X300 XJR spins freely but just won't fire

So, I bought A '96 XJR several years ago. It’s been my daily driver. It’s been so reliable that it looks like I stopped even logging in here about 2 years ago.

So everything was good until this week. Been out of town for two weeks so car just sat. The first time I tried to start it, it fired right up and ran smoothly in reverse for about 30 feet until I got to the end of the drive. Then it just quit. I have cranked and cranked, killed the battery, recharged, and cranks again. I have cranked for over 20 second at least a few times. I have swapped out first the fuel pump relay, and then all the relays in the trunk. No change.

So, no error codes, the engine turns strong and free. It just won’t fire. Doesn’t even seem to try. Oh, NO smell of petrol in exhaust even after lengthy cranking.

Sorry I haven’t been around in a while to help anyone else. I got too comfortable in my good fortune. My old familiarity with typical X300 gremlins has clearly waned in the mean time. Guess it’s time to get back up to speed. ANY suggestions or tips on any usual suspects VERY much appreciated!

P.S. I believe the XJR has an extra fuel pump relay in the trunk. There is an extra blue relay against the fire wall that does not appear in my n/a X300. I have tried swapping that to no effect. But there is also a large, black, 5 bladed relay in the same spot. Don’t have that on my other X300 either, but can’t swap it because I don’t have a similar one. Any ideas what the big black one is for?

Firts things first, do you have spark? Have you cracked the fuel line to see if you are getting the initial prime from the fuel pump? Check those tow out to eliminate one of them and then report back with the findings.

Does the Tachometer read about 250 RPM when cranking? If not it’s the CKPS or it’s wiring!

THANKS for the comments, and sorry to be slow responding. Deathly ill the last few days. I believe I’m getting spark but no fuel, and I believe tach is responding appropriately, but I will check to confirm ASAP.

BTW the X300 can also lack of compression due to Washdown also!

If it sounds like it is lacking compression take the plugs out and insert some engine oil into the cylinders, not too much just sufficient to cause the rings to seal.

Doesn’t the 95 thru 97 xjr have a secondary fuel pump also? Did u check the fuel filter?

Thanks for the suggestions. The weekend is here and health is on the mend, so I will definitely accomplish more diagnostics today and tomorrow.

Will try a bit of oil in the cylinders. If it matters, this oil change is full synthetic and has around 500 miles since last change. It has been over 100 degrees F here in Dallas for a while, so I’m running 10W-40. Car only has 58k miles, so I can’t imagine it would have a compression problem for any other reason barring washdown.

I have spark (at least on one plug) but I don’t think I’m getting fuel. When I turn the key on, i get an audible click from the Auxiliary Positive Relay in the trunk followed by a click in the Fuel Pump #1 relay right next to it, but I am not hearing the tell tale whir of the fuel pump pressurizing for a couple of seconds. Could just be quiet. I haven’t had a chance to pull the fuel line from the rail to be sure. I’ll do that and then jump the relay to see if I get anything. Health prevented that this last week.

May be putting the cart before the horse, but can anyone confirm how exactly fuel pump #2 is activated? Should it be coming on with the ignition as well, or does it not kick in until 4k RPM? Also, if it doesn’t kick in until later could I switch the connections to make pump #2 into pump #1 to see if that starts the car? If so, that would seem to be a perfect and easy way to confirm a problem with pump #1.

Again, many thanks to all.

P.S. … and yes, it has 2 fuel pumps, but no, I haven’t checked the filter yet. Quick and simple change though so will try that this weekend as well.

Yep bad primary pump. Had to replace twice in 2 months on my kitty due to non jaguar pump. Burned out fast trying to maintain pressure with the cheap part mechanic ordered. Got jag omaha from jagbits and no issues since. Makes sure to have extra hose and clamps…mine were in poor condition and replaced hose in tank as well as in tank filter. Dropping the tank was a pia. From other jags I have seen the rear deck cut out for access. Next time I go that route and save the $450 in labor for dropping the tank. Watched a gentleman with cutting wheel do that method and cut replaced pump and closed up in an hour in his drive way. Much more straightforward just remember to seal back up.

Typical tow-truck get-you-going tip for failed fuel pump:

Whack the tank with an axe handle a few times. :wink: This often causes the pump motor to spin up past the dead spot and run for a while (until it stops at the same place again)

Sometimes a useful diagnostic tool, i.e. if it runs if you do this, you need a pump.

