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Re: [T3] Compression?


On 13 Jul 99, at 13:16, John Kaminski wrote:

> Like I said, the car's a '69 SB, all n.Sth the fuel-injected 1600
> engine.  It's a bitch to start, but I can usually get it going within a
> half-dozen tries, sometimes less, but sometimes it can take 5 minutes or so
> of repeated crankings.  I assumed this is due to the fuel-injection system.
> Usually if I turn the key to the "on" position, then "off," then "on," and
> repeat this four or five times, she'll start.  My understanding was that
> this process adds gas and eliminates excess air in the cylinders.  The
> mechanic, however, said the fact that it's so hard to start sounds like "low
> compression" to him, not the FI.  By turning the key on and off, I'm helping
> to add air to the cylinders therefore building compression.  I admit that
> I'm a bit worried about the compression.  I can forget about moving from a
> dead stop on a steep uphill grade when stopped at a red light.  It just
> ain't gonna happen.  But why immediately jump to the idea of a compression
> problem when the FI system seems like an obvious culprit?  And doesn't he
> have it wrong about turning the key off and on?

Turning the key ON and OFF several times runs the fuel pump and fills 
all the fuel lines so that there is gas all ready to be injected when 
you try to start. It adds neither gas nor air to the cylinders. Nor 
does it do anything for the compression.

If this helps, then you probably have some kind of gas leak that 
allows the gas to leak out of the lines and be replaced by air 
overnight. The most common cause of this is old fuel lines. If you 
think you might have a problem with these, then you should replace 
ALL of the lines which are under the 30 psi pressure, some of these 
are under the gas tank and some are around the engine. This requires 
10-15 feet of good quality 5/16" fuel line.

This reminds me that I think I have all the info that I need to make 
my fuel line kits available. I'll post that soon.

There is some merit to considering compression a problem, but that is 
easily verified with a compression test. Do it. Jumping to the 
assumption Af~is a FI problem is no more supportable, but that 
conclusion is most often reached because someone doesn't understand 
it and views it with suspicion. What about the ignition system? What 
about the valve adjustment? What about the vacuum and mechanical 
advance? What about the charging system? What about the ...?

Jim
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*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
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