vacuum issues

[Rex]

Hi, Group,

I have been struggling with some vaccum issues on my car for several months now, and I hope you call can provide some insight. If I understood the diagram that Barrry was kind enough to send me, vacuum goes from the intake to the fuel pump and from there branches to the rest of the system to run the heat, wipers, antenna, etc. I now believe I have everything connected, but I still have very feeble vacuum at the tees feeding the wiper, a/c solenoid and antenna hoses.

My question is does the vacuum that runs from the intake run directly to the fuel pump in such a way that if that diaphragm were split, one would lose almost all vacuum? I want to bypass the fuel pump and attempt to run the wipers directly from the intake just to see what happens.

The car had a CA style pcv valve installed in the 1970's running off vacuum, and I thought this was robbing the rest of the system, but disconnecting that and checking and rechecking all the other connections has made no difference.

Am I missing something?

[Barry Wolk]

A hole in the diaphragm would exhibit itself as a vacuum leak that would affect all systems. Simply by-pass the pump and you should see good results. The pump is only there to give you working windows, heater controls and antenna under acceleration. The rest of the time there is sufficient vacuum to operate the systems. It'll run better, that's for sure.

I think you answered your own question.

[Rex]

Thanks, Barry. I hope that will prove to be the answer. With about a mile of vacuum lines, it can be frustrating to trace problems down. Rex

[Barry Wolk]

If you have a cracked "T" it may be hard to detect. There is a surefire method to detect vacuum leaks, though. At low idle, spray all the vacuum hose connections with carb cleaner. If it's sucked into a vacuum leak it will change the engine rpm. Spray around the base of the carb and along both connections where the intake meets the head. Any vacuum leak will change rpm as you're sucking a different combustable into the air/fuel mixture.

The problem could also be your antenna switch or your wiper motor itself. If not adjusted properly the rubber slide valve on top will leak like a sieve. Spray that, too.

Also, could be a hole in the vacuum advance or retard if a '56 with a t-pot carb.

[Don Henschel]

Is there not a vacuum canister that likes to rust out as well?
http://www.markiiforum.com/showthread.php?t=78&highlight=vacuum+canister