Quote:
Originally Posted by LuluBelle
"Don't forget to check the fuel pump relay ground too. You would only need one working ground to activate both relays by splicing between the relay coil ground sockets.".......? I don't understand what you mean?.....my fuel pump stays on after priming
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Occasionally I've seen on the TJ section on Jeepforum.com PCM ground has failed on either the fuel pump or ASD relays. When this has been diagnosed, and pulse confirmed on the other relay, the 'fix' has been to tap the working ground over to the relay with the non working ground.
This means the PCM is using only one relay ground to operate the two relays. This can be done as both grounds operate in exactly the same way, ie. initial pulse on, then on during cranking or running.
Hope that's a better explanation for you. Possibly it was getting ahead of where you are up to since pulse and continuity hadn't been fully confirmed.
As far as the fuel pump relay sticking on, we know the relay coils grounds so I would remove the relay and check what the coil ground does at ignition on. If the ground is continuous I'd check the output from the PCM. If it pulses as it should I'd swap the relay, as it could be bad.
A couple of times recently I've had my engine stay running after removing the key from the ignition. The first time it happened the engine stopped as I pulled the relay. The hood was open at the time as I was just doing initial cam break-in. I'd replaced cam and lifters while the head was off to replace pistons due to a broken skirt. The second time it happened was the next day but the engine stopped before I could get the hood up to get to the relay. I swapped my ASD relay for the horn relay and the problem hasn't recurred. I did have problems starting before and after the break in which could have also been down to bad relay contacts. I've now replaced my bad relay and will probably replace the others too for peace of mind.