Possible clutch issue? - I can't diagnose problems very well (read: at all). (1 Viewer)

[JamesR]

While driving around 60mph my 1986 60 started to "buck" . (Sort of like a person learning how to drive a manual transmission and having problems engaging the clutch while first moving.) I engaged the clutch and the problem stopped, for awhile. It happened twice again within about 6 miles.
So, all of you great diagnosticians out there where do I start?
Thanks.

 

[micruz60]

Fuel pump, fuel filter.
When you are in neutral and press the clutch pedal in, does a shift go smoothly, and all thru the gears? -do not engage the clutch, just move shift lever 1st, 2nd, 3rd, 4th.
Is there a whinny sound when clutch pedal depressed (disengaged)?

 

[JamesR]

Sitting still, engine off, engaging the clutch to move to N, disengaging the clutch, the shifter moves through the gears without issue.

 

[micruz60]

Sitting still, engine off, engaging the clutch to move to N, disengaging the clutch, the shifter moves through the gears without issue.

Okay, with the engine running, do you have a whinny / spinny sound in neutral? , if so then when you press the clutch pedal in, does the whinny / spinny sound go away?
This would merely indicate that there is contact at the throwout bearing. Not a 'bad or good' thing, the clutch pressure plate could be worn out.

More information needed: how many miles on the rig, and do you know if it is the original or replacement clutch?

I still think it may be - fuel pump is not keeping up under load.
Another test is to put the transmission in 3rd gear while running and let out the clutch (engage it) if the clutch is going / slipping the engine will not stall, do this with room in front of the truck to roll.
@OSS does this sound right?

 

[joebattle1]

This reads like bad gas or a failing motor mount.

 

[JamesR]

With engine running and tranny in natural - there is no whinny sound.
With engine running, 3rd gear engaged, - release/engage clutch the vehicle moves forward with no difficulty.
Mileage - unsure the odometer shows 150+K Before I retired I only drove it on the weekends, probably less than 100 miles a month. I'm retired now and I drive it when my wife isn't with me (it's a challenge for her to get in the passenger seat).
Engine rebuilt about 10 years ago - I don't think the clutch was replaced.

 

[micruz60]

When the engine is under load, rolling at 60 mph, and bucking / surging - really points to fuel delivery. Crud can get into carburetor and foul passages, fuel pump is a wear item and gives this sort of indication when beginning to fail, try new fuel filter as least cost / first fix?
Your clutch is probably fine.

 

[JamesR]

I don't think it's the clutch. What you guys are telling me doesn't sound like the clutch but more like a fuel issue. I'll start there (filter) first.
Thanks.

 

[JamesR]

Today I did a visual inspection of the fuel pump after I cleaned off the gunk, without the engine running. Saw nothing unusual. Started the 60, let it idle on "high" visually inspected the pump again, nothing unusual. I felt the pump and didn't feel any moisture/gas leaking. The fuel filter is a clean plastic. I could see fuel flowing without any obstruction. It is less than 3 yrs old. I had a new one (I always buy 2.) so I installed it. The fuel seemed to flow as easily through the new one as it was flowing through the old one. I then drove it on the road ran it fast and I "got on it" from a dead stop, something I don't do but I wanted to put a load on the pump. No issues.
So, I'm not sure what caused the "bucking". I also, while it was running, I felt and jiggled the spark plug wires (at the boot). This didn't effect the idle.

 

[micruz60]

Replicating the initial bucking and surging can be tough, maybe a bit of crud in the carb got pulled through and now it’s fine. Throwing this out there- egr clogged?

 

[JamesR]

I was thinking the same thing. I'll need to locate the EGR. - Thanks for your help with this.

 

[Godwin]

If this was an isoloated incident may have been nothing more than water in the fuel and it's now passed through the system.

 

[JamesR]

I've been driving it for more that a week. All seems to be working as it should.
Thanks to everyone who responded.
I sure enjoy this forum.

 

[g-man]

If it comes back it may be an EGR problem. I had a symptom like almost stall hesitation when starting out in low gear. Like 1st or 2nd and moving out into an intersection. It only happened very intermittantly like once a week or so. I had to get off the gas quickly to keep it from stalling. Like it wanted to bog down but it wasn't fuel related. Another symptom was hesitation while running at certain rpm range and while just steady on the gas. It felt like a miss and was very annoying. It would run fine while accelerating. The problem was a stupid hesitation while trying to keep steady on the gas around 1800 rpm range. My EGR was fine but the EGR modulator failed vacuum test and the EGR VSV failed as well.

 

[kody472]

Okay, with the engine running, do you have a whinny / spinny sound in neutral? , if so then when you press the clutch pedal in, does the whinny / spinny sound go away?
This would merely indicate that there is contact at the throwout bearing. Not a 'bad or good' thing, the clutch pressure plate could be worn out.

More information needed: how many miles on the rig, and do you know if it is the original or replacement clutch?

I still think it may be - fuel pump is not keeping up under load.
Another test is to put the transmission in 3rd gear while running and let out the clutch (engage it) if the clutch is going / slipping the engine will not stall, do this with room in front of the truck to roll.
@OSS does this sound right?

I have the spinny sound now after replacing my slave cylinder. Is there a way to remedy this? Is the clutch adjustable? It stops when the clutch is engaged, but makes that noise when sitting in neutral.

 

[BamaHeel]

If it was under load (ie acceleration/going up a hill) maybe the timing?

 

[kody472]

Never mind. Fixed it.

When searching this forum, I found where the PO had the same problem and adjusted the clutch. When I replaced the slave cylinder, it must have put the clutch pedal back where is it supposed to be. Adjusted pedal. Noise resolved. It's nice to be able to see what the PO has done to this vehicle in other posts.

 

[OSS]

@OSS does this sound right?

Yes!