Hesitation when accelerating, Carb, Coil or Ignition - Finally Fixed

[Weber Sarge]

I think I had described the procedure earlier - remove the carb and idle jets (don't lose or hit those o-rings with cleaner !) and blow out the idle circuits with compressed air from the throttle plate side , you'll see the series of small holes just above the throttle plates . While you have it off , rinse out every hole you can find to remove any dirt . Don't sweat the nozzle system on the 38 unless one side isn't working . You can remove the nozzle but it takes a really wide driver to remove the bolt - do not mess that thing up as it's expensive . There are a simple pair of copper washers that seal the banjo bolt on the accelerator nozzle - one on top , one on the bottom of the nozzle . You can then clean the nozzle tips in reverse with brake cleaner and compressed air .

If you have rubber fuel lines and are using ethanol fuel it may be causing the lines to deteriorate inside - look at the ends of them for signs of this . You'll see black particles inside the fuel screen as well - it's a common issue showing up with this new fuel and tough to find hose that isn't destroyed by the ethanol . Report back with what you find ...
Sarge

 

[ErikinSC]

FINALLY ! RESOLVED !

I pulled the carb, disassembled the two halves - and didn't loose the clip!

I found a small 1/8" square piece of crap on the bottom of the bowl, see it there :

Removed jets, sprayed cleared, cleaned the fuel inlet screen of some sticky gunk :

I removed the needle and cleaned that passage as well. My mechanic thinks I'll need to replace the needle next rebuild.

And checked the float bowl adjustment - IT WAS OFF BOTH WAYS !

Corrected to Weber specs :

And reassembled everything :

Had to pull the carb off the mounting plate to connect the throttle cable to trunion, and put the worlds smallest cotter pin back into the trunion.

DROVE LIKE A CHAMP, best throttle response since I've owned it ! Time to refill with some Ethanol free gas !

Thanks all !

 

[Solace in Solitude]

Congratulations Erik!! Perseverance paid dividends!! ... With some pro guidance from @Weber Sarge !!

 

[ErikinSC]

Oh yeah, yourself Danny, @Weber Sarge, @Pin_Head, @Pete, @shawnfj40, @robbs6940, @thebigredrocker, @sggoat and others ! Thanks to EVERYONE that gave input !

 

[thebigredrocker]

Victory!! Wonderful news. Feels damn good to have success don't it? Mud is good.

 

[Weber Sarge]

Pretty simple once you try it , most are just afraid they will screw something up - congrats .
Sarge

 

[ErikinSC]

Well maybe not quite yet. @Weber Sarge The hesitation (lack of ability to accelerate) came back after driving for 30-40 mins continuous. It seems like fuel starvation maybe....

I'm cleaning, and replacing the gaskets and needle valve this time - last was just a clean and adjust float level. Then I'm gonna re-set idle circuit fuel mixture and idle speed. * the carb had the slightest vibration to it as I started to remove it today. Didn't notice it last time, maybe something with warping - maybe not.

2 questions:

1) when I removed the fuel line from carb inlet, there was a slight vacuum on the line - heard it equalizing as hose came off the carb inlet. I have the CJ vented filter 12" from carb on fender w-return to tank, vented gas cap (checked and verified after swapping back)

2) the carb fuel floats were set per notes I found online search previously. I have plastic floats.

Redline tune-up kit has that X'd out with another note (see pic). WHAT VALUES SHOULD I TRUST?

 

[77wagon]

Erik,
I spent a while dealing with similar issues thinking that cleaning my fuel lines was good enough. I finally replaced them. Now the fuel filter is always clean. Someone said earlier about the lower lines- these were the problem on mine. They are cheap and easy to bend. If you have a new tank, switch out your lines, one more quick carb clean and I bet you'll be done with this. My2 cents. From your neighbor in Beaufort.

 

[ErikinSC]

so i cleaned the carb (again) and rebuilt it with the Redline kit i got from TPI Bob. The Main Jet (?) needle and seat that was in the Weber was a 250; the kit came with a 200. I used the original 250 seat, but swapped in the new needle - i couldn't see any measureable difference. I reset the float heights to 40 and 50, and then I set-up the idle circuit - kinda - but i wasnt happy with the way it drove.

The lower adapter plate (with the studs in it) was slighlty loose on the intake manifold. I tightened it, and re-tightened the the upper plate also. HTH.

