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Unread 12-17-2011, 08:36 AM   #1
1976s
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1976 CJ7 
 
Join Date: Mar 2011
Location: The Beach, Virginia
Posts: 6
81 CJ-7 stalls between 1000 and 2000 RPM

1976 CJ-7 with:
- 1981 258 engine
- EMPI carb (weber 32/36 style) rebuilt 5 months ago
- DUI distributer
- Painless harness (installed correctly according to Painless help line - called no less than 6 times to verify and went through several operators)
- New delco-remy distributor
- New Optima red top battery
- 8mm plug wires
- new plugs

One year ago began restoration, and the Jeep ran like a champ. Plenty strong through all gears. The only change made to the engine was a new valve cover. Compression was strong. Upon getting it all back together, it started right up, but would sputter out and stall once given higher RPM. Of note, it will run fine at higher RPM (above 2500), but will not transition to or from idle. Almost all of the older fuel, which had been treated with Stabil was run through and new fuel was added about five months ago when a new fuel filter was added and carb was rebuilt, and fuel lines were blown with an air compressor. Four month ago I had to put the Jeep back into layup due to a deployment. The same problem is still lingering. It will start and idle fine, and run at higher RPM but will spit fuel (5 feet hight) out of the carb top and stall when transitioning. (the air filter is off so I can see what is going on).

Attempts to ID the problem already tried:

- I have substituted fresh fuel directly from a jerry can to the pump - no change.

- I have installed a new alternator since the previous one was only putting out 12 v and hunting between 14 and 10 volts at times. The new alternator put out 14 volts the first day it was installed, but now only puts out around 12v at idle. Upon opening the throttle it will reach 14v before the engine stalls. Painless blamed the alternator and/or the carb.

- No leaks from the manifold or base of the carb (as tested with carb cleaner while engine running).

- Added additional 10 ga grounds from the negative battery terminal and the alternator bracket at the swing bolt for the alternator (bottom).

- tested voltage at the excitor terminal of the alternator while at idle -~ .01v

- have tuned and adjusted the carb every way I can imagine. Same effect throughout the fuel mix range, and unaffected by carb cleaner into the intakes with respect to the stalling.

- timing adjustment does not provide a remedy. Currently timed a 9 without vacuum advance connected. With advance on the dist it goes to about 12.

- added a fuel flow regulator - no change. Of note, the fuel pump is pumping plenty of fuel.

- have checked all electrical connections on the front passenger side of the engine, all are in contact.

- jumpered out the maxi-fuse - no change.

- have tried various gaps on the plugs from .035 to .050 given the HEI - no change.

- I'm no pro, but this is the second time I have added a painless and DUI to a 76 CJ, (with a weber 32/36), and didn't have problems anything like this on the last one.

- Had two of my best gearhead friends with lots of Jeep and muscle car experience take a look at all of this and they are stumped too.

I'm about ready to have it towed to a shop, but for the life of me I don't have a shop in my area that I trust. Please help.

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Unread 12-17-2011, 09:06 AM   #2
TrebleHook
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1979 CJ7 
 
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Location: Charlottesville, Virginia
Posts: 342
Just guessing from my experience (as limited as that may be)....

Vacuum advance is too limited and can't "carry over" the advance between initial and centrifugal....

Can you adjust the amount of vacuum advance at the distributor? I could on mine (GM clone).

This worked for me.

Hope you get it figured out. I am sure someone here can chime in with a solution.

Cheers,
TrebleHook
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1983 CJ8 Scrambler Laredo - 258 MOPAR MPFI/T-5/Dana 300 - 4.10 Dana 44 Rear/Dana 30 Front w/ ARB lockers front/rear - 4" BDS Suspension w/ Fox 2.0 Shocks - Ground Pounder Fab Front Shorty and Rear Spare Custom Bumpers - PSC Steering w/ Borgeson Shaft - 33x10.50 BFG KM2 on 15x8 Mickey Thompson Classic III - Work in progress.....
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Unread 12-17-2011, 09:49 AM   #3
Stumpbumper
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Your vac advance is connected to manifold vac.
You should not advance the timing at an idle. only at raise of RPM.
Connect the vac advance to ported vac and see how it does.
Currently you already have you dist advanced, so there is nothing there for it until the mech advance picks up!
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Unread 12-17-2011, 10:04 AM   #4
TrebleHook
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Location: Charlottesville, Virginia
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Quote:
Originally Posted by Stumpbumper View Post
Your vac advance is connected to manifold vac.
You should not advance the timing at an idle. only at raise of RPM.
Connect the vac advance to ported vac and see how it does.
Currently you already have you dist advanced, so there is nothing there for it until the mech advance picks up!
Yeah! What he said!!

Cheers,
TrebleHook
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1983 CJ8 Scrambler Laredo - 258 MOPAR MPFI/T-5/Dana 300 - 4.10 Dana 44 Rear/Dana 30 Front w/ ARB lockers front/rear - 4" BDS Suspension w/ Fox 2.0 Shocks - Ground Pounder Fab Front Shorty and Rear Spare Custom Bumpers - PSC Steering w/ Borgeson Shaft - 33x10.50 BFG KM2 on 15x8 Mickey Thompson Classic III - Work in progress.....
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Unread 12-17-2011, 01:37 PM   #5
1976s
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1976 CJ7 
 
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Location: The Beach, Virginia
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Treblehook,
I'm not sure if my DUI unit has that capability, but I will do some research.

Stumpbumper,
I have the distributor advance connected directly to the port on the carb. Any idea why it would cause and advance at idle? It doesn't raise the RPM that much when it is connected at idle as opposed to when it is disconnected at idle. Could there be some sort of odd problem at the distributor side of the vacuum line?

Latest developments - I can get it to stay running upon increase in RPM, but it stalls on the way back down to idle, and for some reason, at idle, the alternator is only putting out 12.6 V instead of something in the neighborhood of 14V, but at higher RPM it will increase to up to 16V. I'm off to take the alternator to get checked, but it seems odd that three alternators have shown that same problem...
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Unread 12-17-2011, 01:44 PM   #6
gt4660
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2008 JK Wrangler 
 
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Location: Arkansas
Posts: 167
DUI dizzys are connected to manifold vacuum. They suggest 12 btdc then adjust from there. I know that doesn't help your stalling issue, but that's a baseline. Set the initial timing with rpms at about 500 with the vacuum advance line disconnected and vacuum port plugged. When it is set and you plug the vacuum line in the advance will jump approx 15 more degrees.

I had to call performance distributors( that's who makes DUI) and confirm with them. If you are still having issues give them a call Monday. They will help you out.

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Unread 02-04-2012, 04:29 PM   #7
1976s
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1976 CJ7 
 
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Location: The Beach, Virginia
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Mystery solved!

Just closing the loop on this one - after looking into distributor, alternator, carb, fuel, vacuum, and wiring harness issues...it turns out an after market tachometer was the problem. It was draining power during the transitions. As soon as it was disconnected, she ran like a dream again. FML!
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Unread 02-04-2012, 06:34 PM   #8
dslywalker
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Wow who would have known.Glad you got it going.Thanx for finishing the thread.There are a lot of useless threads on the forum because their never completed
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