive things before I start taking the carbs apart.

ive had a similar thing with the left hand side of the carb not working so it was only running on 2 cylinders. it turned out to be one of the valves, from memory it was the bypass air cut off valve.

Yes, I'm more inclined to think it's lack of fuel in one of the carbs rather than an ignition thing.

As I mentioned turning the ignition off and re starting the van seems to temporaraly cure it. Does anyone know how I can check if these valves are working correctly?

Thanks again.

I took the bypass valve off and covered the hole with my finger to stop the petrol coming out.
where abouts are you?

I'm in South Gloucestershire/North Bristol

As I mentioned I can't seem to recreate the problem on my driveway. Ticks over perfectly and does not misfire at high revs. It only seems to happen when I'm out on the road.

I also renewed the connectors on the wires coming from the valves to the coil. they looked really old and dirty.

The idle unit can give all kinds of running problems when it craps out..

Yeah could be a fuel starvation thing then.. have you checked the fuel filter to see if there is any crud in it..

Yep, I've renewed the fuel filter.

The wires in the coil/left carb area are a bit crudy but not sure of the function of the bypass valves to be honest. Something intermitent would suggest something lose maybe? But would that prevent fuel to the carb?

I think you are going to have a look at each system and eliminate it as you go.. we are only best guessing here...

Agreed, I've got a few things to go on now so thanks.

I will post back any findings.

Dale

Worn fuel pump pushrod can give enough fuel for pootling about but starves them of fuel when on a run ......

I had the same problem with my first T25.

After months of just 'getting by' I finally changed the ignition unit and all was well.

Congrats Toomanytoys

I would appear to have been the idle stablising unit. I mananged to cover 30+ miles over the weekend without the problem occuring.

I will now leave the thing disconected as you rocommend. What task does it actually perform apart from the obvious name in the title. I would be interested to know.

Going back quickly to the symtoms I suffered in case anyone else has the same problem. It was like the engine suddenly dropping to an idle speed and having no control over it. Pull over, switch ignition off and would usually fire up fine again.

Fingers crossed that's the end of it.

Thanks again.