Hi all, I was feeling fairly confident that I was getting on top of the issues that I have spoke of on other posts so thought I would take the Beasty out for a short drive. As usual she started reasonably quickly and I reversed out of the garage. We got down the road and onto the main road that we need to go on to go anywhere around here and the car started to miss, and play up. Almost like no fuel but I know there was fuel in the tank. I managed to get a short way further when it just died going around a corner. I manage to pull over and called road service for some help. He checked a couple of things and then the injectors which he said were not working. I got a ride home with car on a tow truck and pushed it back into the garage. The Jaguar Walk of Shame.
So today I started over with checking stuff. Hereâs what I have found so far.
Check for spark on distributor lead yes
Spark from spark plug leads yes
Check Voltage at battery 12.69V
Voltage at coil +ve 12.09V
Voltage at coil -ve 12.09V
Resistance across the leads from the amplifier to distributor 3.9K ohms
Voltage drops at the negative post of coil when cranking.
Fuel pumps when key turns on.
Fuel pumps when AFM flap is manually opened
Fuel pumps when pump relay is bypassed at the Green/White wire relay plug.
Injectors do not work.
The injectors have not been an issue until now so not sure what the problem could be. I do know I have recently been working on the wiper switch, so, all around the ignition switch, could I have dislodged a wire that affects the injectors. Everything else seems to be good just no injectors. Does anyone have any suggestions?
Hi,
Injectors not working - now does that mean they are not clicking open and closed? or that they are opening and closing but have no fuel to inject?
The ECU uses pulses off the Negative terminal of the ignition coil to time injector pulses. If that connection to the coil is disrupted the injectors will not operate. Check the integrity of the connections to the coil - note this is independant of ignition system operation so you can still have a good spark as you describe.
Another possibility is the temperature sensor - the one that feeds the ECU not the one that operates the temp guage on the dash. If this is open circuit, either due to a fault or due to poor connections the ECU will not âfireâ the injectors. Something else to check.
I should add too check the bunch of ground terminals that are bolted to the firewall end of the water rail. A fault here will also stop the injectors from operating. As always with electrical connections, dissassemble, polish to bright bare metal, lube and reassemble.
Finally, have you got a way to measure fuel pressure at the injector rail? If thereâs no fuel pressure the injectors operating wonât make any difference.
Hi Andy,
I have checked the fuel injectors by putting a test light on the injector plug while cranking the motor. I saw no pulsing at all just a steady light. I checked the injectors themselves by using a 9V battery and connecting that to the injectors they all clicked when the contacts were touch cheddar with the battery wires. The CTShas been checked before and seems to be in spec. Havenât checked the ground point but know where you mean so will do that tomorrow. No way at present to measure fuel pressure but seems to be fairly strong at the rear of the fuel rail where the hose connects. Of course that still may not be enough but the car has been starting and running ok up til last Sunday, Thanks for your suggestions
Con
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Have you actually listened to the injectors âclickingâ regularly while cranking, Con - using a âstethoscopeâ rubber tubing/long screwdriver held to the earâŠ?
Not that I doubt the road service people, but you have to sort of familiarise yourself with the procedure - and for verification, like the excellent description of what you have already done.
Even if you have spark, a routine test of the ign amplifier is relevant. Connect a test lamp between coil â-â and ground and turn ign âonâ - the lamp should be fully lit. While cranking, the lamp should dim and flicker regularly - failure is a positive sign of an ign amp fault, but not the other way aroundâŠ
Then, with an injector connector disconnected and ign âonâ; measure voltage on both wires to ground - it should be â12Vâ. Measure voltage between the two wires; it should be 0V - but should show âunsteadyâ voltage while crankingâŠ
Ideally, this test should be done with an injector test lamp (a noid) readily available and useful - it can be used for the previous ign amp test etc. Connected to the injector plug; ign âonâ - no light. While cranking; the noid will flicker - basically indicating that the ECU sending trigger signalsâŠ
To elaborate; one wire on each injector is connected to the main relay through the injector resistor pack - giving â12Vâ to the injector in ign âonâ and in âcrankâ. The other wire is connected to the ECU which grounds the wire to let current flow through the injector - opening it. The duration of the opening determines how much fuel is injected - calculated by the ECU based on sensor inputs and itâs âprogrammingâ.
