UK Car Repair: VW transporter 91, dirty fuel, float chamber

Question
QUESTION: We've just recently bought a white hi-top 1991 VW transporter conversion.  Its a 1.9 Litre petrol engine.  You'll be going along quite nicely then it looses power-you put your foot on the gas and there is nothing so you change down gears gradually to 2nd then its fine again. It also sometimes splutters.  We thought it may be dirty fuel so changed the pipe but after 200miles it started again - not all the time though. Is it likely to be dirty fuel or shall we have the carb checked?  I would be so grateful for some advice as we dont know much about cars and we're due to go on our first tour with it next week.  Will it be safe to drive still or is it likely to completely die on us?

Thank you
Suz

ANSWER: so you have a week to sort it, I'm on it :-), love the VW's...

Is this carburettor or injection engine?

first things first, when it starts to lose power does the engine actually stop if you dip the clutch, or will it tick over, just has no power - EG is it LOW power or NO power when it starts cutting out. need answers to these two questions to progress further.







---------- FOLLOW-UP ----------

QUESTION: thanks for getting back to me - it has a carburettor also to answer your next question it is low power-so you'll be going along at 55mph then have to drop down gears but the engine does not actually stop altogether - by the time you get into 2nd it picks up again and you're off.... theres no telling when it will happen again - could be 100 miles or 30!!  What do you think?

Many thanks

Suz

Answer
tough one.

Sounds like its sparking good all the time, so ignore ignition for now.

Sounds like a lack (but not total loss) of fuelling.

You already swapped the fuel line - I'd check the fuel filter, and then fuel pump. You may have to get the fuel pressure tested at a garage (not expensive) -> if the fuel pressure is fluctuating then the fuel pump is on its way out, if there's good fuel pressure then I'd be looking at the float chamber, float valve and the float level in the carb itself as the reason for loss of fuelling...

SO:

Check fuel filter isnt blocked,
Check fuel pressure -> if bad - change fuel pump, if good have carburettor serviced, focusing on float chamber/valve and the float itself. (the more I think about it the more it sounds lika a sticking float - it sticks into the valve then doesen't fall again as the fuel is used up, when the level is really low it drops out of the valve, letting fuel in and off you go...)

Google "float chamber" and you'll see what I mean about the valve, it's at the top of the chamber and can get dirty, cause the float needle to stick, then only when the level is very low (not enough to run the main jet but just the idle jet,m hence the lack of power) can the float wiggle around a bit and come loose from the valve under it's own weight.

Likely to happen over very smooth roads more often, probably never happens on a bumpy road???