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  1. #1
    Join Date
    Sep 2004
    City/State
    Claflin, KS
    Scrambler Year
    1985 CJ8
    Year Purchased
    90
    Posts
    653

    Problem with engine running; idles but dies when trying to move the Scrambler

    I am having a problem with my '82 CJ8 with the 151 Iron Duke 4 cylinder and a T-4 transmission. Back story:

    Bought the '82 CJ8 from the original owner this past Thanksgiving. It hasn't been run in over 10 years but I got it running a few weeks ago. Changed all fluids, plugs, plug wires, cap, rotor, fuel filter, and rebuilt the carburetor (stock Rochester 2 barrel Varajet). At the initial start up, the Jeep would idle good and rev a little rough, but after a few seconds it would smooth out and idle/rev great! The rough reving I am referring to sounds like a carbureted engine warming up.

    Anyways, after checking the brakes, fixing a flat tire, and changing the ignition lock cylinder I had the Scrambler running and stopping great! I have been driving it around our land for the past couple of weeks and it has done great. Last weekend (Friday) I decided to take it up to the lake (approx. 35 miles). The CJ8 cruised down the road great at 60 mph until about 25 miles into the trip. At this point the Jeep would periodically miss out, but not enough to affect the way it drove. This problem began to worsen until it got to the point the Jeep died. I was able to start the Jeep a few more times by pumping the gas pedal many times but it got to the point it wouldn't start at all. Luckily I made it to less than a mile from the lake so I was able to get a tow. I got a ride home for work Saturday and brought my Grand Cherokee back up with my tow bar to get the jeep back home.

    My initial thought was the problem that caused all of this was a bad fuel pump. I got a new fuel pump and installed it today thinking that was the problem. After installing the new fuel pump, the Jeep fired right up although it would still run slightly rough if I raised the RPM's above idle for a few seconds but it smoothed out like it normally did. I left in the Jeep to go down our driveway for a test drive and after about 100 yards it died. I was able to get it going again but if I would try to let out on the clutch to go, the Jeep would die. If I would not put it in gear, it would start, idle and run good but if I tried to move the Jeep under its own power it would die. I was able to put the Jeep in 4 low to get it back to the shop.

    its like the Jeep will start and run fine until I begin the drive it. It will make it about 100 yards and die. If the Jeep is sitting it will still rev up fairly well, it will even start easily the first time when it hasn't been run for a little while. But if it dies while trying to drive it, the starting gets much tougher; I have to really pump the gas pedal. Does anyone have any ideas what would cause this? I have though maybe something in the carburetor but the problem began a couple weeks after it was rebuilt and I have driven it quite a bit since then. Would a clogged pickup screen in the fuel tank cause this? I would think a clogged screen would not let it idle even. Any help is appreicated!
    1985 CJ8, Dana 60 frnt/70 rr, 5.13's, Detroits, NV4500/Atlas II/AMC 360, 40"x13.5"-R17" MT/R's, RE 1.5" springs SOA, Warn 9.5ti, STC full length soft top
    85 CJ8, current frame off with world cap/postal/overlander top and doors
    85 CJ7, T5, Junkyard 4.0 head swap, MPFI
    84 CJ7, 258/TF999/D300, HP44/HP60 w/discs, 4.56's, Detroits, SOA w/1" Alcans, 37" Cooper STT's, PS rocker knockers, Warn M8000
    84 CJ8, garnet interior and paint, long term project
    2-84 CJ8 Postals, one stock 26K miles,the other one getting body work and a 4.0/aw4 transplant
    82 CJ8, 151ci, T176, stock, nutmeg whitco soft top and doors, farm truck
    82 CJ8 Laredo
    53 CJ3A
    87 Grand Wagoneer
    02 Dodge Ram 2500 CTD HO 6 spd 4x4, Triple DiPricol Pillar Gauges, Edge Comp "Hot", 5" straight pipe w/ 6" Tip, Toy Hauler rolling on 18's
    05 Wrangler Rubicon Unlimited Sahara Edition, 0002 of 1000, 6 spd, stock
    06 GC "Overland" Airaid CAI

  2. #2
    Join Date
    Mar 2010
    City/State
    Manhattan, KS
    Scrambler Year
    '81 CJ8
    Year Purchased
    2010
    Posts
    2,370
    Oh boy, sounds like you're in for some trial and error. I have no experience with the 151, but here's some things that come to mind:

    Vacuum advance. Is it connected?

