I have a compression tester, but haven't run one in a while (out of
o-rings). I guess that will be the best place to start.
I should fire over the brand new motor in my 88 conquest next week sometime.
Once I've got it as a backup, I can start looking into the dak.
mm
----- Original Message -----
From: "Bernd D. Ratsch" <fasstdak@swbell.net>
To: <dakota-truck-moderator@bent.twistedbits.net>
Sent: Friday, October 03, 2003 5:57 AM
Subject: Re: DML: Re: 3.9 smoke on hard accel
>
>
> Factory Spec: "Compression should not be less than 689 kPa (100 psi)
> and not vary more than 172 kPa (25 psi) from cylinder to cylinder."
>
> All of the new engines i've checked are all at an average of
> 140-150psi.
>
> If the cylinders are all low (at or below 100psi)...either get a
> better compression gauge or you've got a very tired engine (or one
> heck of a vacuum leak).
>
> - Bernd
>
>
> On Fri, 03 Oct 2003 06:40:29 -0400, raymond.irons@gm.com wrote:
>
> >
> >
> ><snip> If your reading anything under 100psi, you've found the problem.
> >
> >Not necessarily so Gary. You're not looking for a minimum pressure
reading
> >so much as you're looking for relatively equal readings on all cylinders.
> >Now if all cylinders are at 50 psi then I start looking for a hole in the
> >engine somewhere. The FSM should list the tolerance range for engine
> >compression. A new engine may read 125 psi +/- 3 psi on all cylinders for
> >instance and that same engine with 200K miles on it, even if it has been
> >well maintained, may read 98 psi +/- 5 psi on all cylinders. Does this
mean
> >this engine needs major repair or rebuild? Not in every instance. If all
> >other diagnostic data point to no major problems then is it worth the
time
> >trouble and expense of removing and rebuilding or replacing the engine?
> >Probably not. Now if we take the same engine and do the same compression
> >check and find 5 cylinders with 98 psi +/- 5 and one that has 70 psi then
> >we've found the culprit in that cylinder. However more diagnostic is
needed
> >to determine the cause of the low reading and probable repair.
> >
> >
> >Ray Irons
> >Dover, DE
> >
>
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