94 Caravan - fuel pump won't run

Grounds are good, but no power on pin 3 with key on.

I agree with D.S., trace the Red/White wire back to the battery. Looking at
the 1991 wiring diagram, I'll bet it's very similar with the possible
exception of a fuse instead of a fusible link. It should be powered at all
times, not just when the ignition is on. The diagram shows that pin #3 has a
red/white wire that goes back to a 22 gauge white fusible link, then changes
to a 10 gauge red, then to a junction at a 6 gauge black (battery feed).
Trace it back and find where you're loosing continuity.

 

It may have been mentioned already, but I can't find it in the
old posts. Which engine is in this thing?

I'll print the wiring diagram and post which pins have battery
voltage and which pins are powered by the ignition switch.

But I need to know which engine for your benefit so you don't go
on a wild goose chase.

 

He's got the Mitsu 3.0

 

It's the 3.0 V6, 2WD.

Thanks for the help.

KC

 

Okay, a 3.0 it is...
Pin 3 gets 12 volt battery feed via the 15 amp 'engine' fuse in
the underhood power distribution center.
This should be 12 volts all the time.

Pin 9 is 12 volts ignition feed (ignition switched) via the 10
amp #16 fuse in the instrument panel fuse block.
This should be 12 volts with the ignition in the start or run
position.

Pins 11 and 12 are power grounds.

 

It's supposed to be above 5 degrees this evening, so I'll try to get
back to it. I seem to remember at least 2 other pins being switched
12V, though - maybe like 31-32, or 32-33? It sounds like pin 3 is the
problem child, though.

KC

 

Pin 31 is 'Low speed fan relay'.
Pin 32 is empty.
Pin 33 is for 'cruise control'.

If pin 3 is dead, and the engine fuse in the PDC has no voltage
on either side, I'd be checking inside the PDC for a broken buss.

 

Check the ignition switch, check the bulk head connector, for 12 volts on
both inside and outside of it,

 

The ignition switch has nothing to do with B+ voltage on pin 3 of
the PCM.

 

Found it. The red/white wire feeding B+ to pin 3 of the SBEC was
corroded badly about 5 inches from the SBEC. I was pulling on it to
get a little slack to jumper it, and it broke. Green copper doesn't
conduct well, apparently. Strange place to corrode, but there it was.
I jumpered it to the correct fuse in the box (soldered, heatshrinked,
and taped), and it started right up.

Thanks to all you guys for the help, especially Daniel Stern and
aarcuda. Trying to fix electrical problems is next to impossible
without the factory wiring diagrams. Plus, a logical approach to
troubleshooting really helps.

Signing off for now
KC

 

Excellent!