[xj] Bypassing "main" and "pump" relays for testing, was 1985 XJ6 will start, won't run

Here’s a tip which may help Mr. McCoy or others.

If you’re stuck by the roadside with a dead relay or want to eliminate the
relay for diagnostic reasons, here’s how to do it. Dirt simple. (Series III
XJ6, BTW)

“Main relay” this is on the firewall and provides voltage to the
injector ballast pack and the fuel pump micro-switch inside the Air Flow
Meter. It has white, black, brown, and brown/slate wires. You’ll need (to do
this neatly) a 4" jumper wire (14gauge) with a 1/4" male spade terminal at
each end. Remove the connector from the relay. Find the sockets associated
with the brown wire (battery voltage) and the brown/slate wire (to ballast
and AFM switch). Jump these two terminals/sockets with your handy-dandy
jumper wire. You now have now bypassed the control portion of the circuit
and have voltage to the injectors and the AFM switch at all times. (If
you’re using this to limp home don’t forget to unhook the jumper when you
shut off the car)

“Fuel pump relay” this is next to the main relay and has white,
white/purple, white/green (2), and black wires. As above, you’ll need a
jumper wire but this time you’ll want two loops and three 1/4" male spade
connectors (cut two 4" sections. Strip the ends. Twist two ends together and
crimp on a spade terminal and then put an additional terminal on the other
two stripped ends). Remove the connector from the relay. Find the sockets
associated with the white wire (ignition switched voltage) and the two
white/green wires. Jump these three terminals/sockets with your wire. You
have bypassed the control portion of the circuit and the fuel pump will run
anytime the key is “on”. (Why two white/green wires? One goes to the pump,
the other to the aux air valve. Jumping the terminal for the aux air valve
is not required for testing of the pump circuit but I’d recommend doing so
if you are in limp-home mode !)

Doug Dwyer
Longview, Washington USA----- Original Message -----
From: “Chuck Renner” crenner@dynalivery.com

If you haven’t done so already, take a look at the newbies page:
http://www.jag-lovers.org/newbies/series_III/xj6seriesiii_intro_page.html

I would especially review the “Engine cranks but no start” segment. Since
your car is starting initially, you can skip through the first several
steps. However, I would concentrate on steps 7 through 9, which cover the
fuel pump control system.

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1 Like

This is very awesome and very good…