I changed the fuel pump in my XJ40 which has a very similar setup (tank out etc.) Not a difficult job, but quite a lot has to be removed to get the tank out …however, if you’re methodical and you’ve got a place to work, it ain’t that bad.

O.K., hotter than hell today, but I’m slowly working through diagnosis.

  1. Tach shows movement to 250 or so when starter engages.
  2. Confirmed that both fuel pump relays are working properly.
  3. Confirmed both fuel pumps are working. Man, they are quiet, but the whirring sound was audible.
  4. Checked fuel at rail. I don’t have a gauge, but when I jumped one pump and then the other, I got a fairly strong, steady stream at the rail from each. I also confirmed that a get a two second burst at the rail when the ignition is first switched on.
  5. Pulled all the coils and they look pristine.
  6. Pulled all 6 plugs and they look o.k. They probably don’t have 10k miles on them. The ceramic insulator up the sides on the outside shows brown streaks from high heat. Maybe I should switch plugs, but these were working great before.
  7. Trying oil in each cylinder now. I’m going with a few cc’s in each cylinder. Is that enough? Too much?

Still haven’t found the problem, so any suggestions welcome.

Hi Jeremy,
Sounds odd to have fuel and spark but no action - even low compression should be enough to cough and splutter a bit. If plugs are out, spin over with finger in spark plug hole us usually enough to see if it is breathing.
You mentioned that you checked for spark on one cylinder - how did you do that? and could you repeat for other cylinders since you are running out of options? I once had an instance of an old car that gave one spark only - drove me nuts because I thought I had spark and spent ages looking for other causes. Replacing the coil fixed that but I’m not suggesting that in your case - it was an old four cylinder points/distributor car. Point is it may be worth your checking for repeated spark and on more than one cylinder.
One other suggestion is to check that air is getting into the intake manifold…may seem odd but that’s the third side of the fire triangle. Maybe a mouse nested in your intake and it or its nest got sucked in during the trip down the driveway…Cats do eat mice after all.
Sounds curious - good luck.
Munro.

Ugh! I’m out of ideas and out of energy for the day. I’ve tested everything I can think of.

I’ve tested literally every fuse in the car and swapped almost every relay with known good ones a few at a time including, but not limited to, both fuel pump relays, the starter relay, and the ECM controlled relay. I have also tested the relays individually with test lights and a 12v source on the bench and all functioning properly. I have pulled all six coils and they look pristine. I have pulled all six plugs and they look fine. I tested one by taking it out and grounding to the block while cranking, but didn’t check the rest. I pressed the reset on the inertia switch, but it didn’t feel like it had been tripped.

I have fuel at the rail. I don’t have a proper fuel pressure gauge, but when I jump the pump #1 and then the pump #2 relays, I get a fairly strong, steady stream at the rail from each. I don’t see any water or contaminants in the gas pulled from the rail. I swapped the fuel pressure regulator with a known good one. The old one had fuel at the top end, but was dry at the bottom end, so it looks like it was holding pressure. No fuel at the vacuum inlet.

I am reluctant to use starting fluid on a super charged car (primarily because the can says "Do NOT use on super charged cars). Nonetheless, I did shoot a few short bursts into the breather line after the MAF sensor. (Pulled it off, shot in a few bursts, put it back on, then tried to start.) It tried to start and ran weakly for few seconds with starting fluid, so… whatever that means. But I think it at least means that I’m getting spark. (That’s why I didn’t bother with checking the rest for spark, plus, it started perfectly and ran smoothly to the end of the driveway right before it died last week.)

I checked every ground in the car that I could find. I pulled the ECM and looked it over. It looked brand new, no corrosion of any kind, no bent or damaged pins. Ground at the ECM was good.

It may be worth noting that the ECM had a sticker on it that said manufactured in May of 1996. But, it also had a sticker that said “R493 LNA 1410SF Date 5/12/02 SAGEM PROM Ref 9359.” The date was written in by hand. I assume that was related to reflashing the EPROM or something as part of some factory mandate???

I also put maybe 5-10 ml of fresh engine oil into each cylinder through the plug hole. Made absolutely no difference.

And I’m still not smelling any fuel at the exhaust even after extensive cranking.