    Vapor lock. Do you have a dual-outlet fuel filter, with a return to the tank? Perhaps your tank isn't venting through the traditional check-valve system, or the el cheapo vented gas cap? Pull the cap to check if there is a vacuum.

    How's your timing?

    Vacuum leaks? Manifold, carb base, etc.

    You probably have way more experience troubleshooting this sort of thing than I, but those are some things that come to my mind.
    -N

  3. #3
    Join Date
    Sep 2004
    City/State
    Claflin, KS
    Scrambler Year
    1985 CJ8
    Year Purchased
    90
    Posts
    653
    Update:
    I have been messing around with the Jeep for the past hour or so and now the Jeep is getting to where you can't even rev the motor much without it dying. Actually the Jeep won't even run now (it is acting like it is flooded, when I hold the throttle to the floor it will barely run but very rough at about 300 rpm, but the second I let the trottle off the floor it dies. I did have a pretty good backfire out of it and there is fuel getting to the carb. I even had another brand new rochester carb I threw on real quick to make sure the carb. wasn't the problem and I got no change with the new carb on. It is definitely getting fuel. I pulled a few of the plugs and they are getting a good spark when I turn it over. walkerhoundvm, the vacuum advance was hooked last I checked (I'm going to take a look again though to verify!) I don't think vapor lock is an issue since it does it even when it has just been started. Any other ideas?
    Last edited by JeepScrambler; 07-20-2010 at 09:26 PM.
    1985 CJ8, Dana 60 frnt/70 rr, 5.13's, Detroits, NV4500/Atlas II/AMC 360, 40"x13.5"-R17" MT/R's, RE 1.5" springs SOA, Warn 9.5ti, STC full length soft top
    85 CJ8, current frame off with world cap/postal/overlander top and doors
    85 CJ7, T5, Junkyard 4.0 head swap, MPFI
    84 CJ7, 258/TF999/D300, HP44/HP60 w/discs, 4.56's, Detroits, SOA w/1" Alcans, 37" Cooper STT's, PS rocker knockers, Warn M8000
    84 CJ8, garnet interior and paint, long term project
    2-84 CJ8 Postals, one stock 26K miles,the other one getting body work and a 4.0/aw4 transplant
    82 CJ8, 151ci, T176, stock, nutmeg whitco soft top and doors, farm truck
    82 CJ8 Laredo
    53 CJ3A
    87 Grand Wagoneer
    02 Dodge Ram 2500 CTD HO 6 spd 4x4, Triple DiPricol Pillar Gauges, Edge Comp "Hot", 5" straight pipe w/ 6" Tip, Toy Hauler rolling on 18's
    05 Wrangler Rubicon Unlimited Sahara Edition, 0002 of 1000, 6 spd, stock
    06 GC "Overland" Airaid CAI

  4. #4
    Join Date
    Apr 2002
    City/State
    richmond, va
    Scrambler Year
    1981
    Posts
    2,003
    It sounds like either a fuel issue or maybe the ignition control module.

    You say it is definitely getting fuel...Is that because you changed carbs and it ran the same, or because you pulled the fuel line off the carb and watched fuel spew out while you cranked the engine? If you haven't pulled the fuel line, then do that and then have a helper crank the engine a little. You probably already know this, but if everything is working right, then you will get a pretty strong fuel flow out of the line. If there is a weak stream of fuel, you may have a bad fuel pump or a clogged pickup filter.

    At different times, I have had both a bad ICM and a pickup filter which would get coated with rust particles. The ICM was hard to diagnose because it was intermittent, and the jeep usually started and ran fine when cool, but then stalled the motor once it got warm. It was a bit erratic, too.

    The clogged pickup filter symptoms allowed the jeep to idle fine (because it didn't need too much gas to idle), but then once the rust in the tank got stirred up by driving, it would begin to stall the jeep. Couple of ways to tell if this may be your problem without dropping the tank: 1. Jeep will run better with a full tank of gas because it "dilutes" the rust concentration. 2. Jeep will run better for a short period after you stop because the rust particles or trash in your tank will settle to the bottom. Once you start driving again, they get stirred up and coat the pickup filter.

