Code 76 - Ballast bypass relay open or short
1992 XJ. It has been cranking longer before it starts for maybe 3 weeks, so I did the key thing (on/off/on/off/on) and it showed code 76.
I WONDER:
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Given the way the circuit works, I wonder how/why this fault produces that effect.
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I also wonder about repercussions of simplifying the circuit if I don't understand #1 above.
TESTING & CIRCUIT LOGIC:
The white/blue wire is broken just before it reaches the relay socket (seems this particular wire likes to spontaneously break). That is pin#5 which is the ground side of the coil (if I'm grokking the diagrams).
A sort of mind bending linguistic detail about this circuit is that when the coil is powered, the Ballast Resistor By-Pass Relay does NOT by-pass the ballast resistor, but powers it. When the coil is deactivated, the ballast resistor is by-passed.
As it happens, the Jeep starts and runs with the the ballast resistor unplugged, so it seems that it is truly being by-passed at all times due to the broken blue/white wire.
Also, it starts and runs if I remove the Ballast Resistor By-Pass Relay and jumper past the ballast resistor. In this mode, one does not hear that priming of the pump when you first turn the key, as that is enabled via the Ballast Resistor By-Pass Relay.
If I remove the Ballast Resistor By-Pass Relay and do not jumper past the ballast resistor, then no fuel, no start. As expected.
OPTIONS:
A) Get a new relay socket with pigtails. = Repaired back to full OEM functionality.
B) Leave the wire broken. Stick the relay back in the socket. Jumper past the ballast resistor. = Full OEM functionality in terms of practical results, but not in terms of the circuits used or the way the computer wants to control it.
C) Leave the wire broken. Leave the relay out of the socket. Jumper past the ballast resistor. = As with #B above, except the pump will not prime when the key is turned.
D) ? Some smarter/wiser way to by-pass this whole by-pass thingy?
But back to #1 above. WHY is it slow to start with this fault? The pump primes when the key is first turned. The ballast resistor is by-passed ALL THE TIME due to the fault, so the pump is getting full voltage at startup (as intended) and all the rest of the time too. Sense makes this?
Posted Aug 14, 2026, 12:32 AM UTC