Alarm Removal; '86 930; Fuel Pump Runs Continuously

spoke · 07-15-2018, 06:43 PM

I've owned my '86 930 for almost 10 years and never activated the factory alarm with the key in the driver door. This weekend, the alarm would sound if I opened the door all the way and sometimes as I'm opening or closing the door. Chances are the wires in the door hinge are broken and with the door open causes the alarm to sound.

I decided to remove the alarm completely and followed the jumper arrangement mentioned in many alarm threads including the 2 below.

I jumpered 61-61 and K1/87A-15. 61-61 powers the GEN light and K1-15 powers the DME.

One side affect now is that the fuel pumps run continuously. Likely the alarm provides power to the DME briefly after the key is turned to start and then removes power.

I believe the alarm parallels the airflow switch in the intake only activating when the car is being started. This is why the alarm doesn't disable the car once running and the pumps will stop if the engine stalls or doesn't start.

Has anyone seen the pumps running full time after removing the alarm?

I like the pumps not to run if the engine isn't running and thinking of putting the alarm back in but cutting the wires to the door switch and adding the correct resistance to fool the alarm that the key is off and connected.

What resistance is the switch when off?

TIA,
Spoke

911 sc alarm bypass

Alarm going off - AFTER bypassing

spoke · 08-17-2018, 05:21 AM

I found on other threads and by measuring the switch resistance of 4.6k ohm with the switch off and 3.5k ohm with the switch on.

I didn't like the fuel pumps running continuously so I disconnected the one wire from the switch (the other wire is ground) and installed a 4.64k ohm resistor right by the alarm. Now the fuel pumps only run for a second when the key is turned on and they stop running if the engine dies.

T77911S · 07:08 AM

i really have not looked into the alarm system on these cars yet so I don't know much about it.

first, you don't have a DME. those threads are for EFI fuel systems that have a DME.

look at the sticky at the top of the page and go near the end and look for my post explaining how the fuel system works..

how or why the pumps run without the resistor I cant tell ya. actually from what I understand about the alarm if anything the opposite should happen. the resistors are there so that if anyone tampers with the alarm the alarm should go off, disabling the car I would think. running the pumps all the time does not disable it.

from what little I have looked at the alarm it gets a signal from the tach output from the CD, which of course also goes to the speed relay to cut the pumps for the rev limiter.
this is an assumption, but I am guessing that the alarm can also disable the FP thru the speed relay. this cant run the FP but it can stop them.

I have said this before, I really need a good clear set of diagrams for the 930. I could really help out a lot with electrical if I had a good set.

HA!!!
I have learned something new.
the alarm DOES indeed parallel the AFM SW. THAT is how it disables the FP to kill the car.

I will go back to what I said above. if the resistors are no there then the alarm should KILL the FP, not run it.
also, if you have the alarm module unplugged how is it doing anything?

spoke · 08-20-2018, 07:12 AM

I didn't see a connection to the tach for the alarm. There is a connection to the GEN light, a switch in the front trunk, and the alarm key switch.

The alarm does shut off the fuel pumps but not sure how it does that. With the alarm disconnected, the car won't start. There's relay contacts in the alarm which when jumpered, allows the fuel pumps to run full time.

The issue with the alarm is a common one where the wires to the key switch in the driver door break after a lot of use and the alarm goes off. I've seen resistances at the alarm of zero, infinite, and the expected 4.6k or 3.5k depending on switch position.

Your comment about obtaining wiring diagrams is on top of my list of stuff needed. Does anyone sell the wire diagrams for the 930?

T77911S · 08-20-2018, 07:15 AM

I cant read the pin numbers very well on the diagram but if you jumpered B7 and 15 that will run the pump all the time.
I think 15 is 12v and B7 is the OB rly.

spoke · 08-20-2018, 07:17 AM

Quote:

Originally Posted by T77911S

I have said this before, I really need a good clear set of diagrams for the 930. I could really help out a lot with electrical if I had a good set.

HA!!!
I have learned something new.
the alarm DOES indeed parallel the AFM SW. THAT is how it disables the FP to kill the car.

I will go back to what I said above. if the resistors are no there then the alarm should KILL the FP, not run it.
also, if you have the alarm module unplugged how is it doing anything?

I think we had our signals crossed as I agree with the resistors of the key switch either open, shorted, or the wrong value, the alarm will activate and the car cannot be started.

BTW, what wire diagram are you looking at? I'm looking for the official diagram for my '86 930.

spoke · 08-20-2018, 07:20 AM

Quote:

Originally Posted by T77911S

I cant read the pin numbers very well on the diagram but if you jumpered B7 and 15 that will run the pump all the time.
I think 15 is 12v and B7 is the OB rly.

I think that's the pins. Many threads about the 911 say to jumper those 2 along with the 2 for the GEN light. Pump runs all the time which I do not like. The alarm is back in the system with the key switch wire cut and a 4.64k ohm resistor installed to ground right at the alarm.