Spankrjs 1985 Spring Special CJ-7

[spankrjs]

Took some of the top parts off the carburetor so I could remove and clean the idle tubes.

Reference picture for me:



Took this top plate off to take a look, everything moving freely, no debris in here, looks OK.



Take these parts off:



Then you can get to the idle tubes.



Two screws and the entire venturi cluster comes out.



NOTE: I also removed and reinstalled the little check ball to blast out a few more ports with carburetor cleaner. Be careful with this, very easy to drop it down into the intake/engine!!

Using torch tip cleaning kit to check/clean the idle tubes for obstructions.



Blast carburetor cleaner through the tiny port inside the big circle. One for each tube. This is how fuel gets inside the brass tubes.



Blasted out all the little ports in this part with carburetor cleaner, too.





Make sure to reinstall the little check ball before reinstalling the removed parts. Be careful!!



Then reassembly.

 

[spankrjs]

Good news/bad news: no real gunk or varnish observed, no blocked idle tubes or ports that jumped out at me.



Restart took a bit of effort, all the fuel and carburetor cleaner flooded the engine when I was screwing around. Finally started up, idled like crap for a bit, finally cleared up. Quick test drive, maybe marginal improvement.

Little bit more screwing around, unplugged the vacuum advance, engine did not immediately drop RPM which I thought was odd? After a few seconds RPM would drop. Vacuum advance hose definitely pulling. Plugged that hose back up, unplugged the 4"/10" vacuum switch and drove around. Not a good idea, you have to really baby the throttle to keep the engine from falling flat on its face. So, just assuming that thingy is doing what it is supposed to. Plugged it back in, another quick drive, a bit better. Drove some more, sometimes almost no issues, then they would come back. Very intermittent.

I improved the situation or it improved itself, at least it is not violently bucking/surging during light throttle anymore, but the stumble is still there.

Sprayed brake parts cleaner around carburetor and intake, no vacuum leaks were found. Maybe a vacuum hose leak somewhere?

Things Jeep does perfect:

Starts right up
Shuts right off (no run on or dieseling)
Idles perfect
Choke working properly
Sol-Vac working perfectly
High speed operation perfectly
Heavy and light acceleration perfect

Things Jeep does not do well:

Steady light throttle to maintain constant speed, slight surge or buck. Better but still present. From 5 -40ish miles per hour.

The same buck/surge is also felt while decelerating, either with foot 100% off pedal or normal slow lifting of foot off pedal to slow down with vehicle in gear.

Did not notice a "light show" from spark plug wires with hood up/engine running outside in the dark.

So, maybe a carburetor blockage that is slowly working it's way out?

Maybe a slight vacuum leak leaning out mixture?

Maybe idle mixture set a hair too lean (was not a problem 6 years ago).

Maybe timing off (was not a problem 6 years ago)

Maybe vacuum/mechanical advance not working properly in the distributor, maybe sticking? Did have this issue 6 years ago.

More work/diagnosis needed, that's it for now.

 

[spankrjs]

Piddled with this one some Saturday morning.



Decided to investigate the distributor/timing.



Distributor installed, twisting the rotor, it would spring back but the weights were not swinging back consistently each time, at least the one I was looking at through the square hole in the pick up base plate. That might be normal, not sure.







So, decided to investigate. Pulled the center gear thing off (don't lose the roll pin), then the pick up coil. First thing I noticed, one of my springs is loose, providing no "spring" back at all.

Loose spring:



Tight spring:



I kept both the original springs I removed from the distributor with these two aftermarket light springs.:





Comparison, left to right:

Too loose original spring
Spring I had installed, too loose
OEM spring I reinstalled



Unfortunately, no real data on what springs are used in what OEM application. Only way to verify is to map the Advance curves, which I did before, probably need to do again. I imagine some tension at rest is better then none. With none, getting some mechanical advance at idle, besides the initial advance you set.

 

[spankrjs]

Spring installed, note dry oil wick/sponge in top of distributor shaft.



A little drop of oil added. I imagine this dried out due to the Jeep sitting up a long time. A little dab will do you.



Put a little plastic safe oil (rc car crossover product) to the plastic bushings on the Advance weights.



Took apart the Advance plate to add a little lube here, too.



A little dab on the three yellow dots and on the center raised metal portion.



None of these parts were sticking on the bench, but a little lube won't hurt.

Reinstalled everything, don't lose the little PIA roll pin!



It is easier to slide gear down the shaft, then install the roll pin.



Quick test drive, a bit better, but still have the surge when transitioning from idle to low speeds. Better, but still annoyingly there. The whole engine/Jeep is not bucking anymore, bit still not right.

So, hard to know if anything I have done has improved anything, or maybe I still have a carburetor blockage that is working itself out.

 

[spankrjs]

Checked the timing, some information. Just remember, this Jeep is still using the MCU to control timing, so not like a regular carburetor/timing set up.

Everything hooked up, engine running at idle speed of around 600 RPM, only 8 degrees advance showing.

Unhooked vacuum advance and vacuum switch, total timing at idle of 600rpm is 6 degrees. So MCU only allowing 2 degrees of advance at idle?

So, looking at my underwood sticker, checked the timing at 1,600rpm, around 20 degrees total (this is with switch unplugged and no vacuum advance).



Should be 11 max, I was around 20 degrees.

Adjusted down, idle drops to 400 rpm.

Shut engine down, hooked up vacuum advance and vacuum switch, restart, base idle at 500rpm with 6 degrees advance showing.

I just added a bit more advance, so probably back where I started. Quick drive, a bit better. So, Shut Jeep down, came back took it on a 10 kile trip, it was crap. Not bucking, but terrible low speed operation. If you.are barely on gas it surges. If you give it more pedal it is fine. Drove it to my buddies house, it stayed parked about 8 hours. Drove it home, much better, but still present.

Very inconsistent. Wondering if I just have a carburetor blockage that is working it self out. I'll work on it some more next week when I get back from Hot Springs.

That's it for now.

 

[Belizeit]

I know you, are going to figure this out. But that is probably the reason a lot of those were replaced by owners eventually.