Smoke Testing, Did I Do It Right?

[rwest]

Hello,

Been chasing drivability issues on my '77 with CIS. Decided to go at it systematically- yea, I know more fun to just throw parts at it and pray!

I bought this homemade smoker off of eBay a few years ago and finally gave it a whirl. Put a plumbing cap over tail pipe and ran the smoke into it at 4psi like instructions said.

I ran it for a long time since it took awhile for the can to heat up and supply smoke. I did pull it out of the tail pipe and it indeed was supplying copious amounts of smoke. The cap also was pushing out under the pressure. I got zero smoke from the CIS parts.

It is possible that my CIS is actually sealed since last year I replaced just about every seal, gasket, hose and the airbox.

Thoughts?

[boyt911sc]

Rutager,

Are you testing the exhaust system for leak? Why not inject the pressurized air with smoke directly to the air box? Keep us posted.

Tony

[rwest]

Hi Tony,

I figured and was most likely wrong that it was all a connected system and by putting the smoke at the the tailpipe I would "see" the whole thing. I will try again with injecting the smoke at the fitting for the booster, unless there is an even better place?

Thanks,
Rutager

[boyt911sc]

Rutager,

There are some convenient spots or locations to inject pressurized air into the CIS air box namely:
a). Brake booster vacuum tube by the side of the air box.
b). POV (pop off valve) with a big rubber stopper as adaptor.
c). Top of the throttle body.

Keep us posted.

Tony

[martyjr]

I always use the brake booster port on the driver's side of airbox and had good results. Keep in mind that it does not require much air pressure. BTW, I have a similar smoke unit and it works great.

Good luck,

Marty

[rwest]

Well, I went out and hooked it up on the booster connection and two issues came to light: one, it appears like the unit will not heat up, might have burned out the heating element the first test? and secondly, system won't hold any air pressure, so obviously I have one or more good sized leaks.

Without the smoke, I'm going to have to try a water bubble test, I guess. Seems like smoke would be the easiest way to spot the leaks, going to be hard to get soapy water to some areas.

I took off the boot over the fuel distributor and throttle body and put a glove over the top of the body and it did fill up with air very loosely.

Thanks for all ideas and suggestions.

[merlinfe]

Rutager,

Skip all the fancy stuff. Go buy a couple cheap cigars and puff into the brake booster port. Works pretty good and only cost a few bucks.

-Steve

[jlex]

Originally Posted by merlinfe

Rutager,

Skip all the fancy stuff. Go buy a couple cheap cigars and puff into the brake booster port. Works pretty good and only cost a few bucks.

-Steve

Ha... yeah, that's how I found the manifold leak on my BMW X3. Effective, but it can make you sick if you're not used to cigars...

[walt]

Tony recommended this system to me which I used successfully. I applied 2-3 psi air thru the brake booster hose following a partial engine drop.

Oscillating Idle

Walt

[dino_jr]

Originally Posted by boyt911sc

Rutager,

There are some convenient spots or locations to inject pressurized air into the CIS air box namely:
a). Brake booster vacuum tube by the side of the air box.
b). POV (pop off valve) with a big rubber stopper as adaptor.
c). Top of the throttle body.

Keep us posted.

Tony

Hi Tony, do you have a pic of item (a)? I plan to check for air leaks tomorrow on my SC, thanks.

[rwest]

Originally Posted by dino_jr

Hi Tony, do you have a pic of item (a)? I plan to check for air leaks tomorrow on my SC, thanks.

Dino,

Here's a couple pics, one in the car and the other on an old air box. The inlet you want is the one just below the throttle body towards the back of the in car photo with the brass threaded fitting. The fitting that is closer and in the car picture that has blue tape on it is the emissions fitting for the fuel vapors and goes into UNMETERED air with the filter and intake and will not give you any useful results.

On the old air box, you can clearly see a threaded port just below the big hole where the throttle body would be. This is metered air and a good place to test. Although remember to test the actual line to the brake booster as it can develop leaks too and using its port, you take it out of the test.

[rwest]

Finally got back to the garage this morning; last couple days it was around 90F and the afternoon sun beats on my garage door- this is my fun car, don't want to be tortured while working on it!

With the smoke portion not working, I just used about 2lbs of air into the booster port and sprayed everything with some soapy water- no bubbles, not real surprising since last year just about everything that could be renewed was, including the large expensive "y" hose piece.

When I was squirting the water around, I noticed the snorkel piece that normally connects to the boot and covered it with my hand and the glove or the throttle body popped right off, so I put a hose clamp on the glove and then covered the snorkel- glove blew up like a balloon- see pictures. So after those couple tests, would it be safe to say I'm probably "Vacuum tight?"

Thanks for all the previous replays and any on this.

[rwest]

I think the previous test shows my intake area being in good shape, but almost 100% positive my brake booster system is not sealing. Putting a mity vac tester on it and it doesn't hold nor build up vac.

What should I expect and how should I test it?

Thanks.

[rwest]

So I put everything back together and fired it up- all normal. I let the idle settle out and started to remove the booster line; didn't even get it all the way off and the engine almost died, pushed it back on and engine leveled right back.

I then turned the car off, removed the booster hose and plugged the intake to engine side, started the car back up and no change in idle or difference in engine sound from when it was connected.

Safe to assume that I have no appreciable vacuum leaks on the booster circuit either?

[walt]

You say the problem is a "drivability issue". Can you explain further, maybe something other than a vacuum leak.

[rwest]

Hi Walt,

Not sure what is causing the issue, so I decided to work through the tests and since vacuum leaks can cause all sorts of problems, I wanted to eliminate them first.

I had planned to start a thread on it when I gathered all the basic test info: vac and fuel pressures.

So, I have several issues, one is really flat throttle response up until about 2500rpm, then she accelerates nicely. This has been this way ever since I've owned the car- 27years.

Second issue is a shudder or bucking when not under acceleration; it is fairly mild, sometimes hard to tell if it is bumps in the road or engine bucking. Very pronounced at constant throttle.

I haven't ruled out spark issues, although I have replaced, wires, plugs, rotor, points, cap and checked timing. Strongly thinking about getting distributor rebuilt.

Best,
Rutager

[boyt911sc]

Rutager,

I have not seen your control fuel pressure data. Have you collected these data earlier? Keep us posted.

Tony

[rwest]

Hi Tony,

Not yet, that will be my next step in my trouble shooting. I have gauges and a factory manual, so should be able to get good data.

Does my analysis of my vacuum system seem solid and basically leak free to you?

I'll start a new thread at that point since this one was centered on the vac leak detection and for people searching in the future it probably would be more helpful if the title was a CIS drivability issue.

I look forward and will be very appreciative of your help when I get you some numbers.

Thanks,
Rutager