1991 vacuum hose modification with diagram

[Crisd]

Hi all, I just finished up removing all the AIR components, both three port CTOs in the front and the dual CTO in the rear and installed a two-port EGR CTO in the front. Installed all new silicon hoses and re-routed them as shown in the diagram I've attached. I studied all the various years on the OlJeep website and compared them to the sticker on my '91. It's my opinion that of all the stock OEM variations I could find the '91 setup is best... and of course, my variation is even better
The EGR and PCV systems work as well as the two vac motors on the air-cleaner. The distributor is straight to manifold vacuum. see pic

Does anyone see where I've made a mistake in understanding how the different systems work and how I've wired them (hosed them?) lol.

91WagoneerVacReRouting320.jpg

[will e]

Nicely documented.

Your goal was to remove the AIR system (yeah!) and the CTO that controls distributor vacuum while leaving the EGR, fuel evap and engine heating functional?

[Crisd]

Hi Will, Yes I kept the the EGR because the EGR system gives proven thermal efficiency benefits for SI engines which improve vehicle fuel economy, as demonstrated through literature and production applications. The thermal efficiency benefit of EGR is due to lower in-cylinder temperatures, reduced heat transfer, and reduced pumping losses. Because it never operates during cold warm up or under high loads, it has no negative effects when anyone would care. EGR is a win/win system. The fuel evap system has zero negative impact on engine performance. In fact it slightly improves performance and fuel economy while removing the smell of gasoline fumes, again a win/win. The engine heating function really only helps during the winter and during prolonged driving in cold humid conditions as it warms up the engine quicker and prevents carb icing. If you live in Florida or similar state that never sees temps under 40 degrees, then keeping that system could be removed.
I did not retain the CTO that controls the distributor as it is plumbed directly into the manifold vacuum. The reason is "Ported vacuum sources are a result of emissions laws and manufacturers doing whatever they could to get big V8 engines to pass smog before the incorporation of the catalytic converter. The idea was that by using little to no spark advance at idle, the exhaust gas would leave the cylinder still-on-fire and help maximize the efficiency of antiquated air injection systems. Engines from this era often ran very, very hot, were prone to warped exhaust valves, cracked cylinder heads and all other manner of issues. Using a ported spark advance will still allow the vacuum advance to do its job at steady cruising, but all of the benefits of idle cooling will be lost." https://www.motortrend.com/how-to/1601- ... on-timing/

[tgreese]

Hi - do you have a complaint about how it performs now? I don't see anything obviously wrong in a ca 3 minute look-through.

I would point out that my '82 has a catalytic convertor, and still uses few devices to modulate spark based on temperature. I expect you only need the ported vacuum to shut off EGR at idle (and bypass the tank purge), if you can accept some extra NOx at idle.

TAC is a win-win too, IMO. JMO - for all this effort, I would go TBI with either the CARB-certified Howell kit if you are someplace that requires it, or another kit like Holley Sniper or Hamilton.

[Crisd]

Hi Tim, right now it's running crazy rich. I believe the previous owner had adjusted the carb with all the old rotted hoses that had air leaks in them. When I decided to put all brand new silicone hoses on it, I determined that I was going to also cut down on a lot of crap I didn't need. When I initially fired it up, after putting all the hoses on in the configuration shown, it instantly started up but I had to keep my foot on the gas so that it wouldn't stall. After it warmed up and I let off the gas it immediately stalled and would not restart. Looking at the tailpipe it was black with soot and the ground below it was pounded with black soot as well. When I pulled the plugs they were also black as night.
Today I'm going to try to lean it out. I'm not a carb expert by any means but I believe my first step is to turn the idle screws in. If you have any other suggestions please let me know!
As far as going to EFI, I've already secured an entire 1998 Chevy 1500 wiring harness with intake, throttle body, injectors, all sensors, and MAF. It's going on my '88 Waggy, not the lifted one, that one is on the Dodge 2500HD chassis. My next task for that is making a crank trigger and a cam signal. From there drilling and tapping the block and intake for the sensors and making an upper intake to mount the throttle body and MAF.

[tgreese]

Maybe you have the power valve hooked up wrong or not at all? Assuming you have the factory 2150 - there is a nipple under the front of the carburetor that goes to the power valve. Vacuum holds it closed, so lacking the connection, you will be enriched constantly. This can also happen when the power valve diaphragm is punctured by backfire or from attack by modern fuels. Pretty common.

The only thing you can adjust externally, other than the accelerator pump shot, choke and idle speeds, is the idle mixture. The cruise mixture and power enrichment are determined by your choice of parts (ie power valve and main jets). The idle jets turn off above idle, so if you have rich idle and you can't adjust it with the idle screws, something else is wrong. You should also be able to kill the engine either by leaning out the idle jets or with the curb idle stop on the linkage. If the engine keeps running, you have an idle air leak or something is broken in the carburetor (ie power valve).

[Crisd]

Thanks Tim. The power valve is connected straight to the manifold vacuum which also has a tee to the cruise control circuit. I'm going to plug that port (to the cruise control) since I'm not using it. I'll start it up and see how it runs. If the same, I'm going to lean in the idle mixture a 1/4 turn at a time to see how she runs. If I can get it to idle without me on the gas pedal I'll spray carb cleaner all around to look for vacuum leaks. There shouldn't be any... I just put on all-new silicon hoses! Tip... don't use metric-sized or "universal" metric/imperial-sized hoses... they don't fit well and require spring hose clamps.

[tgreese]

If you take the hose off the power valve, it should be dry. It sits right underneath the float bowl, and a puncture will drain into the cover. Common failure with these.

I would first crank in both idle jets until they stop, and count the turns. Then put them back. They should be the same, and something like 1.5-2.5 turns. Helps to know where you are. Again, with the jets all the way in, the engine should stall at idle.

By '91 it might have changed, but the usual setting was "best lean idle." Turn them in until the next 1/4 turn makes the engine stumble.

NP! Glad if this helps.

[Crisd]

Tim, I just saw your post and didn't check the power valve earlier, I will in the morning. But I did plug the second port that fed the cruise control and I checked the idle control screws... they were 4.5 turns to close them. I backed them out 1.5 turns and restarted it... started right up and idled nicely with no additional throttle. It then started to warm up and died.... I may be out of fuel this time, lol. Tomorrow is 5 gallons in the tank and check the power valve. Thanks for the tip on how to check that!

[Crisd]

Well I pulled the vacuum line off the carb and it was dry. I filled the tank with 5 gallons and tried it again. It started right up this morning in the cool crisp air. Once it was almost all warmed up it began to stumble and then died. Trying to re-start it sounded strained and it wouldn't fire back up. So now I'm reading on the internet for possible fixes to this problem. It does have a brand new coil, new fuel filter, plugs, and wires. The cap looked newish so I didn't buy a new one... maybe I should just to cover that base. Any further suggestions?

[tgreese]

Spark and fuel. I find a can of starter fluid to be a very helpful diagnostic tool. No start or no run: a shot of ether and anything fuel related should run. No start, likely spark. Then go on to pull wires and such.

You have the original ignition? Suggest you unplug and clean the connectors between the distributor and ignition module. I have a post about this somewhere ...

Et voila - https://www.fsjnetwork.com/forum/viewtopic.php?t=17734

I'm sure there are other equally helpful posts on this topic, but I remember mine.

[Tripwire]

Love the hand drawn diagram, brings back memories - well done (-:

[Crisd]

Thanks Trip. I was going to use all straight lines like the schematic sticker on the radiator support but I wanted a picture that represented what is actually under the hood.

[ScottinTexas]

finally a diagram I can understand !! good job, thanks for sharing it,