94 vacuum test

[Reachej]

Apologies if this is addressed already somewhere, I couldn't find it. I'd like to do a vacuum test on my 94. I've tried propane and so on without a positive result but would like to make certain so I can rule that out of my rough idle issue. Can I do a decisive test using a vacuum meter and if so how exactly is that done? If not what is the official way? TIA

 

[CharlieS]

Are you trying to find a vacuum leak? I use smoke testing to find those.

 

[Reachej]

Are you trying to find a vacuum leak? I use smoke testing to find those.

Thanks for the reply. I am looking for a leak. Where do you apply the smoke? I also am looking for a quick yes/no vacuum test. That way if it's no I can move on quickly. If it's yes I can work on locating.

 

[Rifleman]

Reachej You can buy a can of carb cleaner or a can of starting fluid from any auto parts store and spray it around spots where you think you may have a vacuum leak with the engine running, If you have a leak you'll notice the engine RPM's will change when you hit that spot with carb cleaner/ starting fluid,​

 

[CharlieS]

Reachej You can buy a can of carb cleaner or a can of starting fluid from any auto parts store and spray it around spots where you think you may have a vacuum leak with the engine running, If you have a leak you'll notice the engine RPM's will change when you hit that spot with carb cleaner/ starting fluid,​

Except it doesn't actually work that well... Smoke test my friend. You'll thank me later.

 

[Reachej]

I appreciate the responses and I do know those methods. I'm specifically interested in the best place to tie in a vacuum gauge on a 94.

 

[Rifleman]

Except it doesn't actually work that well... Smoke test my friend. You'll thank me later.

If i still owned my auto repair shop I'm sure I'd invest in a smoke machine, but since i closed my shop and am now retired, I have zero interest in investing any more money in automotive tools, so at this point i think I'll just stick with the low cost approach, like carb cleaner, Cheers my friend!

 

[localarray]

I appreciate the responses and I do know those methods. I'm specifically interested in the best place to tie in a vacuum gauge on a 94.

Use the rubber line that goes into the brake booster

 

[Reachej]

Use the rubber line that goes into the brake booster

Thanks. Worked great.

 

[Fj80oregon]

Thanks. Worked great.

So what did you learn from testing your vacuum at the brake booster?

 

[Reachej]

So what did you learn from testing your vacuum at the brake booster?

Well, if it reads correctly does it not indicate that there is no vacuum leak?

 

[DaviMH47]

Well, if it reads correctly does it not indicate that there is no vacuum leak?

What reading is correct?

 

[Reachej]

What reading is correct?

My research says 18-21 PSI. Mine was at 20.

 

[sjpitts]

My research says 18-21 PSI. Mine was at 20.

Doesn't vacuum change with RPM? So is the 18-21 PSI at a certain RPM? Or just at IDLE?