XJ XJ8 / XJR ( X308 ) 1997 - 2003

Not another nostart thread...

 
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Old 05-13-2019, 07:50 PM
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Default Not another nostart thread...

The time has come for me to agitate the hive-mind and see what squirts out. What I am dealing with is a 2001 xj8 that ran and drove but had blown engine.
I swapped a good junkyard motor in and now it wont start. Now the fun part!
For your consideration, the following are the steps I have taken and the things I've checked:

I have dealt with the bore wash/sticking rings/bad mood from being in storage and have good compression.
I have ~11.5 volts while cranking.
I have no security light on while cranking.
I have battery level voltage at all of my injectors.
I have battery level voltage at all of my coils.
I do not have any pulse signal at my injectors or coils, I also checked at the the PCM itself to be sure it wasn't a wiring issue between the PCM and the coils/injectors.
I checked the signal coming from the CKP at the PCM and I'm getting an ~80-85hz pulse from the sensor.
My inertia switch is good and in the normal state.
New CKP sensor.
I have also spent an unreasonable amount of time searching for a solution and I'm at a loss

My thinking is that considering 2001 was a split model year apparently, and given that I used the flex plate (flywheel) from the junkyard car, I'm wondering if perhaps there is a subtle yet meaningful difference between an earlier and a later model flex plate, since that is the only thing I can think of that would affect both fuel and ignition pulse.
Any thoughts?
 
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Old 05-13-2019, 10:58 PM
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Hi transponder7,

Welcome to the Jaguar Forums! It's great to have you with us.

Assuming the starter motor rotates the engine but the engine will not start, my first thought regarding your lack of pulse at the coils and injectors is that they are all operated by the ECM connecting them to ground at the appropriate time. So a problem with an ECM ground could cause your symptoms. The three grounds referenced by the ECM are the EMS LH Ground Stud and the EMS Bulkhead Ground Stud. You might check those to be sure the post, nut, washers and harness eylet terminals are clean and the nuts tight, and that all of the appropriate wires are connected. Here's a diagram showing the locations of these ground studs:






If you have a scan tool that can read Live Data, you may be able to view the sensor signals with the key in position II (ON) without cranking the engine. This might tell you if any of the critical sensor signals are absent or implausible.

You may also now have some diagnostic trouble codes (DTCs) stored in memory from failed starts. Those may give you some clues.

In addition to the crank position sensor (CKPS), the camshaft position sensor (CMP), mass air flow sensor (MAFS) and engine coolant temperature sensor (ECTS) and probably some others are referenced by the ECM at startup.

Another thing to check are the electrical connections to the throttle body, which include the throttle motor, throttle position sensor, pedal position sensor, and air assist close valve.

Cheers,

Don
 

Last edited by Don B; 05-13-2019 at 11:06 PM.
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Old 05-14-2019, 04:57 AM
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there are a number of things that can inhibit fireup...
The flex plate is certainly one. The surefire way of identifying your car's engine and system is by showing us the throttle body.
The AJ27 also has 2 cam sensors as against one on the AJ26. Cam and Crank signals have to be present for ignition.
 
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Old 05-14-2019, 07:14 AM
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I do not know about AJ27 but AJ26 (single cam sensor) will start and run fine with the cam sensor completely disconnected. The normal start may be a bit difficult (will require a number of cranks) but if you keep the ignition on for some 40 seconds before cranking, it will fire-up straight away.
 
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Old 05-15-2019, 08:22 AM
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Don't worry, I'm not letting this die, I just have a rather hectic week. I was able to check the bulkhead ground and the throttle body connections and they're all good.

I've been using a snapon zeus scanner for some of the diag work up to this point, and from what I've seen all my sensors are on-line and giving good(?) data.

I am reasonably sure i have an AJ-27, as I wanted to avoid the headache of the composite headgaskets and the marvels of nikisil. As for DTCs, its been a while since I've worked on it but if memory serves, there was not anything out of the ordinary listed, and certainly nothing that would inhibit startup.

I will have better information later in the week. Also as requested, a picture of my throttle body:

 
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Old 05-15-2019, 08:46 AM
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The AJ27 has composite head gaskets and could be nikasil. What is the engine serial #? I think nikasil production aug. 13 2001.
 
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Old 05-15-2019, 09:44 AM
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The first steel-lined engine came off the production line on 18th August at 10.43am, i.e. the steel-lined engines are from Engine No. 0008181043.
 
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Old 05-15-2019, 11:10 AM
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I was confusing nikasil with tensioner date. Anyway, nikasil liners will outlast steel liners as long as the engine is not severely overheated.
 
 
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