What makes my john deere 2030 diesel engine fire

Question edited for a lot more clarity.
Question moved from Cars and Trucks to make model category.

Gator Diesel service manual Page 59

https://radionerds.com/images/4/4e/Technical_Manual_for_the_M-GATOR%281%29.pdf

https://www.google.com/search?q=John+Deere+Gator+6x4+with+Yanmar+Diesel+engine%2C+head+bolt+torque&

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Edited text with a wild guess at the maker. Make model (what it is) in all questions please.
Category moved to John Deere Tractor.

If it was working before, there is no need to worry about the firing order as that never changes. Things to look at;
Clean and correctly gapped spark plugs,
Clean gas,
Fuel filter?
and a clean carburetor, float bowl and jets.

John Deere 3020 Engine Engine Detail John Deere Firing order: Starter volts: Oil capacity: 9 qts 8.5 L 13 more rows •
Jul. 10, 2020

TractorData.com John Deere 3020 tractor engine information

John Deere 3020 Tractor Service Manual - Jensales

https://www.jensales.com > products > John-Deere-302...

This John Deere model 3020 Gas and Diesel Tractor Service Manual is a digitally enhanced reproduction of the original manufacturer-issued Shop Manual.
US$120.98 · ‎In stock

operators manual for john deere 3020 tractor owners ... - eBay

https://www.ebay.com > itm

3020 Tractor Operators Manual. This operators manual includes Gas, Diesel, Lp. This comprehensive manual includes. Fully Covers Serial No.
US$15.97 · ‎In stock

JOHN DEERE 3020 Gas and Diesel Tractor Service Manual

https://www.ebay.com > itm > JOHN-DEERE-3020-Gas...

This is a new reprint of John Deere Service Manual SM2041 for the John Deere 3000 Series Tractors shown above. It is dated June 1961. Includes 3010 & 3020.

If its an over head cam engine then yes you would have to do the valve timing, if its a push rod engine then no you do not.

Probably not

Visit the on-line store, know as reliable-store, they have the repair manuals. I'm sure you will get the solution of your problem.
Best Manuals

injector pump right behind the alternator shaft driven off the front crankshaft ? why?

he main manufacturers of diesel engines for boats: Caterpillar Marine, Cummins Mercruiser, Detroit Diesel, John Deere, MAN, Westerbeke, Mecruiser Diesel, John Deere, Volvo Penta, and Yanmar.

For more information on these manufactures, check out these websites: http://marinefuel.com/marine-engine-manufacturers-diesel/ and http://www.discoverboating.com/buying/types/engines.aspx?id=80

Visit the on-line store, know as reliable-store, they have the repair manuals. I'm sure you will get the solution of your problem.
Best Manuals

it can be one of three problems fuel pump leaking injectoin pump or a injector over fueling

I will assume you have bled the fuel system per the owners manual to ensure no air lock in your system. This is especially critical after replacing the injector pump.

The next step is to ensure you fuel filters are good and flowing and last but probably the problem is the screen on the petcock (fuel shut off) in the fuel tank. Remove this shutoff valve and clean the screen with a fine wire brush and carburetor cleaner.