back firing

lbm · Jun 22, 2008

tractor was running then started to miss and back fire and quit. Tried to start back after checking fuel flow that was o.k. Now it won"t start,only back firing through carb. Any ideas ?

Thanks

Janicholson · Jun 22, 2008

Probably the rubbing blosk of the distributor points is worn and there is no dwell. Open the distributor cap, pull out the rotor, (and then the dust cover if it has one). The dist. cam has four lobes, turn the engine until one of these (any) is directly under the rubbing block, and then adjust the points to .020". If it has a mag, let us know, there are different instructions. It could be a coil proble, or a bad condenser, but check the points first. Jimn

lbm · Jun 22, 2008

Checked gap setting at .020 and it still won't start just back fire. Thanks

Janicholson · Jun 22, 2008

Put a different condenser in the distributor. try it. Use a known good coil. Try it.

Next, Pull the plugs. Turn the engine untill #1 pumps air out past your finger. Then put a piece ov copper wire about 8" long in the #1 hole, and turn the engine with the fan till the wire stops moving up. This is TDC. The timing mark will also be aligned at this point. The rotor should be pointing to the 1:30 position. The wire attached there is #1 plug wire. If it is not, The Engine may have slipped time. JimN

Mike Farmer · Jun 22, 2008

Try this when all else fails. Inlet valve badly worn or sticking open so the fuel is coming back under compression and firing in the manifold. Or very weak mixture. This is not exactly a rare condition. Unless you have altered something your ignition settings should not be at fault. MTF

El Toro · Jun 22, 2008

The distributor may have sheard a key or the cam
gear. Do as Jim suggested and bring No1 piston to TDC on the compression stroke and see where your rotor is pointing. I would use a large handled screwdriver so you don't lose it. Hal

Allan in NE · Jun 22, 2008

Backfiring is "almost always" caused by a fault at the primary ignition.

I'd look at the points.

Allan

TomH in PA · Jun 22, 2008

Replace both points and condensor. Just setting the gap isn't enough, but at least file them and make sure you have good electrical contact with a meter.

Red Mist · Jun 22, 2008

I'm with Mike Farmer on this one - if the ignition checks out perfectly, I'd start looking for a partially stuck valve or failing valve train. mike

Tom Fleming · Jun 22, 2008

I was going to suggest a hung intake valve if the timing is correct. If the tractor ran fine before and just started doing this, I suspect that an intake valve needs to be "unstuck".

Owen Aaland · Jun 22, 2008

Check for carbon tracing on the distributor cap. You might have spark jumping to the wrong cylinder.

Don Swindall · Jun 27, 2008

I agree with El Toro. I have a Farmall 100 and you could get #1 piston up and set the distibutor for the correct timing. It would start real easy but would die and the timing would be off again. It was the gear on the distributor. It was dished out and would jump time. Hope this helps.

back firing

lbm

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Janicholson

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lbm

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Janicholson

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Mike Farmer

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El Toro

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Allan in NE

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TomH in PA

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Red Mist

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Tom Fleming

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Owen Aaland

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Don Swindall

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