Based on all of this, I feel like I’m not getting fuel, but it’s available at the rails. I can’t imagine that all 6 injectors would go out at one time. But what would keep the car from telling the injectors to fire?

My X300 diagnostics are rusty, (so PLEASE CORRECT ME IF I’M WRONG ABOUT ANY OF THIS) but I don’t think it’s the CAM position sensor (CPS) because even when I crank for a long time, it still doesn’t start. I don’t think it’s the CRANK position sensor (CkPS) because I’m seeing 200 rpm on the tach when cranking.

I don’t have a noid light, and as I recall I can’t check to see if injectors are firing with a test light. The pulse is just way too short. Could it be a throttle position sensor? I’ve never cleaned the throttle body on this beast because I can’t figure out how to remove it with the super charger.

WHAT AM I MISSING?!?!?!

Seeing as you have tried most things would it be worthwhile flooring the accelerator pedal and cranking? I appreciate that you say there is no petrol smell at the tail pipes but it might be worth a try?
You should be able to ‘hear’ the injectors clicking if you have a stethoscope or even a screwdriver.
On my 2.9 I physically removed the injector rail from the Cyl hd and cranked the engine to check if they were emitting any fluid.
The throttle position sensor can be checked by back probing the wires, you should have about .4-.6v at idle through to <>4.6/7v at WOT

WOT is no good as the ECU will cut the fuel off if it thinks the car has has flooded, use half to threequarter throttle. Also check the inertia switch near the pedals.

I seem to recall in the dim dark past being told not to use the throttle when cranking unless the engine was possibly flooded, if it was flooded flooring when not firing caused the ECU to cut the injectors so that the cranking would clear the excess fuel.
We need to know if the injectors are clicking or physical evidence that they are spraying fuel.

Jeremy,

I have read elsewhere of something similar to your problem caused by injectors not triggering, that suggests tracing power to the injectors. I’m unsure of the rules in this situation so have not posted a link.
The gist of it is that a single brown wire provides 12v to all 8 injectors - the ECM then grounds as needed. With a test light you should be able to confirm if there is power to all injectors.
Fuel injectors get power from the Fuel Injection Relay which in turn gets power from the Engine Management Fuse Box.
Check for power at pin 3 on the relay (input) and on pin 5 of the relay with key in run position (brown wire, power output to all injectors - you can measure this at pin 2, brown wire, of each injector connector). You don’t need a noid light for this.
There is a junction point in the brown wire, where the single wire from the relay splits into eight wires, one to each injector. If you have a digital VOM then you could measure resistance from pin 5 on the relay connector to pin 2 on each injector connector - should be very low resistance - if not, the junction is suspect.
If you are able to trace 12V all the way to the injectors and the injectors are not triggering, then the problem is in the ECM or input signals to the ECM. This is for a 98 V8 N/A. May not exactly match your vehicle, but probably the same process applies. None of this is original. Hope this gets you closer. I wonder how much a noid light costs and how available they are to fit the Jag.
Regards, Munro.

From exerience 3/4 throttle is IMHO the best to clear excess fuel. Takes a good minute or more of cranking and needs a good battery or booster pack/jump leads!

Also when it does fire it’s usually as lumpy as hell and needs nursing by blipping the throttle and don’t come off the key before it’s become even.

Here’s the latest update:

Too hot to work on car during the week, plus I’ve got to work. Spent the week indoors refurbishing some injectors off of my shelf to swap out. Got them in good shape, but realized they were for a normally aspirated car, so wasted time.

I did check the circuit to the fuel rails as suggested. In fact,I just pulled all six plugs, turned the ignition on, and then probed to ground. All 6 were hot, so they have power. (Whether they are each getting a separate ground signal from the ECM is another question.) I believe that means that the ECM controlled relay is powering up correctly. Can anyone confirm?

While I was there, I probed all six injectors. All six tested at 17 ohms if that means anything. Then, running a ground to one prong and a test light from positive to the other, I checked all 6. All 6 showed a good light, but I only heard 2 of them click on and off. Those 2 were clear and distinct. Could I possibly have 4 bad injectors? That all went bad at one time???

I have pulled the rail and all 6 injectors and ordered another rehab pack with o-rings and orifice filters. I built a little rig earlier in the week to refurbish the other six, so I’ll use that to pressurize and test them then report back.

Ugghhh!!! If it just wasn’t so hot!