CJ7 Bucking/Sputtering in third gear/4th gear. Behaves like out of gas - JeepForum.com
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post #1 of 19 Old 09-27-2021, 03:50 PM Thread Starter
Italbot
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CJ7 Bucking/Sputtering in third gear/4th gear. Behaves like out of gas

Hi all,

I recently bought a CJ7 1986 Jeep. It has an Inline 6 258, 4.2 L engine. Recently its been sputtering/bucking in third gear as if its running out of gas. It'll lose power, catch and regain power at times when i let off the gas to let it slow down. If I keep the pedal down it'll continue to buck and until i have to downshift into second to regain power. I'm unable to pick up speed past 45 mph's due to this issue.

It starts up immediately no issue, and idles at 800 RPM no problem. 1st/2nd gear driving I have zero issues, no sputtering.

I replaced the fuel filter, replaced the spark plugs, tuned the carb (Previous owner had the mixture screw 4x's out) and still haven't had any success.

The carb is a Weber 32/36, i have a stormcar FPR on her that is currently set at its highest setting but still no luck.

I dont think its a fuel pump issue given how clean the start up and idle is, but I'm not super familiar with how that operates at higher gears.

My next thought is possibly the jetting in the carb? Maybe I need to rejet to get more gas into the engine?

Thanks for any help.

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post #2 of 19 Old 09-27-2021, 06:04 PM
Girth83
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Someone who knows better will correct me...... but for some reason I thought the regulator went on the return line? Wouldn't any restriction in the feed line, just force more fuel to the return? Hard to see, but looks like yours is plumbed into the fuel feed, and your return port on the filter is clocked to the side? That return port on the filter is meant to be clocked at 12 o'clock. (maybe that's just the picture though) You changed plugs and tuned the carb.... assume you checked timing too? Beyond that, I got nothing.
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post #3 of 19 Old 09-27-2021, 06:56 PM
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Hello Italbot, good pics, Did you remove the carb and clean it? So the carb (for me) is a POE thing. Process of elimination. So here are some items to consider looking into besides what you've done. Removing and cleaning to assure air and fuel metering is clear of foreign objects. Carb float level adjustment (yours might be too low), vacuum leaks, EGR valve stuck partially open, timing or the vacuum line to distrib is not advancing the timing, fuel filter position for vent hose, choke pull off before engine is warm, internal carb setup for extra power demand, and Fuel pressure, but it looks like a new pump... Note: Pressure is different than flow rate and a pinched fuel line will restrict flow but provide a good pressure check.
Float level, Personally, if I had that problem that is what I would check first. Sounds like its a not enough gas or too much air issue. And I would turn the fuel filter more vertical and designate the top line for tank return.

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post #4 of 19 Old 09-27-2021, 08:30 PM
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Lets look at post 11 in this link https://www.jeepforum.com/forum/f8/t...ilter-4410199/

Guessing or going by the numbers on the regulator ain't gonna cut it!

You need a gauge and set up your system like in post 11.

Before I figured out that pressure builds before the return line,

I have placed the regulator

Before the filter

Between the filter and carburetor

Yes, I was using a gauge.

I found that the gauge would constantly "fast" bounce between "zero" and just whatever pressure remained and did not run down the return. Like a windshield wiper on Hyper speed!

Example, It might build 5 or 6 pounds (max) and I could turn it lower---just not higher.

When I moved the regulator to the return, it trapped and built pressure behind it (from the pump and to the carb)

This forces the fuel pump to maybe produce it's max pressure----and the ability to actually dial in to zero PSI or dial in and get the max pressure from the pump----and any "extra" goes down the return.

I could turn the regulator up and restrict the pressure to be behind it-----only letting a little escape through the return (I now could get 10 PSI)

OR

Turn it the knob other way and lessen the restriction, this will drop the pressure behind the regulator, pressure/ fuel now goes down the return a lot EZer, the guage now reflects a lower PSI reading.

This was the most noticeable change----The needle on the gauge is now reading a number, and it's steady and there is no flickering as with the other way.

I'm no engineer, But with it being steady and holding on a number (such as 8 PSI on the guage) I think the flow of fuel into the carb is now constant and steady,

keeping the bowl full -----VS:---- OFF/ ON/ OFF/ ON/ OFF/ ON (maybe intermittent) filling the bowl---Possible starvation with the bowl not able to keep up.

----JEEPFELLER
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post #5 of 19 Old 09-28-2021, 03:35 AM
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Just a thought here, but if it's sputtering and he down shifts to regain power he is raising the RPM's of the engine, so he isn't using less fuel. I would look at spark issues. Possibly bad cap,rotor,,wires or coil.
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post #6 of 19 Old 09-28-2021, 03:47 AM
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Quote:
Originally Posted by ECJ-7 View Post
Just a thought here, but if it's sputtering and he down shifts to regain power he is raising the RPM's of the engine, so he isn't using less fuel. I would look at spark issues. Possibly bad cap,rotor,,wires or coil.
I was thinking spark issue as well. A higher load on the engine will make the spark want to jump somewhere other than across the plug if it can.

The float could also be low. It would have to pretty damn low, though. Since it's been mentioned, I'd dump the pressure regulator all together. It's not needed when the bypass filter is used. Shoot, I'd ditch that first and see what happens.


Shawn
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post #7 of 19 Old 09-28-2021, 09:20 AM Thread Starter
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Quote:
Originally Posted by Shawn Watson View Post
I was thinking spark issue as well. A higher load on the engine will make the spark want to jump somewhere other than across the plug if it can.

