Author Topic: EPVS...  (Read 637 times)


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« on: February 06, 2017, 08:13:51 PM »
I know the '71-3's are not that well represented here... but there appears to be a lot of overall Mustang knowledge so I will give this a shot:

As seen in the attached photo, my '71 429 "J" Code convertible appears to have come with an electric ported vacuum switch vs. the more prevalent ported vacuum switch found on most of these cars that had the BB engine installed. Unfortunately, the wiring and hookups were long gone by the time I got the car. I am at the point on my restoration where I am trying to restore this EPVS on my original engine. I have tracked down the correct wiring/connector as shown in another picture below, but I am now trying to determine the correct electrical connection procedure for the top side of this engine as it relates to this switch.

I should note that the car did come with the Rochester carb c/w the electric solenoid (anti-dieseling). The original firewall harness does have the white bullet connection which as I understand it, was used for emissions type connections as it only receives power when the ignition is on. This would also coincide with the carb electric solenoid as it would only be activated with the ignition turned on. In absence of true electrical schematics covering this topic, I believe this same principal can be applied to the EVPS as well (for the time being). You will note that the EVPS wire connector (rectangle at the valve cover in the photo) also has an additional bullet type connector (at the valve cover in the photo), which at this time I believe is used to connect to the carb solenoid. In this manner, these two electric devices would then terminate together at the white bullet connection mentioned above.

Does anyone know if there is anything in writing out there from the factory relating to the correct hook up of these two devices on my engine and does anyone have a reasonable assumption as to why some cars got the EPVS vs the more widely used PVS? I understand the reason has to do with the fact that the car came with A/C, but have not seen this confirmed one way or another. I have researched numerous Ford publications and I cannot find any detailed information on the electrical wiring aspect of the EVPS on the '71 Mustang and these publications all refer to the EPVS install solely on the basis of "depending on the engine installed" scenario. It appears the factory had many applications available depending on the car, engine, accessories, and possibly final location of the car for initial delivery. Helpful thoughts appreciated!
« Last Edit: April 06, 2017, 09:30:17 AM by mac1971 »

Offline J_Speegle

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Re: EPVS...
« Reply #1 on: February 06, 2017, 11:24:51 PM »
Yes ran across this subject when I was building my 71 CJ and wanted to be sure of which one I needed for my application. I'll leave this thread marked for me so that I can get back to you in a few days unless someone else gets to it first

Just wanted to acknowledge that someone saw you post ;)

Would request that you post if your car is an AC or non AC car (think it may make a difference) already know its a non SCJ. Is it an automatic or 4 speed car?
« Last Edit: February 06, 2017, 11:31:22 PM by J_Speegle »
Jeff Speegle

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Offline krelboyne

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Re: EPVS...
« Reply #2 on: February 07, 2017, 12:36:04 PM »

The MPC's (Ford and Mercury) show that to be a Type 4, distributor vacuum control valve. Ford part number D1AZ-12A091-A.

We have only found a couple of them, not very common. A co-worker owns a Oct 1970 Dearborn built, 1971 M code Cougar convertible with C6 and no A/C. I asked if his car had the distributor modulator, and he said no.
Scott Behncke - Carcheaologist
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