I followed the directions in the kit, first setting the idle speed low, then pre-setting the idle circuits. I adjusted each mixture screw unitl i could discern a change in the idle - then backed it off 1/2 turn. Took it for a test drive and I had to stop & ajusted it 3 times, while driving around the neighborhood.

Can I measure the vacuum (at brake boosster) to see where the highest vacuum level is - as a means to set the idle mixture also?

Will be driving the rig to work in the AM - guess I'll get to know how well i set it then.

 

[Weber Sarge]

Need to verify if you have a vacuum leak - that would cause a hesitation . Don't sweat the notes from Redline about the float , the new figures come from them using an aftermarket float and if you are using the original it doesn't apply . Float settings are a bit of a unknown - if someone has previously bent the float arm the settings won't do any good . Top closed setting at the valve should result in the float sitting basically parallel with the top cover without compressing the internal float valve spring . I just set the drop limit from there at 10mm for offroad use .

Did you ever blow out the idle circuit from the throat side in those transition holes above the throttle plates ?
Sarge

 

[ErikinSC]

Did you ever blow out the idle circuit from the throat side in those transition holes above the throttle plates ? Sarge

Yes, @Weber Sarge - I think I blew out the idle circuit from every way possible - with carb cleaner and air. I removed the jets, but not the emulsion tubes. I did not have a vacuum leak idling previously - but the loose adapter plate could have been casued by heat, as was suggested previously (by you, I believe). I'm going to check vacuum again today. As a matter of fact, I'll go do it now.

Drove OK this AM; the electric choke let it idle higher (than normal) to warm up in the driveway.
My idle RPM is now down to around 750 currently.... it was closer to 1000 PRM.
Throttle response was OK - not as crisp as it was last time - but I adjusted the idle circuit this time, it it might not be as good as it was.

2 questions :

1) Any problem using the original 250 seat with a new Viton needle? The rebuild kit came with a 200 seat, but thought I should keep the original sized one in it.....

2) Can I measure the idle mixture by monitoring the vacuum level? I saw one youtube video that indicated that you could tune the carb and use the vacuum level to peak the idle mixture.....

 

[ErikinSC]

Holding 20-21in when measured off the brake booster. Sprayed brake cleaner around base of carb, adapter plate and intake manifold at head - no vacuum change measured.

Vacuum gauge JUMPS when accelerating with no load, vacuum climbing and dropping but area dies out back at 20-21in.

Disco' the CJ filter to see if it was an issue with fuel returning to tank... Test drive and once it warms back up.... The problem returns.

Beating my head against wall.

Considering installing a cookie pan for a heat shield until I can find one (haven't checked Beno or Classified yet) and then adding an electric fuel pump to bypass the mechanical OEM pump.

At this point, it seems to me that it keeps going back to temperature driven - either affecting the fuel / fuel in bowl or carb itself.

Any other ideas to check the temp cause idea?

 

[Weber Sarge]

When this condition appears , may want to check the spark quality - might have a coil overheating over time and starting to fail . The carb definitely needs a heat insulator below it otherwise it will boil out the fuel easily . Don't sweat the fuel inlet size , that engine won't outrun a 200 size needle/seat valve .
What exact distributor are you using and do you have a vacuum advance hooked up ?
Sarge

 

[ErikinSC]

Gotcha. I found the Weber T-shooting guide that @JohnnyC had posted previously while searching last night.

I will drive, warm up and then check the spark this afternoon. Actually told my shop mechanic (I have a staff mechanic that this is stumping also) I wanted to do this also. I am searching for the carb insulator (10"x 20"metal tray that mounts above the intake & exhaust manifolds, not just the adapter plate sized spacer). Distributor is from TPI - it is a non-USA vacuum advance aftermarket unit (pics coming). the Coli is a Mallory - all installed @ 2012 or 2013. Vacuum advance is hooked up from carb base to dist.

 

[Pin_Head]

You may have rust or dirt in your gas tank.

 

[tuloyuser]

I second the rust and dirt in the gas tank. I had similar issues and attributed to heat related as well. I would drive around and after "x" miles or "x" minutes it would die. So I added an inline filter where I can see how clogged it is. What was happening for me was, dust like rust would reach the filter and eventually clogged it and after sitting or stopping the dust will settle to the bottom of the filter and will let the engine run again, but once I drive again it will start to clog the filter again. This would happen until after I eventually replaced the gas tank.

