LUVTruck.com

Hey everyone,
My engine has been running a little rough lately and stumbles (for a lack of a better word). I have an 81/82 ignitor/coil installed, new distributor (old one worn out)/cap/rotor, cleaned up the plugs, adjusted the carb, and adjusted the timing to 6BTDC (according to the book) but it still stumbles. I still need to get a new set of wires yet. I played with the timing and adjusted it to mabye 2BTDC to 0BTDC and the stumbling stops. Is this common or something else wrong that I'm missing here besides installing a new set of wires? Any and all suggestions would greatly be appreciated.
Thanks in advance,
Dozer

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"Fork: an instrument used chiefly for putting dead animals into the mouth." - Ambrose Bierce

Hmmm, sounds like you already hit almost all the likely culprits?

Couple of insultingly simple things: I'd check ALL vacuum lines to make sure none are dry, brittle or leaking.

Also with engine shut off & distributor cap removed pull vacuum line going to distributor and suck on the end of the line & see if it pulls the advance plate that points are attached to. You can pull a vacuum that way & hold it for a second to also make sure vacuum cannister doesn't leak down. If it doesn't move then a faulty advance cannister, leaking hose or sticking plate etc.

If you have a propane torch then with engine running and torch valve open, but with torch NOT LIT play the escaping gas around the intake manifold & carb gasket surfaces. If rpm's suddenly increase that indicates a gasket leak. You might find one but keep going until you've checked all, to know where all leaks might be.

Always necessary to make sure your grounds are good, at engine strap and battery etc. Clean bare metal contacts, good & tight.

Under the circumstances I'd give a once over to all electrical connections, including Ignition Switch. Doesn't take much of anything to cause a stumble. Eyeball the wires to make sure there's no nicks etc. Make sure coil wiring is nice & tight & clean.

Check to see that you have nearly battery voltage going to coil and that battery is fully charged. If it's marginal and regulator hiccups it can cause a miss.

An old trick is to open the hood, start the engine and turn all lights out so engine is running in the dark, watch for any sparks etc. indicating faulty connections & electrical leaks. Obviously, be careful to not stick head, hands, face, hair, clothing jewelry or small animals [except cats] anywhere near engine compartment in the dark like that.

If nothing shows up you may want to inspect for a sticking or faulty distributor advance weight or spring under advance plate that points are connected to & make sure they move easily.

Inspect distributor cap under bright light looking for carbon tracks. That can cause cross-firing of cylinders. If plug wires are real bad and too close to each other you can get cross-firing or shorts that way too.

Somewhere in the fuel line fairly close to carb I like to use a piece of clear fuel line to be able to easily check for bubbles or interrupted flow. There's some really cool stuff for snowmobiles etc. that comes in colors.

The accelerator pump can cause a stumble both when you hit the gas & at cruise. The original Hitachi carbs had a pure genius brass plunger in the aluminum carb pump bore with no o-ring! VERY prone to failure, no real cure. Causes a stumble.

Hopefully one of these will reveal the problem.

This is the most recent post on accelerator pumps. Mine is the solid brass type, I am looking to fix it. I've seen about JimmieD's trick of scribing rings on it for a better seal, anyone try it? (Sorry if I missed that you did it JimmieD)

-NAPA appears to sell a replacement accelerator pump for these carbs that looks to be the modern design,

http://www.napaonline.com/MasterPages/N ... +Resistant

anybody every try one?

Also tundrawolf suggested he thought about putting o-rings in the grooves, that occurred to me too, anybody try that? Seems like a damn simple solution, providing I can figure out the right gasoline-proof material. Not worried about size, they come in any size under the sun.

Forgive me for trying to fix the Hitachi but it works great, no vacuum leaks right now so I'm going to wait on getting a Weber for a while, especially if I can fix this tip-in bog thing. I was quite disappointed to see that there is no provision for adjusting the size of the accel. pump shot like there is on my 4bbl Quadrajet. (I know, you all have Quadrajets (Or Quadrajunk, Quadrabog, ...) but that's what I have.)

OK guys, I guess this is an OK spot to post this.

I fixed it, it was the float level.

Long story short I finally decided to try and raise the fuel level in the float bowl (up to the line scribed on the glass) and that along with replacing the needle and seat (which I did before the float level) has fixed my bog. Imagine that, the truck runs properly with the carb adjusted properly.

Anyway let that be a lesson to me to me.

Good deal and good job. I tried an accelerator pump from napa and my truck had an instant hesitation. I didnt fight it just put the old one back in and it was fine. I kept the new rubber boot up top and the new gasket.

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1980 4x4