Last time I ask for help on this issue... trans shifts?
#1
Last time I ask for help on this issue... trans shifts?
I know the xjs was set to shift early even at wot. I’ve read some governor changing or weight shaving can increase shift rpm. My issue goes beyond that. If I shift “manually”, it hits around 5k and bucks like it hits a rev limiter. I can rev the engine in park to 6k(don’t do that often), but if I try holding a gear it will not go that extra 1-1.5k rpm! Did pump, filter, plugs, wires, coils, cap and rotor and advance and magnetic pickup etc all in the last year or 2. I’m guessing it’s a fuel issue since it takes a couple times of priming the fuel pump to start the car. Hmm writing it out is now making me wonder if the fpr is junk...
#3
#5
#6
#7
Well I took a couple vids. The first is first gear where it hits 5k and I nearly drop the camera it’s so jarring. The second is flooring it in park. I guess it doesn’t want to go to 6k. It seems to fart and burble just under 5k. Sounds like it’s missing.
https://i.imgur.com/wU7qAMx.mp4
https://i.imgur.com/HXlXatu.mp4
https://i.imgur.com/wU7qAMx.mp4
https://i.imgur.com/HXlXatu.mp4
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#8
I suspect it is an ignition fault. It sounds like it is loosing spark. If it lost fuel pressure I would expect a bit of a softer failure, loosing power instead of misfiring like it does. I see you are running a single coil, I wonder if maybe the coil you have is failing, or is not up to the task. You can test the pickup coil resistance with an ohm meter from the plug at the ignition module. Anything that requires excess coil output could also do this, including an open in the coil wire to the distributor cap, or even spark plugs that are not gapped properly. The V12 plugs should be gapped at 0.025", this is to minimize the required coil output. Going back to your comments on shifting, are you sure the kickdown switch is operating correctly at full throttle? And that you have the proper signal vacuum signal to the modulator? I would expect wide open throttle shifts near 6000 rpm with your foot to the floor.
Also, check for a stuck centrifugal advance in the distributor. Possibly that could lead to a high rpm misfire by crossfiring in the distributor cap. Check the vacuum advance while you are at it but that should not affect hard acceleration, only light throttle operation.
Also, check for a stuck centrifugal advance in the distributor. Possibly that could lead to a high rpm misfire by crossfiring in the distributor cap. Check the vacuum advance while you are at it but that should not affect hard acceleration, only light throttle operation.
Last edited by Dleit53; 12-27-2019 at 02:19 PM. Reason: additional information
#9
I suspect it is an ignition fault. It sounds like it is loosing spark. If it lost fuel pressure I would expect a bit of a softer failure, loosing power instead of misfiring like it does. I see you are running a single coil, I wonder if maybe the coil you have is failing, or is not up to the task. You can test the pickup coil resistance with an ohm meter from the plug at the ignition module. Anything that requires excess coil output could also do this, including an open in the coil wire to the distributor cap, or even spark plugs that are not gapped properly. The V12 plugs should be gapped at 0.025", this is to minimize the required coil output. Going back to your comments on shifting, are you sure the kickdown switch is operating correctly at full throttle? And that you have the proper signal vacuum signal to the modulator? I would expect wide open throttle shifts near 6000 rpm with your foot to the floor.
Also, check for a stuck centrifugal advance in the distributor. Possibly that could lead to a high rpm misfire by crossfiring in the distributor cap. Check the vacuum advance while you are at it but that should not affect hard acceleration, only light throttle operation.
Also, check for a stuck centrifugal advance in the distributor. Possibly that could lead to a high rpm misfire by crossfiring in the distributor cap. Check the vacuum advance while you are at it but that should not affect hard acceleration, only light throttle operation.
#10
Hello 944
In regards to coil. I last had my XJS going August this year - when I finished getting the fuel tank, ect back in the boot. Started ok.
Finally got under the bonnet completed Christmas eve and tried to start it boxing day (as I did not want to get depressed on Christmas Day) and I have a no-spark situation.
These are the steps I took to realize my coil is stuffed
1) Disconnect the battery negative terminal
2) Get my multimeter - set on 200 Ohms and measure from the + terminal to the - terminal of the coil - should give a real small number (1.5 to 1.7)
3) Disconnect the HT lead from the coil, change the setting of the multimetre to 20K Ohms, leave the red on the positive terminal and the negative in where the HT lead lives. Should give you a resistance of 13.5.
Could not find the minimal range for the Jag, but for the Chev - a reading of 11.0 or less will result in a no spark situation. I am presuming with the V12, it would have to be more around the 12 mark.
My readings were 4.7 for 2) and 8.65 for 3). So a new coil is on the way.
