J10 Loosing power going up hill in high third

[BEAVER]

My j10 is chugging out in high gear when the accelerator is over half down. It runs great as long as I don't gun it. I have replaced the fuel pump and put in a new Weber carb in the rebuilt 258 I have to adjust the timing low for it to run. It's almost as if its getting to much or not enough gas when the throttle is down in high gear. Any suggestions?

[jsinajeep]

Give us a little more detail on your set up. Tranny Auto or manual, gear ratio, tire size. Did you change anything
on the rebuilt.

[jsinajeep]

This need to be moved to the tech section

[Stuka]

I moved this to the tech area.

As for your issue, few questions.

What transmission do you have, what tire size, and what gearing do you have?

Have you put a vacuum gauge on the engine?

Also , when you put the weber on, did you follow the tuning steps exactly as the instructions state?


Sent from my iPhone 5S using Tapatalk

[haminawag]

Also, did this problem just suddenly crop up? Or had you done these mods and THEN started having the problem. When something like this happens I always check the quality of the fuel first. Gasoline carburetors don't usually digest ethanol very well, or water.

[BEAVER]

The j10 is a 3 speed. Not sure of the brand of transmission. Tires are small 245. Axels are Dana 44 3.54 ratio. The truck has had problems since I purchased it. I have now taken it to the Jeep dealership. Timing adjusted to 10. All vacuums are working. Adjusted carb to specs. They can't figure out what the problem is either

[AwesomeJ10]

You took it to the Jeep dealership? Well that's fine, but you have to remember that most guys working at a Jeep dealer have never messed with carbs. They won't have any real practical experience with tuning them.

You are describing a lean condition. When you are going up hill in third gear, it requires a lot of fuel to do so. You carb might not be dumping enough fuel into the engine to make it run properly when wide open.

Check the power valve. If it's a 4 barrel, then also check the secondary barrel engagement. Also check fuel pressure/filter.

[DarkMonohue]

^ Gotta agree with Blake here. Other than the name on the tailgate, your truck has nothing in common with the stuff dealership mechanics are trained on. It is older than many of the mechanics! You'd be better off taking it to someone who is familiar with old vehicles and carburetors in general, and Webers in particular.

Blake mentioned a fuel filter. I had a clogged fuel filter on my J20 and it produced the exact same symptoms you are describing. Replacing the filter cured it. Get under the truck and look for extra fuel filters between the engine and the fuel tank. Replace them all. That's the cheapest, easiest, most likely fix. If that doesn't do it, you will have to start paying a mechanic for his time...or randomly replacing parts and hoping you stumble onto the fix, which is not the recommended course of action!

I wrote up a couple of pretty significant articles that might help you. The first is on freshening up an old vehicle. This deals with eliminating many of the problems old cars and trucks develop from neglect and unsympathetic owners:
http://www.sv3power.com/?page_id=250

The second article walks you through the tuning process of a Weber 32/36 DGV carburetor, step by step:
http://www.sv3power.com/?page_id=371

Each of those articles is written in multiple parts, so read them all.

Read and follow the first article before messing with the carb. All other problems must be corrected before you adjust the carburetor - period.

[letank]

Very good post above.... indeed the fuel tank sock that tend to collapse.... fuel pressure check?

Then you can check yor Distributor timing: you said base timing at 10.. what is total timing at 2000 rpm?.... now we need to know if ported or manifold vacuum.... yes I am opening a can of worms!

[DarkMonohue]

yes I am opening a can of worms!

That's a good thing. You absolutely have to get rid of the worms before you can do anything with the can!

...or something like that.

[letank]

yes I am opening a can of worms!

T hat's a good thing. You absolutely have to get rid of the worms before you can do anything with the can!

...or something like that.

Just browsed your website.... very cool, I must say... dealing w real TDC. distriburless ignition.... but the best is the dyno audio based... which addresses a very important point that people should be getting together... so they can compare their set ups or even taken on rides .... so they can feel the pull of other's drivetrain.

Years ago I had a passenger with a better hearing detecting a lean condition at part throttle... so we stopped and put an extra 1/4 turn or 1/2 turn on the idle screw, yes, they are for idle... but can greatly mess up your performances!
And last summer... 1200 mikes to Ouray.... gave me plenty of freeway time to mess up the timing... and move to manifold vacuum.... what a blast to go up the passes full speed, keeping up with modern vehicles.... or even passing them!

