Slight Misfire on 2.0 Aircooled

[Tug]

Morning....

Wondering if any one has any ideas why my camper has developed a slight misfire in 2nd / 3rd above 3000 rpm.

Cruises nice in 4th up to 60 (Dont drive it no faster than that).

The problem seams to be when the engine is under load...Would this have anything to do with new push rod tubes being fitted....have adjusted the rockers as per Haines manual and Im not a amature to mechanics...Have adjusted them the sames as I would with any others ..Engine Cold , Turn the engine through its cycle etc etc.

Could this be a carb problem do you think....Fuel starvation.

Note camper had been stood since last October due to a refurb...

Glenn.

[VWCamperfan]

Could be ignition coil related if it happening under load although I would have thought this would happen in 4th as well.
Could also be the rev limiter in the distributor cap (if it has one). The spring may have become weak over the years and causing the HT side to short out to keep revs down.
As it has been standing for a while the fuel can become less effective over time. If you havn't put in new fuel for a while it might be worth a try to pop to garage and stick some new stuff in!

[Tug]

Thanks for the response.

It has had £100 of juice replaced during our trip down to south wales, Pembroke, The Mumbles etc and it ran very well. It just developed this misfire while under load.

The Dizzy cap and Rotor arm have been on 3 years and done approx 5k so would hope that it is not these items. They were also genuine Beru items.

The leads were replaced before I had the van 3 years ago also. The only thing that looks original is the coil...So you suggest replacing this ?

[DaisyAirHead]

Hi Tug,
Just a thought re misfire under load.As the van has been standing for a while try replacing the inline petrol filter which should be somewhere under the van between the fuel tank and fuel pump/carbs.
I had a very similar experience last year on my first long run out of the year.The filter had become partially blocked.The van would start and run fine,but would misfire when under load.Spent a long time changing/cleaning sparkplugs,checking timing etc before the penny dropped!!Replaced fuel filter.Very cheap from GSf parts.Couple of quid I think,changed it and Bob`s your strange Uncle who no-one talks about,she ran sweetly again with no hiccups!!
Maybe worth a go
Best Regards

[Rozzo]

The problem seams to be when the engine is under load...Would this have anything to do with new push rod tubes being fitted....have adjusted the rockers as per Haines manual and Im not a amature to mechanics...Have adjusted them the sames as I would with any others ..Engine Cold , Turn the engine through its cycle etc etc.



Glenn.

i'm sure i read somewhere that the info for setting the hydraulic tappets in the haynes manual is wrong. could be that they're too loose or too tight. someone will be along who knows i'm sure but if not post in general about the haynes info.
just found this in the wiki https://club8090.co.uk/wiki/Pe ... nder_heads" onclick="window.open(this.href);return false;
good luck with it

[phade]

The first thing to do is to leave the hydraulic tappets alone !!! The sticker on my campervan's original rocker covers had a sign telling me not to adjust them at all !!

Another cause of a slight misfire is the idle jet(s) being partially blocked on one or both carburetors. A very simple cure for this is the following:-

- Replace the fuel filter
- Start up the engine and warm it up to operating temperature
- Switch off the engine
- Undo the air filter unit and lift up the rubber elbow from the left hand carburettor. Leave the right hand rubber elbow on top of the right hand carburetor.
- Start the engine
- Now put one hand over the top of the left hand carburetor, leaving a small gap between your fingers
- Rev the engine up and down. The engine may sound like a lawnmower at this point. The idea behind doing that is to force out the blockage by means of a vacuum. Repeat this process until the blockage has cleared (the engine will sound better after the blockage has cleared and your fingers will become damp with fuel).
- Refit the left hand carburetor rubber elbow and lift up the right hand carburetor rubber elbow
- Repeat the process for the right hand carburetor

Also, another very important thing to check (this has caused my carburetors to become partially blocked in the past) are the fuel hoses !! If any of them feel knackered or look perished, cracked, chaffed or are leaking then they must be replaced at once !!! Only replace fuel hoses with BASU and/or DIN compliant fuel hoses.

You should be able to get fuel hoses from your local motor factor or failing that eBay (eg. Goodyear hoses from eBay seller ID 44nmj). The following fuel hose sizes (I have found out at least) are the following:-

- Fuel tank to fuel filter: 7.0 mm (I managed to get 1/4 inch hose to fit after dipping it into hot water)
- All other fuel hoses to the carburetors inlets: 5.5 mm (5.0 mm fuel hose will fit with some hot water)
- Carburetors balancing hoses (except top right hand side of the left hand carburetor): 8.0 mm (I think approx 9.0 mm would provide a better fit)
- Top right hand side of the left hand carburetor: 10 mm (I think this size fitted properly)

Also use brand new fuel hose clips where ever possible.

[Rozzo]

The first thing to do is to leave the hydraulic tappets alone !!! The sticker on my campervan's original rocker covers had a sign telling me not to adjust them at all !!

yes but he says they have already adjusted them so therefore they could be adjusted wrongly which could cause the misfire under load

[phade]

Oops misread the original post.

In which case they will need to be adjusted to thier basic setup (I can't remember what settings they should be since I've never touched them, I'm sure other people on here will know). The hydraulic tappets should then (eventually) settle down by themselves.

[VWCamperfan]

To adjust tappets... Make sure hydraulic tappets are 'pumped up' be letting engine run until they are quiet.
Take off rocker heads and adjust each one until the adjuster is just touching the pushrod, ie. no movement on rocker.
Turn in adjuster one and a quarter to one and a half turns and no more.
Job done!

[philippacman]

recheck your tappets, change the leads,cap,rotor arm and plugs, alot can happen in 3 years nomatter how low the miles, get a standard rotor arm not a rev limited one, see how that helps

[Tug]

Thanks All for the response.

It seems ....like it was the fuel filter. I have changed this for a new one and.....Done away with the two in the engine bay...not sure why these were on it but hay ho ....I have put new pipes from the `Y` piece which to be honest I am not happy with. I have ordered a new brass `Y` Piece with an 8mm hole so it will fit nice and snug in the 7mm pipe.

All in all i have had no misfires and it pulls lovely up to 60mph. The old filter was full of rust and silt...probably from the old tank. Although I did change this filter about 3 years ago and it has done only 5 - 6k.

I will give it a run to Worcester later to see if it has totally settled down.

Glenn.

[DaisyAirHead]

Hi Glenn,
Thought it might be the filter!
Hope it is sorted.
As a matter of course I change mine annually as they are only a few quid and modern additives in petrol seem to "eat" the filter innards in a short period of time if left standing.
Best Regards
John