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VW Bus issues

posted Jun 16, 2016 14:11:00 by Keith
Ok, a friend has a 1960's bus fitted with a tuned 1700cc motor with dual down draught carbs, ignition is still points.

Issues.... Number 3 is not contributing at all, number 4 seems to contribute less than 1 and 2 but much more than 3


Checked..

Compression, all within 10%
Ignition, all plugs firing
Fuel, all seems fine
Timing, spot on (IR at least as near as possible with a non vacuum advanced distributor at idle)

Changed recently...

Plugs, leads, points, condenser, coil. Carbs rebuilt. Distributor replaced. Valve clearances checked. Oil changed. Fuel tank cleaned out and also new filters fitted.

When idling you can hear a slight miss but it runs fine and drives well, Rev it slightly seems to go away. But once running for a while the miss becomes very much more evident and the van almost cuts out. This happens faster if put under more load by towing caravan.

I've not yet had a scope on it to get any images of spark etc

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4 replies
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AndyMacFadyen said Jun 16, 2016 21:11:19
As you have renewed the distributer the probably rules out a distributer problem although checking the contact breaker gap on each lobe of the distributer might be a good idea.
However my first move would be to check the carb butterflys are properly in synch. What type of carbs ? some types of Weber are prone to the cold start mechanism sticking on.
Beyond that you need to re-check the carb float level and clean the jets.
"Rust never sleeps"
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Keith said Jun 16, 2016 21:32:13
Carbs are twin Dellorto drla 40's, freshly rebuilt (after issue started)
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AndyMacFadyen said Jun 17, 2016 06:38:13
It could be an excess fuel pressure issue Dellorto and Webers are sensistive to fuel pump pressure, excess fuel pressure causes the float valve to pass fuel.
Istr the spec for fuel pump pressure is 2 to 2.5 psi.
"Rust never sleeps"
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Steve Harris (65Westfalia) said Jul 05, 2016 18:32:05
Re-check valve clearances...especially #3. Engine must be C O L D. Specs. are .006 for both intake and exhaust. Also, check the line(both hard and hose) from the tank to the dist. block to the carbs. I've had small amounts of debris cause intermittant fuel flow issues before. One time it was a collapsing fuel hose only at full throttle. Bugger to figure out.

Last ditch would be to pull the dual carbs and throw a stock single solex on there. One of the reasons I never run dual carbs on any of my busses. They're not hot rods ya know ;-)
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