Mike S

Small engine fire that made most of the wiring harness heat shielding crispy but the wires inside appeared to be fine. At the time of the fire I checked all the wires I could and everything appeared to be functioning.
Here's what I have so far:

No start condition on a known running car prior to the fire:

1) Checked resistance of Reference and Speed sensors....both are good according to Clark's garage.
2) Have fuel pressure to rail
3) Didn't have spark initially, however I found a small short on the speed sensor that I have now fixed (pulled the wires apart so they're not shorting for a temporary fix), I now have spark
4) Tach is jumping when cranked
5) MAP system shows 200-300RPM when cranking
6) Have voltage changes on the TPS according to the MAP system (i.e. pushing the gas pedal makes the voltage change)
7) Power to DME verified
8) Power to MAP system
9) Plugs are wet so theyre getting fuel

At this point I'm wondering if there's a short on the reference sensor.

If I have spark does that rule out the Speed sensor?
Is there a way to check at the DME for Reference sensor operation?

Bill

Mike,

You need three things to make an engine run:

Fuel
Compression
Spark

If you have spark at the plugs (pull plug, ground, crank, see spark) then your ignition system is ok. The spark plugs are the end of the line of the ignition system, look elsewhere. Double check the firing order on the plug wires though.

Do you have injector pulse?

Mike S

Yep, that was the theory I was going on but it looks like I may not actually have fuel. I have compression and spark. I have fuel at the rails, but when I put a test light to the fuel injector wires they all light up on either pin of the fuel injector harness. Is this normal?

The reason that I ask is that I just pulled the fuel rail and it looks like the injectors aren't firing.

Mike S

Looks like I found the problem! I used a test light and didn't notice any pulsing to the fuel injector wires. I peeled back the insulation on the #1 fuel injector wire and found that the insulation had cracked and the wires were shorting. I pulled the insulation off the reamining wires and all showed the same thing. Looks like the heat from the fire must have brittle the wires inside and cracked the insulation. Looks like i'm off to rebuild a fuel injection harness.

Bill

As I suspected. Check all affected wiring with a fine tooth comb. Would hate to kill the DME by shorting it. Congrats on the fix!

Sam Lin

It probably wasn't the fire, but the force of the extinguisher - my stock injector wires are identical, try to flex them and the insulation shatters, and that's just a result of 15 years in AZ heat.

Sam

Dan87951

I would install a new harness if I were you. Sure would hate to have the DME and KLR short out on you. I had to install a new harness in my 87 951 because it was old and brittle and the Speed and Reference sensors were shorting out. We did the install in about a day. We took our time and organized everything and had a few breaks in there but it can be done fairly easy. I have a feeling if you just keep temp fixing it that you will have bigger problems a head.

Mike S

Do you have a source for a new harness or would I just have to buy one off of a salvage yard?

turbite

Good to hear that your fire didnt cause major damage!

Claus Groth

If you want to replace only the injector leg of the harness, I can check this evening if the one that I have is in good condition.

Mike S

Looks like I need a whole new harness. I got the injectors firing but the car won't stay running. It starts for a split second then dies. The speed sensor wiring is really crispy. I pulled part of the wires apart and fixed a small short, but the rest of the wiring is shielded and I think its been damaged.


Anyone have a lead on a new harness for the car?

turbite

I have a spare 86 harness I think.
I'll check when I get home.

Mike S

Will the 86 work? A couple of salvage yards have told me that the 86 harness is different. I know the 87 has airbags and ABS but i'm not sure if that plugs into the DME or not.