EGR fun

[brad_fsj10]

1980 I6...

I hooked up the vacuum plumbing to try and get my emissions stuff working again but have had bad results. I followed some diagrams others have suggested (the diagrams are for a 79 I6) but I get vacuum to the EGR at idle and a whole LOT of vacuum at part throttle. Needless to say it doesn't want to run worth a Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogley.

This truck only has two emissions related vacuum routing valves; a 3-way in a water line near the front of the engine, and a 2-way screwed into the block below the manifolds, forward of the carb. I assume the one in the block is an Anti-Knock sensor, the 3-way is temp of course.

I'm guessing I have a bad (open) vacuum valve or I'm routing wrong for a 1980. Does anybody have a diagram for a 1980 they can scan and send?

They look for emissions components for vehicle inspection here, they even looked for an EGR on my 72 Newport. Maybe I should get it registered in SC. smile.gif

[Panoscopic]

There should be a schematic on the front right side of the engine bay (as you look at the engine from th front).

[brad_fsj10]

Yup.... "should be" being the key to that phrase.

I really need to get a FSM.

[crispyboy]

would you need to route this through a CTO valve so egr operates only after thorough engine warm up?
Does it run any different if you temporarily plug the egr valve?
this egr probably needs engine backpressure to fully operate anyway.

[brad_fsj10]

I'm sure that's true. The 79 schematic calls for one "spark CTO" 3 nipple valve, and one "EGR CTO" 2 nipple valve. But it didn't matter if cold or warmed up, it ran poorly.

I disconnected the EGR and plugged the line and it now runs pretty good again. I mean I can't balance a nickle on the air cleaner, but it doesn't appear to have a radical cam either.

[tgreese]

Should be no vacuum at less than 180F (or thereabouts), and ported carb vacuum at operating temp. Under no condition should the EGR see vacuum at idle.

It may run too lean at op temp if the EGR is disconnected, since the EGR exh gas normally dilutes the air/fuel charge and lowers combustion chamber temp. Thus too much air for the amount of fuel.

The spark CTO is for your distributor vacuum, and the EGR CTO is just an on-off switch, based on the op temp. The hose for EGR should go to the tap near the base of the carb (not sure which one this is on a BBD), then to the CTO, then to the EGR valve. The EGR CTO is open or closed, so its non-directional.

hth TIm

[tgreese]

BTW the 2-nipple CTO in the side of the block is the EGR CTO.

[letank]

of course make sure you throttle plate are closed

I had the vacuum on EGR with the 85... like 10 at idle. But this is a V8, and thus different carburetor: the 2150

what i did is look for another port that did not have vacuum at idle... and i used the one for the distributor... not the manifold vacuum, but he other ported vacuum

what i heard is that a plugged canister would give you high ported vacuum...

But with my set up i passed smogged

let us know

Michel

[brad_fsj10]

Originally posted by tgreese:
BTW the 2-nipple CTO in the side of the block is the EGR CTO.Makes sense. I'm going to put a vacuum gauge on the CTO cold and see if its bad (open) and then start the truck and test the two vacuum ports to see if either is reading zero at idle.

In fact, I'm going to start over setting the timing and idle with the ports disconnected and capped and then check vacuum at idle figures. I'll go from there and let y'all know.

Thanks for the memory joggers.

[brad_fsj10]

Originally posted by Michel:

But with my set up i passed smogged
I don't think they're checking for actual output as much as covering their Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogleyes by documenting "Emissions Equipment Installed".

[tgreese]

The ported carb vacuum I'm referring to comes from the passage in the venturi that originates at the level of the throttle plate. The throttle plate is supposed to block this passage (and any vacuum) when the throttle plate is closed and you're running on the idle circuit. You may get some small bit of vacuum from this port, but nothing like what you get from manifold vacuum at idle. The vacuum at this port should also increas a lot when you crack the throttle open.

[brad_fsj10]

Thanks.