mbogucki

I have a 1979 super beetle that I restored that doesn't want to start up very well.  It stalls out the first few tries, and then if I let it sit (idle) for 5+ minutes it's good to go....if I try to drive before that, there is a "slapping/knocking" sound which goes away after a few minutes of driving.  Please help! 

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MY72BUG
Hi mbo and welcome to the forum:   When you say that you restored the Beetle did you do anything with the engine?  What do you know about the history of its maintenance?  It sounds like the car might benefit from an overall tune up.  The formula for a working engine is pretty straight forward.  The fuel injection(which should be in your ' 79) delivers fuel-air mixture to the cylinder and the ignition delivers the needed spark at the correct time.  The mechanicals of the engine produce compression in the cylinder.  You need to know if this symphony of components is lacking one or more of these needed elements.  Dirt in the gas tank or in the fuel lines is a common culprit.  Do you have a plugged fuel filtre or blocked injectors?  If your Beetle still uses points are they worn?  How about the spark plugs, distributor cap and the plug wires?  Is the timing set correctly?   Have you done a compression check on the engine?  If the valves are worn you will lose compression and the engine will perform rather poorly. Don't overlook simple things like a plugged air filtre.   The slapping sound can be serious or minor.  First, go through the process of setting your valve lashes, the adjustment between the valve stems and the rocker. Set these gaps at the recommended settings.  Don't be tempted to overtighten these gaps to reduce the slap.  You will damage your valves. If one of these is very loose you will hear knocking until the engine warms up.  Any good VW service book such as a Haynes book will walk you through the process.  If this doesn't cure the slap you may have more serious problems such as connecting rod or crankshaft bearing troubles.  If you take a systematic approach starting with a tune-up and some engine diagnostics you will root out the problem(s)
I'd rather have a partial bottle in front of me than a partial frontal lobotomy.
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mbogucki
thanks for all the tips.  I did rebuild the engine during the restoration, including new valves, gaskets, and bearings.  I will take your advise to look at it systematically...but do you know why it would seem to run great after those first 5 minutes?  There is absolutely no slapping if I let the car warm up before driving, but if I don't give it enough time, the slapping comes with acceleration.


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MY72BUG
What you may be experiencing is not bearing related at all.  The important clue here is that " the slapping comes with acceleration".  Go through the process of setting the timing again.  If the engine is cold and the vacuum advance in the distributor is not working correctly you will get some knocking as the spark arrives in the cylinder too early as the piston is still coming up to Top Dead Centre.  Do you have vacuum lines going to the distributor or is your distributor advance mechanical like the Bosch 009?  Either way, you need to know that this spark advance is doing its thing right or you can get some nasty knock as you try to accelerate.  Some of these have vacuum controls through heat sensors in the air cleaner.  Look for a vacuum line heading in and another coming out right beside it.  The little joining box in between senses the temperature and either allows vacuum through or not depending on the temperature of the unit.  Try putting the whole unit into the freezer for a few minutes.  Try to suck air through the vacuum switch device.  Then warm it up and try again.  One way should allow vacuum and the other should shut off the vacuum.  My old Ford has the same sort of stuff to control various things with the carburetor.  If the vacuum switch is open both hot and cold or closed both hot and cold it is not working right. 
      It might be running great for the first five minutes because it is getting an extra rich fuel mixture with the choke on or whatever the rich mixture circuit is for fuel injection.  When the rich mixture is off the engine starves for fuel.  Again; the systematic tune up approach should point out if this is the source of the problem.  Let us know what you find out and track down the vacuum lines with particular attention to old dry and or split vacuum hoses and non-performing thermal vacuum switches.  Good luck with it.  If all of your bearing work was up to snuff, your knock will turn out to be something simple like what I have sketched above.  Dan (MY72BUG) snowbound in Goderich

I'd rather have a partial bottle in front of me than a partial frontal lobotomy.
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