Hi. Thanks for having this available! Our 1991 Isuzu Rodeo V6 suddenly wont start? It cranks great, and obviously has fuel by sight and smell in the throttle body. Even quick-start couldn't get a puff out of it? I figure it's ignition but where do I start? What is the mostly likely culprit in your experience? I REALLY appreciate any help because it's an hours drive each time I try a new part plus the wait just to get it. Thanks !!!!! ;-)

For the 1991 Isuzu Rodeo with the 3.1L V6:

Firing Order:
1-2-3-4-5-6
Cylinders:
....(back).....'.5...........6.'
'.3...........4.'
'.1...........2.'
....(front)
Distributor:
.....(back)
.................(+)-screw
..........4
..3
...................5
2
.................6
.........1
(+)-screw
.....(front)
Rotation: Clockwise

auto or stick shift transmission?
correlation is not always causation.!!!
example: if I open the glove box, and the engine stalls, It probably is not the glove box lamp doing that.

The 97 cars have very few learn modes.
in fact, none kill engines dead, ever.

the trouble with your post is it says nothing useful. sorry.
1: cranks robustly but will not start?
2: will not crank, or just clicks, or the starter motor is silent.?
the starter can also chatter, or free run, spin fast but engine not.
if it wont crank ,
jump start it, if it will not cranks still , crank in NEUTRAL.
PRNDL move lever to N per the steps in the operators guide.
3: cranks ok, there are 50 reasons for that.
if your car reads statistics, the spark plugs are bad, ignored.
do say this time what the engine did. exactly , you did not.

4: cranks ok , do so with wide open throttle to clear floods
this is secret mode in the op. guide that cuts off the fuel injectors.
V6, 3.1., 3.2 , 3.5Liter?

If the spark to all plugs is healthy and that spark coincides with the introduction of the fuel then it should start. Is it catching at all when being turned over
Have you had the timing checked?
Is the fuel pressure good?
I would....personally speaking, perform a compression check and, if that proved okay, I would have an OBD scan to check for error s then go from there

your problem may not be electrical at all... have you done fuel
pressure test ? simple things like a blocked fuel filter or pick up, will be trouble starting. also check fuel pressure regulator.

To clarify, if it turns over it cranks.
If you know it is not getting spark to the plugs, you will need to have someone check the rest of the ignition system including cap and rotor, module, and pickup coil in the distributor. (V6)
The first thing a mechanic would do is make sure the coil has voltage.

fuel pump

throtle body fuel injected

should be under hood on or near fire wall, under plastic cover 

http://www.bulldogsecurity.com/New%20Wires/New%20Wires/Wires/isurodeo96-03.htm
http://images.google.com/images?q=1998+isuzu+rodeo+electrical+diagrams&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&ei=5h6gSbHpEYKEsAPjwIDHCQ&sa=X&oi=image_result_group&resnum=1&ct=title
HEre are two different links hope they work for you