The Stovebolt Site Forums The Shop Area Engine Shop Engine misses

Hi Bolties! I drove my 49 tonight, and it started to mis once in a while, going down the road. Kinda like it was sputtering out.Then on the way home, it missed continously on acceleration. It even back fired once or twice when I was giving it the gas. Wasn't sure I was going to get it home. It don't seem to mis at idle. I think it is most likely a fuel problem, maybe the accelerator pump. The carberator isn't in too bad a shape, and the engine is fresh from the rebuild shop. Any thoughts?

Check the charging system. low or no charging voltage will make it miss and backfire as the battery voltage gets low.
Jerry

Thanks Jerry (HRL). I will check that. I don't think the batt is low, the volt meter gage seemed to be on the positive side, but I will check it and make sure.
KT
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49 Chevy 3/4 ton

Sounds like fuel starvation. A plugged filter or line or a weak fuel pump may be the cause. Start with the cheapest, the fuel filter then go from there. I usually put a clear filter on any vehicle that hasn't been driven much just to see what gets sucked from the tank and into the fuel system. Today's fuel will slowly clean your tank and send the crud down your fuel lines.
Just my 2 cent worth,
Scott

Sticking valve or lifter?

I had the same exact problem and it turned out to be the coil.

Ditto with the coil. I actually had a new coil on mine, but my alternator was overcharging the battery. So, the coil got friend. Just my 2 cents. John

Thanks guys. Well, the tank has just been cleaned and sealed, so I don't think it would be the tank. It has a brand new fuel pump on it and it is working well, you can see the fuel moving in the glass bowl when it is running. I just put a new fuel filter on it about 3 weeks ago, but that was B4 I cleaned & sealed the tank. I guess it's possible it could be plugged. I actually did wonder about the coil though, because when we first got the new engine running, we had a similar problem at that time and we changed out the old coil (I didn't put a new on it at first like I should have) and it ran great. It has a new coil on it, but I did wonder if by chance it could have went bad. I don't know. I thought tomorrow I would check the points gap, and some other things & go from there.
Thanks!
KT
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1949 3/4 ton Chevy

I'm leaning toward the fuel filter. It sounds identical to the problems I was having. Actually I still am because I haven't gotten my new tank yet, but the crud was plugging up the fuel filter and the symptoms were exactly what you are describing.
Dave

I'm not familiar with the '49 3/4 ton, but my '53 3100 has a vacuum advance on the distributor.

You originally mentioned that it sputtered on acceleration but not so much at an idle. Could it be that the vacuum advance isn't working properly?

Ok Bolties, the saga goes on! Tonight I did some more checking on the ignition system and here's what I found. With the dist. cap off, a friend cranked the engine over, and there is fire at the points. We then put the cap back on, and removed the number 1 plug, left the wire on it, and cranked the engine. There was no fire at the plug, and the plug was pretty black with carbon when we pulled it out. That is telling me a couple of things. First, either the cap is bad, and or the plug wires including the coil wire to the cap is bad, and second the spark isn't hot enough, which could be a result of faulty wires,
or bad coil. Even though it is new. I am going to get a new cap, wires, and coil tomorrow and see if that will fix it. Time will tell. Thanks to all who gave tips and advice! I will report back after replacing these items and let you know the outcome.
Thanks!
KT
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49 3/4 ton-5 window Chevy Truck

Ok, tonight I put on a new coil, and a new dist.cap. I also changed out the points. They are getting fire. I checked (with a test light) & key on and there is fire to the coil and out of the coil to the dist. but, still no fire to the plugs. I have to say that I'm stumped. I can usually figure these things out, but this one is a real deal. Anymore thoughts?
Thanks!
KT
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49 3/4 ton Chevy

You didn't mention but assume you checked to make sure rotor is contacting both the terminals on inside of distributor cap. one from coil and then the outgoing to spark plug wires. If you have a little debris the cap won't catch the little notch on distributor and seat properly and that would cause lack of fire to the wires

Hi kb3csw! I put a new cap on lastnight, along with a new coil. I'm pretty sure the rotor is contacting the the areas. Today at work, I got to thinking about the problem. I had fire from the ignition switch to the coil, and from the coil to the dist. I never thought to check the wire from the cap to the coil. Tonight I borrowed the new wire off my wife's truck, and I now have fire to the spark plugs. But, I still can't get the truck to fire up and start. I have made sure the points are setting on .19. I have even tried another set of points, and another condensor. The battery was starting to get weak, so I hooked it up to the charger. I will just have to keep trying to get to the bottom of the problem... Thanks to all who have been so helpful!
KT
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49 3/4 ton Chevy

Did you try putting a little gas down the carb, just to be sure?

Hello again bolters! Well, here's the latest. Today, I put a complete new set of plug wires on the truck. I bought a new condensor, and set of points. I checked and made sure the plugs had fire and they do. I pulled the new cap to coil wire out a bit and cranked the truck over just to make sure I have fire from the coil to the dist. cap and the fire was really jumping out of the coil. So, there is most definately fire there. But,,, the truck still won't start. I have to wonder now if it may be in the carb. Chuckthetruck, yes I have poured gas into the little horn of the carb trying to get it to start. I have never had such a problem that kept me stumped me like this one. I feel it must be something really simple, but it really has me puzzeled. :confused:
KT
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49 3/4 ton Chevy

This gas we get know can carbon up the spark
plugs when you get to much of it. I believe
you mentioned the plug was dark with soot.
Try cleaning the plugs.

Hi Wrenchbender! Yes, I did clean the plugs. Didn't change anything. I have to wonder if the problem is in the carb. There is fire every where it is supposed to be in the ignition system.
KT
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49 3/4 ton Chevy

just a idea. Change the cabels on the distributor for 180 degrees. It happened to me several times. You put in the distributor, set the engine on first OT and the car refuses to start.

It was the wrong OT. Remember this is a 4 stroke engine so you have 2 OTs.

So for a quick check (just to make sure) reconect the wires on the dizzy for 180 degrees. So #6 is your new #1 - 5 is 2 - 3 is 4 - 1 is 6 - 2 is 5 and 4 is 3.

hope that helpes

Hi bolters! Well, the engine problem is over. In summary, here's what happened. The coil wire from coil to dist. cap was bad, which was the original problem. In attempting to find the problem, and replacing some ignition parts, I replaced the spark plug wires. The reason it wouldn't start, it because I had the plug wires off 1 hole. I hate to say, but that was it. The sweetest sound was when the stovebolt started & ran so smooth!
Thanks for all the great help you all offered. It's hard to diagnosis a problem when you can't see the vehicle.
KT
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1949 3/4 ton Chevy