TPS or computer fried? - no start
 

My XJ broke down on me, threw the parts cannon at it, ended up cleaning the C101 and it fired up. After getting the motor running i went back to readjust the TPS voltage, since i had removed and reinstalled it, so during my attempt to adjust the TPS voltage, backprobing with safety-pins, i think i shorted something.. the TPS or maybe the computer. It cranks and cranks, no start. I do still get 5vdc at the TPS. Thinking about just buying a computer off of ebay, i'm out of ideas.

Forgot to mention, I did buy a new TPS and it still won't start.

If you still have the 5-volts supply from the computer, then I doubt it's fried. Will it start if the TPS is unplugged? Still see good ground on the black wire ground wire to the connector? Do you have spark or injectors going?

I haven't tried to start with the tps unplugged, nor checked the ground. I"ll go try that now.

I have good ground, it doesn't start with the TPS unplugged. It tries to start when spray a little throttle cleaner down the throttle. Perhaps the injectors aren't getting a signal.

When you turn the key to the ON position, do your gauges move? If you leave the key on for 15 seconds or so and your needles don't move and "NO BUS" shows up on the odometer, chances are the PCM is dead. Ask me how I know.

He did mention the C101 connector, so I'm assuming pre-1989 and has an old school dash, not one driven by the PCM.

That is correct, I have an 88'. I do have issues with the fuel gauge, replaced the fuel pump over a year ago. Maybe a loose instrument panel ground, but i don't think that would cause a no start. So, there are 5vdc at the TPS "A" wire, could it be the signal side that got shorted? Going to replace the injectors today and clean up those connectors, I got some 746's last week.

This is what i've done, so far:

replaced ignition coil
cleaned up engine grounds and sensor grounds
replaced IAC
replaced TPS
replaced fuel filter
replaced a couple vacuum lines

and to reiterate, it was running(rough) til i screwed with the TPS.

Might be worth trying another computer at this point. I can't see how shorting the TPS signal wire to either +5 or ground could damage it though, since the since swings between those two voltages. The Renix TPS voltages run backward from the HO TPS, in that 5-volts means closed throttle and 0-volts means wide open (also the reason for the dual output TPS if you have an automatic). I thought maybe the single wire could be shorted to ground and the computer was trying to do flood clearing, but you said you measured 5v on the signal wire with it disconnected.

Is it possible for a bad coolant temp sensor to keep my XJ from starting? When I crank the engine, only the engine temp light comes on, no battery light, no oil pressure light, etc..only the engine temp light.

No a bad coolant temp sensor would only make it run rich thinking the engine isn't warmed up.

His is a Renix fuel injection system. Doesn't work that way.

Makes me wonder if you have a bad ignition switch. Check the 5 volt reference on the TPS for starters.

I have 5 volts at the TPS.