The Stovebolt Site Forums The Shop Area General Truck Talk one cylinder 235...

ok here's the deal. i have a old chevy 1952 2 ton dump. the truck is great. it just has to be sweet talked all the time. It knows when you talk bad about it. the motor seems to only work on one cylinder. a friend pulled all the plug wires off except one and the truck ran the exact same. all spark plugs are probably fine as the first 4 plugs all checked good spark with a spark tester. the plugs are all new. the wires are new. the coil is new. the points are new with condenser. timing is right. gas tank is like new now with red coat on the inside. carberator was just rebuilt with a new float. new fuel pump. and the engine has good compression!! does anybody know what the hell is going on with the engine running only on cylinder 3? the engine's big vacuum line for the brake booster has been plugged with rubber plug.

Dorf123; I'd look at the distributer cap first. It may be cracked or just worn out. Stan

Dorf123,

I have never heard of a engine running on only one cylinder...until now.

If the other 5 cylinders were able to develop even a tad of compression, the engine would not run on only one. This of course would not be true if the flywheel weighed 600 lbs.

I would pull the valve cover and look things over. Stuck valves would be at the top of my list. I would double check the compression test results. This is interesting, be sure to keep us posted, and WELCOME to the site.

Stuart

I had a 270 gmc running on 3 cylinders once. I pulled 3 of the spark plugs off, and left them off while it ran with no difference. Thought I had finally blown it up. Then I looked at the firing order and figured I had wired it @$$ backwards. Rewired it correctly... 1-5-3-6-2-4, and it ran like a champ on all 6 cylinders. I would find it highly unlikely that a 6 cylinder engine would run on only 1 cylinder.

running on only one cylinder???....don't know ,,but you can't beat a Chevy Engine..

this may be a long shot, but if there is a build up of carbon in the cylinders that got hot enough to glow wouldn't that fire the cylinders with the plug wires removed?

well we pulled all the spark plug wires but 3 and it ran the same. i'll double check the compression stuff.

Do you have the plug wires in the right places?

Turn the engine to #1 TDC compression stroke, then put the wires on the cap in the correct firing order, considering the rotation of the distributor and with #1 wire where the rotor button points.

If you are absolutely sure that is right then start checking each plug wire for spark at the plug while running if possible.
Check to be sure your plugs are good, if it seems to run the same with 3 plug wires off switch those 3 plugs with the other 3, if it still acts the same with the same 3 off then plugs may be OK.

Also check for a bad cap, try another one and see if it makes a difference. Also if your wires look like they have seen better days it would not hurt to change them. If you grab all the wires, or run your hands over them while it is running and have an unpleasant feeling, change the wires.

If compression is good, wires and plugs and wiring order is right then it will run on all 6.
Unless for some reason someone pulled your intake off, stuffed rags in some of the ports and put it back on. Or you have split exhaust and one side is plugged.

What else would cause these symptoms?

Do things look happy with the valvecover off?
No bent or missing push rods?
All valves move up and down while cranking?
All valves have clerance at some point in the rotation of the engine? if not then the compression should be off.
No excessive clerance, like 1/8"? I set mine to 0.008" and 0.015" intake and exhaust with a hot engine.

Make shure the point gap is right. If they are too close & barely breaking can cause this. Like the guys said pull the valve cover & see if all are opening & closeing. Worn cam lobes. Look at the valves if 1 or more are sticking up higher than the others. Wallered out valve seats.

A worn distributor shaft bushing will do this.It closes the point gap when it wobbles.It is very easy to check.Hook a dwell meter up and you shouldn't have more then 4 degrees dwell variation between idle and say 1500 RPM.Also you can rebuild the dissy with a new GM housing for a taxi(if it is still available from GM)This has two bushings that last forever.Hope this helps.

There seem to be two questions in one here.

1. Why won't the truck run well on all cylinders?

2. How could the truck actually run on only one cylinder?

The first question is the standard test/troubleshoot/tune item that pops up weekly.

The second question is unique...could it really continue to run on one cylinder only. If that answer is 'yes', it might narrow the search for clues to question #1.

I like Carryall Jerry's 'auto ignition' theory..a diesel in drag!

Stuart

It sounds to me like it is not even running enough to get warm. Plus, it first has to fire on those cylinders to get the carbon hot so it will run without plug wires.
I don't think the diesel thing is happening here.
If it were it should run good when cold, sounds like it is hardly running.

Grigg,

I agree..it was a tongue in cheek comment!


Stuart

well i should be able to test the stuff later. after i get into the shop i'll double tap on the compression. the spark is good. all wires are new. and the compression is also very good. we double checked the firing order in the past week too. we used the 15 is to young, 36 is too old, 24 is just right method of figuring the firing order. anybody else have any ideas on getting the nuts off the intake and exhaust? regular sockets don't seem to fit and i'm about to go back to the trusty alabama speed wrench to pull off the nuts. (Monkey wrench)

ps i already replaced one bent pushrod so all the pushrods are straight and put together with roughly the same gap.

I'd keep the thing as it is. Make some money. You could get plenty of bets ..........

Actually, I'm betting your intake manifold is loose. Better find that socket. I once had a later model 250 six. Ran on two or three cylinders. Could remove 3 or 4 plug wires and replace in any order--- no effect. Tightened the manifold, could hear it picking up speed as I tightened. Ran like a top.

I saw a plug fire once when I had it pulled from a motor and it was sticking out of the end of the plug wire, and this was without the plug being even near a ground source. It just hung there in the open and fired....Must have gotten some ground down the plug wire insulation or something.
Strange things happen.

After the engine runs a while "on one cyl", are the plugs fouled or wet?

I can't emagin a 6 cyl. engine running on just 1 cyl. Will the engine run if you leave all the other cyl.s connected and unplug just #3?

Are all the pistons installed?