Ok,with the Optical Sensor unplugged and CPS plugged in the engine should start with extended cranking.
No start and you know the CPS is bad and should be replaced with AC Delco ONLY-all aftermarket sensors are junk and most don't work right out of the box so don't waste your time.

With the IOS plugged in and CPS unplugged the truck should also start with extended cranking and that tells you the OS is good.
No start that way can be 1 of 2 problems for a 94,95,96.

A bad OS electronic noise filter or a bad OS.

For 94,95 the OS noise filter can be removed and the harness plugged dircetly into the OS-you then need to go to radio shack and buy enough ferrite core to cover each OS harness wire.
For 96 you ccan do the same but you don't need the ferrite core.

For a bad OS the best soloution is another IP,otherwise you can replace the OS yourself with a used one from the wrecking yard folowing this guide-but be very attentive to the details,it MUST go back in the EXACT same location as it was removed:
Roy Halvorsen

 

i think i understand how you talk about eliminating which sensor is bad. but the problem im having if you unplug either one of the sensors you get no smoke no spitting or sputters, almost like its not getting any fuel. the only time you get a reaction out of the engine is if they are both plugged in. after cranking her for a bit of time you can get her to start but only for a second (revs up to 2k then right back down). matco man has a snap on scanner for sale and a matco scanner. new price 3k so being used (about 1 year) hes asking 1.5k would either one of these do me any good if the engines not running?

 

I wouldn't spend that kind of money on a scan tool for just an old truck,there are less expensive options.

A snapon mt2500 with appropriate cartridge and cables are usually on ebay for less than $500.

Or you could go with a good laptop program and cables:
FYI
Autoenginuity:AutoEnginuity
Carcode:OBD-2 Vehicle Explorer Scan Tool Browser

I have carcode and it does work but is the worst I have seen for being user friendly-no users manual and is not at all obvious what menues to use to get where you want.

I am afraid that you likely have 2 or more problems,bad CPS,bad IP and/or bad PMD.
More info is required though.
The CPS and PMD are least expensive to change.

 

My dad does have a mt2500 but he's off in another state. So was wanting to get a new scanner. But I did replace the cps with acdelco and after the replacement is when it stopped at least starting. Pmd is good was able to throw it in a known running truck and it started right up. I just don't understand why if you unplug one sensor or the other it stops getting fuel.

 

PMD is simple swap out,but make sure that you have a resistor to install in the new PMD,be it the 1 from the PMD you are replacing or buying a new resistor with the PMD.
(amazon has drastically dropped the price of PMD's/FSD's and the warranty is supposed to be great,it's about $120 now)

 

pmd is new, it was doubled checked by putting it into another 6.5 and the other truck started right up

 

If you unplug the CPS and it won't start after extended cranking,that tells you there is a problem with the OS in the IP.(or the electronic noise filter on 94-96 trucks)

Likewise when you unplug the OS and it won't start with extended cranking,that tells you that the CPS is bad.

 

Right but if I unplug either one it won't even try to start. The only time it will try to start is if both are plugged in.

 

I would say you have isues with both in that case-have you removed the OS electronic noise filter yet?

Have you installed a new AC Delco CPS?

Did it have any trouble codes before you tried unplugging the sensors or have you cleared the codes and saw what codes returned?

Where is the IP/PMD harness ground wire fastened?
Is it on the IP or elsewhere-It MUST be fastened to the IP and/or drivers side battery ground ONLY.
Is it clean and secure?

 

think the ground is still on the ip. never cleaned it so it could be a problem.
the cps is new from ac.
ill see on the noise filter i know its still there but kind of hard to get to with my hands, but it seamed like there wasnt enough wire there to bypass it

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im thinking something about how the old pmd was burnt up. it was either the c or d pin that was burnt. and it was the only pmd to work most the time (engine reving to 2k) but im wondering where those wires c and d go to. if the fuel solenoid could be damaged cause of the melting problem. would the koko relearn with out a scan tool screw with anything?