This is the 2nd one that I have had fail on me, the first one was a falcon that I fueled up that day, loaded the car up and was about to hit the road, than had a no-spark situation.
So I don't think your problem is coil related, but only takes a moment to check.
For video 2
If I was going to guess - I think you have fuel supply issues. Good for 'normal" driving, but isn't enough pressure when hammered
For video 1
No advice, but would expect some sort of shutter when changing at those revs
Cheers
Steve
In regards to coil. I last had my XJS going August this year - when I finished getting the fuel tank, ect back in the boot. Started ok.
Finally got under the bonnet completed Christmas eve and tried to start it boxing day (as I did not want to get depressed on Christmas Day) and I have a no-spark situation.
These are the steps I took to realize my coil is stuffed
1) Disconnect the battery negative terminal
2) Get my multimeter - set on 200 Ohms and measure from the + terminal to the - terminal of the coil - should give a real small number (1.5 to 1.7)
3) Disconnect the HT lead from the coil, change the setting of the multimetre to 20K Ohms, leave the red on the positive terminal and the negative in where the HT lead lives. Should give you a resistance of 13.5.
Could not find the minimal range for the Jag, but for the Chev - a reading of 11.0 or less will result in a no spark situation. I am presuming with the V12, it would have to be more around the 12 mark.
My readings were 4.7 for 2) and 8.65 for 3). So a new coil is on the way.
This is the 2nd one that I have had fail on me, the first one was a falcon that I fueled up that day, loaded the car up and was about to hit the road, than had a no-spark situation.
So I don't think your problem is coil related, but only takes a moment to check.
For video 2
If I was going to guess - I think you have fuel supply issues. Good for 'normal" driving, but isn't enough pressure when hammered
For video 1
No advice, but would expect some sort of shutter when changing at those revs
Cheers
Steve
The following 2 users liked this post by Bez74:
944xjs (12-28-2019),
Greg in France (12-28-2019)
#11
Hello 944
In regards to coil. I last had my XJS going August this year - when I finished getting the fuel tank, ect back in the boot. Started ok.
Finally got under the bonnet completed Christmas eve and tried to start it boxing day (as I did not want to get depressed on Christmas Day) and I have a no-spark situation.
These are the steps I took to realize my coil is stuffed
1) Disconnect the battery negative terminal
2) Get my multimeter - set on 200 Ohms and measure from the + terminal to the - terminal of the coil - should give a real small number (1.5 to 1.7)
3) Disconnect the HT lead from the coil, change the setting of the multimetre to 20K Ohms, leave the red on the positive terminal and the negative in where the HT lead lives. Should give you a resistance of 13.5.
Could not find the minimal range for the Jag, but for the Chev - a reading of 11.0 or less will result in a no spark situation. I am presuming with the V12, it would have to be more around the 12 mark.
My readings were 4.7 for 2) and 8.65 for 3). So a new coil is on the way.
This is the 2nd one that I have had fail on me, the first one was a falcon that I fueled up that day, loaded the car up and was about to hit the road, than had a no-spark situation.
So I don't think your problem is coil related, but only takes a moment to check.
For video 2
If I was going to guess - I think you have fuel supply issues. Good for 'normal" driving, but isn't enough pressure when hammered
For video 1
No advice, but would expect some sort of shutter when changing at those revs
Cheers
Steve
In regards to coil. I last had my XJS going August this year - when I finished getting the fuel tank, ect back in the boot. Started ok.
Finally got under the bonnet completed Christmas eve and tried to start it boxing day (as I did not want to get depressed on Christmas Day) and I have a no-spark situation.
These are the steps I took to realize my coil is stuffed
1) Disconnect the battery negative terminal
2) Get my multimeter - set on 200 Ohms and measure from the + terminal to the - terminal of the coil - should give a real small number (1.5 to 1.7)
3) Disconnect the HT lead from the coil, change the setting of the multimetre to 20K Ohms, leave the red on the positive terminal and the negative in where the HT lead lives. Should give you a resistance of 13.5.
Could not find the minimal range for the Jag, but for the Chev - a reading of 11.0 or less will result in a no spark situation. I am presuming with the V12, it would have to be more around the 12 mark.
My readings were 4.7 for 2) and 8.65 for 3). So a new coil is on the way.
This is the 2nd one that I have had fail on me, the first one was a falcon that I fueled up that day, loaded the car up and was about to hit the road, than had a no-spark situation.
So I don't think your problem is coil related, but only takes a moment to check.
