Can’t get rebuilt engine to run properly - totally stumped
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Joined: Aug 2023
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From: Tucson, Arizona US
I think it would he worth your while spending some time checking the fuel injection system harness wiring.
I would meter out all the connections from the ECU to the engine, and in particular to the injectors and AFM. It is not unusual after many years of use to get fractures in the wires, especially in the engine bay area which gets very hot.
When I bought my Series 3, it had been out of use for several years and did not run. Among the many problems I found were some fractures in the wires to the AFM. This kind of fault can be intermittent as the wire can make and break with slight movement or temperature change.
To check the wiring, you will need a long piece of wire as an extension so that you can connect a multimeter probe at either end of the car. For example from Pin 1 of ECU to the ignition coil. Give the wires a wiggle as you check them for the aforementioned reason. Work through all the pins of the ECU connector plug one by one.
Another check would be to see if you still have 12V at the injectors when the engine cuts out. If not, suspect the Main Relay which supplies them with 12V (via the power resistors) as well as the 12V main feed to the ECU and AFM.
I would meter out all the connections from the ECU to the engine, and in particular to the injectors and AFM. It is not unusual after many years of use to get fractures in the wires, especially in the engine bay area which gets very hot.
When I bought my Series 3, it had been out of use for several years and did not run. Among the many problems I found were some fractures in the wires to the AFM. This kind of fault can be intermittent as the wire can make and break with slight movement or temperature change.
To check the wiring, you will need a long piece of wire as an extension so that you can connect a multimeter probe at either end of the car. For example from Pin 1 of ECU to the ignition coil. Give the wires a wiggle as you check them for the aforementioned reason. Work through all the pins of the ECU connector plug one by one.
Another check would be to see if you still have 12V at the injectors when the engine cuts out. If not, suspect the Main Relay which supplies them with 12V (via the power resistors) as well as the 12V main feed to the ECU and AFM.
I haven’t checked for intermittent shorts in the injector wires to the ECU. I am a bit doubtful that will be the issue in this case just due to the fact all 6 are cutting at the same time. However I do think the AFM wiring is worth checking…will dive more into this.
One thing I am trying to understand…. I mentioned that the injector pulses quit before the engine dies (which presumably causes it to die). I didn’t expect this to be the case with spark, since it isn’t controlled by the ECU. However when I watch a spark tester flash it seems to be the same - flashes stop at about the same moment. I thought it would continue to flash until the engine stops rotating.
Maybe I’m overthinking these details…
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Joined: Aug 2023
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From: Tucson, Arizona US
This car sat for a long time until I rebuilt the engine. When it first fired up (on the two cylinders) and ran for a while the ballast resister next to the coil smoked a little bit, I assume just dirty inside. It hasn’t since. Anything there to check?
I traced through wires a bit and found a ground connection in the canister purge valve circuit had broken off. Fixed that but it didn’t affect anything.
Last edited by Incipheus; Jun 2, 2024 at 08:51 PM.
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Joined: Aug 2023
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From: Tucson, Arizona US
Found it!! Or at least I think so. I was thinking about my comment in last update about the ballast resistor and I decided to try bypassing it. Car runs! Not sure if that means the BR is bad or if it’s indicative of something else, but for now it works! The new coil states right on it that it’s meant to be with an external ballast resistor. I’ll pick up a new aftermarket one tomorrow and see if that still works.
Found it!! Or at least I think so. I was thinking about my comment in last update about the ballast resistor and I decided to try bypassing it. Car runs! Not sure if that means the BR is bad or if it’s indicative of something else, but for now it works! The new coil states right on it that it’s meant to be with an external ballast resistor. I’ll pick up a new aftermarket one tomorrow and see if that still works.
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Joined: Dec 2011
Posts: 782
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From: Central California
Found it!! Or at least I think so. I was thinking about my comment in last update about the ballast resistor and I decided to try bypassing it. Car runs! Not sure if that means the BR is bad or if it’s indicative of something else, but for now it works! The new coil states right on it that it’s meant to be with an external ballast resistor. I’ll pick up a new aftermarket one tomorrow and see if that still works.
I would get the new coil that doesn't require external resistor.
https://mossmotors.com/jxj-14545-dis...xj6-series-iii
Rgds
David
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Joined: Dec 2011
Posts: 534
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From: australia
Hi Incipheus. One thing that caught me out when first working on these motors is that Jaguar numbered the cylinders from the rear and not the front like most other vehicles. Means that the distributor is 180 degrees out, and engine will not fire properly.
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