Re: no power to fuel pump

[Audinamx@aol.com]

<< I need some help regarding a fuel pump problem, I can't seem to get
 consistent power to the pump through fuse #13. I hooked up a light and
 noticed that when the light goes on and power is sent through the fuse
 the car starts right up and runs fine.  It just is not consistent... Any
 ideas???
  >>

... I checked the '87-'88 5kTQ wiring diagram in the Bentley.  I was 
surprised to find that the fuse (S13) is actually in the circuit AFTER 
the fuel pump relay!  This means that there is no protection for the 
FP relay itself if the output is shorted to ground before the fuse ... 

I'd say that you've got one of 2 problems, ranked in my estimate of 
likelihood ... 

   1) poor contacts in the FP relay
   2) The ECU sees something so bad that it decides to shut down 
the FP relay

If I had this problem, I'd open up the FP relay and check the relay 
contacts, burnishing them if they looked like they were oxidized/
pitted.  If I could scrounge up another relay I'd probably test with 
that for a while.  If that didn't do the trick, I'd run the ECU output 
diagnostics [activated by inserting a fuse in the top of the FP relay 
when the ignition is on but the engine isn't running] and make sure 
that the ECU was controlling the FP relay properly.  The diagnostic 
procedure works on the '87-88 5kqs ... actually it probably works 
on all 5kTs with the MC engine ... and is well described in Bentley.  

Good luck Jon!

Steve Buchholz
San Jose, CA (USA)