When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
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...
Might be cheaper to treat yourself to a New FPR for 'B' Bank if your old one has been on there for sometime, as they don't last for ever and if that's not the problem then at least you'll have a spare
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.
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.
Last edited by Dleit53; 12-27-2019 at 02:19 PM.
Reason: additional information
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.
well I went to the junkyard today and got a fpr. I’ll probably toss it in on Sunday or Monday to make sure that it’s not that. I assume the regulator from the junker is good as it still had fuel in it. I went to get the ignition amplifier off it but it was already gone. So we’ll see. I did plugs and wires a year or so ago all gapped properly. The single coil I’m not sure what brand or where I got it. I’ve done so much I can’t remember. Eventually I was going to change the trans vacuum module. The car will kick down at times but a lot of the time it holds the gear it’s in. It’s definitely still a work in progress. I would like to drive a “perfect” xjs to see where mine is at in comparison
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
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
hard to tell from video but in video one it like hits a wall and then bucks if you stay in it. It’s very jarring so of course your first instinct is to let off the gas. Basically it does what video 2 does only you’re moving pretty quick.
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.
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.
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
i have thought about it. Since you basically have to do the same work in order to hook up a tester, I might just get a small gauge. Monday I’m going to put in the other fpr I got.
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
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
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
yeah I’d like to get a gauge still. Fuel pump and filter is probably 2yrs old as well. Everything is about 2-3yrs old. In tank filter cleaned probably 1.5-2yrs ago. I’m trying to do this stuff as we have an unusually warm winter here in northern Illinois. It was almost 60 degrees today. It should be about -10 with a foot of snow. I need to get a gauge or atleast a tester to fully rule out fuel before I start tossing money and time at the electrics again. I witnessed to day how these cats light on fire all the time. If there was the slightest leak at that injector my xjs would be done.
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!
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.
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
hard to tell from video but in video one it like hits a wall and then bucks if you stay in it. It’s very jarring so of course your first instinct is to let off the gas. Basically it does what video 2 does only you’re moving pretty quick.
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
12-26-2019 | 12:47 AM
Last time I ask for help on this issue... trans shifts?
