[Vwdiesel] [SPAM] Re: Cold starting procedure?

[William A. Thompson]

Resistance to ground could be used but isn’t the best way.

The best test is with an amp meter in series with the plugs. I got a meter meant to mount on the dash which is available at most auto parts stores. The cheaper kind with “0” at center scale and +/- 60 amps at both ends. a set of 4 new plugs typically pretty much pegs the meter.

First disconnect the wire going from the fuse to the glow plug bus bar at the first plug and insert the amp meter in series. Turn the key to the “run” position to feed current thru the amp meter to the plugs and make your reading.

What you should get is something near, and likely above, 60 amps for a set of four new glow plugs. The current they draw will reduce with age. Anything less than 40 to 45 amps is very suspect.

To find which plug is defective completely disconnect the bus bar from all the plugs. Test each individual plug by inserting the amp meter in series between the supply wire from the fuse and each glow plug separate from the rest. Test each plug individually and separate from the rest.

A single new plug can draw up to 15+ amps. Any plug which is not glowing at all will draw zero amps. I replace plugs at anything nearing 10 amps since by that time they aren’t far from failing.

    ... Bill

From: Joe 
Sent: Thursday, December 23, 2010 12:27 PM
To: 'Val Christian' ; vwdiesel at vwfans.com 
Subject: Re: [Vwdiesel] [SPAM] Re: Cold starting procedure?

Interesting point.  Couldn't I also measure resistance to ground?  What's
the resistance of a single glow plug?  If I knew that, I could calculate the
expected resistance:

http://www.physics.uoguelph.ca/tutorials/ohm/Q.ohm.intro.parallel.html



-----Original Message-----
From: Val Christian [mailto:val at mongo.mongobird.com] 
Sent: Thursday, December 23, 2010 1:52 PM
To: Joe; vwdiesel at vwfans.com
Subject: [SPAM] Re: [Vwdiesel] Cold starting procedure?

Joe,

I could be quite a few things.  Poor compression, injectors not quite 
working right, timing off a bit, or, yes, even glow plugs.
And it could be starters, grounds, battery connections and even
the battery.

Your best bet is to eliminate each one.

Since it's a 82, one place I would start is with the glow plugs.  You can
mess with the strap, or if you can get access to a DC current probe,
you can meaure the current going to the group of four plugs.  
Depending upon the plugs, expect 35 to 60 amps when glowing. 
You'll need a hall effect current meter, and a friend to flip the
switch while you test.

Val


> 
>  
> I've been meaning to ask another question and always forget.  My 82 Rabbit
> n/a is nearly impossible to start at anything under 40 degrees (F) without
> using the block heater... But I find I must also depress the throttle
> significantly (like an inch) as well as have the advance pulled out and
the
> block heater cooking for at least an hour.  Nice big cloud appears behind
me
> and lasts maybe 10 to 15 seconds.  Won't idle well for at least a minute
or
> two without gently stepping on the throttle.  (I don't floor it)  Is this
a
> sign of one or more glow plugs being out or clogged injectors or both?  It
> purrs like a kitten once warm and still gets 42-45 MPG at 70 MPH.
> 
> Thanks,
> 
> Joe
> 
> _______________________________________________
> Vwdiesel mailing list
> Vwdiesel at vwfans.com
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> 


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