Vacuum Testing

[jeepsrock]

I want to test my vacuum lines this weekend, so i went to autozone and rented a vacuum pump and gauge from them. I am guessing that i should plug in the gauge/vacuum pump to certain lengths of hose and see if they hold vacuum. My question is what is a reasonable pressure to vacuum too ? Would it be at all useful to have the gauge connected with the jeep running , to monitor vacuum readings ? What should they be ?

Thanks
pete

[fizassist]

I want to test my vacuum lines this weekend, so i went to autozone and rented a vacuum pump and gauge from them. I am guessing that i should plug in the gauge/vacuum pump to certain lengths of hose and see if they hold vacuum. My question is what is a reasonable pressure to vacuum too ? Would it be at all useful to have the gauge connected with the jeep running , to monitor vacuum readings ? What should they be ?

Thanks
pete

The first step is to check the vacuum at the throttle body. (pull a vacuum line and hook up the gauge.) It should run about 20 psi. If it's much lower, then you probably have a leak and should check the hoses/manifold/etc. If not, donworryboutit. :)

[Matthew Currie]

For hoses and fittings, you should test to the max the pump will pull. They should not leak down at all.

It's a good idea to monitor vacuum with engine running too, to see if there are any manifold leaks. While you're at it, it will tell you a little about the condition of your engine, valves, etc.

[jeepsrock]

Yesterday i plugged in the vacuum pump with the engine off and i kept pumping but got little to no vacuum. I was able to hear a slight psss but havnt identified from were yet. I was planning on getting some vacuum hose from the auto store but after i went today they wanted 1.10 a foot, isnt that a bit expensive especially if i wanted to replace large portions ? What size do i need ?

pete

[jeepsrock]

Today i found the vac leak from the vacuum canister. Apparently the canister itself was cracked, i went to the delaer picked up a new one and replaced it. After installing it i have vacuum if i use the hand pump.

Also i used the gauge like matthew currie suggested with the engine running. On a cold start idle my vacuum was at 15inHg or -50Kpa. The needle pretty much stuck to those numbers and moved less than a mm in one direction every once in a while.

So what does this mean ?
Pete

[jeepsrock]

anyone know the proper spec ?

pete

[ezeman]

I have heard 20 in of Hg, but I am still trying to confirm, mine is at 8 right now and my car runs like crap

But it sounds like the canister may hvae fixed your problem?

eze

[langer1]

20inhg after it warmed up and in closed loop mode.

[87manche]

ok, as a newbie can comeone give me the proper procedure to test the vacuum?
Is it as simple as pulling a vac line and plugging in the guage?

[langer1]

yes it is

[87manche]

well, that's about the easiest thing I'll have done to the jeep so far.

[XJ4PLAY]

Today i found the vac leak from the vacuum canister. Apparently the canister itself was cracked, i went to the delaer picked up a new one and replaced it. After installing it i have vacuum if i use the hand pump.

Also i used the gauge like matthew currie suggested with the engine running. On a cold start idle my vacuum was at 15inHg or -50Kpa. The needle pretty much stuck to those numbers and moved less than a mm in one direction every once in a while.

So what does this mean ?
Pete
Out of curiosity, what did the canister cost?

[jeepsrock]

From the delaer it was under 12$. I have the part number if you need it.

pete

[old_man]

Parts that have a high usage volume tend to be pretty cheap. The flexible vacuum harness for the D30 disconnect was about $10 as well.