Compression check question
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Tuned
Joined: Oct 2020
Posts: 260
Likes: 12
From: Lakeville, MN
Compression check question
Last summer I tried to do a compression test, but when I cranked the engine to get a reading, the starter would disengage. Therefore, I was never able to get a consistent reading. Any ideas on what was going on there?
Hotshot
Joined: Feb 2004
Posts: 10,743
Likes: 2,587
From: The Shenandoah Valley
You had all the plugs out and holding the throttle wide open I guess, you maybe holding the gauge ... threaded or push in connection at plug hole.
How were you operating the starter ... button remote starter switch with clamps ... or a helper in the cab ... or what?
If using a clip-on remote starter button, might have been just not clean enough. If using a helper in cab, maybe they let off prematurely ... or maybe the ignition switch or solenoid or Bendix was kicking out.
How were you operating the starter ... button remote starter switch with clamps ... or a helper in the cab ... or what?
If using a clip-on remote starter button, might have been just not clean enough. If using a helper in cab, maybe they let off prematurely ... or maybe the ignition switch or solenoid or Bendix was kicking out.
Laughing Gas
Joined: Aug 2020
Posts: 821
Likes: 292
From: Pelham Alabama
I am not a mechanic but I have done many many compression checks and can think of no reason for the starter to disengage if everything is operating properly.
Maybe some others may have had that happen and may have an answer.
I would follow Tbears instructions and try it again to see what happens..
Alex
After thinking more about this maybe F5FordGirl may have the answer.
I will try to explain my thinking:::
Maybe the bendix is weak and when cranking with plugs in there is enough resistance to keep the bendix engaged.
then with the plugs out, there is lots less resistance and the teeth will walk off the flywheel???
Just thinking deeper for a reason.
Maybe some others may have had that happen and may have an answer.
I would follow Tbears instructions and try it again to see what happens..
Alex
After thinking more about this maybe F5FordGirl may have the answer.
I will try to explain my thinking:::
Maybe the bendix is weak and when cranking with plugs in there is enough resistance to keep the bendix engaged.
then with the plugs out, there is lots less resistance and the teeth will walk off the flywheel???
Just thinking deeper for a reason.
Last edited by Old Guy F-250; Jan 11, 2023 at 09:08 AM. Reason: thinking more about it
Thread Starter
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Tuned
Joined: Oct 2020
Posts: 260
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From: Lakeville, MN
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Tuned
Joined: Oct 2020
Posts: 260
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From: Lakeville, MN
It's the original starter-'78-maybe I should just replace the whole starter(?) What do you think?
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Laughing Gas
Joined: Nov 2013
Posts: 1,207
Likes: 60
From: S.E. Louisiana;so far USA
When you say "the starter would disengage", does that mean:
The starter would stop running
OR
The starter would continue running, but the starter drive would not turn the engine.
The starter would stop running
OR
The starter would continue running, but the starter drive would not turn the engine.
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