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With no injector action, that seems likely, David - the ‘why’ then becomes the focus…
Incidentally; the ECU wire is routed via the injector resistor pack to the bullet connector. We have had incidents where the wire was broken between the coil neg and resistor pack…
Frank
xj6 85 Sov Europe (UK/NZ)
**
…but we can easily find out if there is a pulse via the wire. If they click, the coil is powered. If they don’t, check if you have spark, check the wire for continuity,
Does it go to the resistor pack? I can’t see why it would and don’t remember an extra wire there. But the exact routing might be interesting later.
Here we are on unsafe ground, David…
On mine, the wire uses the resistor pack as a connection point for two separate wires; coil neg to resistor pack - and resistor pack to bullet connector. But that may differ from car to car - chafing breaks near the block may have induce a modification?
No relation to the resistor pack function, of course - just a convenient connection point…
Frank
xj6 85 Sov Europe (UK/NZ)
**
Both my (non-original) old and (perfect, concourse condition) new wiring loom can’t reach the resistor pack and just make the coil, with a lucar (spade) connector on that end. Interesting.
These are UK/Swiss engines. I‘ll look at where it goes from the two big connectors aft of the water rail.
Okay David I put the ignition key to position 3 and disconnected & connected the one wire connection, which I believe is the wire, and I do not get any clicks! The shift lever is in the Park position. From this, what does this tell me? Where do I go from here?
Lee
That should read 2 if 3 is crank-if you have disconnected and connected the wire several times and there was no clicking noise, I‘d like you to look for spark.
It should tell you that one of the following things might be bad:
You might have no power to the coil.
The wire we just looked at is disconnected or got gnawed on. I don’t know which polarity it has, but you could measure it.
The signal does not arrive at the ECU.
I understand that the ECU is powered on as you have voltage on both pins of the injectors.
Another idea might be to make sure the bunch of black wires at the rear of the intake manifold is grounded well.
I have rigged up a small bulb that I can attach to the coil to
distributor wire. Which one is it? I plan to see if the coil is
getting the proper signal from the distributor. Then if I do I will
disconnect a sparkplug perhaps or wire. I think the sparkplugs are
getting voltage but no fuel through the injectors. Yes I checked the
cliking on position 2. Position 3 is crank. Is that correct?
Lee
Yes.
This is the ignition system - 1 is the ‚amplifier‘; A (sensor) goes to A‘ and B go to B‘ at the coil. That’s all there is.
The wire that sends the signal to the ECU is connected to one of the coil terminals. To test the spark I would simply pull the center lead off the cap and place it close to ground and crank, standard procedure. If you have spark we will have to look at ground, and then ECU.
**
I was wrong, David - it is actually the coolant temp sensor that is connected to the ECU via the injector resistor back. Obviously to share the loom to the ECU…
Sorry for the inconvenience - air force dictum; check, don’t remember, memories are frail…
Frank
xj6 85 Sov Europe (UK/NZ)
**
**
It’s uncertain whether he checked with the plug connected to the injector, David…
In which case voltage from the resistor pack would show up on both pins even if the ECU is unpowered, or the wire from injector to ECU is broken. Voltage must be checked on the (disconnected) plug…
Apart from injector activity; this and the coolant temp plug is the only(?) verification that the ECU is powered up with the ign ‘on’…
Not that I actually suspect the ECU for the problem, but still…
Frank
xj6 85 Sov Europe (UK/NZ)
**
Frank & David thank you so much for your help. I am going to wait until tomorrow when I will have some additional help to hold the spark wire while I crank etc. I do have another question or two however. The single wire bullet type connector that you told me to disconnect & connect to hear the injectors click. This produces no clicking. I disconnected and got 6v on the coil side and no voltage on the amplifier side. With the power off, I checked the resistance of the wire going back to the amplifier. I essentially got an open circuit up in the megohms. Is that what I should get? Also there is no voltage on that lead with the ignition power on. Is this all normal? What is that metal piece with two push on wires bolted to the positive terminal of the Distributor? Was going to send a picture but somehow my computer got fits and won’t recognize the camera. Lee
I can’t follow what you’re saying, but it’s late and I‘ll visit this tomorrow.
I‘d say Frank has it figured out better than I could yesterday.
Look for spark, then look for continuity.
Also, did you look at the grounds?
Frank. The bullet connector is associated with the ignition amplifier - the amplifier gives the signal, by cutting (I believe) the voltage at every signal from the distributor. That short drop is sensed by the tacho, the ECU and it lets the field in the coil collapse, generating the spark voltage in the secondary coil. Something like that.
But with a working spark, all(!) that matters is continuity from coil terminal to connector, and if good, likely something aft of the bonnet.
**
Your voltage an resistance readings are all wrong, sort of, Lee - and also misdirected…
To elaborate. Providing that you are on the correct bullet connector; the connector is directly connected to coil negative. With ign ‘on’ and bullet disconnected; it should show 12V (bullet’s coil side) - as should coil neg.
