Hi All,
New to the forum since I recently purchased a non/running 76 XJC V12. I’m still learning about the car and it appears to have an HE engine with the D-Jetronic injection system. I’m assuming the original engine would have been pre-HE and is it common to see something like this or am I looking for trouble with this type of set up?
Darrin,
you are right. This car is too early for HE. It’s certainly worth to investigate whether the FI matches the rest of the car or whether it came with the HE engine.
While Jag parts are typically quite backward compatible, in this case I’d probably prefer an as extensive swap as possible, including fuel management, ignition, power train and periphery, if it has been cleanly executed …
Good luck
Jochen
75 XJ6L 4.2 auto (UK spec)
An original injected non-HE engine would have D-Jetronic. An HE should have Lucas Digital P injection. A few non-HE engines got Digital P between sometime in 1980 when it was introduced, and July 1981 when the HE was introduced. AFAIK, no D-Jet HE’s were ever built.
Of course, early XJ12s had carbs, before injection was introduced.
EDIT: The best way to tell what engine you have is the serial number of the block. It’s stamped just in front of where the transmission bolts up, on top of the block.
Jon
Not anything more than with any other non-runner, Darrin…
As other say; find out what you actually have - and run a compression test…
Frank
xj6 85 Sov Europe (UK/NZ)
An easy way, meanwhile, is to compare plug positions/angles. It has been a long time to recall which is which, but one has more splayed plugs and study of suitable engine pics will soon reveal all.
pre_HE engine spark plugs are angled toward the centerline of the engine.
Hello Peter ! SD Faircloth
Thanks everyone for the responses on this. The angle of the spark plugs are straight up and down, I’m now positive it’s an HE engine that was running with opus/d-jetrinic setup. I would have thought if someone was going to go through the trouble to replace the engine they would have put in the later ignition system as well and was wondering what the experts out there thought of that decision and if I’m looking for trouble. It looks like it was done seamlessly and after I replace the gas tanks and blow out the fuel system I’m going to attempt to get her running as is.
Thanks
Darrin
The pre-HE D-jet system fired the injectors only once per engine cycle. The pre-HE injectors had a much greater flow than HE injectors.
The Lucas HE fired each injector twice per engine cycle, and had lower flow injectors.
You need to determine what injectors you have. An easy method is what color is the plastic body of the injector. Pre HE are dark green. HE are a light tan.
Mixing HE injectors with pre-HE injection system or visa versa…( pre-HE injectors with HE injection system) doesn’t work.
FYI…pre-HE injectors are as rare as hen teeth.
SD Faircloth www.jaguarfuelinjectorservice.com
Hum
this reminds me of my post
“how hard is it to replace a series 2 engine by a series 3 engine”
https://forums.jag-lovers.com/t/how-hard-is-replacing-an-xj-v12-series-2-engine-by-a-series-3-he/433268/9
is the car in Italy ?
No, I’m in the US
The ‘D’ had a trigger unit in the distributor, Darren - firing the injector once every revolution, same as later versions. Ie, the ‘D’ injection triggering was separate from the ign system, so the early and later ECUs are incompatible…
Apart from that there should be no principal problems running a HE engine with a pre-HE ignition system, which is likely why it was retained. However, the trigger unit in the distributor, easily identified, is a bit frail and replacements likely to be scarce - if it fails.
Also, the ign timing set-up of the HE is somewhat complicated and the HE will not be happy with the original pre-HE ign set-up. The respective ECUs are not involved in ignition timing…
Frank
xj6 85 Sov Europe (UK/NZ)