For video 2
If I was going to guess - I think you have fuel supply issues. Good for 'normal" driving, but isn't enough pressure when hammered
For video 1
No advice, but would expect some sort of shutter when changing at those revs
Cheers
Steve
#12
coil resistance
[QUOTE=Bez74;2171919]Hello 944
In regards to coil. I last had my XJS going August this year - when I finished getting the fuel tank, ect back in the boot. Started ok.
Finally got under the bonnet completed Christmas eve and tried to start it boxing day (as I did not want to get depressed on Christmas Day) and I have a no-spark situation.
These are the steps I took to realize my coil is stuffed
1) Disconnect the battery negative terminal
2) Get my multimeter - set on 200 Ohms and measure from the + terminal to the - terminal of the coil - should give a real small number (1.5 to 1.7)
3) Disconnect the HT lead from the coil, change the setting of the multimetre to 20K Ohms, leave the red on the positive terminal and the negative in where the HT lead lives. Should give you a resistance of 13.5.
Could not find the minimal range for the Jag, but for the Chev - a reading of 11.0 or less will result in a no spark situation. I am presuming with the V12, it would have to be more around the 12 mark.
My readings were 4.7 for 2) and 8.65 for 3). So a new coil is on the way.
I read, possibly in Kirby Palm's book, that when replacing the original dual coil setup with a single coil, the primary resistance, plus coil terminal to minus coil terminal, should be .0.6 ohms.
In regards to coil. I last had my XJS going August this year - when I finished getting the fuel tank, ect back in the boot. Started ok.
Finally got under the bonnet completed Christmas eve and tried to start it boxing day (as I did not want to get depressed on Christmas Day) and I have a no-spark situation.
These are the steps I took to realize my coil is stuffed
1) Disconnect the battery negative terminal
2) Get my multimeter - set on 200 Ohms and measure from the + terminal to the - terminal of the coil - should give a real small number (1.5 to 1.7)
3) Disconnect the HT lead from the coil, change the setting of the multimetre to 20K Ohms, leave the red on the positive terminal and the negative in where the HT lead lives. Should give you a resistance of 13.5.
Could not find the minimal range for the Jag, but for the Chev - a reading of 11.0 or less will result in a no spark situation. I am presuming with the V12, it would have to be more around the 12 mark.
My readings were 4.7 for 2) and 8.65 for 3). So a new coil is on the way.
I read, possibly in Kirby Palm's book, that when replacing the original dual coil setup with a single coil, the primary resistance, plus coil terminal to minus coil terminal, should be .0.6 ohms.
#13
Hello Again
Have you considered installing a fuel pressure sensor just before the fuel rail. You can then run wires to a gauge into the cab and see what is happening when you open her up.
For an example - they can be purchased from glowshift, depending on your level of originality, can either be a temporary setup or permanent.
Just a way of getting real data
Just a suggestion
Cheers
Steve
Have you considered installing a fuel pressure sensor just before the fuel rail. You can then run wires to a gauge into the cab and see what is happening when you open her up.
For an example - they can be purchased from glowshift, depending on your level of originality, can either be a temporary setup or permanent.
Just a way of getting real data
Just a suggestion
Cheers
Steve
#14
Hello Again
Have you considered installing a fuel pressure sensor just before the fuel rail. You can then run wires to a gauge into the cab and see what is happening when you open her up.
For an example - they can be purchased from glowshift, depending on your level of originality, can either be a temporary setup or permanent.
Just a way of getting real data
Just a suggestion
Cheers
Steve
Have you considered installing a fuel pressure sensor just before the fuel rail. You can then run wires to a gauge into the cab and see what is happening when you open her up.
For an example - they can be purchased from glowshift, depending on your level of originality, can either be a temporary setup or permanent.
Just a way of getting real data
Just a suggestion
Cheers
Steve
#15
well changed the fpr and nothing different. Then noticed a nice big blue sparking going from the boot of the plug wire to the injector plate holder. How is this possible?! It literally looked like it was going through the rubber. I saw no cracks in rubber. They’re like a year old. Anyway I Twisted the plug a bit right and no more arc but alas didn’t solve the no high rpm revs. So I’m starting to think it might be an electric thing and not fuel. Any ideas? Can the spark travel up the side of a plug wire from a cracked distributor even? I guess I need to just rip it all apart someday
#16
Hello Again
Regarding your sparking lead - quick read from the below website - apparently happens pretty often
Trouble-Shooting Sparking Ignition Leads - Topgun Ignition
If it was me - I would still install the fuel pressure gauge to see if we have a starvation issue.
1) How old is the fuel pump - is she still maintaining the designed PSI out put?
2) When was the last time the filter in the surge tank was replaced, these get pretty dirty, maybe it is clogged up
3) When was the last time the pre-filter before the fuel pump was replaced.
