Air cooled 2ltr CU in Portugal - running like a pig.

[porthyt]

Hi,

I have posted this on FB as well so apologies if you are in there also. Urgent help pls!! Currently in Portugal with our air cooled 1981 2l t25, fine whence parked it up. However we parked on a really steep hill, nose down for 2 days. Started up fine, drove for 1 mile fine and then lost most of our power. We can’t drive above 40miles and hour and can only get up a hill in first or second. If we stop and let it Cool for 15mins, then it will drive fine for the first mile again and then the same. Have checked the oil, changed the fuel filter and replaced a completely burnt out rotor cap and it still is the same? What would cause the rotor cap to do this? Checked the spark plugs and although sooty they were all sparking. Replaced the dizzy cap, changed for a spare coil and checked for vacuum leaks but still running terribly.

A guy on the campsite fixes up vans and he has a compressor - I am thinkninh if using it blow through the carbs to dislodge and crud (steep hill and not much fuel when we started). Without full disassembly how do I blow through the carb - just through the lines and the inlet valve bit?

Today the van also started a sort of knock/click/clunk from the rear - what mechanicals could do this? Can the Dizzy cause this noise?

Sorry for the essay but I hope you can throw some ideas out for me to try tomorrow.

Cheers
Josh

[937carrera]

I think you're on the right lines

Low fuel, causes debris to block jets. Van runs better when cool because the choke is on enriching the mixture.

What does the new filter look like - more debris being pulled through ?

Put some more fuel in the tank to stop pulling more stuff through, replace the filter again if clogged, remove carbs and clean out jets. I suspect you will need to remove the carbs you will get better access to the jets and tipping at different angles may help dislodge bits.

My first port of call for the knocking would be CV joints

[porthyt]

An disappointing update: Still no better. Today I checked the resistance on the coil (all good), checked each lead was sparking, checked spark plugs were correct code and gapped correctly. Checked fuel was clean and coming to both carbs, replaced the fuel pump, checked the oil (just over max), checked the electronic ignition, checked the chokes operated evenly! All of this and she still drives like a pig. Idles and revs fine but as soon as there is any load (above 2k rpm) or the slightest incline (even my camping ramps were tough) then she bogs and almost stalls! I'm thinking dirt in the jets.

The filter is clean, the fuel was clear and clean at the carb end.

[937carrera]

I suspect you've done pretty much everything except the thing you need to..... carbs off and blow the jets out.

The unwillingness to rev is indicative of a lack of power, which is going to come from lack of fuel or timing absolutely miles out. We spend a lot of time adjusting timing on our old motors, generally compensating for wear on the points, so i doubt it will be timing unless the dizzy is loose.

Beware, running the engine when the mixture is lean will cause high combustion / head temperatures.

Have a look at the plugs & I think that's what you will see which will help confirm the diagnosis.

[tobydog]

I'd take the carbs off and clean them out. 13mm spanner and flat screwdriver. Go easy taking the top of the carbs off to avoid breaking the gaskets. Blocked main jet(s)?

[porthyt]

Ok. Thanks. If I take the carbs off will it adjust all the mixtures etc as I spent all day with a mechanic before I left getting these set up correctly. Can I just unscrew the top bolts and lift the lid off without disturbing these or the gaskets?

[937carrera]

It shouldn't adjust the mixtures so long as you don't move the adjustment screws....... or if you do make sure you count how many turns in / out they are set at.

I would remove the whole carb from the inlet manifold, rather than splitting the carb in situ. If you drop something you might never find it.

Double check the balance / crosspipe elbows too. I don't believe there is anything wrong with them as it's idling fine, but if they are leaking it can cause havoc.

[tobydog]

If you take them off, it won't change the mixture. Don't screw/unscrew any of the external jets. It's better to take the carbs off one side at a time. Take care of the small circlip holding the choke linkage. When they're off and the tops are off you can empty them and clean them out. From memory, there's a blanking plug for one of the jets through the bottom of the bowl, unbolt it and unscrew the jet and blow through it.

