96 850 Turbo Wagon - No Start, Wiring Harness Issue

bnzelener · Post by **bnzelener** » 26 Sep 2015, 10:51

Hi all!

About 6 weeks ago I made a foolish mistake and tried to jump my 850 off another lead acid battery I have. I connected red to red and black to black on accident for a moment, and fried a wire going to my wiring harness. Was able to get everything working with replacement fuses EXCEPT my windows and sunroof. So I pulled out my wiring harness (removing a bunch of relays in the process) and spliced the incoming hot wire from an unused circuit breaker spot into the incoming for the power windows.

That worked! I had windows and doors back. I plugged all my relays back in and booted the car. The lights for ABS, SRS, and Traction Control were on, and my radio and AC/Heat/Fans had no power. Crappy, but the car still drove and had power windows, so I used it for a couple weeks as was.

Last night I decided to pull all the relays again and put back to see if I could get my AC and radio back magically (that usually works, right?). Well, good and bad news. My radio, AC/Heat/Fans seem to work great, but now my baby doesn't start. I get plenty of crank but zero start. We pulled out a spark plug to check and it looks like there's no spark happening.

I've now pulled out and put back the relays 3 or 4 times, just blindly hoping she'd start again, but no love. I have a multimeter and I'm ready to start testing, but I need some educated insight on where to begin. I've read a lot about the Cam Position Sensor causing the no spark - but I doubt mine went bad instantly when I started working on the car...

Any pointers are greatly appreciated!
Brennan

bnzelener · Post by **bnzelener** » 26 Sep 2015, 11:48

Another strange thing to add to the mix - right now when I turn the key into ACC position 2, I don't get any feedback from my gas tank gauge. Could they be related?!

bnzelener · Post by **bnzelener** » 26 Sep 2015, 16:10

Still trying multiple attempts at removing the relays and re-connecting but no luck yet. Anyone have suggestions of what to test or where to look on the wiring harness?

Thanks!
Brennan

bnzelener · Post by **bnzelener** » 28 Sep 2015, 09:24

Hi folks! Bumping on this again to see if anyone has suggestions. Thanks!

Post by **mecheng** » 28 Sep 2015, 10:16

is your fuel pump relay okay? yes your cam position sensor can go bad at any time.

bnzelener · Post by **bnzelener** » 28 Sep 2015, 10:32

I *think* the fuel pump relay is okay. Is there a simple way to test it? And is there a simple way to test the CPS?

bnzelener · Post by **bnzelener** » 29 Sep 2015, 21:14

Hi everyone, is there a simple way to test the fuel pump relay in the Volvo 850?

Thanks!
Brennan

Post by **erikv11** » 29 Sep 2015, 23:00

Yes, you can "jumper" the relay i.e. put in a wire from pins 15 to 87 to bypass the relay and see if the pump turns on. If you search you will find dozens of posts about it; probably Robert's video explains it well (I haven't watched it but they are usually good!):

bnzelener · Post by **bnzelener** » 02 Oct 2015, 16:43

An update here. I tried jumpering pins 15 and 87 and my fuel pump does not run. It looks like power is not getting to the fuel pump relay somehow.

My inclination is to take out the wiring harness, but I can barely raise it 6" out of the car before tugging on most of the wires. That's probably how I got into this problem in the first place.

Has anyone removed or taken apart the wiring harness on an 850 and lived to tell the tale?

bnzelener · Post by **bnzelener** » 02 Oct 2015, 17:18

Progress abounds. We discovered that there was no power going to the Fuel Relay fuse. Jumpered the fuse and the fuel relay works! However, the car still doesn't start.

When the key is in the accessory position right now, I'm not seeing power on fuses 2,3, and 4. Which are the Fuel Pump, "Courtesy Lamp Control Signal", and Immobilizer in that order. Trying to jump all of those fuses to test if she'll run.