301 diesel backfiring

Case addict · Sep 24, 2016

I just got in a 301 diesel that I purchased as an Internet bidder. It was advertised as a runner and I know that usually means barely running. Anyway someone had put a new radiator on it but not the correct one with the cutout for the air intake pipe. As a result the intake pipe was just open a few inches from the manifold. When we started it sounds like it is missing on one cylinder and it backfires though the intake just like a gas tractor would. It doesn't smoke or produce any knocks other than the miss. I'm thinking a bad injector or bad valve. Any idea's from your wealth of knowledge?

Dieseltech · Sep 25, 2016

First check the simple things, I've seen this happen when an exhaust valve is not opening as it should, or not at all on other engines. What happens is the trapped compressed/burned charge can't get out, but when the intake does open there will be a loud pop when the charge can escape. May be a push rod off, set screw loose, or worse a severely worn cam lobe. Worth a look..

Joe (Wa) · Sep 25, 2016

Check the rest of the exhaust too. High back pressure can make it bark.

Joe

oldproudvet · Sep 25, 2016

I bought a "poorly" running Racine 400 years ago at parts price because of the same sympton. Advertised as needing overhaul. Exhaust rocker on #3 adjusting nut backed all the way off, the ex valve couldn't open, leading to all sorts of weird running issues. The owner had even taken the pump in for a check out. Simple first

David G · Sep 25, 2016

Check that the exhaust valves are opening correctly.

Cameano · Sep 25, 2016

What Dieseltech said. I've seen backfiring in the intake from both broken exhaust rockers and flat cam lobes on exhaust side. A simple trick to figure out which one it is is to touch the intake runners as it's running. The problem cylinder's intake will be much hotter than the others. Or shoot temps with an infrared thermometer if you have one.

Case addict · Sep 25, 2016

Thanks everyone. I will check that first as soon as we get a break from harvest.

301 diesel backfiring

Case addict

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Dieseltech

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Joe (Wa)

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oldproudvet

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David G

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Cameano

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Case addict

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