fuel, ignition, start problem on my '95 T100
It appears I have identically the same problem on my '95 T100 EXT 4x4 and I have been troubleshooting for eight hours. I did exactly as you did (spark, starter turns, etc.). I changed the fuel filter just in case - no joy although the Toyo Dealer changed it the last time and I found it cross threaded..uuhh it was tough coming off..oh well the new filter went on crossed and thank God it doesn't leak. Anyway, I followed the wiring from the top of the fuel tank and located a connector under the driver's seat, I seperated the connector halves and checked my Chiltons manual then identified the fuel pump wiring (wht/blk = ground) and (blue = hot). I found the resistance between blue wire to chassis ground was around 30 ohms - probably pump winding. Wht/blk to chassis ground was and should be zero ohms. If this is good then obtain two pieces of insulated 18g wire and run one from the plug wht/blk pin to chassis ground without you holding it. You will need a longer wire for the blue pin so you can run it outside the truck directly to the battery + terminal. All set?? -- touch the blue wire to the battery and wait approx. 5-10 seconds. If the fuel pump works you will hear it running and you will hear fuel pressure flowing through the engine hoses. If you do not hear this - double check your ground and blue wire connection - still no joy? - you either need a new fuel pump or wiring repair up to the top of the tank/pump. If you hear fuel then your fuel pump and wiring is in good shape like mine. If you pressurized the fuel line then at this point you have two options. 1) reconnect your electrical connection and start your truck then drive it to the dealer to troubleshoot the electrical/ign system or 2) start your truck and breathe a sigh of relief it's not the fuel pump then shut her down after a bit and prepare to troubleshoot further (this is where I am as of today). I suspect a faulty relay at this point since all my fuses appear to be good. There's a circuit cut out relay and the ignition start relay that work in series to send power toward the pump when the key is turned on and right now I do not hear the pump operating when the key is turned on and I should - I will be looking at these relays tomorrow if I can locate them.
Here's an easy way to find out if your starter relay and circuit cut out relay are routing 12vdc to your fuel pump. Go back to the connector under the driver's seat. Find the blue wire on the male connector and rig up your meter to read vdc + on blue wire and chassis ground. Put yourself in the driver's seat and place the meter where you can see it. Turn the ignition key on (see 0vdc) then turn to start there's a slight delay for the relays to switch then 12vdc is measured. If you see this then your ignition circuit is good through the circuit cut out relay. By the way, if it does not measure 12vdc you need to do the same procedure at the next component which would be the circuit cut out relay (I had to ask the dealer where this was) located behind the glove box on the interior right side (blue). Disconnect the relay and measure 12vdc at the blue wire on the connector (follow the same start sequece as before). If you measureed 12vdc that's good all you have to do is replace the circuit cut out relay ~$82.00 or repair the wiring from the relay to the connector under the driver's seat. If you do not measure 12vdc at this point you have either a faulty starter relay or wiring between the two relays is an issue.
Ironically after all this troubleshooting I have not found the problem with my truck and strangely I have not been able to duplicate the discrepancy since my hot wire check of the fuel pump and hearing it operate but I learned a lot. Such as, the pump does not come on until the start sequence has begun but most believe it comes on when you turn the key on - not so - the relay sequence prevents it. For lack of other easier ideas I plan to change out the fuel regulator because it's the fuel regulator the maintains fuel line pressure after the engine is cut off. What lead me to this was the fact that when removing the fuel filter fuel just dripped out of the fittings rather than spray out which indicates "no pressure." The problem with changing the fuel regulator on the 3.4L is - it's buried under the throttle body and intake plenum and will take personal time (hours) and several hundred dollars in parts to do it. Thankfully I have a friend who's willing to plunge into this with me.
After four hours my friend and I changed the plenum gaskets, valve cover gaskets, plug seals, and the fuel regulator. I also found a vaccum leak in one line going to the intake plenum. After charging the fuel lines like I did in my first write-up the truck started without hesitation. I will monitor for a few days and let you know what happens.
It's been four days now and it appears the discrepancy is slowly returning. Instead of a 2 second start it's taking 8-15 seconds before it starts. Also noticed when the truck is parked on a slight decline (nose down) overnight it has more difficulty starting than when parked on an incline or flat surface.
Filled the fuel tank max and noticed 3 second starting. Back to monitoring the truck position, fuel tank level, and timing the start.
Poured in Slick 50 fuel additive cleans injectors etc. and have not had a reoccurence of long delay or hard starting since. Wish I had done this to begin with.
Last entry hope it works out for you.