Vacuum Solenoid Test

["DMC Joe" <dmcjoe@xxxx>]

Travis,

Here is an easy test to determine if the solenoid valve is functionally
properly. Place a vacuum gauge on the output line of the solenoid valve,
there should be no vacuum during normal and high idle. After engine warm up
there should be no vacuum at idle and vacuum at high idle. Be sure that you
have the correct vacuum hose spigot. The center spigot is vacuum input and
the outside spigot is output to the distributor.

DMC Joe
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----- Original Message -----
From: "cdrugly" <tgoodwin@xxxx>
To: <dmcnews@xxxxxxxxxxxxxxx>
Sent: Monday, April 15, 2002 9:26 PM
Subject: Re: [DML] Does a tune-up ever go right? Not when I do it...


> Joe,
>
> Thanks for the heads up. It has helped me diagnose the problem. See
> what you think:
>
> I took the solenoid off and repaired the broken electrical connection
> and still got the same results. As long as I don't really hammer down
> on the accleration, the car will accelerate fine. At around 65, it's
> like a swift kick in the ass as the car takes off.
>
> With the solenoid repaired, I checked the timing again. I found that
> it was advanced almost 25 degrees. How it was even starting, I have
> no idea. So, I checked the vacuum coming from the solenoid, and it
> did exist, even at idle. According to D:08:01, the microswitch should
> energize the solenoid and close off the vacuum when the throttle
> plate is closed.
>
> When I disconnected the line to the distributor vacuum advance, the
> timing returned to 13 degrees.
>
> Hmmm. So, it looks like the thermal vacuum control valve is open
> correctly (the only reason it would close would be for emissions, I
> assume) and is sending vacuum to the solenoid. With the solenoid
> stuck open, there is a vacuum during idle causing the 10 degree over-
> advance. I'm thinking the solenoid is hosed.
>
> So, did I do good?
>
> --- As a side note, I noticed the when the vacuum is disconnected and
> tested the timing, pulling on the throttle advanced the timing.
> Question is, does the D utilize mechanical (centrifugal) advance as
> well as vacuum advance?
>
> Thanks for the advice,
>
> Travis
> 3512