Hi Jaglovers
About my canadian XJ12 SIII (1987):
Have a question about the EFI.
My injector harness had more short circuits cause the wires were baken
like explained in Kirby’s book.
Now I’m kind of scared…
Does a shortcircuit damages the EFI?
How can I test the EFI?
Thank you and best regards, Gregor
A severe or sustained sort circuit might cause a problem…although the injector ballast provides protection for the ECU. Reports of injector harness problems are common. Reports of damage resulting from them are not.
Yes, the EFI can be tested in various ways for various faults but worrying about what might be wrong shouldn’t stop you from repairing what is known to be wrong. Replace your injector harness (about $600 from vendors) or build your own (more popular).
If you have additional problems they can be addressed if and when they occur.
Cheers
DD
Fuel injector harnesses for pre facelift HE’s and series III XJ12 are closer to $400 now! I’ve made my own before but would seriously consider buying at $400…
https://www.sngbarratt.com/us/#!/English/parts/1c04adfa-ba49-47fd-afac-3f2e635f27d2
Thank you Doug & John for your response.
I thougt to made my own harness.
Is the harness @sngbarratt made of heatresistant wires
or is it made like the orig. one?
I’m kind of scared it will be cooked again?
I don’t know what materials are used in the new harnesses.
In my opinion the root of the problem isn’t the materials. The root of the problem is that Jaguar decided to clamp most of the wiring directly to the engine, deep in “the vee”.
Whether you buy a new harness or make your own I think the most important improvement is to route the wires as high as possible, away from the vee, to reduce the baking. I run the wires right alongside the fuel rail, personally.
Cheers
DD
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Likely the latter, Gregor - heat resistance is a relative term. As Doug says it's the routing of the wires that causes problems - and plain old age is also a factor…
And as Dough further says; repair what is found wrong - the best test of the EFI is a running engine, no testing of the EFI is then required…
Frank
xj6 85 Sov Europe (UK/NZ)
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Hi Frank, Doug & John
So this weekend I had some time and tested it out.
Got an injector Harness from an XJS12 and it works
fine, no stalling etc.
The harness locks also suspicious so I’ll buy or make one.
Question, is there something to lock about? How about the
length of the wires for each injector? is that kind of relevant?
Does it matter where the -/+ poles are?
Thx and best regards, Gregor
**
The lengths of the wires are immaterial beyond reaching the respective connections points, Gregor - with the necessary slack for routing…
The polarity of the injector wires are likely irrelevant; the injectors are operated magnetically by wire coils moving metal - which works the same irrespective of polarity. But ‘+’ is always at the resistor pack, and ‘-’ in the ECU…
The consistency in the original harness relates more to a an orderly mind and the need to positively identify each wire - but it doesn’t hurt to try and mimic the original set-up…
Frank
xj6 85 Sov Europe (UK/NZ)
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Hi Frank
Thank you for your awnsers and help.
I learned something more.
I appreciate that.
Best regards, Gregor