For me - mechanical things are fairly easy to fix - electrical issues that have not completely failed, a bit harder to diagnose
Cheers
Steve
Regarding your sparking lead - quick read from the below website - apparently happens pretty often
Trouble-Shooting Sparking Ignition Leads - Topgun Ignition
If it was me - I would still install the fuel pressure gauge to see if we have a starvation issue.
1) How old is the fuel pump - is she still maintaining the designed PSI out put?
2) When was the last time the filter in the surge tank was replaced, these get pretty dirty, maybe it is clogged up
3) When was the last time the pre-filter before the fuel pump was replaced.
For me - mechanical things are fairly easy to fix - electrical issues that have not completely failed, a bit harder to diagnose
Cheers
Steve
The following users liked this post:
944xjs (12-29-2019)
#17
Hello Again
Regarding your sparking lead - quick read from the below website - apparently happens pretty often
Trouble-Shooting Sparking Ignition Leads - Topgun Ignition
If it was me - I would still install the fuel pressure gauge to see if we have a starvation issue.
1) How old is the fuel pump - is she still maintaining the designed PSI out put?
2) When was the last time the filter in the surge tank was replaced, these get pretty dirty, maybe it is clogged up
3) When was the last time the pre-filter before the fuel pump was replaced.
For me - mechanical things are fairly easy to fix - electrical issues that have not completely failed, a bit harder to diagnose
Cheers
Steve
Regarding your sparking lead - quick read from the below website - apparently happens pretty often
Trouble-Shooting Sparking Ignition Leads - Topgun Ignition
If it was me - I would still install the fuel pressure gauge to see if we have a starvation issue.
1) How old is the fuel pump - is she still maintaining the designed PSI out put?
2) When was the last time the filter in the surge tank was replaced, these get pretty dirty, maybe it is clogged up
3) When was the last time the pre-filter before the fuel pump was replaced.
For me - mechanical things are fairly easy to fix - electrical issues that have not completely failed, a bit harder to diagnose
Cheers
Steve
#18
Ok so I got out to test the coil today and I’m not sure if it’s ok or not? + to - I got about 1.1 with a resistance of .4-5 touching the leads together. So that comes out around .6ohm. Which is what it’s supposed to be for a high volt coil correct? My second number from + to HT lead was about 7.0... that’s supposed to be like 13 isn’t it? And check out my sweet ngk wires!
#19
I got my new coil delivered the other day, so the ohms I got from the primary circuit (+ to -) was 2.4, which was a bit higher than I was expecting, But I don't really think this will matter to much, as the primaries acts as an earth as the rotor in the dizzy rotates to make the spark.
Though the secondary winding (+ to the HT) - I get 14.25 ohms, which is better than I was expecting.
Another thing I noticed is my original lead from the coil to the dizzy was a bit sus, so I purchased a new one. When I tested the secondary winding\s with the new plug attached - I got 16.65, When I installed one of the original leads on - it stayed 14,25, so the new lead amplifies the resistance a little bit more.
Old coil - primary circuit = 4.7 ohms
- secondary circuit = 8650 ohms
New coil - primary circuit = 2.4 ohms
- secondary circuit = 14250 ohms
With a reading of 7000 ohms, your car is going pretty well considering - unless I am way off the mark
With the spark plug leads like they are - you might be losing a bit of spark which is affecting higher rev performance . Very surprising for 1 year old plugs
Anyway - I think you have found "a" problem - might not be "the" problem
Cheers
Steve
Though the secondary winding (+ to the HT) - I get 14.25 ohms, which is better than I was expecting.
Another thing I noticed is my original lead from the coil to the dizzy was a bit sus, so I purchased a new one. When I tested the secondary winding\s with the new plug attached - I got 16.65, When I installed one of the original leads on - it stayed 14,25, so the new lead amplifies the resistance a little bit more.
Old coil - primary circuit = 4.7 ohms
- secondary circuit = 8650 ohms
New coil - primary circuit = 2.4 ohms
- secondary circuit = 14250 ohms
With a reading of 7000 ohms, your car is going pretty well considering - unless I am way off the mark
With the spark plug leads like they are - you might be losing a bit of spark which is affecting higher rev performance . Very surprising for 1 year old plugs
Anyway - I think you have found "a" problem - might not be "the" problem
Cheers
Steve
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944xjs (01-04-2020)
#20
Are you still running two fuel regulators?
I know you just replaced the B-bank unit (I think) but do you still have the inlet (A-bank) regulator in place?
If so, bypass it and see if anything changes
Long story short I had a terrible bucking/cutting out problem with my '88 XJS and it was the inlet regulator that had failed
Cheers
DD
The following users liked this post:
944xjs (01-04-2020)