[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]

Re: [T3] Dead Injectors Puzzler

On 11 Jan 2001, at 23:20, Mark Fuhriman wrote:  

> Problem transformed into intermittent loss of signal (and I know
> for sure it was power loss) to two injectors: 1&4. 2&3 kept the
> engine running. 

??? Last week you reported that 1 & 3 failed.  ???  

> Now, tonight I have confirmed the hunch of several who guessed the
> wiring to the 3/4 injectors was switched.  It was indeed. Started
> the car up with the injector wiring fixed and with the spare brain,
> let it run for a while.  Drove around the block and let it idle for
> a bit.  When at temp, the idle dropped.  Sure enough, injectors for
> 1&3 were not firing anymore.  

I'm glad to hear that the wires WERE switched. This brings your 
symptoms back into the reality again....  ;-)  

Brain fade? I suspect that now it was 1&4 that failed. When 
properly wired, 1&4 are triggered by the same trigger point. Sounds 
like you could use that double brain swap that Greg offered. ;-)  

> Shut car off.  Following the advice of many, I suspected the
> trigger points.  So I cleaned up the prettiest of the two spares I
> have with electrical contact cleaner to make it sparkle.  Let it
> dry completely (took my time) and I changed the trigger points
> out. The set that was in there didn't look any worse than the
> replacement, but I changed them anyway.  

Well, I would have expected this to fix it, too.  

> Put everything back, started the car (started right up on all 4).
> Within about 10 minutes it happened again.  I lost 1&3.  Keep in
> mind I have ruled out the injectors themselves because when I
> corrected the wiring, the problem followed the wiring and did not
> stay with a particular injector.  And the problem only occurs with
> pairs of injectors, not just one. 

Again, I assume you actually lost 1&4.  

Here's what I would do next:  

Look over the injector wiring carefully again for any possible bad 
connections or potential/intermittent shorts. Wires twisted together 
wires aren't good enough; they should be crimped or soldered.  

Check all the injector wiring from brain to ground. Verify that you 
have 2-3 Ohms along each of the 4 paths, and it doesn't change as 
you gently wiggle each connector along the path, including the 
path to ground. Verify that unplugging each injector makes its path 
resistance go to infinity, but doesn' t change any of the others. 
Verify that disconnecting the ground wire for either side makes the 
resistances for the injectors on that side go to infinity and doesn't 
change the resistances for the other side.  

There are only 3 kinds of problems that could cause the problems 
you report: Trigger points, brain, or some kind of wierd injector 
wiring problem. Bad trigger points and brains are rare enough that it 
seems really unlikely that you picked 2 in a row, but anything is 
possible. Try another brain and another set of trigger points.  

> I remembered the dwell problems reported by Steve and Jim.  The
> boot on my trigger connector at the dist is gone, so I was able to
> jam my VOM probes into the top of the connectors to make contact
> with the wires while the engine ran.  With the car still running on
> just 2&4 (1&3 not firing) I measured voltage in turn between the
> outer connectons and common (the middle one).  For both sides I
> measured a pulsing signal that varied between 2 and 3 volts.  Does
> this tell me that my dwell for both trigger contacts is similar? 
> Can I rule out trigger points?  Keith, you mentioned something
> about resistance across a rivet in the trigger points.  Like from
> top to bottom? Please elaborate just a little for me here.. 

This is a pretty good test. Do it again WHILE the engine is running 
on just 2&3 (failure mode). That would show up a problem in the 
trigger points or the trigger point wiring.  

With the engine off, measure the resistance from center to each 
side of the trigger points. You will have to move the engine to get 
each side to close while you measure it. Once closed it should be 
a GOOD contact. I would not expect to measure more than 5 
Ohms. If you measure more, take the points out and trace the 
resistance thru them until you find the part of them where the 
contact is not good. Look at the way the little copper pigtail is 
dressed in there, just inside the connector; make sure it is not 
close to shorting out.  

Jim Adney
Madison, WI 53711-3054

Pitch in!  Send your pledge of support!  mailto:support@vwtype3.org

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [New Search]