924Board.org

[FASTdan]

Hi Chaps,

I have been investigating the reasons behind the fuel pump not running over the last few days after purchasing a new relay (993 item) because the old one was missing when i bought the car.

It seems that the 2nd switch in the relay is not activating because pin 9 (which i believe should be permanently grounded) is switching to live on the turn of the ignition key. Because of this the 2nd switch is not closing and therefore i get no voltage at pin 4 - if i bridge 2 and 4 the pump works. I am getting power at pin 8 as expected when i turn the key.

Tracing pin 8 on the wiring diagram this appears to run to pin 20 on the DME unit. Therefore I have since tested all pins on the multiplug that should be grounded - eg pin 19, 17, 16....among others. All these appear to be grounded fine. This tells me that my DME unit is grounded ok, though i am no electrical engineer!? So, the question is, would this point to dry joints in the DME unit? OR am i on completely the wrong track?

I am right in thinking that the fuel pump should run when the key is in the 2nd position right? because someone did suggest to me that perhaps the ECU doesnt want the pump to run and therefore provides 12V to pin 8 on the relay....but i am thinking the pump should run at this point...

Any help/advice much appreciated, cheers!
_________________
1980 924LUX

[Paul]

Try this:

http://www.clarks-garage.com/shop-manual/fuel-05.htm

http://www.clarks-garage.com/graphics/dme-na-1.jpg
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Paul]

The last section of this will help later in the process:

http://www.clarks-garage.com/shop-manual/eng-15.htm
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[FASTdan]

thanks Paul, that site is brilliant isnt it!! Cant believe I've missed it till now!
_________________
1980 924LUX