Egr bog- missing VSD valve?

[kansasboy001]

My '83 Cherokee with 360 and newly rebuilt motorcraft 2150 bogs and backfires through carb when egr is connected under light throttle. The egr functions property and does not stick. However once I increase throttle the car runs great, as well as if I disconnect egr.

Now I am missing the vacuum dump valve and have egr hooked strait to the tvs. Could this be causing my problem, also does anyone know where to get a VSD?

Thanks

[csuengr]

How do you know the EGR is working? These are exhaust backpressure type EGR's. They need exhaust pressure before they will open, and they only open under light throttle. The last time I did this, I hooked the EGR directly to the carb (front right port on carb) and it ran fine. Sounds more like a vacuum leak.

[kansasboy001]

If it was a vacuum leak then the car wouldn't run flawlessly with vac line from tvs to egr capped. Now egr works fine over 2000 rpm it's just at very light throttle like going around 20mph. In park when I throttle to the same rpm range the egr kinda pulses, once I'm over around 2000 rpm it's fully up. This is the correct egr for 1983 Cherokee. I tried a valve from a 86 j20 which has a much larger orface the the problem is worse. That makes me think that I need the VSD. According to the tsm it doesn't allow ported vac to pass until throttle is open enough for manifold vac to drop.

By the way I have found that the VSD is actually a Ford part which they call egr load control valve

[az chip]

Most that I know run the EGR to the front vacuum control switch. I cannot remember which port. The air cleaner TVS is not reliable.

[letank]

Interesting, subscribed.
I do not have a dump valve on the 85, and I need to address a small bog but no backfiring slighlty off idle...

[tgreese]

How emissions compliant do you need to be?

When you say light throttle, under what driving conditions? On the highway with light throttle, or accelerating around town with light throttle?

I would double check that I had no vacuum leaks after carburetor replacement. Was this carburetor rebuilt professionally, by a shop or a reman factory? Did the carburetor have this problem before rebuilding?

My '82 arrived without the VSD. It did have a TVS but it was all connected in a screwy way. Really, I had more trouble with the spark plumbing than the EGR. Connecting the EGR simply with ported vacuum through single-circuit side of the thermal switch (dual CTO) seems to be fine.

If your '83 EGR valve does not work without the supporting VSD and TVS, I would go earlier, not later. As the years go by, the emissions laws were getting stricter and stricter, and charge dilution by the EGR was getting more and more aggressive. To allow this, the manufacturers added more control elements to throttle back the EGR in situations where engine performance is affected. RockAuto shows the '79 EGR valve available from several makers - not cheap, but you'd have an EGR valve and it should work fine with a single-hose connection ...

Look at the '79 vacuum diagram on the OlJeep page - http://oljeep.com/gw/vac/79/79-FSJ-360_Vacuum.jpg - this is more or less how my '82 is connected, except I retained the HDC CTO (heavy duty cooling) without the non-linear valve. The valve was present and seemed to not function. All the HDC CTO does (that I can figure) is provide straight manifold vacuum to the distributor when the HDC CTO is opened. The spark side of the Dual CTO switches between manifold vacuum when warming up, and ported vacuum at operating temperature. You can eliminate the spark CTO circuit entirely (if you won't run afoul of emissions laws) and connect the distributor directly to manifold vacuum.

[babywag]

Add a vacuum delay valve, if you need/want keep EGR. Should eliminate problem.
NAPA has them, other stores probably do too, but you'll probably have to give them a part#.

[Tatsadasayago]

Add a vacuum delay valve, if you need/want keep EGR. Should eliminate problem.
NAPA has them, other stores probably do too, but you'll probably have to give them a part#.

X2

The earlier (77-79) valves were red and black I recall.

[kansasboy001]

Ive tried Napa but they were unable to find a single forward delay valve. But I can definitely get a Ford VSD in my junkyard. A vacuum leak is possible I suppose since I do have a high pitched whine in idle sometimes. It's very random and has persisted across a different carb body.

[babywag]

I've got a whole bag of them if you're not in a hurry.
But a competent tech should be able to find one lol.

[kansasboy001]

After searching my junkyard for a Ford egr lcv or a simple delay valve all I could find was a vacuum amplifier out of a 1979 Dodge tuck. Upon investigating the vacuum diagram it takes in a manifold vacuum source, a ported vacuum, and has an output to the egr. It stores manifold vac in a canister and releases it on a curve once ported vac reaches a specified amount. It outputs about 5hg at 1500rpm and maxes out at 15hg around 3000 rpm. It works perfectly once the engine is good and warmed up, even warmer than when the cto lets vac pass. When cold it still could use a delay valve. But the vacuum amp looks cool on the manifold so it's a keeper

[babywag]

egr shouldn't be active until engine is warmed up.
in stock configuration it goes through CTO that prevents cold engine egr operation.

[kansasboy001]

egr shouldn't be active until engine is warmed up.
in stock configuration it goes through CTO that prevents cold engine egr operation.

Which it is. I have a dual cto back by the pcv on the heater hose. All I'm saying is with the Dodge vacuum amplifier system the cto should be swapped for a higher temperature one for perfect operation.

[babywag]

ah gotcha

[kansasboy001]

Just an update, BWD part number EC315 is the correct forward delay valve for us. In combination with the vacuum amplifier egr functions without bog or performance impact