850 starts runs 20-30 seconds then dies
 

95 850 Turbo sedan 190k ...
I work in a church garage fixing cars donated cars for people who need cars, and for those who cant afford a garage to fix.
Anyway:
It starts up fine every time runs for 20-30 seconds then dies.
No codes
Fuel pressure measured at rail never drops below 38lbs.
Swapped out all relays at fuse box
Swapped out Coil assembly
Cam sensor reads correctly
Swapped out crank sensor and it runs about 5 seconds longer
Swapped out ECU
Swapped out AIC
Noid light shows injectors working
New plugs and wires etc.
Vacuum hoses look good
disconnected MAF just threw code... everything else same
New ignition switch
NOTE - if I keep pushing the ignition just short of grinding (and sometimes grinding) the starter... it keeps running.

Any suggestions?

Is the ignition switch new or used new? If new new you have a bad wire somewhere.

new switch.... :( but which wire? Documentation shows I need a fancy adapter to plug in to back track each wire to ecu. very frustrating.

This is telling you the problem is in the ignition switch. You replaced the electrical portion, yes? Take it (electrical portion of switch) out of the mechanical portion and see if it still does it (dies). Assuming it doesn't, need the mechanical portion too.

See if this fits the mold.

What GDog said. It would seem the ignition switch is your cause. Either the electrical side isn't making proper contact or the mechanical side is holding it in the wrong position.


Rspi, if it fits that mold what is the cause?

I wouldnt count out that MAF. I had the same kind of problem on the red 854. swapped the maf as a last resort... boom it fixed it

I unplugged a MAF yesterday and one of the pins was corroded. Not sure why but it was. The car was loosing power randomly.

there is something in the metal they used in 94-94 there is a lot of corrosion especially with the T-5R's

thanks for the ideas..
first - new switch / tried running using screwdriver to rule out mechanical/key issue.
second - fuel pressure stays up the whole time, does not drop as in video
third - With MAF unplugged car should start and run in 'limp mode' correct? Car starts just fine runs 20-30 seconds then shuts off.
I agree - may be a bad wire.... finding it is the "B" aaaarg

Not necessarily.. I ran my car for an hour with the maf unplugged with no change.. Replaced the maf and the problems went away

Fixed!
 

Go figure.... Pull the AC fuse and the car runs fine.

If you can pull the AC fuse it might indicate that the AC compressor is internally locked up and once the heater/AC control calls for the pump to kick in and engages the clutch it kills the engine ? ? ? ?

You should reach down and try to turn the outer most part of the clutch by hand. The belt will spin on the bearing so you need to try the thin part of the clutch furthest away from the pump, just past the belt. That is the part that is attached to the shaft and turns with the AC compressors guts.

With the ignition switch instead of "us" thinking it wasn't making proper contact and moving it to the ends of it's travel was restoring proper function it might be that the switch was good and you were moving it to a point where it was disconnecting the offending circuit. :rolleyes:

Also, switch off the A/c in the cabin and do not have the settings on Defrost (or the A/C will come on by itself) then put the fuse back in and start the car. It should run. When its running turn on the A/c and see if you can then reproduce the issue.

No belt on the AC right now.
I did try with the AC switch off
Tried pulling that local fuse on the A/C no luck,
Tried unplugging AC (coupling on the compressor) no luck.
So now I'm pouring over the wiring diagrams.... looks like the security is on that circuit?
Thanks for the suggestions.

final fix
 

After going over the wiring diagram I found that there is an AC sensor just there behind the right front headlight. Disconnect that and the car runs fine.
I'm buying a short belt to take the AC compressor out of the loop and it's a workable car.

Go figure!

Thanks for all the suggestions etc.