3.0 liter doesn't start

[mb911]

I have been doing a conversion putting a 81 sc motor in a 77 chassis. For the most part everything is straight forward. My question is what would cause no accessery power in the engine compartment? I have 12 volts all the time but the ignition or accessery 12volts does not kick on. Every where else in the car it does. I checked the 3 fuse block in engine compartment and nothing. I should mention that I disabled a alarm system from it the day before this happened. Any guesses?

Ben
77 911 3.0
75 914-6 2.7

[ruf-porsche]

The alarm system might had a relay to prevent power going to the ignition circuit and starter. How did you disable the alarm? Factory alarm?

[mb911]

No just some piece of junk that some one put in. I don't think it worked but I guess I could be wrong. All I did is cut it out with a wire cutters. Is there a junction block or something for the engine compartment? I looked at the wiring digrams with no luck. The starter runs fine and the car will start right up if you power the accessory wire with 12 volts. The majority of the alarm parts were under the clutch pedal wraped in two roles of tape (approx). The major problem is the owner before me is un willing to help in any way or he may be able to clue me in as to how the alarm was installed. If you can clue me in on were to start looking for the leads that go to the engine compartment I can figure it out "I think". I am not familer with were the wire looms are on the 911 but surely could tell you on a 914-6. I asume I am looking for the red/white wire?

Thanks
Ben

[ruf-porsche]

If you don't have an electrical diagram for your car try this link. If you are familar with Porsche electrical you should be able to trace the circuit for the 3 fuse panel in the back of the car.

http://www.pelicanparts.com/911/911_Parts/911_electrical_diagrams.htm

See if you can contact Targa80 he's pretty good with circuits. And he's a great guy when it comes to helping out fellow Porsche owner.

[mb911]

I have tried looking at that and can't tell where everything is located on the car example being routing of wires. I tore the back seat out nothing. I do believe it to be the red/with white tracer but don't know how to get at it. This is getting to be something like when you just want to bring it out to the curb for the trash man. I know a little extreme but how bad can the project get? Thanks for the suggestion
Ben

[ruf-porsche]

Ben

If you have the Bentley manual for a 78 to 83 SC on Page 970-4 it shows the power distribution. I hope that your 77 is similar to my 82.

The rear power is feed from the ignition switch, color is red/black.

The following accessories are also powered with this feed

fuse 12 25A
Fresh air blower (I assume that the one on the left side of the engine and not in the front trunk)
Rear window defroster

There is a connection between fuse 12 and fuse 11

fuse 11 16A
Back up light
Hazard Flasher

Fuse 18 is also jumper to the red black wire
fuse 18 25A
Fuel Pump Relay
RPM Limiter Switch

Fuse 22 is also jumper to the red black wire
Fuse 22 25A
Heater Ventilator Relay

The Electronic ignition system is also feed with the red/black wire from the ignition switch.

I think what might had happen is that the alarm was spliced into the red black wire from the ignition switch. When you cut the alarm wire, the red black wire became an open circuit.

I would check the ignition switch and locate the red/black wire and see if any of the old alarm wires were splice into the redblack wire.

If you don't figure this out by Monday, I will bring my manual to work so that I can scan the diagram for you.

Since your car is a 77 the color might be red with white tracer like you indicated in your previous post. Maybe some earlier owners has the Bentley manual and can verify this.

[ruf-porsche]

Ben

Check where the old alarm wires were splice into. Perhaps you can tell if they cut the original harness.

[mb911]

Thanks ruf-porsche it is exactly as you thought. Right behind the pedals they spliced in and that was the problem. Thanks so much maybe someday I can return the favor.

Ben

[ruf-porsche]

Hey Ben

Glad to hear that your car is running again. If you live in Burlington WI and attend some Road America Events perhaps we can get together and talk about Porsche over Brat and Beer.

[mb911]

Sounds good to me I am on the way. You could stop up on your way or what ever. Shoot me an email when your in the area. bimn@genevaonline.com Hopefully I will have my wifes 911 running great by then. I have often thought about running up there .

Thanks
Ben