[DarkMonohue]

Thanks. Glad you enjoyed the read. I am a big, big fan of instrumented testing. It's saved me countless hours of guesswork and prevented many very wrong decisions based on convincing, but incorrect, seat-of-the-pants impressions.

[Stuka]

The j10 is a 3 speed. Not sure of the brand of transmission. Tires are small 245. Axels are Dana 44 3.54 ratio. The truck has had problems since I purchased it. I have now taken it to the Jeep dealership. Timing adjusted to 10. All vacuums are working. Adjusted carb to specs. They can't figure out what the problem is either

Weber carbs are not adjusted like normal carbs, they are somewhat picky. They also really need a fuel pressure regulator in front of them. But if this problem existed before the weber, it most likely is not the main issue. But if it was not tuned the exact way weber says to do it, you will have issues.

Fuel filter sounds like a great place to start as others as mentioned. As well as the screen in the fuel tank if the filter is fine.

I would also inspect all your fuel lines for cracks. If there are cracks, its possible to suck air in through them, but they may not be large enough to let fuel out.

[acct21]

Completely agree that if you call in professional help, make sure they are qualified to actually help fix your problem.

Last year I fought a Motorcraft 2150 for the better part of two months after buying it from the PO. It had been 'professionally' rebuilt about six months before I bought it. Could not get it tuned under any circumstances. Finally broke down and interviewed a few local shops. One had a part-time (semi-retired) guy who was a former trainer/instructor for Ford. Said he knew the Motorcraft carbs backwards and forwards.

Long story short: he pulled it, cleaned it, and reinstalled it. After he worked on the carb for about an hour he called to tell me it was "trashed." Recommended another rebuilt unit -- which I couldn't believe was necessary. Agreed and he put a replacement unit on (charging me one hour labor for the entire repair).

Rig starts and runs like new.


Sent from my iPhone using Tapatalk

[BEAVER]

Thanks guys. I have spent a lot of money and time with three different mechanics trying to figure out the problem. I have a new gas tank with new lines, filter and pump. One of the mechanics at the jeep place rebuilt two J10s from the ground up and assured me that he could figure it out. The fuel pump is mechanical in the side of the engine. Should I replace it with some kind of electronic pump with a regulator? Forgive my ignorance.....
Thanks!

[Stuka]

Thanks guys. I have spent a lot of money and time with three different mechanics trying to figure out the problem. I have a new gas tank with new lines, filter and pump. One of the mechanics at the jeep place rebuilt two J10s from the ground up and assured me that he could figure it out. The fuel pump is mechanical in the side of the engine. Should I replace it with some kind of electronic pump with a regulator? Forgive my ignorance.....
Thanks!

Your mechanical pump is fine for the Weber, although it should still have a regulator. Wouldn't hurt to do a flow check if you chose too. The mechanical pump on my 258 hits 11-12 PSI at times. Weber says no more than 3 PSI for the 32/36 DGEV carb. The symptoms of having too much pressure is the engine loading up on fuel. It will start to put out black smoke if it gets real bad, as well as hesitation and bogging. I run mine at 2.5 PSI and its pretty happy. If the pressure is higher, fuel actually gets pushed past the needle and seat.

Also, if one of the shops messed with any of the other adjustments, you have to go through the process to get those set back to stock. Oh, and this was a Weber that was purchased for a Jeep right? Weber jets them according to their application. And is it a 32/36 or a 38/38?

If you have your weber instructions, step through the tuning process for it. I have the instructions in PDF if you need them.

I know it may not be your issue, but I know from experience that it can run poorly if not done right. And your symptoms could be a fuel delivery issue or a carb issue.

[BEAVER]

Thanks so much! I will try a regulator. The weber specs are in the truck at the dealership. The carb was purchased from weber to replace the Carter that was in the truck. Any special regulator suggestions?

[DarkMonohue]

Forgive me for stating the obvious, but don't forget to set the correct fuel pressure on the regulator (you will need to use a fuel pressure gauge to do that) - just bolting on parts is not always enough.

[Stuka]

Thanks so much! I will try a regulator. The weber specs are in the truck at the dealership. The carb was purchased from weber to replace the Carter that was in the truck. Any special regulator suggestions?

I am running a Holley regulator with a gauge. I am using holes that are already in the aluminum valve cover that I have.








Sent from my iPhone 5S using Tapatalk

[BEAVER]

Thank you! I am going to pick it up from the dealership after work before I waste any more$! Will let you know as soon as I get it in and adjusted in a few days.