Adjusted float, now 2F is running rough and dieseling?

[GeologistFelix]

Ok, so, I have a trollhole carb (with desmog) that was hesitating and stumbling on acceleration etc., and had a fuel level way at the bottom of the sight glass. So, I adjusted the float as per the FSM, and now the fuel is sitting right in the middle of the glass...HOWEVER

1. It has a hard time starting, when hot, without the choke out.

2. Adjusting the idle mix screw doesn't seem to have any effect on idle RPMs or vacuum pressure. (vaccum is running about 16, vs. 19ish before my float adjustment)

3. While the pedal response is great, and it does feel like it's got more power, now the engine dies on releasing the accelerator pedal after applying a load (i.e. I give it some gas, move a few feet, and depress the clutch and let off the gas).

4. The engine is running rough in general, and doing a few seconds of revving higher and then a few seconds of idling lower.

5. When I kill the engine (on purpose), it diesels for a second or two, which it never did before.

6. The timing is...odd. At idle, my timing gun suggests it's at about 30 degrees of advance, vs. the 11 or so that I thought I had it set to before I adjusted the float.

Any suggestions on where to start?

 

[REDBACK62]

It sounds like it is time for a rebuild of that carby or swap out to another type. My old one on my 3F was doing similar. Turned out to be the rubber seals and gaskets on the inside were leaking and had deteriorated. I put a Custom built Holley 350 on my engine. It was built by the same guy that did my 3F engine and customised for offroad use, similar to the Holley truck avenger, but he is a wizard and builds race engine for the pros over here so he set it up specially for my engine. But I did have a Holley 350 on mine before the engine build that replaced the stock carby and it ran very strong.

 

[GeologistFelix]

It's a brand new carb that was running 'perfectly' except for the hesitation problem, before I adjusted the float. So, I'd say I'm virtually certain the gaskets and o-rings aren't a problem.

 

[REDBACK62]

Next thing is a good valve adjustment and timing check. But keep in mind that just because it is new does not mean it is right! Could be the accelerator pump seal not mating properly or could be a vacuum leak. I have seen many NEW items not what they were supposed to be. Not saying this is the case but it does happen. A proper valve adjustment on these engines goes a long way to running right.

 

[Pighead]

#4, searching for an idle speed sounds suspiciously like a vacuum leak...That, and you say your vacuum is lower now. Where are you taking the vacuum off of the carb for your dizzy? And you are disconnecting the vacuum to the dizzy when you time it?

 

[GeologistFelix]

The part that's really confusing me is that it did absolutely none of this until I had opened up the carb and adjusted the float. It idled smooth as butter, it cold-started easily, and so on.

Anyway, I haven't been disconnecting the dizzy's vacuum, now that I think about it. Vac for the dizzy is coming from the port under the idle mix screw. It's a super-simple (no HAC or decel cutoff) desmog, so there isn't really a lot going on vacuum system-wise.

So, how about things I might specifically have screwed up on carb reassembly?

- The new airhorn gasket seemed to be ever so slightly 'off' on the Trollhole, and there might be 1 or 2 passages that are partially blocked off by gasket.

- It's possible a little bit of gunk got down into the carb, but I was very careful and things were mostly clean around it when I was taking stuff apart.

- I *did* do one 'quick and dirty' adjustment to the float after initially setting the up/down clearance per the FSM. I know the fuel level is right where it needs to be now, but is it possible that the needle valve is opening to far/not far enough when the float descends/fuel is used?

 

[GeologistFelix]

Ok, during my hour between a double shift at work yesterday, I got the timing reset once I actually took the line off of the dizzy.

I also sprayed every conceivable area there could be a vac leak with WD40 and it didn't do anything.

Then, when I was on my way back to work in my other car...I realized that I may not have tightened the idle cutoff solenoid in all the way, and/or that its metal washer might be seated funny, and that it was one area of the carb/engine/etc. I didn't hit with the WD40.

So, I'm gonna go check on that.

However, I'm still curious about the possibility that, although the float is keeping fuel at the correct level, the 'hanging down' clearance with the needle valve (vs. the one where you have the airhorn upside down and the float resting on the valve) might be too much or too little.

Also concerned with the possibility that the gasket is covering some little passage, so I'm going to check that as well.

 

[2mbb]

if the fuel is 1/2 up the sight glass, then the float is set properly. I think you need to make sure that everything is connected properly after you removed the carb and replaced it--linkage, vacuum hoses, ICS, etc. Also go back an inspect the vacuum hoses. Make sure there are not any cracks or cuts, etc.

 

[Mslewis00]

Ok, so, I have a trollhole carb (with desmog) that was hesitating and stumbling on acceleration etc., and had a fuel level way at the bottom of the sight glass. So, I adjusted the float as per the FSM, and now the fuel is sitting right in the middle of the glass...HOWEVER

1. It has a hard time starting, when hot, without the choke out.

2. Adjusting the idle mix screw doesn't seem to have any effect on idle RPMs or vacuum pressure. (vaccum is running about 16, vs. 19ish before my float adjustment)

3. While the pedal response is great, and it does feel like it's got more power, now the engine dies on releasing the accelerator pedal after applying a load (i.e. I give it some gas, move a few feet, and depress the clutch and let off the gas).

4. The engine is running rough in general, and doing a few seconds of revving higher and then a few seconds of idling lower.

