No Ported Vacuum

Because the vacuum at that port depends on load? Have you triple-checked to make sure that it is the correct port?

Earle

Then I would guess someone put the carb's base gaskets on wrong. There are channels in them that direct the vacuum flow.

Do you have manifold vacuum at any ports?

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

One other thing, the hole could just be plugged. Maybe try spraying some carb cleaner into the nipple to see if it comes out on the inside.

Mike

Mike Roma>

Thanks for all the advice...but, I have checked if the port is clear (sprayed cleaner through it), the carb gasget has never been removed or replaced, and I do have vacuum at the manifold ports. When you say the ported vacuum depends on load, should I still get some vacuum if I just rev the engine?

If I remember my emissions control theory right, the EGR is supposed to work at part throttle, not full load, when the mixture, caused by the other emissions controls, is too lean. You inject exhaust gas into the too-lean mixture, and it makes it less lean, without making it richer. This lowers the combustion temperature, and theoretically oxides of nitrogen. If you think about it, this means that your EGR isn't designed to kick in when you are idling, or playing with the throttle in your garage. You have to be going down the road, with a certain amount of air flowing, burning a certain amount of fuel, to get appreciable vacuum at that port.

This means also that your state emissions compliance program isn't going to succeed in testing the operation of your EGR valve, unless they have a chassis dynamometer, and maybe not even then. I had a car in Washington State pass with flying colors, even though they put the car on the dynamometer and ran it at 30 mph, with the under-vehicle part of the EGR plumbing, completely rotted through and brazed shut. Why do you want the EGR working? It isn't going to do anything, except plug the filter, rot the plumbing, and eventually stop working by itself. The theory is somewhat plausible, but the effect on emissions is negligible at best.

I don't really know why you are not getting vacuum at that port, but I suspect that you may not, with the vehicle in the garage. Are you absolutely sure it is the correct port for the EGR?

Earle

I have the top valve cover side nipple on my BBD hooked via a T-fitting to my distributor and CTO valve. The CTO valve then powers the air filter switch for the EGR valve. The EGR valve has a vacuum delay disk in the line. If this disk is backward, the EGR will not see vacuum.

When I am sitting at an idle and I give the engine a shot of gas, I can see and hear my distributor advance physically move in perfect time to the gas pedal.

When I punch it, I have full advance.

I don't understand how there can be no ported vacuum if the nipple sprays clear with cleaner.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

steve alleged...

If you briefly crack the throttle maybe a quarter open, you should definitely see vacuum at the port. You should be able to feel it with your finger, and it's enough to pull the EGR open slightly. Assuming you find that you do indeed have ported vacuum, the EGR should still not work if the engine is not warmed up. Check this diagram:

for vacuum at the carb port, in/out of the CTO, and in/out of the TVS in the air cleaner. Check the canister purge line for a massive leak.

The mid 70's Dodge system was similar. Vacuum only at raised engine speeds, none at idle.

One possibility is that the carburetor was rebuilt, and somebody used the wrong gasket. I have seen carburetor rebuild kits, with two or three gaskets for the same job. If you pick the wrong one, then something winds up not connected, or connected wrong. This would explain your port being open, but no vacuum.

Earle

When I took auto shop back-in-the-day the instructor drummed it into us to be careful with carb gaskets as they would often seem to fit perfectly upside down and that replacements did not always have to correct holes and we were to line the new and old gaskets up and compare them.

This won't help in this case unless he was to get a card kit and rebuilt it himself now.

Other than a gasket or clog somewhere I am at a loss to figure where the problem unless he has 2 hoses crossed which used to be quite possible. There used to be a number of similar sized vacuum hoses under the hood.

Another couple thoughts.... has the OP checked to see that the hose is not leaking or hasn't collapsed midway along the length?

When you spray cleaner into the port.... does the engine sputter or stall?

I can't see how you can have 0 vacuum on the ported and still have manifold vacuum.

There are a couple of 'mechanics' here who say they know these carbs really well, maybe one of them can chime in once all our guesses run out?

I would be guessing the carb is loose or the base gasket has blown out or the intake manifold is loose.

How is the idle?

How are the brakes?

Any oil puking into the air filter?

Ok, let's back up a bit..... The 'ported' vacuum nipple is in the 'side' of part #60 right under the horizontal line from part # 43 and is about 1/8" around.

Just above that are two larger nipples that are just the float bowl vents. They are not shown in the diagram and are connected to the charcoal canister.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

You're pretty much screwed if you don't have the original gasket to go by. You have to find someone who actually knows how a carburetor works, or figure it out by yourself, like Bill did with his accelerator pump float gasket problem. I vaguely remember trying to order an exact replacement carburetor gasket from a dealer, when the stuff in an aftermarket kit didn't work right. They didn't know any more than we did.

Earle

"Tampered/gross-polluter"