News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

77 Seville, External Fuel Pump Relay

Started by Jasperwashere, May 06, 2022, 09:40:34 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Jasperwashere

So I ran into the issue of my fuel pump not working which I narrowed down to the relay in the ECM failing. So I came across this method to wire in an external relay as seen in the picture below. After getting it hooked up, the relay did not trigger.

It's getting power from pin H, but no power from Pin J/C which act as the trigger wire in this set up. Pin J and C are wired together with 85 on the relay.
Can I just grab something else to use as a trigger wire? Or else is this repairable?



bcroe

#1
The fuel pump circuit is a weakness.  Running current to
2 pumps can strain the ECU relay, the circuit board traces,
and the connector pins (the most common failure).  There
is a tendency for that  relay to vibrate in some situations,
causing more wear. 

The external relay will generally avoid the stress on the
ECU.  It could in theory burn out, but burning a cheap
generic relay is much less of a problem that burning out
a rare, expensive ECU. 

If your ECU internal relay has already burned out, it needs
to be replaced.  That relay is still available new, I have
replaced many.  But there is also an ECU circuit that triggers
the relay when the engine is turning, this is another failure
possibility, not so uncommon.  For a 77 Seville, that circuitry
is on a big 2 in X 3 in ceramic.  In those cases, I add a simple,
one transistor rotation detection circuit, to save all the rest
of the stuff on the big ceramic. 

I have repaired all these problems, usually for less than the
postage.  The vibration issue gets fixed at the same time. 

Bruce Roe 79 Eldo EFI owner since 1995    bcroe@juno.com