 

[ErikinSC]

I drove it almost down to empty this AM. I'm going to pull the tank, drain it, remove the sending unit (carefully to prevent damaging the seal) and wipe out the inside of the new(er) poly tank. I'll remove and blow the new fuel lines next. Ill find something to pull thru and clear the inside of the metal lines. Ive been running Ethanol free gas in it for probably 6 -tanks now.... but pre-existing damage to the hoses could still be there.

There are 2 NEW fuel filters; an OEM between hard line and the mechanical pump and a 3 port, vented CJ style filter 12' before the fuel inlet (see post 43). The carb fuel inlet screen is clean (see post 24 and 62).

SHOULD I DO THIS : I'm going to see if I can get a fuel pickup sock to put onto the brass pickup tube also. This would keep trash in the tank, and never let it get to the inline filter. Good idea / bad idea? In time the sock could get dirty....

 

[ErikinSC]

@Weber Sarge : The distributor is a Toyota Non-USA

 

[Weber Sarge]

What rpm is the idle speed set at ? If it's too high , the throttle plates will port vacuum to the distributor when cold - after the carb gets some heat soak it will idle a bit lower and may be shutting off the timing advance enough to cause the hesitation . Needs to be at the spec 650 revs when fully warmed up . Also , make sure that advance is working and the diaphram isn't blown out .

Also , have you ever adjusted the screw on the front linkage gears on that 38 ? That is a very touchy setting to time the throats together at rest and full throttle - requires a lot of tedious work and experience to set those gears .

Need more info on exactly when that hesitation occurs - pedal position as well as all engine conditions . It could be something as simple as heat soak to a much more complicated combination of issues .
Sarge

 

[ErikinSC]

What rpm is the idle speed set at ? If it's too high , the throttle plates will port vacuum to the distributor when cold - after the carb gets some heat soak it will idle a bit lower and may be shutting off the timing advance enough to cause the hesitation . Needs to be at the spec 650 revs when fully warmed up . Also , make sure that advance is working and the diaphram isn't blown out .

Sarge

G'morning Sarge! I'm pretty sure it was closer to 700+ while I was adjusting last weekend - it was NOT less than 650. Bob at TPI asked same thing yesterday when I was placing an order for a dizzy tune up parts (cap, rotor, points, conds). Also, I had the vacuum line attached while setting lean low idle - and that might have given me an improper setup. Bob suggested removing it, re-setting timing first before setting low lean idle.

So - I'm going back to zero - While I'm waiting for @CharlestonG8R to meet @jfz80 in N Carolina this weekend and bring back the carb insulator /heat shield (thanks guys ! )..... I'm pulling poly fuel cell, adding a pick up sock (since there is no inlet screen), clearing & cleaning the flex and hard fuel lines under the truck. I also picked up a hard fuel line from the mechanical pump to the carb from @caboulto - I will have to modify it slightly and route it to the CJ style vented fuel filter on the fender - that will be installed this week as well. I'm also going to address a valve that is tapping while I'm tearing into everything again; I had the valve cover gasket, may as well adjust and stop a nagging slow oil leak on the valve cover while I'm at it. Then, I've got new OEM plugs, wires, timing to set, oil change (to a ZDDP product) to do as well. If I'm going to get the carb right, I'm going to hit everything else and remove all doubt.

I got a timing light and engine analyzer (dwell, tach & etc) from my dad, so - it's time for me to SET all of the baseline items, rather than trust theat they were all right before hand. I'm also going to do a dry and wet compression test as well - the PO had the motor at rebuilt in Jan 2012, including Rings, Pistons, push rods - and the "F" head on the "2F" block was redone at a machine shop then as well. Once I KNOW my baseline numbers, then I can probably solve this issue, and be done with it.

Also , have you ever adjusted the screw on the front linkage gears on that 38 ? That is a very touchy setting to time the throats together at rest and full throttle - requires a lot of tedious work and experience to set those gears .
Sarge

NO SIR ! I read your note NOT TO TOUCH THAT somewhere along the line..... and I have not.

It'll be a couple of days before I am back and ready to address the hesitation - I'll probably document the tune up process for my build thread, and post some notes and pics of that. Until I'm back, have a good few days, and thanks for sticking with me.