No crank condition

[Redrocket06]

Car started and drove fine to work and back home. When I got home I forgot to cancel out of the datalog I was doing on the SCT, not something I haven't done before. I was on graveyards so I got home around 7am, at 4pm I went out to start it and it had dashes on the mileage readout and then it changed to 'check charging system'. The pump never primed and keying to start did nothing, no click, nothing. Checked voltage it was 12.2, jumped it off of my truck with 14.2v and had the same results. I checked all fuses and relays on the BEC and SJB, blew them all out with air to look for moisture getting in them. Now the strange thing it I can plug in my SCT with the FireWire that lets it read my LC1 and it will start but run real rough and the pump volts read 0 to negative 2. After fiddling with the fpdm it lined out, turned it off and restarted with the same rough idle and messing with the fpdm did not help this time. I tried a different relay than the one that came with the pump wire upgrade, no change. If I just plug in the SCT without the FireWire it will not crank. With the key on and only the sct plugged in the sct will not power on unless the firewire is connected, key off it will power on without the firewire. Also tried starting with maf unplugged, all gauges unplugged from 12v power, same thing with needing SCT plus FireWire to start and run like crap. While running, unplugging FireWire results in engine turning off.

Tomorrow I want to pull the battery and alt for testing and unwire all my addons that the car doesn't need to run and see if something is grounding out.

Any ideas will be helpful.

 

[lito]

Check for power to the PCM fuse, PCM relay, etc.

Whenever you put the key on and it shows the mileage really quick and then dashes is that the IC is not reaching the PCM, usually is power.

 

[Redrocket06]

Took your advice Lito, spent some time checking the PCM power circuit in the BEC. everything in the BEC is good. Only strange thing was with key on and fuse F40 pulled out I get 12.3V on the relay side and 8.5V on the other, with fuse in it sees 12.3V.

After that I keyed it on and started wiggling harnesses. When I wiggle C175B on the PCM the pump primes and all seems well, then back to crapped out again. So I have a short in the harness. I have verified pim 35 and 36 on C175B are good, but can't get pin 37 to show continuity from the PCM relay pin 85. Wire diagrams show it to be pin 37, but I have no wire in 37. There is a brown with pink stripe in pin 40 (no continuity) and pin 47-50 all have good connections to PCM relay spot 85. Going to work some more on it tomorrow.

 

[Redrocket06]

Looks like I found something. 85 spot on both PCM and fuel pump relay in the BEC go to C175B connector on the PCM pin 47-50. There is a short in those wires, all 4. Moving the harness makes the continuity test go true/false. Just have to hunt down the bad section.

 

[lito]

I don't know if you already disassembled the BEC, there is a typical issue with the FAN power lines melting, I've seen two cases where this induced issues in the body harness part that goes to BEC and inducing PCM and fuel pump issues too.

 

[Redrocket06]

You were right on with PCM power issue, thank you for the guidance. I narrowed it to the grounding splice that those C175B grounds go to, before I started stripping the harness back I went to unscrew the bolt that grounds all them to the chassis, damn thing was finger tight. I havnt messed with that bolt for months! But it worked loose. Cleaned the contacts and tightened it down, also had to replace the fuel pump relay, it was bad too. Everything works now, car started right up without the SCT and FireWire. What I think was happening was the pcm was using the firewires ground back to the battery but it was too small of a ground while it tried to run, along with a bummed pump relay.