Grrrrr

[adsm08]

So, I have my truck all back together finally. It won't start. It cranks over wonderfully, sounds like its running, but the second you let off the key, it's like you just shut it off. Gassing it doesn't help, have spark, fuel pressure, air, the works. Smells like a freaking lawnmower too.

The only thing I can think of is that the engine is pretty heavily modified. Last time I swapped in a new computer with an old engine it ran like ass for a few minutes. New modded engine, old computer, may be doing the same thing, but it should at least be idling poorly by now.




Pissing me off.

 

[adsm08]

Confirmed that my issue is related to key position. Rigged it up so I can hold it in start but cut the starter out, engine stayed running until I released the key back to "run".


Its an 87 truck, with 88 engine and dash harnesses swapped in, and the 88 neutral switch. The donor truck ran just fine before I took it apart.


Ideas guys?


EDIT: It also shuts down, not stalls, just turns off, if I release the clutch.

 

[BRUTUS_T_HOG]

check for power at the red/lt grn wire coming off the ignition switch when you release the key from the start position. it should have power from on to start and back.

if it has power in start, but not run then the ignition switch is probably bad or has a bad connection.

 

[adsm08]

check for power at the red/lt grn wire coming off the ignition switch when you release the key from the start position. it should have power from on to start and back.

if it has power in start, but not run then the ignition switch is probably bad or has a bad connection.

Bad connection maybe, I stole the switch from the 88 column and tried it too, did the same thing. I can rule out a bad switch.

 

[BRUTUS_T_HOG]

are you losing power on that wire? im looking at a wiring diagram for both 87 and 88. there is a splice in the harness that connects the red/lt grn wire to the brn/pink wire for starting. if that splice is damaged it might be cutting the power off of the harness from the switch.

find out if you lose power to the red/lt grn wire at the switch

 

[adsm08]

I have full power at red/green.

I also noticed with the starter out of the circuit (less noise) that even the fuel pumps aren't coming on until the starter enable conditions are met.

 

[4.0B2]

mine did this... it was the wiring harness in the steering column not making a good connection. i ziptied it up.. i'll get you a pic of what im talking about.. its not at the switch but closer to the dash.

 

[adsm08]

mine did this... it was the wiring harness in the steering column not making a good connection. i ziptied it up.. i'll get you a pic of what im talking about.. its not at the switch but closer to the dash.

I'd appreciate that.

 

[4.0B2]

Were they angled zip tie is.. That connection has a broke clip and if you hold it up it runs. But with it not held it just turns over

 

[4.0B2]

That's just to the front of the ignition on the left lower side of the column

 

[adsm08]

Nah, that is the switch itself. The part you actually turn is the lock.

I'm pretty sure my connection there is good, I've had it off and on both switches so many times, I doubt I'd get it only half plugged in that many times. Also, it runs all day as long as I hold the key in start and the clutch down. I can kill the starter and it keeps running fine until I let the key out of run or let the clutch out.

 

[BRUTUS_T_HOG]

thats pretty weird. sounds like that splice has a problem. the red/lt grn wire is supposed to take over supplying power to the ignition coil and TFI module after you go from start to run.

there is a red/ lt blue wire that runs from the clutch safety switch to the TFI module, but i don't see why that would affect it from running when its not meant to have power at all times.

i can post the wiring diagram if you don't have one. without being there i'd have to say its the splice that runs the ignition primary circuit. try to see if you're losing power to the red/lt grn wire at the ignition coil and TFI module

 

[adsm08]

thats pretty weird. sounds like that splice has a problem. the red/lt grn wire is supposed to take over supplying power to the ignition coil and TFI module after you go from start to run.

there is a red/ lt blue wire that runs from the clutch safety switch to the TFI module, but i don't see why that would affect it from running when its not meant to have power at all times.

i can post the wiring diagram if you don't have one. without being there i'd have to say its the splice that runs the ignition primary circuit. try to see if you're losing power to the red/lt grn wire at the ignition coil and TFI module

I have the 87 diagrams and I have access to AllData if I need to see the 88 stuff. They are pretty similar.

 

[adsm08]

12 volts to both the coil hot and the TFI power in with the key in run. Guess the next step is to check power at the computer on the same line.


EDIT: Computer has no power on that line in run.

 

[BRUTUS_T_HOG]

ok check power at the ign coil then. and then find s207 and check it for problems.