The point of these testing is to possibly get some idea of what is wrong - and whereâŠ
But while you were driving; did you change to the other tank as the engine started to falter? This is an important diagnostic tool; if the engine instantly recover it implies a fault with fuel feed. Requiring a different approach than if the engine does not.
Also; a simultaneous glance at the tacho will show if the cause is ignition - if the tacho drops to zero while the engine is still turning; ignition is lostâŠ
Thank you Andy,
I may have the same issue as @con244 Iâve got a similar post; and have had similar issues with my '86 XJ6; among other things - but thatâs for another post. Iâve got a post on this too âanother Xj6 that wonât startâ
The one thing that I did do that isnât listed in this post is remove the air pump. There is a 2 wire connection to the air pump that looks like is connected to the temp sensor if the wire is disconnected; will this keep the injectors from firing? if so, any suggestions on the best way to complete this circuit - without letting the smoke out?
I will be following this post too. Thanx @con244 for having the same issue. OH, and another thing, the PO had the battery hooked up backwards. I have driven the car since I put the battery in properly; so it doesnât appear to have cooked anything initially. this $400.00 XJ6 is becoming less of a bargain.
Hi Frank,
I cannot hear the injectors working at all when cranking. Tried the hose trick.
I connected a test lamp between coil -ve and ground. The lamp glowed brightly when the ignition was turned on and dimmed and flickered while cranking.
I have 12.11V between each side of the injectors plug and earth and 0V between them and fluctuating voltage while cranking.
I have to admit that in the panic of turning into traffic and losing power I didnât think to change thanks or check the tacho, basically I panicked.
I am starting to think that my problems may lie in the wiring to the ecu. It seems to much of a coincedence that this has happened right after I had been fooling around near the ignition switch while repairing the wiper switch. I wonder if I have knocked a connector that has something to do with the ECU.
I almost wished for a problem with the amplifier but that does not seem to be so.
Hi Mark, I have been following your thread as well. And yes they do seem similar. I donât think my car has a vacuum pump. It is the Federal version. I may be wrong on that score, maybe someone will put me right. Having the battery in with reversed polarity seems quite serious. Iâm surprised the car ran at all, although I seem to remember changing the polarity of a Morris Minor which was +ve earth was fairly simple just reversing the battery leads and changing the starter leads over. Still no computer in those days. I wonder if your problem stems from that battery reversal. Good luck on your search for an answer, let me know if you do find it
Con
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Your tests show that injector wiring to the ECU is intact, Con - and the ECU does its internal thing as it should. That you also have spark and the test lamp at the coil shows ânormalâ indicates that the ign amp works as it shouldâŠ
Test the injectors individually by applying power directly to their pins - very brief connections as they are not meant to have continuous 12V. The injectors should duly click - signifying they are in electric working order. Back up by ohming; the resistance in the injector should be 2,4 ohms - though 6 injectors failing is unthinkableâŠ
This is mystifying, and the next test is somewhat circumspect. Voltage checks with voltmeters are deceptive - they do not show power. One wire to each injector is connected to the main relay via the resistor pack - full power. The wires to the ECU has âparasiticâ voltage, but has ânoâ power. Use a hefty test lamp to verify that it is fully lit on one wire - with little reaction on the other. Any power failure directs attention to the injector resistor pack - a flat tin with lots of wires; low forward right in the engine compartmentâŠ
The lack of injector reaction while cranking is cause enough for the non-start - to be pursued. The injector set-up is an independent subsystem; triggered from coil negative, the ECU computes injection duration based on CTS and AFM inputs - injectors being permanently powered. Basically, the injectors will âclickâ even with some faults presentâŠ
Given the positive results on previous tests; non of your actions should have interfered with vital elements concerned with injector operations. With an obscure fault; it is advisable to revisit the âcrank/listenâ test at intervalsâŠ
Frank!
6V is enough for the injectors! mine all clicked on 6v batteries. Also, the resistor pack is there for a reasonâŠ
mark, you still have your air pump around to quickly connect, donât you?
The injection via ecu can be tested by ignition on, and connecting-disconnecting the bullet connector near the fuel rail quickly. The ecu will fire the injectors every second âignition pulseâ from the coil terminal.
If itâs a federal car, then it does have an air pump. Mine is also a federal car â I live in Washington State. The car has been driven since the polarity was reversed. I noticed that before I put I drove the car. When I got it, the diode pack in the alternator was cooked and thus it would over charge the system. The sad thing is it cooked the factory radio. Thatâs a bummer. I havenât had an opportunity to work on the car, My daughter just turned 18; and has decided she can run the streets; and not come home. Needless to say everything else has taken a back seat. I can only pray that she has enough sense to stay out of harmâs way.