    Oh, well. long answer, but maybe it will help. Keep us posted!
    Quote Originally Posted by rustycrawler View Post
    I'm in the process of "upgrading" a new Scrambler of mine. It needs a couple things starting with a new frame, body, drive train, and uh...well...it needs just about everything. Right now it's just a pile of rusted unusable parts..

  5. #5
    Join Date
    Feb 2009
    City/State
    Biloxi, MS
    Scrambler Year
    1983 (I think SR?)
    Year Purchased
    2009
    Posts
    2,964
    My Scrambler was acting the same way. I finally dropped the fuel tank, and the pick up filter was completely clogged up. Might not be the cause of your problems, but since the jeep was sittting up for a long time it is probably worth it to to drop the tank and inspect it/clean it out

  6. #6
    Join Date
    May 2002
    City/State
    Spring Hope, NC
    Scrambler Year
    1984
    Year Purchased
    2003
    Posts
    1,577
    It might do to drop your gas tank and make sure it's clean. Like WT said - trash in the tank can settle after stopping and then re-mix with the fuel when running. First maybe install another fuel filter. If it cranks and runs a little bit you'll know that's the problem. You said it cranked and run shortly with a new pump. I suspect it's just pulling trash from the tank.
    '84 CJ8
    '85 CJ7
    '98 XJ

  7. #7
    Join Date
    Jul 2004
    City/State
    Arcadia, IN
    Scrambler Year
    ???/1983
    Year Purchased
    2004
    Posts
    1,322
    When you changed your fuel pump you did put on new fuel lines and a new filter...right? A clogged filter would cause those symptoms. And, when you change the filter...you should always put on new lines. Always use the 1-in 2-out fuel filter and make sure you replace the return rubber lines while you are at it (verify that the return line is not clogged too). Make sure the small line is on top (at the 12-o'clock position) so that vapors and excess fuel are pushed back to the tank.

    I am afraid you will need to drop your tank. If you have the stock tank and pick-up, the screen (or fuel sock or what ever you like to call it) could be clogged. I have also had issues where the screen was cracked (or had a pinhole in it). Once the fuel level dropped below the crack/pinhole, it would suck in too much air and create those issues.

    Similarly, a hole in your fuel lines (from the tank to the fuel pump) can cause an issue like this too.

    Finally, remove your gas cap and listen. If you hear an inrush of air, it could be possible that your charcoal canister and gas cap need attention. I have had issues where the tank would not vent properly and create negative pressure (vacuum) inside the tank. Eventually, it was too much for my fuel pump to overcome...and it would stall out.

    I just went through all this with my Grand Wagoneer. I decided to throw everything at it. Replaced the fuel pick-up screen, new fuel lines from the tank to the hard steel lines on the frame rail, new fuel lines from the hard steel lines to the fuel pump, new fuel pump, new fuel lines from the pump to the filter, new filter, and new fuel lines from the filter to the carb...oh, and a rebuild on the carb... AND, now she runs perfectly!!! Sorry to say, you may want to do the same... Figure, those lines may have never been changed...stuff doesn't last forever!

    Good luck!!!!!!!

  8. #8
    Join Date
    Oct 2002
    City/State
    Findlay, Oh
    Scrambler Year
    82 CJ8
    Year Purchased
    2001
    Posts
    783
    I may have missed this in all the posts but after sitting for 10 years, I didn't see where you drained the old fuel in the tank?

    I think everyone is on target but I do know that water condensates and will do odd things to a vehicle. It actually pockets in the carb and tank and until it is gone, it won't ever run right. If you added new good fuel to the old fuel, it will cause an intermittent problem like this.

    Again, tank down.

    Rudy
    www.Rudys-CJs.com

    85 CJ7 350FI w 44 Front & Rear, Fully Locked, Alcan Springs, 37" Creepy Krawlers, 4 wheel Disc: Likes to play with Rocks, Not afraid of trees

