[AT] How about this orange tractor, Attn: Travis

[charliehill]

David I have a good story about that.  I have an 89 GMC that I bought new 
and have now put out to pasture.  When it was maybe 7 years old or so it 
started to miss and buck when the cruise control was on.  I tried for some 
time to find the problem and couldn't so I stopped using the cruise control. 
Well in time it started to do the same thing without the cruise control.  I 
still couldn't find the problem so I put a Jacobs ignition system on it. 
That solved the problem for a while as well but after a time, probably 2 
years from the start of the problem it started to run ragged again.  It 
eventually got to the point that it was barely drivable.

Then I started looking very hard for the problem.  As you probably know 89 
was in the beginning years of computer controlled stuff and was the OBD I 
system which is much less involved than OBD II.   I bought aftermarket 
manuals and started checking every sensor, voltage and ground I could find. 
I never could find a problem.  I finally worked my way to the cruise control 
system (where the problem began) but the aftermarket manuals didn't have any 
cruise control information in them.  I was at a stopping point.  So, I went 
to a small local dealer about 15 miles away.  I knew those guys and knew 
that they had good mechanics.

When I went there I told the mechanic all that I had done and asked if he 
had the specs for the cruise control system.  He said yeah had them in his 
factory manual BUT he wanted to look for the problem his self.    We talked 
about it and I understood why he wanted to retrace my steps.  He went to 
work but he allowed me to go in the shop with him.  (that's why I chose that 
shop).
I stayed out of the way and let him work.  He checked everything I had 
checked and finally decided it was the ignition module so he replaced it. 
The problem didn't go away so, to his credit, he took that part back off and 
put it back in on his shelf.  Finally after an hour or so he got around to 
checking the cruise control.  He took his volt meter and checked the 
resistance between one of the lugs in the cruise control wiring harness and 
the stud on the thremostat housing where a ground wire was attached.  He 
looked at me and kind of said Hmmmmm.  Then he took his 9/16 wrench and 
tightened that stud.  We drove it down the road and the problem was gone. 
The stud was double nutted on the ground wire and that was tight but the 
stud was about 1/4 turn loose in the intake.  Since that stud goes into the 
water jacket some coolant had seeped up around the threads and it wasn't 
reading the right resistance.  Problem solved.  I realized after the fact 
that I had changed the thermostat just before the problem started a couple 
of years before.   That ground wire is kind of short and it's hard to get 
the stud tight and the double nut tight on the ground wire without twisting 
the stud a bit and that's what happened.

As Farmer says,  check the grounds.  It blew the mechanics mind and I know 
it probably doesn't make any sense to some of those reading this but I swear 
to you it's fact.

Charlie
----- Original Message ----- 
From: "David Bruce" <davidbruce at yadtel.net>
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
Sent: Tuesday, February 10, 2009 6:16 PM
Subject: Re: [AT] How about this orange tractor, Attn: Travis


> Or farmer's favorite - bad ground.  Took me a couple rollback trips to
> the mechanic to find that one (and he is generally pretty good at
> diagnostics).  Along with the rollback trips I brought him here one time
> to look at a non running car - of course it ran then <g>.
>
> David
> NW NC
>
> charliehill wrote:
>> Henry,  the computer can tell you that a sensor is out of range and that 
>> a
>> control can not pull it back into range.  The computer can't tell you if
>> it's a bad sensor, a bad control, a vacuum leak or a burned valve.  If it
>> can I'd love to hear you elaborate on how?
>>
>> I'm not trying to be argumentative.  I just want to understand.  Also, 
>> I'd
>> like to know more about your diagnostic equipment.
>>
>> Charlie
>
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