Fuel pump relay....RPM limits

["Barry P. Lewis" <barry@ctron.com>]

For those of you that wanted a reversed engineered Audi fuel pump relay,
RPM limit circuit, here some of it. Does anyone know what the MC14538 is?



         ---------------|  ---------------------
        |               |  |                    |
        |      16 |  |  |  |  |  |  |  | 9      |
        \        -------------------------      \
   100K /       |     MC14538             |     /  37K
        \       |                         |     |
        |        _________________________      | 1 uf
        |        1|  |  |  |  |  |  |  | 8      | 
        |------------|--|_____|     |___________|_| |_____ gnd
                     |     |                      | |
                     |     \
                     |     / 120K 
                     |     |
    gnd   ----| |----|- /\/-  
              0.1 uf

The ignition pulse seem to come in on pin 10. Pin 4 goes to the relay coil.
Pins 1, 8, 12, 15, and 16 are connected to a common ground.
Pins 6 and 9 are not connected to anything.

It appears to be a timing circuit. Probably changing the 120K or the 37K
resistors (or the caps) would affect the RPM limit.

If anyone has any info on the IC, let me know.

Barry
'86 4000CS Quattro