I am about at my wits end

Starts perfect when cold
will only start with a shot of starting fluid when hot
I have replaced fuel temp sensor, coolant temp sensor
new injectors a month ago
new fuel pump 6 months ago, new fuel filter 2 weeks ago
this problem started about 3 4 weeks ago
pcv, vacccum lines plenum throttle plate, IACV, MAF have all been thoughly cleaned
good pressure at the rail

So I am looking for ideas

as always any help is appreciated

 

Check resistance of the fuel temp sensor, and associated connector, check for + volts at the common to fuel injectors (they get grounded to squirt), fuel pressure is 32-34 PSI? Which coolant sensor (single wire just runs gauge, two wire one talks to ecu). If you have a scanner, what coolant temp is shown by ECU when cold or hot)?

 

The coolant sensor should read between 9200 and 175 ohms; (-22F to +212F)

The Fuel temp sensor should read between 9100 and 150 ohms (-14F - +212F) -- a GEMS sensor reads different values.

 

with the engine hot enough to not start fuel sensor reads 1220 ohms and engine coolant sensor reads 340 ohms both connectors with out sensors read 1900+ ohms

 

Reading connectors without sensors implies that you are in effect ohming wire toward ECU. While this does not show a ground, the voltage from the ECU can make ohm meters read strange.

Would make sense that engine coolant is a different temp than fuel line, so that would be why those sensors are a little apart. I believe the fuel sensor has a fallback value of about 98F, you might try running with it unplugged for testing.

Can also check F7 in underhood fuse box for a hairline crack, it supplies power to injectors.

So when this happens, you have fuel pressure and you have spark? Inertia switch firmly reset?

You can see on attached page from circuits diagrams that the fuel temp, coolant temp, MAF, and TPS are share a common point on the ECU, and each have separate other points.

 

So spent the day messing with the truck and here is what I've got: 35psi at the rail when trying to start hot, spark plug tips white and seemingly dry, spark at the plug tip, 12.5 volts at the injectors (although when I go from either wire in the connector to the block I have 12.5? I don't understand that), changed out f7 fuse, checked resistance on both sensors when wont start and they are in range. As the day progressed I could sometimes get it start by unplugging a fuel or coolant sensor but not everytime, sometimes I could start with everything pluged in and now when I was driving it tonight sporadicly lost I lost all throttle response and truck would either just go to idle or roar back in response to throttle or just die. Got the truck back home shut it off and then was able to restart it while hot but then it died after 1-2 mins of idling. I am starting to think there is some bad wire in ther somewhere, but where to start?

What I am I missing

 

TPS (throttle position sensor). Like a volume control on an AM radio it can be "scratchy". You can read resistance, or a scanner may show percentage of position, minimum is about 9%. Should be smooth transition.

You are also correct about wiring, it could be a "rub" where insulation is worn away and allowing a wire to ground. Shake the harness, poke it with a stick, etc.

 

If you can make it hot and repeat the problem, let's hunt for the sensor ( or eliminate sensors) by spraying them with your can of brake cleaner. Old TV repair method, they would spray the suspect part that made picture go crazy when warmed up.

 

I noticed last night that I was pretty low on coolant and ended up adding almost a 3/4 of a gallon, I am wondering if I had a air bubble right at the coolant sensor so I was getting goofy readings because today hot start problem seems to be gone, also engine is running cooler per dash temp guage - however now (this started a few days ago) the sudden cutting out of the engine seems to be getting worse, so I pulled the VSS and rebuilt it today but still having the problem, can the vss go bad besides just the guide bushing wearing out

 

We have the rebuild article on the VSS, plus you can unplug it and test vehicle (speedo and cruise won't work - honest, deputy).