Thursday, January 08, 2009

Green Cheese of Death

If you've worked on cars long enough you have encountered the "green cheese". Other people may have a different term they use, corrosion comes to mind, my favorite is people that use scotch locks to make electrical connections which will always be guaranteed fail and I kindly refer to them as shit locks because your always going to end up in it using them.

The wonderful part about the green cheese is it normally causes headaches, frustration, anger and a overall pissed off attitude about electrical problems on cars. I'm sure the seasoned veterans that may spend time reading my rambling thoughts are nodding in agreement and know exactly what I am talking about.

This particular case in point was on a 92 Chevy 2500 4x4 5.7L with a "cranks but won't start". On arrival we verified it had good spark and injector pulse but no fuel pressure. I went underneath with a test light and verified I had voltage. Mind you, I didn't say battery voltage. With that I assumed we had a dead fuel pump. We dropped the tank, removed the rusted sending unit and pump and then bench tested the pump after removing it. Nothing, the pump wasn't responding to any voltage sent to it. Case closed right? Wrong. We installed a new pump and sending unit. Plugged the tank back in, cleaned and tightened the ground and then fired the truck up. It took off right away. We figured we had it licked. I backed the truck out, let it warm up and then took it for a test drive. Everything seemed fine until I returned. I shut the truck down and tried to restart it, nothing. It then restarted, ran for awhile and started running "rough" and died.

Oh crap.....

We brought it back in and I again checked for voltage going to the pump and I had it. But again, I used a test light. Then a little bulb (or my common sense) went off and I said to myself "How much voltage?" Upon checking with a DVOM I only had 7 volts. Off to the races and I started checking the wiring where I found this little monster in the harness











The Green Cheese. I spotted a section that was repaired at some point. It was about halfway between the firewall and tank. It was also placed back in the harness and the section looked unmolested. I just happen to start testing and spotted it. What happened? Someone repaired a section of wire by just wrapping the two wires in tape. No solder, no heat shrink, nothing.

I cut the section out, repaired it properly by soldering then heat shrinking it and then dropped the truck down and it fired right off and ran perfect. A constant battery voltage at the tank. I suspect the pump has been fighting for its electrical life for awhile since it hasn't been getting good voltage I would assume and then it finally had enough and died. My taking the tank down most likely stretched the harness to the breaking point. It had enough to start and run but then after a rough drive it just gave up. I'm just happy it happened for me and not after the customer took it. That's why test drives after the work is done is just as important. It's not just me going for a joy ride ;)

Lesson learned for me, trust, but verify. I should have grabbed the DVOM to test for voltage but the test light is always fast and handy. The only problem is if you don't have a full 12 volts the test light can still light up. Mine will at 7 volts :) I think it means time for a better test light, one that is not going to lead me astray again.

Anyway, there is the green cheese. Remember it, hate it, do everything in your power to stop it before it drives you nuts.

I do deserve the Miller Lite tonight.

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