5. When I kill the engine (on purpose), it diesels for a second or two, which it never did before.

6. The timing is...odd. At idle, my timing gun suggests it's at about 30 degrees of advance, vs. the 11 or so that I thought I had it set to before I adjusted the float.

Any suggestions on where to start?

Hello - I'm new to the forum, but have owned 40, 60 and 2 different 100s. I just bought a 60 with no rust, been sitting in a car barn for about 12 years. It's a 1986 one owner California truck that has been de-smogged and has a weber 38 conversion kit. I have no experience with the de-smogged 2F and am not a mechanic. This thing runs out stronger than any I have had before, but it won't cold start worth a darn and it won't idle below 1100 or 1200 rpm. Can adjust this carb for that? I did put a new gas tank, fuel lines and pump and filter on it.

 

[GeologistFelix]

Ok, pulled the carb off and took a look at everything...

- Idle solenoid was seated nice and tight, took it out and the o-ring and metal gasket/washer were seated properly.

- Airhorn gasket wasn't covering any passages (the weird fit seems to have fixed itself).

- There was a fair amount of gunk (bits of gasket, a few tiny metal filings/chips from lock-washers I'm guessing) in the bowl and so on; I blasted every passage in the thing clean.

- It seems like the discharge weight is sticking in the carb body a little bit. I have no idea _what_ the discharge weight does, though, so I don't know if that has anything to do with my troubles.

- Even though I didn't have any positive indications of a vac leak on the manifold gasket, I'm gonna retorque the manifold bolts in sequence just to be safe. It's a lot easier with the carb off, after all.

 

[GeologistFelix]

Hello - I'm new to the forum, but have owned 40, 60 and 2 different 100s. I just bought a 60 with no rust, been sitting in a car barn for about 12 years. It's a 1986 one owner California truck that has been de-smogged and has a weber 38 conversion kit. I have no experience with the de-smogged 2F and am not a mechanic. This thing runs out stronger than any I have had before, but it won't cold start worth a darn and it won't idle below 1100 or 1200 rpm. Can adjust this carb for that? I did put a new gas tank, fuel lines and pump and filter on it.

I don't have any experience with non-Aisin style carbs for the 2F, so take whatever I say with a grain of salt...

First of all, does that Weber have an electric/automatic choke? If so, that's the first thing I'd check. When a carb is cold, it's going to run 'leaner' because the fuel droplets won't atomize as finely, so it drops just as much fuel into the engine but it won't burn as much of it. The choke effectively reduces the amount of air going into the cylinder for a given amount of fuel, so it has closer to an optimal air/fuel mixture.

So, if you choke isn't working on the Weber, it would tend to be running too lean while the carb is cold, which would make for a hard start and trouble idling at low speeds (kinda like when you've got a big vacuum leak).

If the choke is working, my guess is a vacuum leak.

Anyway, you should start a new thread if you want more specific help.

 

[GeologistFelix]

Reinstalled carb. Manifold bolts were all at spec, vac lines were all intact, linkage is all correct.

Still running rough, having trouble holding an idle speed, and dying when I give it gas and then let it try to fall back down to idle.

Gonna check to see if the plugs are fouled...I'll let you guys know how that goes.

 

[88bj73]

Best thing to do right now would be to call Marshall. He'll help you figure it out really quick.
Cheers!

 

[GeologistFelix]

Yeah, looks like I'm gonna call him tomorrow. I'm hoping it'll just be a matter of tearing the whole carb down and looking for a chunk of crap stuck in one of the passages in the lower assembly, or something like that.

This is so frustrating...it worked fine except for stumbling on cold acceleration, for like two and a half months of daily driving, and as soon as I adjust the float, it takes a crap and refuses to run. I wish I just had the money (and months to wait) for a Jim C. rebuild on my original carb...

 

[lovetoski]

Yeah, looks like I'm gonna call him tomorrow. I'm hoping it'll just be a matter of tearing the whole carb down and looking for a chunk of crap stuck in one of the passages in the lower assembly, or something like that.

This is so frustrating...it worked fine except for stumbling on cold acceleration, for like two and a half months of daily driving, and as soon as I adjust the float, it takes a crap and refuses to run. I wish I just had the money (and months to wait) for a Jim C. rebuild on my original carb...

Marlin will rebuild OEM carbs. Takes about 2 weeks. Mine works great.

 

[GeologistFelix]

Most people who know me would say I'm fairly smart (or at least a fairly big smartass).

In reality, I'm an idiot.

It was the idle cutoff solenoid.

Somewhere along the line, I buggered the connection to it, and it blew the 10A engine fuse.

So, I changed the fuse, 'bench-tested' (read: used jumper wires on the solenoid on top of the radiator with a flashlight in my teeth), and determined it was working.

I screwed it back into the carb, got it tightened back up, and plugged in.

Started right up, no weird vac-leak like symptoms, although it was idling pretty high (maybe because I'd previously adjusted the idle screw until it was running off of the main fuel circuit, hahaha).

Gonna have to reset all the idle stuff to know for sure, but I'm pretty sure that fixed it.

 

[klinetime574]

Good news. You're a smart man.

 

[88bj73]

Woops!!! I was thinking something was up... Since marshall's carbs have a really good rep and I haven't heard of any problems with them so far.
Cheers!

 

[LAMBCRUSHER]

Marlin will rebuild OEM carbs. Takes about 2 weeks. Mine works great.

OH REALLY? good to know. always wondered what a professionally built carb could do to my motor...