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smoke machine for diagnostics

smoke machine for diagnostics
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thistle3585

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1979 Jeep CJ5 with '72 304 V8, MC2100carb,T150 trans, AMC20 rear diff with locker, Dana 30 front diff, Dana 20 Tr Case, Procomp Springs, Gabriel Ultra shocks.
So, I'm done trying to chase down a vacuum and/or exhaust leak so I have decided to make a smoke machine. Has anyone done this? My thinking is to seal off the top of the carb, plug all the vacuum lines then hook the smoke machine tube to the manifold port on the adapter plate. Is that okay or should I try a different spot? Also, by doing that will it flow into the headers or should I run smoke through the tailpipes in to the headers? Also, any suggestion on the proper air pressure to use?
 
thistle3585 said:
So, I'm done trying to chase down a vacuum and/or exhaust leak so I have decided to make a smoke machine. Has anyone done this? My thinking is to seal off the top of the carb, plug all the vacuum lines then hook the smoke machine tube to the manifold port on the adapter plate. Is that okay or should I try a different spot? Also, by doing that will it flow into the headers or should I run smoke through the tailpipes in to the headers? Also, any suggestion on the proper air pressure to use?
Click to expand...

:)
I assume your still trying to find this Vacuum leak? Have you tried a non-flammable type spray? Some of the Brake Cleans are non-Flam and work quite well.........with the motor running , slowly spray around each potential area that could create vacuum.............and your exhaust would not normally be one of them.

While the motor is running once the spray hits a Vacuum leak , for a split second a noticeable change in RPM and tone will be heard. BINGO!

Non-Flammable only!

:D:D:D:D
 
Yes, tried a number of things flammable and not as well as sudsy water. I figured it might be easier to find it by where its coimng out than being sucked in. Hope to do it this weekend.
 
Ditto on spray... crank engine , warm up, spray small sections at a time, when engine stumble..BINGO... As far as smoke machine, tap into induction and let er rip, diregard anything coming out of air filter.. and exhaust( valves will be open in some spots.OH WD40 works best
 
Just dawned on me.. vacuum leaks and exhaust leaks are 2 total diff things.. What is the problem your having?
 
I have a vacuum eak and an exhaust leak. Separate issues but thought I could use smokemachine to locate both.
 
Find your nearest smoker and have them blow smoke into one of the vacuum lines. It works
 
I did the smoke test today with and without the carb on. I found three leaks. One being the oil fill cap, the drivers side of the oil pan between the pan and block and where the throttle arm comes out of the carburetor. I'm going to redo the oil pan gasket and replace the oil filler cap and go from there. Not sure what to do with the throttle arm. I had to turn the pressure up to 8 psi before it began to leak, so not sure how much of a problem that actually is going to be.
 
A slight vacuum leak at this location on the carb is normal, just shouldn't be excessive. If it took 8 psi I'd say yours is good. If I spray brake cleaner on my new weber where the linkage shaft meets the carb body it will respond.

Leaks at the oil cap and oil pan shouldn't have any effect on the way it's running. Your primary concern is leaks in the intake tract.
 
Would a bad manifold gasket internally cause some sort of vacuum leak? I'm not finding any areas other than the three I mentioned to be leaking during the smoke test.
 
What is your engine vacuum at warm idle?
 
Posi said:
What is your engine vacuum at warm idle?
Click to expand...
Its about 15 on the vacuum gauge.

I've been chasing this around for the last six months through several threads on this site. I appreciate all the help and have learned far more than I ever imagined but I'm throwing in the towel and taking it to a mechanic. See if they can figure it out. It will probably save me in the long run.
 
Try this, and it's simple. Find your PVC valve. If yours is like mine it will be up behind the carb. running from the back of the engine (center) to the side of the carb. It will be a small metal pipe with a nipple on the side. The two big ends will go from the manifold to the carb. The nipple will go to the charcoal canister. The idea was that the port vacuum would purge the vapors from the canister in a controlled manor. Since mine is a hybrid or 1975 body with a 1982 engine and god knows what age canister I hooked up things the way they seemed to need to go. After trolling around for answers much like you are doing I pulled the hose from the canister nipple and plugged it off. No more vacuum leak. Give it a try, even with the proper canister set-up the canister valve might be leaking letting in to much air.
 
thistle3585 said:
Its about 15 on the vacuum gauge.
.
Click to expand...
Do you have a cam? A mild cam, vac specs would be 15-17" lower for more aggressive cam.
Have you checked your timing? Retarded timing would show lower vac
Did you tune your carb using a vac gauge?
If you haven't already I would do a compression check, low compression can = low vac.
 
I don't have a canister. The compression is 130 and within a couple pounds all the way around. I know that this is low, but I've had this setup running well last year. Not sure what has changed since then to cause this. Yes, I have made every attempt to get the timing and carburetor properly tuned. I don't know anything about the cam. I'm taking in to a mechanic next monday and see what he says.
 
So, you don't have a PVC valve either?
 
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