my friends early V12 has no injector signal / firing…so whats up !
Bad points in the distributor??
Faulty injector resistor pack??
bob
are there any points in the FI cars ? I know my HE does not…this is a 78 model
The old XJS 5.3 might have had 2 sets of points in the base of the distributor to fire the injectors in sets of 3 x 2 (6).
This is for the old ‘D’ Jetronic FI.
I think some of the ‘D’ Jetronic FI had a set of points in the dist (BMW, Volvo, VW?) but might have reed switches to signal the ECU to trigger the injectors.
I have not worked on a 5.3 with ‘D’ Jetronic in over 20 years. I have forgotten most of what I knew back then.
More reading and info on this forum.
http://www.jag-lovers.org/books/xj-s/07-FuelEFI.html
bob
**
Bob is probably on to something, Jagart - and there are indeed no points in FI systems…
On the ‘D-Jetronic’ the injectors are operated by a separate ‘trigger unit’ - while the ignition is handled by an electronic switch substituting the breaker points. So if you have ignition, but no injector action; the trigger unit may indeed have failed…
To identify; remove dist lid - a wide bar identify the trigger unit under the dist rotor. Further, disconnect the inline connector at the trigger unit, three connections, marked ‘12’ in the middle, and ‘21’ and ‘22’ at the sides…
If so, the trigger unit can be tested with an ohmmeter - to be explained if relevant…
If indeed the trigger unit has failed it must be replaced - however, spare working trigger units may be difficult to source…
Frank
xj6 85 Sov Europe (UK/NZ)
**
The early V12 has a trigger board inside the distributor that sends an injector signal to the EFI system. The board itself is triggered by a magnet inside the tail of the distributor rotor. The early trigger board was a reed switch affair, but Jaguar updated that to a Hall effect board. You can tell the Hall effect board because it has a 4th wire to it for 12V power – and of course, without 12V you won’t have injector signals!
The rotor for the Hall effect board is different than the rotor for the early reed switch, and the early rotor will NOT work with the Hall effect trigger board and vice versa. And the rotor for yet later cars has no magnet at all, so that clearly won’t work either.
There are no points in a Jaguar V12 distributor of any era. My parents’ 1973 Volvo with early Bosch EFI had those.
I knew I remembered seeing points in a distributor for triggering FI in some car I worked on.
It must have been an old Volvo!!!
Thanks for the memories.
bob
I was driving my parents’ Volvo one day when it very suddenly quit, like someone had flipped a switch. On the side of the road, I used the tool kit from the trunk and got the distributor cap off to see what was up. Everything looked fine, but I happened to look in the cap itself and noticed that the little carbon button in the center terminal was missing. So I used the crummy little Phillips screwdriver in the kit to carefully remove the set of points down in the base of the distributor that triggers the EFI. I veeerrrry carefully slid it out, and it came out with the carbon bush sitting on top of the points! Wouldn’t have been good to drop that! The spark plugs would probably fire without the carbon bush, but it evidently shorted out the points when it sat on them, so no injection.
I took the spring out of the center post of the cap and squeezed the end a bit so it’d grip the carbon bush better. Then I put it all back together, started it up and drove it home. Never had any more problem with that carbon bush.
1 Like
**
Your absolutely right, Bob - with the early EFI the mechanical points were retained, but the actual coil power bypassed the points…
Frank
xj6 85 Sov Europe (UK/NZ)
**
**
It probably would not, Kirbert - the carbon bush connects the coil lead to the rotor…
And you’re smarter than me - when mine failed I changed the whole dist lid. Strangely(?) enough - this was on my 71 Volvo…
Frank
xj6 85 Sov Europe (UK/NZ)
**
Yeah, but the spark will jump that opening!
I believe my parents’ car was a '71 as well. Horrid car. Positively screaming at 70 mph, sounded like 4500 rpm or so. Coupla years after they bought it I learned one of the options was an overdrive. I asked why they didn’t get that. Their answer: “We don’t race.” They also owned a '69 Volvo that was geared properly, so I guess when they introduced the overdrive option Volvo lowered the final drive ratio to effectively FORCE people to pay for the option.
**
Sure will, Kirbert - but arcing will quickly corrode the rotor, besides degrade the actual spark at the plug…
Much can be said about the 71 Volvo I drove for 17 years; spacious, reliable, well heated and reliable, winter and summer. On snow it generally disregarded driver inputs, doing its own thing, but as the speed limit was 50 mph, and usually less, gearing was less of an issue.
Whether they deliberately ‘detuned’ final drive ratio to encourage overdrive I don’t know. But there spare part prices felt like approaching the weight of gold compared to the price demanded for my Ford Cortina’s…
Frank
xj6 85 Sov Europe (UK/NZ)
**
This car belonging to my parents had a colorful history of issues. When less than a year old – but past the 12,000 mile warranty – we were all on a trip somewhere when I thought I smelled gas. Pulled over and opened the hood and found standing puddles of fuel on top of the intake manifold. The short bits of hose to a couple of the fuel injectors were leaking profusely. Had the car towed to a shop where my folks got charged about $1000 to replace three injectors because the hoses themselves couldn’t be separated from the injectors. When we got home from the trip, I replaced the fourth injector hose myself for about $2.
A few years later, the radiator broke and spilled coolant everywhere. Come to find out the primary failure was that a cam lobe had simply worn away, one valve was barely moving. Hence the car had been running on three cylinders – no, my parents hadn’t noted any change – which made it idle very roughly. The engine shaking at idle had yanked back and forth on the upper radiator hose until it broke the inlet fitting off the radiator. So, besides replacing the cam in the engine and soldering the radiator back together, I also replaced the stupidly-designed upper radiator hose with a flex hose that would allow the engine to move on its mounts without stressing the radiator.
I was assisted in the camshaft replacement by my best bud, Alan Eustace. My parents snapped a couple of photos of us with the hood open and radiator out, with Alan and I all butts and elbows in there. I mention this because Alan went on to get a Ph.D. in computer science, then a job running a department at Digital, then VP at Google, and then finally setting a record for skydiving in 2014 by developing a space suit to wear while hanging from a helium balloon the size of a football stadium while it rose to 135,890 feet.
A D-Jet V-12 has a TPS that should trigger the injectors as well. Put the contact on and move the throttle open, you should get injectors firing. If it doesn’t, the actuator in the distributor isn’t the problem.