  9. #9
    Join Date
    Sep 2004
    City/State
    Claflin, KS
    Scrambler Year
    1985 CJ8
    Year Purchased
    90
    Posts
    653
    Hey guys, sorry I haven't posted back up on here yet but I have been out of the country on vacation for the last week and just got home tonight. Hopefully I will get a change to get the tank dropped in the next couple of days. I will keep everyone posted. Thanks again for all the input so far!
    1985 CJ8, Dana 60 frnt/70 rr, 5.13's, Detroits, NV4500/Atlas II/AMC 360, 40"x13.5"-R17" MT/R's, RE 1.5" springs SOA, Warn 9.5ti, STC full length soft top
    85 CJ8, current frame off with world cap/postal/overlander top and doors
    85 CJ7, T5, Junkyard 4.0 head swap, MPFI
    84 CJ7, 258/TF999/D300, HP44/HP60 w/discs, 4.56's, Detroits, SOA w/1" Alcans, 37" Cooper STT's, PS rocker knockers, Warn M8000
    84 CJ8, garnet interior and paint, long term project
    2-84 CJ8 Postals, one stock 26K miles,the other one getting body work and a 4.0/aw4 transplant
    82 CJ8, 151ci, T176, stock, nutmeg whitco soft top and doors, farm truck
    82 CJ8 Laredo
    53 CJ3A
    87 Grand Wagoneer
    02 Dodge Ram 2500 CTD HO 6 spd 4x4, Triple DiPricol Pillar Gauges, Edge Comp "Hot", 5" straight pipe w/ 6" Tip, Toy Hauler rolling on 18's
    05 Wrangler Rubicon Unlimited Sahara Edition, 0002 of 1000, 6 spd, stock
    06 GC "Overland" Airaid CAI

  10. #10
    Join Date
    Sep 2004
    City/State
    Claflin, KS
    Scrambler Year
    1985 CJ8
    Year Purchased
    90
    Posts
    653
    Ok, so I finally got a chance to work on the Jeep again. Got the tank dropped and checked the pickup sock; it wasn't near as plugged with rust as I had suspected it would be. After verifying I was getting plenty of fuel to the carb I rechecked the spark and this time there was none! I went to the parts store and got another coil and put it on and the Jeep fired up! So it seems to me the old coil was going out on me because the last time I checked it there was a good spark.

    I have a new fuel pump, fuel lines, carburetor, filter, and a cleaned out gas tank and the problem was the coil but after sitting as long as the Jeep has, I'm sure these other items were on their way to giving me a headache so I'm glad I got them changed out!

    With the new carburetor I have (Rochester 2 barrel) on the Jeep, if I pump the gas at all before starting it (even to engage the choke) or while cranking over on it, the Jeep will flood very, very easily causing it to be hard to start or usually not start at all. Does this sound like an improperly set up float in the carburetor?

    Also, once I got the Jeep started it was idling fairly high (around 1000 rpm) and that was after I had backed the idle speed adjustment screw off as much as I could. I eventually had to back the electronic solenoid (has a shaft sticking out of it that will push the linkage to speed up or slow down the engine, there is a 1/4" nut on the other side of the solenoid that can be adjusted) nut out to get the idle to drop somewhat but it still doesn't seem quite right. I'm not very good at setting up these Rochester's (I like my Webers ) ) as this is my first one to tinker with. I'm thinking the choke might not be properly set either but the choke housing is rivoted on and cannot be turned so I was assuming it was set up correctly already. Anyone have any experience or advice with these rochesters?

    As always, thanks again guys!
    1985 CJ8, Dana 60 frnt/70 rr, 5.13's, Detroits, NV4500/Atlas II/AMC 360, 40"x13.5"-R17" MT/R's, RE 1.5" springs SOA, Warn 9.5ti, STC full length soft top
    85 CJ8, current frame off with world cap/postal/overlander top and doors
    85 CJ7, T5, Junkyard 4.0 head swap, MPFI
    84 CJ7, 258/TF999/D300, HP44/HP60 w/discs, 4.56's, Detroits, SOA w/1" Alcans, 37" Cooper STT's, PS rocker knockers, Warn M8000
    84 CJ8, garnet interior and paint, long term project
    2-84 CJ8 Postals, one stock 26K miles,the other one getting body work and a 4.0/aw4 transplant
    82 CJ8, 151ci, T176, stock, nutmeg whitco soft top and doors, farm truck
    82 CJ8 Laredo
    53 CJ3A
    87 Grand Wagoneer
    02 Dodge Ram 2500 CTD HO 6 spd 4x4, Triple DiPricol Pillar Gauges, Edge Comp "Hot", 5" straight pipe w/ 6" Tip, Toy Hauler rolling on 18's
    05 Wrangler Rubicon Unlimited Sahara Edition, 0002 of 1000, 6 spd, stock
    06 GC "Overland" Airaid CAI

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