1995 Chevy S10 P/U 2.2 Litre - Will Not Start

Hi,
I am trying to help a friend who is low on cash to get his truck running again. I am a mechanical engineer but by no means an auto mechanic, so I told him there was a 1 in a 100 chance I could help.
Anyway his truck died on him while driving on the interstate with no prior warning.
This afternoon I went out to where the truck was parked and with a boost in place I asked him to crank the engine over. As soon as the engine turned over, a small bang occurred and smoke appeared at the intake manifold. I think this engine has throttle body fuel injection and this is where the back firing like bang emanated from.
I then checked for spark by removing a plug and had him crank the engine one more time. No back firing sound this time and there was spark.
Prior to me arriving he had replaced the fuel filter, but this did not cure the problem. The engine has 135,000 miles and my best uninformed guess is timing chain (or belt - not sure on this engine). This might explain the back fire and certainly account for the engine not starting as it appears it has both gas and spark. I am not sure the easiest way to rule this guess out and then proceed along some systematic path to arrive at the root cause.
Any advice / suggestions would be much appreciated! Many thanks.
Craig
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That engine has Timing GEARS. We had one, a 1997 GMC Sonoma that had a bad gear. Back in 2000. I heard at the time it was a comment issue.
I hate to assume that is the issue your having, but it is one I would investigate. Especially given the mileage. If your friend is really serious about keeping that truck, he should get a factory service manual for it. The factory service manuals will have the diagnostic flow chats to help you diagnose the issue, as well as the proper repair instructions.
Charles
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Charles
To check the timing chain/gear theory, will the valve cover have to be removed, or is there a quicker way?
Thanks
Craig
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I f you are sure the injectors are pulsing and there is spark, do a compression test, this will tell if the gears let go, the valves may be bent at this point anyway.

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Yes of course, a compression test! Thanks for your help.
Craig

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Craig
I did not do that job my self. A associate of the business, who at the time worked for a GM dealer, did it. He did it at home as a "side" job. We sent it out to someone who was experienced with it.
I haven't ever had the chance to work on a Rear Drive 2.2, since then. Most of the 94 and up S-trucks I see are 4.3 trucks. Charles
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