F-body-fan

Hi Guys, I picked up an 89 Z earlier in the week that has been sitting for about a dozen years. 5.0 TPI automatic. Years back the car wouldn't start & the owner figured out the ECU was bad. He replaced it & the car started up & ran fine. Very next day, the ECU was out again. He looked everywhere for a short & couldn't find anything suspect. Tried another UCU. it ran again, but the following day it was fried once more. So the car was parked for a decade until now.


I bought the car not knowing what I would do with it (and I still don't)
But I thought just for giggles I might see if I can get it running. Engine spins over free, but as I was told the ecu that is in there is bad.


I did a little searching on the forum & it doesn't look like that's too common of an issue, so I thought I would see what I can trouble shoot before tossing in an ECU & experiencing the same the guy before me did. Easy enough to test the resistance on all the sensors, injectors, etc. But I am not sure where to look to find a baseline on all the peripherals. I work in electronics for a living so I have just about everything I should need to test things, but don't want to start blind.


Thoughts?

Tuned Performance

iTrader: (92)

What's going out the injector driver ? Bad injectors maybe
The grounds are behind the passenger side head.
http://www.gearhead-efi.com/Fuel-Inj...Information-6E

F-body-fan

It will communicate with my solus, but I thought the RPM's were a bit curious...
Pretty sure that's over redline




.

F-body-fan

PO told me it lost spark, but could be the injectors, or both I suppose. I will put a noid on a injector & check for spark too. But when I saw the RPM listed above, I knew something was wrong. lol

Tuned Performance

iTrader: (92)

Rpm seems legit lol
I've never seen a icm wipe out a ecm but if it's loosing spark I'd think icm or pu coil.

F-body-fan

Well..... maybe I should trouble shoot myself before asking too many questions...

Put a noid on the injector wires & I had good pulses, Hmmmm, checked the spark & yep, there was spark. So, I direct wired the fuel pump (I unplugged it before cranking it) pumped out all old fuel & added a few gallons of fresh fuel. Starts & runs with either starting fluid, but no fuel being injected to run on its own. 40 psi at the rails so that seemed good. Hooked up a pulse tool & all 8 of the injectors are stuck. no noise, no loss of rail fuel pressure during a 50 pulse test. resistance is at 16 ohms +/-

I am going to guess these injectors are stuck from just sitting but I am not sure. Just a guess.
Weird that all 8 are are stuck.

F-body-fan

Pulled the injectors last night. 7 of the 8 injectors came free with a light tapping while cycling them with a pulse tool.
#7 injector did not & I also found it at that time to be nearly shorted internally at only 1.4 ohms. would that take out an ECU? awfully close to a dead short at that low of resistance.

Tuned Performance

iTrader: (92)

I'm not sure if 1.4 ohm would wipe out the injector driver or just shut it down.
https://www.southbayfuelinjectors.co...tors-1985-1992

F-body-fan

Injectors have been cleaned & bad one replaced. It starts right up & runs very nice. Solus now reads the right RPMs, but the tach is about 3X off. says 3000 at idle.
Thats odd.....