I just want to pass on some info about the symptoms I had with a failed hall effect trigger board.
1975 Xj12C, saved from a back yard in Wyoming, sitting 10-15 years. Had to redo the entire fuel system and went through as much as I could before getting it running and driving. Long story short, the age of everything had me worried. Ignition, fuel injection, no history of maintenance from the owner.
So I get a new trigger board (hall effect) along with checking everything, replacing fuel lines, hoses, cleaned injectors(all 12 came back to life)etc etc. Engine running. A few issues nothing major, drive around for a month or so and it started running really rough while out for a drive. Limp home, look at everything, check what I can. Everything seems OK. Next day, starts up smooth then 8 minutes into warming up it starts running rough again. This goes on for months while I trouble shoot and try to learn the D-jet system and check, test, replace a couple things. Nothing worked.
I figured out I was losing 6 injectors after the 8 minutes of running. What causes that. Trigger board, trigger into the ecu, trigger out of the ecu, injector amp, grounding(earthing) I check it all and nothing is making sense. I don’t have an O-scope at the time so I order one and figure I will find the missing trigger. In the meantime I say what the hey and replace the new trigger board with my old reed board and voila problem fixed. I didn’t figure that the new improved trigger board would fail after a couple months and certainly didn’t figure it would lose one trigger after warming up/running for 8-9 minutes.(I timed it).
So just remember that anything can fail new or old and to not dismiss an item just because it is new. BUT also do your best/sensible/rational trouble shooting.
Now there were other issues with my Xj that it wasn’t on the road for a while and so the warranty for the Trigger board expired and I will have to purchase a new one soon, as I am running around Colorado with a 48 year old reed switch trigger board. But it is running better, and I am still tinkering and tuning and I can move on to the next item to fix/improve on the Jag over the winter.
Good luck all
Monte
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To add, Monte - on ‘our’ EFI Jaguars; injection is triggered once every engine revolution for all injectors simultaneously. You have the early ‘D’ system trigger unit where two reed switches, 180 degrees apart, trigger the ECU at alternate revolutions - while the later ‘P’ uses ign coil inputs to the ECU…
As the two main types of ECUs are incompatible; you were lucky to find a replacement trigger unit! If one of the reed switches fail, the engine only gets half the fuel…
Frank
xj6 85 Sov Europe (UK/NZ)
Good to know Monte, thanks for sharing your experience.