The 6V measured at the bullet (disconnected) is confusing, it should either show 12V, or nothing - unless the coil neg also shows 6V. Which, if so, is still wrong - but on a different plane…
The main point is that the bullet connector is nor related to the ign amplifier. One end goes to the coil neg - the other to the ECU in the boot. Which, again with the ign ‘on’, should presumably show 0V - given that the ECU electronincs is meant to have no parasitic voltage…
Ohming should be done between the bullet connector (disconnected) and coil neg. It should show continuity, 0 ohms - showing ‘break’ means a failed wire - which indeed would explain your symptoms…
As the bullet is not related to the ign amp; ohming between the bullet and any wire on the ign amp (except(!) its white/ black which is connected to the coil neg) is irrelevant - but should indeed show ‘break’…
What you can do; jumpwire fro coil neg to the (disconnected) bullet connectors ECU side - this will bypass the wire between coil neg and the bullet. You can the retest injector reactions - and if OK the engine will likely start. If so; permanently replace the wire between coil neg and bullet…
One proviso; the original wire may be shorted, so it should should be disconnected from coil neg while testing…
Frank
xj6 85 Sov Europe (UK/NZ)
**
Well Frank sorry for all the mistakes I made. It was late in the
day and my brain was getting tired I guess. Sorry about the 6
volts. That should have been 12 volts. And I meant to say ECU but
had amplifier on my mind. But yes it is correct that I got
essentially an open when measuring with the power off. So maybe I
have an open wire and that is the problem? Wish I could get my
camera to work with my computer. Don’t know why that communication
quit. No luck at all! A little confused about the wires on the
coil. One terminal has a metal plate connected to it with two
push-on wires. The other has I believe one wire which goes to the
bullet connector which should be the negative. The coil does not
have any + and - indicated on it that I can see. I plan to spend a
little time on the Jag this morning again. I have not located the
ECU as yet. I’m not sure however if I understand your comment about
the resistance to ground measurement of the ECU disconnected side of
the bullet connector. You say that should measure 0 ohms? But that
was between the coil and the bullet connector wire which was okay
because I measured 12v while ignition ON. No I got very high
resistance from the ECU side to ground. That is with power off. Is
that correct? Or do I have an open wire to the ECU? Does anyone
have a schematic of the ECU? Where is the amplifier located? I guess
I got sidetracked trying to check out the spark system also.
Very still confused however. The electrical diagram I am looking at
does not even show the ECU! It shows a wire directly from the
amplifier to the coil negative. I could not even find the ECU on
the diagram I am looking at. They do list an EGR control unit (291)
however could not find it on the diagram. Really confused. Not
working from a full deck. Sure could use a better wiring diagram to
follow things better since I can’t get a clear picture without a
decent wiring diagram.
Lee
Wondering why the full wiring schematic I have, does not show the ECU anywhere on the diagram. Does not make for easier troubleshooting! This is a main part of the electrical system so cant but help wonder why it is not included in the overall wiring diagram. At a loss. So where is it exactly? If it exists which I’m sure it does, why at least isn’t it shown as a part of the overall diagram?
Lee
One picture is the smaller non-cat ecu, which really should be in the diagram, and the other is the setup without ballast resistor. Mind that the wire should be white/black(?), not black.
Look for continuity in that wire from coil terminal to bullet. You can also measure for continuity to the white plug at the bottom.
Ignore what’s not shown and if you have tested positive for spark, ignore the sheet metal box which I believe to be the ballast resistor. What diagram do you have? Pictures would be good, but no pressure.
David
Okay David & Frank. I am at a complete loss!! Yes checked today and I have a good spark! The other day we disconnected two injectors. Applied voltage to one and it spurted out a nice spray. Thus good there!
But then (if I have the correct bayonet wire) leading to the distributor, NO CLICKING! But also when turning over the engine, no fuel out of the injectors! This would lead you to believe it is the ECU or wiring correct? But when I turn over the engine it almost wants to start but will not continue running. Thus the question if it seems like it wants to start how can it do that when on my previous check with the injectors out did it not spurt fuel? Something just does not make any sense at this point. There is something I did wrong in my checking but at this point nothing makes sense. If it is trying to start, my analysis would be that perhaps some of the injectors are plugged. But why didn’t my other check that you advised me to do such as disconnect & reconnect the bayonet wire produce a click? Nothing makes sense and the fact that there is not a decent wiring diagram does not help. I would like to check to see if the ECU is getting battery voltage but cannot determine on which pin to check. The info from Jag unfortunately is not too good. I am an autonut thus have several autos and am presently restoring a 1934 Lafayette. I obviously does not have all the complexity as the Jag. It is a six cylinder and runs fine without all of the complexities. I am more familiar with the older autos with a point system. The Jag complexity almost overwhelms me even though I am an electrical or electronic person. And that is what disturbs me the most, in that I can’t even find a complete wiring drawing that has ALL OF THE COMPONENTS that would allow the engine to run!!
HELP at this point from anyone would surely be appreciated! Seems like it is so close to running BUT WILL NOT!! I even bypassed the fuel filter to make sure it was not contributing to the problem.
Lee
Lou, I‘m not through reading yet, but it will probably start on the blue cold start injector alone. You better keep the fuel filter in line, and I do respect that despite jumping into the cold water you don’t give up. I‘ll look for a drawing.
Yes I have always been of the opinion that there is always a brighter day ahead. Otherwise perhaps I wouldn’t have existed as long on this earth at 89 years!