[937carrera]

Some bedtime reading for you

https://www.thesamba.com/vw/archives/ma ... uretor.pdf

May not be exactly the same but I expect it'll be pretty close

[porthyt]

Today I completely dismantled the carbs and removed the idle and main jets. One had dirt in it - blew through them all and every tube with a compressor and cleaned the float bowls. There was some debris in there. Reassembled but i has no fuel in the lhs carb.
Managed to sort out the lack of fuel but found that the needle valve thing was slightly bent and would stick every once in a while. Would this cause the symptoms or would the fuel be strong enough to push it back down? Took her for a drive and exactly the same. At one point I plugged the leads for the idle stabiliser together and she accelerated normally for 200metres with power and then bogged back to being rubbish. Limped it home and stopped for the time being. If it isn’t fuel related could it be ignition? All the plugs and wires fire but perhaps they aren’t firing strong enough. This morning I removed all 4 plugs (3 were white/brown but 1 was black). Trying to figure out the burnt rotor. It looked like this. Thanks a lot for helping everyone. I did learn a fair whack today!

My train of thought is it runs for 200mtrs as the fuel bowl on the sticky valve side is full- it then doesn’t let anymore fuel in and she is on 2/4 pistons...

[937carrera]

Some thoughts / suggestions:

No fuel in LHS. You fixed it - how ?. Is fuel delivery equal to each carb ?

The needle valve shouldn't stick, can you carefully straighten it

Plugs - all 4 were black, now only one of them is black. Is this carbon or oil

Have you checked all 4 plugs / leads ? Run the engine at a fast idle and isolate each plug in turn. Do they all drop speed evenly ?

It could be ignition, heat related breakdown or usual failure mode of the ignition module / hall sender, but as it all stems from the parking on a hill, I would favour fuel.

[Mr Bean]

Getting back to suspected cause and sorry if teaching Granny:
Did you check for blocked tank breather i.e. loosen tank cap to see if problem disappears?
Or (taking usual precautions re fire risk) connect a pipe and container to the last link in the fuel line (pipe/s to float chamber/s) and run the pump to see if flow suddenly reduces to a lower rate/dribble after a time consistent with your fault developing on the road.

[porthyt]

Hi,

I’m getting pretty desperate now! Ordered a carb rebuild kit from Brickwerks with new needle valves etc, fitted this, changed all the plus, got new leads from BW and fitted, new rotor arm and still no luck.

On top of this I have also replaced the mechanical fuel pump for another one, changed some of the fuel lines (the others are months old), new filter, swapped coil, driven with fuel cap off, checked that each lead affects the running by removing one by one, fuel filter, cleaned all the jets and lines in the carb multiple times.

There is a decent delivery into each carb, bowls have fuel, idles perfectly and revs when in neutral as it should. 1st drive of the day it’ll get 500mtrs fine and then bog down to the point where I am using my hazards to drive. Progressively gets worse each drive. Choke operated as it should, sucking on the vacuum side of the dizzy moves the plate, tightened all vacuum connections and checked for leaks. However if I remove the vacuum from side of dizzy when we are driving there isn’t a noticeable difference - however we are at 2k-3k so not sure when it kicks in.

Can’t work out of its electrical or fuel? Is there a mesh inside our tanks?

Please any suggestions!!! Campsite and car hire is costing a fortune.

Thanks
Josh

[937carrera]

Beginning to sound as if it's the ignition amplifier / hall sensor, coincidence with the parking on a hill. As you are into the Kwik Fit school of engineering, bang those on and see if the problem is solved. Ignition amplifier first.

There is a test for the hall sensor, try a search or look in the wiki

this might be a help http://forum.club8090.co.uk/viewtopic.p ... &p=8192693

[tobydog]

Take the fuel pipe off the outlet of the petrol tank and check the flow of fuel? Could it be fuel starvation?