The float could also be low. It would have to pretty damn low, though. Since it's been mentioned, I'd dump the pressure regulator all together. It's not needed when the bypass filter is used. Shoot, I'd ditch that first and see what happens.


Shawn
What curious about the issue is that for the first 5-10 mins of driving there isnt any bucking in third. I'm able to get the speed up and shift into fourth without any issue. Its only after a bit of driving does the engine begin to feel starved of gas?

The Jeep does smell rich though, so i'm wondering if its more im flooding the sparks? I'll trouble shoot the FPR, one other poster recommended putting it on the return line instead of the feed, do you think that would be more beneficial then removing it all together?
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post #8 of 19 Old 09-28-2021, 11:00 AM Thread Starter
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So I turned the return line to the 12 O clock position, and the FPR to 5.

Shes running smoother, able to pick up speed in third as long as i dont mash the gas pedal down. I was able to bring the jeep up to about 55 mph.

It seems as long as I keep my RPM's down in third and fourth she doesnt buck and i'm able to gain speed over time. Its odd though, i would assume i'm running lean due to this but the jeep smells like a gas tank. Obviously still an issue but she is drivable now at least.
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post #9 of 19 Old 09-28-2021, 11:18 AM
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Sounds like the carb accelerator pump.

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post #10 of 19 Old 09-28-2021, 11:46 AM
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Post #2 https://www.jeepforum.com/forum/f8/c...-rich-4443341/

How is your 32/36-DGEV set up?

1. How far in is the idle speed screw? (1 1/2 turns in is the maximum, choke open warmed up)
2. Where do you find the "LEAN" best Idle with the mixture screw? (2 turns out with a .75 mm idle jet is typical)
3. What is your initial timing set at? (10-12 BTDC, is what we find works very well, then use manifold vacuum to the advance canister on the distributor)
UTN
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post #11 of 19 Old 09-28-2021, 11:54 AM
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Quote:
Originally Posted by Shawn Watson View Post
Since it's been mentioned, I'd dump the pressure regulator all together. It's not needed when the bypass filter is used. Shoot, I'd ditch that first and see what happens.


Shawn
With a mechanical fuel pump, and a by-pass fuel filter (this is a pressure regulator) your fuel pressure should be perfect.
I would disconnect (and keep) the pressure regulator, then get the specs on how your 32/36 DGEV is set up, as mentioned above.
UTN
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post #12 of 19 Old 09-28-2021, 02:01 PM
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uptillnow

So we are happy with the crappy old 32/36 now?

Did they stop making that 38 ?

Maybe the 258 engine got smaller and now is a candidate for the "Too Small" 32/36?

After my 2 year experience of tuning and no improvements I had to save up and get a "Real Carburetor"----A Holley 390!

No wonder that Weber thing ain't working for you! Looks like "They Got You Too"!

----JEEPFELLER
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post #13 of 19 Old 09-28-2021, 02:07 PM
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I have an 86 with the 258 - and I'm still having great luck with my Weber 38. As I've documented well on numerous posts.....I never could get the Weber 32/36 that came on mine to run worth a crap.....despite several years of trying and beating my head against the wall. Best money I've spent on my Jeep so far was the Weber 38 and an HEI distributor......(and it wasn't even that expensive). Just sayin'
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post #14 of 19 Old 09-28-2021, 02:28 PM
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Quote:
Originally Posted by JEEPFELLER View Post
uptillnow

So we are happy with the crappy old 32/36 now?

Did they stop making that 38 ?

Maybe the 258 engine got smaller and now is a candidate for the "Too Small" 32/36?

After my 2 year experience of tuning and no improvements I had to save up and get a "Real Carburetor"----A Holley 390!

No wonder that Weber thing ain't working for you! Looks like "They Got You Too"!

----JEEPFELLER
Not sure why you are asking if we are happy with the 32/36 DGEV on a Jeep? I have never liked them as the 32mm barrel has too little CFM at idle when the Idle Speed Screw is at it's 1 1/2 turn in maximum, too too small to run a 6 cyl Jeep.
I have been able to make them work much better than "out of the box". I have stated this in EVERY post I have been involved with.
The 38-DGES works GREAT and I highley recommend them.

I am trying to help these guys who are struggling and bought the 32/36 DGEV, not use the forum to express my PTSD.
UTN
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post #15 of 19 Old 09-28-2021, 02:38 PM
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Quote:
Originally Posted by Italbot View Post
What curious about the issue is that for the first 5-10 mins of driving there isnt any bucking in third. I'm able to get the speed up and shift into fourth without any issue. Its only after a bit of driving does the engine begin to feel starved of gas?

The Jeep does smell rich though, so i'm wondering if its more im flooding the sparks? I'll trouble shoot the FPR, one other poster recommended putting it on the return line instead of the feed, do you think that would be more beneficial then removing it all together?
Disregard anything that guy says. He couldn't figure it out and is unable to move on.

As Uptillnow said, the bypass filter basically acts as a regulator so I'd just pull that regulator out and make sure the bypass hose is at 12 o'clock. Why don't you pull the primary idle jet out and see what size it is. You may have a hornet's nest of things at play here like a too small idle jet in a too small carb that's bandaided by a choke that hasn't pulled off yet.

When the idle jets are too small, that noxious smell burns your eyes. Is that what you're dealing with?


Shawn

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