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Mon Mar 31, 2003 10:34 am

I drove my '72 bug (1600cc, not a fuel injection) quietly for about 20 minutes, and once back to my garage, I noticed some smoke coming out of the engine compartment and some gaz was leaking from both sides of the carb! Engine was pretty hot as well. Looking to the fuel filter, the gaz was doing some 'bubbles' and I think there was much more gas as usual in the filter.
- It is a problem with the fuel pump ? oil breather ?
It seems that there is 'too much pressure somewhere.
Once the engine was cool, I started it and let it run for few minutes ... everything was OK.

Appreciate your help on that.
Phil.

Mon Mar 31, 2003 12:11 pm

fuel pump

Mon Mar 31, 2003 12:23 pm

What are the 'symptoms' of a worn fuel pump ?

Do you think that the smoke was due to gas rather than oil ?

Mon Mar 31, 2003 9:45 pm

Sorry rossmda, but the fuel pump wont cause leakage at the carby - they work at only 2-3psi and CAN'T over pressure since it;s the spring inside pushing the arm back down which provides the pumping pulse - the cam just lifts the arm for the next swing down.

P-seguret - make sure the fuel lines are all tight - not about to fall off. Check the brass inlet tube in the top of the carby - after 30 years of fuel lines vibratiing on them they CAN work loose - they are only a push-fit in the top of the carby. There is a simple fix if you find it's falling out.

Also check that the carby top it screwed to the main body properly.

Check the needle valve in the top of the carby - these sometimes get sticky and wont shut off properly (cheap enough to replace).

Check the float - if it's holed it ill sink and allow more fuel to flow in. If it's worn where it contacts the needle valve - ditto.

If you engine is bordeline overheating, when you shut down it goes into "heat soak" until the engine start to cool and this can overheat the fuel in the line up to the carby (and the oyther lines too of course) and this can cause more pressure which opens the needle valve and floods the carby with a little more fuel. The fuel in the bowl will expand a little too - making the problem worse.

So check your engine temps - it might not be a fault of the fuel system al all.

Syptoms of a worn fuel pump are either the engine surges when running at speed (not quite enough fuel getting into the carby), or fuel contamination in the oil - the pump diaphragm gets a hole and leaks fuel into the sump. It's easy to check this one - pull the pump and look underneath it - if it's full of grease around the operating arm it's OK - if it's a dilute mess of grease and fuel, replace the pump.

Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.geocities.com/aussiebug1970/

Mon Mar 31, 2003 9:46 pm

Sorry about all the typos - I keep forgetting to proof read, and I'm a lousy typist.

Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.geocities.com/aussiebug1970/

Tue Apr 01, 2003 10:40 am

Tue Apr 01, 2003 10:52 am

Rob,

Thanks a lot for your detailed feedback. I think that I have found the problem: very recently, I have changed the old firewall which was falling apart with a new one. It has been done without removing the engine. In fact, I believe the firewall was not installed properly and it was covering partially fresh air access to the fan.
I have removed the new firewall (which was damaged on some locations because of the heat, it explains the fumes as well) and I have drove the car for 1/2 hour without any problem.
So I believe that the excess of heat in the engine compartment was responsible for the gas leak from the carb.

Talking about overheating, I plan to buy the berg oil temperature dipstick. Do you recommend it ?

Thanks again for your precious help.
Phil.

Tue Apr 01, 2003 10:33 pm

Phil,

The loose firewall padding trick will do it every time. Glad you found it before it closed off the fan opening and fried the engine.

It will be louder in the cabin without any sound deadening there though - you might want to consider that stick-on dense rubbery foam stuff used under "normal" car hoods etc - since it's stick-on, it won't matter if some of the original hooks have been broken off.

I've never used the Berg dipstick sender, but I know it's a very simple and useful tool.

It attaches to the normal oil pressure sender wire so it's very simple to install.

If the oil temp exceeds about 225f the oil light in the dash starts to blink, and it goes on steady if the oil gets even hotter - a very simple warning system.

I have always used the rather crude finger test myself - if I can hold the dipstick in my fingers and not QUITE burn them, then the temp is OK. It's a rough test though - the Berg sender is much more accurate.

Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.geocities.com/aussiebug1970/