How to verify spark AND how to test for fuel?
#21
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#23
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SteveLeighton (03-24-2018)
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#25
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Are you talking about putting that information down at the end of every post? I can do that if that's what you mean.
Thanks
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Isn't the year and model of my jag showing up? Not sure what you mean by 'signature line'. I went into 'User CP' but didn't see a place to add it there. I don't see a 'signature line' anywhere.
Are you talking about putting that information down at the end of every post? I can do that if that's what you mean.
Thanks
Are you talking about putting that information down at the end of every post? I can do that if that's what you mean.
Thanks
#29
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I think I'm at the end of my road with trying to figure out why my car won't start but I do have a couple of questions. It's assumed that I'm not getting fuel because there is no pressure at the schrader valve. I get that part. People have said that you should be able to hear the motor in the fuel pump when you turn the key on. I've never heard it and I can have super hearing when I turn these high tech hearing aids up. Seriously, I'm like Superman with these things.
So...is it possible that I 'pressurized' something like the can the fuel pump is in or the gas tank the first time I turned the key on and I didn't hear it then? How can I know that the pump is even turning on? Does it only make a sound once at first or should it make that sound every time I turn the key on. If it only makes that sound once and pressurizes something, is there a way to make it do it again. Do I really need a second person to put their ear down there and listen.
Now someone posted something about a crankshaft locator or something like that. That and going back in to replace the filters is just about the only thing I haven't done. I think. Is there a way to test that crankshaft locator thing? Would that make it not pump gas? Would clogged filters make it all of a sudden stop starting? Thanks for your help. You guys rock.
LAST SIX DIGITS OF VIN #.. M38 339
So...is it possible that I 'pressurized' something like the can the fuel pump is in or the gas tank the first time I turned the key on and I didn't hear it then? How can I know that the pump is even turning on? Does it only make a sound once at first or should it make that sound every time I turn the key on. If it only makes that sound once and pressurizes something, is there a way to make it do it again. Do I really need a second person to put their ear down there and listen.
Now someone posted something about a crankshaft locator or something like that. That and going back in to replace the filters is just about the only thing I haven't done. I think. Is there a way to test that crankshaft locator thing? Would that make it not pump gas? Would clogged filters make it all of a sudden stop starting? Thanks for your help. You guys rock.
LAST SIX DIGITS OF VIN #.. M38 339
#30
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Based on your VIN, JagV8 is correct in saying you have the 4.0 litre engine. My mistake.
You should hear the pump begin to run when the ignition switch is turned to the Run and Start positions. If there is no fuel pressure at the schraeder valve, the pump is not running, or there is a blockage in the line.
If the Crankshaft Position Sensor stops functioning, the car may not start. If the sensor fails, DTC P0335 is set and the MIL goes on. I have seen engines run using the Camshaft Position Sensors, but will idle roughly or stall.
You should hear the pump begin to run when the ignition switch is turned to the Run and Start positions. If there is no fuel pressure at the schraeder valve, the pump is not running, or there is a blockage in the line.
If the Crankshaft Position Sensor stops functioning, the car may not start. If the sensor fails, DTC P0335 is set and the MIL goes on. I have seen engines run using the Camshaft Position Sensors, but will idle roughly or stall.
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#32
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In other words, if I turn the key on to the run position, right before the cranking position, I should be able to go back to the where the pump is behind the passenger seat and hear it running, constantly? There's not some sort of 'on demand' cut off valve or something that makes it only run when gas is needed?
Timing chain guides and tensioners have not been replaced since I got the car 2 years ago. The last owner might have. But still, wouldn't I still be getting fuel up to the schrader valve regardless?
Timing chain guides and tensioners have not been replaced since I got the car 2 years ago. The last owner might have. But still, wouldn't I still be getting fuel up to the schrader valve regardless?
#33
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Did you have spark now btw?
if no: change the crank position sensor.
if yes: proceed with fuel system
The cps will not always generate error codes which can lead to a lot of wasted time in diagnosing.
It just takes 15 minutes to swap out the bugger.
I diagnose these problems for a living, have been doing it for 20 years. These symptoms on any 4.0 jag are in 95% the CPS or bore wash (bore wash is caused by a bad cps too)
if no: change the crank position sensor.
if yes: proceed with fuel system
The cps will not always generate error codes which can lead to a lot of wasted time in diagnosing.
It just takes 15 minutes to swap out the bugger.
I diagnose these problems for a living, have been doing it for 20 years. These symptoms on any 4.0 jag are in 95% the CPS or bore wash (bore wash is caused by a bad cps too)
Last edited by VortexXL; 03-24-2018 at 01:50 PM. Reason: Added info
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kr98664 (03-24-2018)
#34
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The fuel pump will not run constantly, but it will run for a couple of seconds to prime the system. It can be difficult to hear due to the sound insulation.
#35
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Lisle #20700 is a good tool for checking spark with coil-on-plug ignition:
Lisle Corporation
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SteveLeighton (03-26-2018)
#36
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My hunch is a no-start condition caused by a bad CPS won't generate a fault code because it's not emissions related. The computer is smart enough that it could tell you this, but since that's not how it's programmed, it's not going to do so.
The OBD system used by our code readers and scanners is primarily designed for emissions related faults, so that's all it's going to tell us. A no-start? That's not an emissions problem, so the computer just crosses it arms and makes faces at us.
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Another hunch is some dealer-level diagnostic equipment could probably tell you more about a no-start, but we mortals are reduced to making educated guesses.
Last edited by kr98664; 03-25-2018 at 02:02 PM.
#37
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sorry mate, not true. At cranking the S will show 0 rpm. Older cars did this but the S is already too digital :-)
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