Factory alarm ignition kill?

[911cab_84]

I am having a long standing intermittent starting problem on my 84 carrera. Hot or cold, it will give me full lights and I can hear the relay clicking - but no start.

I would like to know if there is a process in which to begining to eliminate potential things (ie, ignition switch, alarm, etc). Does anyone know where the factory alarm ties into the system?

What are the relays directly behind the dash in the front compartment? The middle relay is getting very hot, so I pulled it... but it didn't have any effect on my starting problem.

Also -I have a black box in additon to my dme under my seat that I can't identify. about 4x6x2 inch black plastic box with 5 wires running into the dme. It looks aftermarket (with electrical tape) , although I am the only owner.


Have:
Replaced Battery - 12.58v at posts engine off. 14.08 engine on
cleaned all contacts
replace battery ground cable
replaced transmission ground strap
replaced starter and solenoid
replaced dme relay
cleaned 14 pin in rear

Thanks in advance. Any help would be greatly appreciated. I'm about to mount a remote starter and get back on the road.

[targa80]

I don't know if the 84 alarm system is the same as what is on the 1980 SC. On the 1980 there is a key shut off switch on the door about 4~6 inches above door latch. there is no remote control for the alarm. To disable the alarm on the 1980 model you need to remove the carpet and the luggage trim board in the luggage compartment. This is the area just under where the wipers are located. Remove the fresh air blower and behind it is a module with 2 plugs on it. one of the plugs has 8 contacts. remove this plug and jumper the 2 terminals marked 61 together on the harness side connector. This will disable the alarm system and prevent it from shutting down the fuel pump. Hope this info helps. As I said it is for the 1980 SC

[911cab_84]

Thanks Pat. So on the SC, it disables the fuel pump? I wonder if on the Carrera the factory alarm just has some kind of ignition kill only, because the car is fine if I push start. I just can't get my starter to fire (occasionally)

[Early_S_Man]

Mike,

Does the 'mystery' box under the seat have the mfr markings ... is it made by Hella? Size sounds too big to be a factory alarm unit by Hella.

One of the few electrical items that the Bentley manual documents well is the factory alarm unit.

[Lorenfb]

Porsche did not have any additional boxes under the drivers seat like
you describe. This is aftermarket and probably shuts down the DME,
but your engine should still crank.

The no crank situation results from;
1. a weak battery,
2. a bad starter solenoid or a bad commutator on starter
3. the ignition switch does not provide enough voltage to the starter solenoid,
4. your aftermarket alarm prevents the ignition switch voltage from
reaching the starter solenoid.

Good Luck
Loren
'88 3.2

[911pcars]

Your open circuit voltage reading appears weak. You might have a borderline battery or one that is discharging by a parasitic current draw with engine OFF. Check battery as well as current draw from car circuit with all systems OFF.

Sherwood Lee
http://members.rennlist.org/911pcars

[911cab_84]

Ended up being the ignition switch not always engaging the starter at keyturn. Replaced the whole thing. Good to go. Thanks to all for their help.

Also, regarding the mystery box under the seat, some who have inspected think it is O2 sensor related and added when imported in 84.