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timc timc is offline
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Join Date: Oct 2006
Location: Chas, SC
Posts: 1,045
This is the infamous Lee Rice mod that apparently puts an end to the FP Fuse/relay problems.

930 fuel pump relay wiring - once and for all

Also, had some problems with the relay under the seat, and my brother took the time to read thru the FSM wiring diagrams to explain how it all works:

my explanation to tim on how it worked:
look at the fuel circuit as 2 seperate circuits. one is the 2 FP relays, the yellow relay(contacts), the rev limiter, and the pressure switch. the other circuit is the yellow relay(coil) and the AFM switch.
the AFM switch removes ground from the yellow relay, de-energizing it when the engine is running.
the FP circuit gets its ground through the contacts of the yellow, then the rev limiter then to the pressure switch.
all the yellow relay is doing is energizing the 2 FP relays. the yellow relay is also (?) what gives the 1-2 sec FP run before starting.

to trouble shoot: no particular order.
with key on
1 ground the wire at the pressure switch. FP should run
2 remove the connector on the AFM or push down on the plate to energize the yellow relay. FP should also run.
3 check for power and ground on the connector to the AFM.
4 jumper pins 30 to 87a on the YEL realy:
the FP relays should energize
power on pin 1 of the rev limiter
power on the wire going to the pressure switch. (wire removed from switch).
(if there is no power on this wire, but there is power on pin 1 of the rev limiter, the rev limiter is bad)
5 jump pins 30 to 87 on both FP relays to test FP's

( this is assuming fuses and wiring are good)

you can really start anywhere.

i am not a 930 guy, this is just based on the drawing and what little i have done on tims car, mostly over the phone.
1986 930
Gone:71,2,4 914's, 70T, 71T(RS),77S

Last edited by timc; 08-05-2011 at 05:40 AM..
Old 08-05-2011, 05:36 AM
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