Con,
It isnât a vacuum pump but an air pump, part of the emissions system. The attached picture shows the engine bay of my 1987 XJ6 Vanden Plas with the air pump circled in red and some of the related emissions system piping circled in blue. I believe that any Federal Series III XJ6 was equipped with this emissions system when it left the Jaguar factory but it could possibly have been removed from your car by a prior owner or his shop if your car doesnât have one. Posts about how to remove the air pump and related piping comes up often on this list. All four of my fuel injected Jaguars have their air pumps because they are checked visually during the CA smog tests every two years.
Air is drawn from the air filter housing throgh pipes by the pump and it is injected into the exhaust gas stream for a short period of time after starting the engine to assist in complete combustion while the engine is running rich for smoother staring. Once the engine and catalytic converters heat up and the fuel mixture is leaned out, the additional air is not required and the air injection is secured. There is a lot of info about the emissions systems in the Series III Maintenance Handbook and Service Manual should you wish to learn more.
Thanks for that explanation Paul. There is no plumbing like that on my car. So I can assume itâs been removed. That also explains the loose vacuum type hoses I have found flapping about on the intake side on the motor. I have also seen a couple of blocked inlets/outlets that look to be related to the same hoses. Once I get the motor running again I might try and tidy all that up. Your excellant engine bay photo stands up well to magnification so it will come in handy.
Thanks again
Con
Demian,
Thank you, I appreciate the kind words especially since I take a lot of time to make sure that my Jaguar engines look as good as they run.
For your viewing pleasure attached are pictures of the engine bays of my two V12 Jaguars, a 1990 Jaguar Racing Green Series III V12 Vanden Plas and my wifeâs Signal Red 1990 Classic Collection XJ-S convertible. The engines are similar but not identical. I have done most of the work on both of these cars, especially in the engine bays.
As Frank said, you seem to have power at the ECU.
However, itâs very easy to check, for peace of mind more than anything.
Go to the trunk/boot and check with your VOM
Also a good opportunity to check if all your sensors comunicate with the ECU.
As far as I understand the (+) side of the injectors is fine but your injectors are not getting grounded.
So either the ecu does not get the signal in order to ground them, or there is a problem with your ground wire(s) from the ECU to the injectors.
Here, dear Constantine, is a slight contradictionâŠ
What do you mean by âfluctuating voltageâ ?
An analogue VOM might show you better what is happening, the Digital ones are too slow to show pulses.
You should investigate further I think and see if, while cranking, the (-) cable of the injector plug sees the ground or not.
It could also be that the ECU stopped doing what it was suppose to do (hope not)⊠a continuity check between engine and ECU pins might help eliminate some of the possible causes.
Test the injectors individually by applying power directly to their pins - very brief connections as they are not meant to have continuous 12V. The injectors should duly click - signifying they are in electric working order. Back up by ohming; the resistance in the injector should be 2,4 ohms - though 6 injectors failing is unthinkableâŠ
Have tested the injectors with a 9V battery and they do indeed click. I have also measured resistance across the two pins of each injector and found 2.5 ohms on each. I also removed two injectors from cylinders 1 & 2 and tried cranking. No spray at all.
What do you mean by âhefty test lightâ? Do you mean a high wattage one?
I have also revisited the work I had done on the wiper switch just to check that something wasnât astray there. Can anyone tell me what these wires do? They hang of the bottom of the ignition switch. They are not connected to anything and I was wondering if they may be responsible for my problems. I cannot see anywhere for them to connect to.
Aristides:
Yes the fluctuating voltage was measured using a digital multimeter so you are correct that they may not be showing is the connection is in fact grounding but the inspection of 2 of the injectors out of the manifold while cranking shows no spraying of fuel at all, not even dripping. I currently have the battery recharging so unable to check ECU but will do so tomorrow. Just a quick question, what should I be seeing at the ECU if the sensors are properly connected. I have found 3 inline fuses at the ECU end of the wiring, these fuses all check ok with the continuity checker on my multimeter.
Everywhere I go on this car it seems that someone has been there before me. The nuts holding the injectors in seemed very easy to get off.
Thanks everyone for your help
Con
