Lurching Issue

I've got a 59' Series II SWB and am having some clutch issues (or so I'm guessing). The problem is a lurching sensation, like when someone who is learning to drive a manual can't figure out how much gas to give it.

When I first start out driving, everything is fine and the transition between gears is smooth (including the double clutching from 1st to 2nd since there are no syncros).

The lurching starts after driving for a bit and really only happens when starting from a dead stop in 1st gear. No matter how hard I try to balance clutch/gas, I almost have to rev the engine too much and let off at a snails pace in order to get the truck moving to the point I can get going without lurching.

I've replaced the master cylinder, slave cylinder and lines, and flushed the entire system multiple times (not a hint of air bubbles). Terrified to hear it's the clutch itself, but with the difference between functioning when it's "cold" vs. lurching when it's warmed up, I'm wondering if that's the case.

What in the damnation am I doing wrong?

Thanks for any pointers

Nut loose on the clutch pedal?

Just kidding!

Wonder if the clutch operation is fine but you have something causing the engine to hesitate when it should accelerate smoothly. Like retarded timing from points that have closed down, ignition advance frozen, carb accelerator pump not working, for example.

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Originally Posted by erik88lr

Nut loose on the clutch pedal?

Just kidding!

Wonder if the clutch operation is fine but you have something causing the engine to hesitate when it should accelerate smoothly. Like retarded timing from points that have closed down, ignition advance frozen, carb accelerator pump not working, for example.

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True ,
This problem could be outside of the clutch and hydrolic system, sounds like I would, check points, timing. Is there enough fuel to carb? It is classic for these issues to happen after truck is warm and running for a while, are there some meter test to do on a coil? good luck.

Your castellated nut at the back of the main shaft of the transmission is likely loose. You will need to remove your overdrive to access it, and use your workshop manual to get the proper procedure.

Lurching might also be caused by weak or broken damper springs on the clutch disc. A harmonic torsional oscillation can be induced in the driveline if the spring rates aren’t correct.

When this was happening on my series II it turned out my rear main seal was leaking enough oil to containment the clutch, replacing the clutch fixed the issue.

What was the final outcome on what was causing the lurching? Thanks!

I'd bet it is insufficient fuel flow. undo the fuel line at carb and pump by hand the fuel pump for a minit or two to ensure you don't have a partial blocking at the tank or someplace. typical scenario: starts off good then when the engine takes up a load (uses more gas) it starts hesitating. after sitting at idle for a minit or two sufficient fuel gets back into the fuel line to run it a bit then when demand picks up it starts hesitating again.
* bets are on !!!

Quote:

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Originally Posted by jimrr

I'd bet it is insufficient fuel flow. undo the fuel line at carb and pump by hand the fuel pump for a minit or two to ensure you don't have a partial blocking at the tank or someplace. typical scenario: starts off good then when the engine takes up a load (uses more gas) it starts hesitating. after sitting at idle for a minit or two sufficient fuel gets back into the fuel line to run it a bit then when demand picks up it starts hesitating again.
* bets are on !!!

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I would agree, except the OP stated.... "The lurching starts after driving for a bit and really only happens when starting from a dead stop in 1st gear"

Fuel starvation would be more likely under sustained load at higher RPMs - like accelerating up an incline on the highway.
I had that problem, connected a fuel pressure gauge at the carb, saw the pressure drop to zero shortly before the lurching started. I put on multiple new fuel pumps trying to find one that would deliver enough fuel, finally installed an electric pump in parallel to the mechanical one with a switch I can flick on if I start to notice lurching. Works great.

I had a similar problem on my Series 3 that I recently fixed. My symptoms were that I couldn't accelerate away from 1st gear when it was cold unless I reved it very hard. Then, I'd get a feedback cycle where it lurched and gurgled. It either jumped forward or choked on the gas...never the right amount of acceleration out of 1st. My wife kept yelling at me to give it gas, but that wasn't it. More gas just drowned the engine.

Eventually, the symptoms progressed to where the engine would die when hot. I would let it cool down 2 minutes and it would run another 2 minutes, then die.

I ended up just nuking everything. New fuel pump ($50), new Pertronix Flamethrower electronic ignition ($100), new Pertronix Flamethrower coil ($30) and new Weber carb ($220). She starts up like a champ now and runs like a new car.

For me, I think it was a combo of the failing distributor and tired fuel system components. You could rule out each system, and swap out just the bits that are broken...test your fuel pressure under load, etc. But, eventually, your 60 year old parts will show their age. I don't regret the fresh components. I spiked the distributer at TDC and bolted on the carb and all my gremlins went away. Very little tuning. I fiddled with the timing to 3 BTDC and turned my idle screw to get a few more RPM, but I could have left it as is, out of the box.

Very much recommend this. I just wish there was a way to try before you buy. But I didn't regret it.