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XJ40 1986 - 1994

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  #1  
Old 03-16-2009, 06:17 PM
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Unhappy 1990 XJ40 fuel problem

Hi everyone,
I have been searching the forums for a while now, and have not found any answers to my particular problem. First of all, I have a 1990 XJ40 (XJ6 Vanden Plas). It has 181,000 miles, and itís got a new transmission, new rack, and seems to run well (when itís running.)

Hereís the issue. I drove the car home after purchasing it. It ran well, but not real powerful. Next day it was running the same way, but no major problemsÖ until I took it through a drive-thru car wash. A few miles later, it stalled, or rather, cut out, at 50mph. After I pulled over, it wouldnít start. It was turning over, but sounded like it was out of gas. (Before anyone says, ďdistributorĒ Iíve checked it and itís fine.) After sitting for a minute or two, it started right up. Cut off again just as I got home (less than a mile.)

Since then, itís done the same thing. Runs for 10 minutes when first started up, then cuts off. Wonít start right away, but if you let it sit with key turned off, itíll start and run. Hereís the odd thingÖ the length of time it will run, after itís initial stall, seems to directly correlate with the amount of time I let it sit. For example, if I start it up a minute later, itíll run for 30 seconds. If I let it sit for 10 minutes, itíll run for 5 minutes. It never starts right after a stall.

It may also be worth noting that with the key truned on after the stall, thereís all sorts of clicking under the bonnet (hood, right?) Also, it I leave the key turned on, it doesnít ďcountĒ towards the sit time. (Does that make sense?) I also donít know if the car wash has anything to do with it. Itís been two weeks with this problem. It might be getting marginally worse.

Iíve figured that itís a fuel supply issue, but thatís where Iím stuck. I have ordered a manual, but as of now, I donít know where anything is located. Well, I did find the gas tankÖ

Car has ĺ of a tank of gas, and Iíve put a bottle of dry-gas into her. Any help would be greatly appreciated!
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Old 03-17-2009, 03:10 AM
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Have you pulled the plugs? are they soaked? sound like its flooding. 181000miles could be the injectors are toast...... or the whole car j/k Pull the plugs let us know.
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Old 03-17-2009, 08:33 AM
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Question I'll give it a try

I didn't think about the flooding possibility. If it has too much fuel, won't the engine surge before it stalls? If I just let it idle, it'll run about 1000 rpm's. This won't fluctuate at all, until it cuts out, no sputter, no surge. Will i need to check all plugs? or will one or two be representative of the rest?
Thanks!
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Old 03-17-2009, 12:29 PM
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Crank position sensor would also be something to give some thought to.
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Old 03-19-2009, 10:16 PM
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Post Well...

Well, i'm starting to consider the possibility of flooding. I haven't been able to get the plugs out yet to check them. Are there any other ways to tell if it's flooding as opposed to not getting fuel? Also, is there a way to check the crank position sensor without taking it to a mechanic and hooking it up to a computer?
It's been pretty crappy weather here lately, so i haven't been able to get much done on the car, and, obviously the car isn't getting any better.
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Old 03-20-2009, 02:19 PM
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Well, pulling the plugs will be the easiest way to check if its flooding. Next route is to hook up a fuel pressure gauge and check that way. But no matter how u go about it, you just have to roll up your sleeves and get in there and fix it .
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Old 03-23-2009, 10:37 PM
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Well, I ran it, let it stall, then pulled the plugs. They were dry, but kind of black and gunky.
I've also notice that when it's cold outside, the car runs for a while before it stalls (30 min +/-). On warmer days, it stalls pretty quickly (10 min +/-). The engine temp doesn't seem to be a factor. This all leads me back to moisture somewhere, a la the carwash mentioned in the first post. Does it sound like I'm way off? I tested the fuel pump and f.p. relay, both worked fine.
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Old 03-24-2009, 08:21 AM
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Hi FirstTimer,

Something similar happened to me when I had a 90 XJ40. Apparently some water got into the plug holes and caused a bad misfire. I had to clean out the spark plug holes, the spark plug cables and installed new spark plugs. After that it ran fine. You may also want to add some fuel injector cleaner (Techron) to your gas tank.

Good luck,

Mike
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Old 03-24-2009, 01:07 PM
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My '90 XJ40 had a similar problem. Start right up in cold weather then would not restart a half hour later. Had to let her sit for awhile..seemed flooded..anyway the onboard computer told me it had a Fuel Failure 14(I think)... it was a bad temperature sending sensor..The fuel injection didn't know what the engine temp was ... .$26.00 for the sensor and I haven't had a problem since.
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Old 03-24-2009, 02:11 PM
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I don't think you have a fuel problem. Typically, you would get some sort of sputter before it died. You haven't mentioned that, so I assume it's not happening. That makes me think it's temp related. Possibilities: temp sensor (as previously mentioned), ignition module, (and also mentioned) crank sensor. Something is cutting hot and shutting the car down immediately. That sounds electrical in nature, not fuel oriented.
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Old 03-24-2009, 09:47 PM
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Lightbulb

Thanks everyone,

I checked my rapair manual, and found info on a "coolant temp sensor" but not a "temp sending sensor." Are they one in the same? Second, can anyone recommend a parts dealer that would carry this? I'm also gonna clean the plug ports and replace plugs. I'll keep you all posted on progress. Thanks everyone!
FirstTimer (aka Jeffrey)
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Old 03-25-2009, 07:58 AM
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Coolant Temp Sensor is correct. Ken at British Parts should have one. If you have a meter you can check to see if there is the correct current running to the sensor. If the sensor is bad it won't give the proper resistance when checked. Proper meter readings are in the manual.
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Old 04-02-2009, 07:18 PM
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Default No Luck

Well, thanks everyone for your input. I changed the plugs, as well as the coolant temp sensor. Unfortunately, the problem is still happening. I can most definitely say it is temp related. It'll run like a champ until it get up to normal running temp (according to gauge) then it shuts down shortly thereafter. Any more thoughts? Is it worth giving up and taking it to my non-jaguar (though rather good) mechanic? I'd really like to solve this myself, with help from ya'll, of course!
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Old 04-05-2009, 11:02 PM
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Default Something new?

So here's what I've learned in the last day or two... The fuel pressure is good, even up until it stalls. After it stalls, the fuel pump relay keeps clicking and clicking, and the fuel pressure bounces up to 35ish, then slowly goes down, then jumps up again, all while not running. If I leave the key in the "II" position, it'll never start after a stall (i know i have to turn it all the way off to crank it again). If I let it sit for even 30 seconds with the key "off" it'll start right up (but only run for a few seconds/minutes). This all leads me back to flooding. My theory: As long as the key is turned on, the pump keeps pumping and the flood can't drain. If it turn the key off, it drains slowly. Does this sound accurate? Is there a fuel return hose that drains gas back into the tank from the engine? Could this be clogged? all help is greatly appreciated!
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Old 04-05-2009, 11:32 PM
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Your post says you have a 1990 XJ6. Have you been checking for fuel fail codes by pressing the VCM button? Coolant sensors won't cause a stall on XJ40, but they will show a code 13 when the sensor (or connection) is intermittant.

The pump relay on a '90 is mounted on a bracket at the brake pedal housing under the hood. Key on, relay activates for two seconds, then clicks off. That's the flood protection, signalled by the ECU 'cause it knows the engine isn't running.

The 1990 pump is mounted on the rear suspension A frame, and makes like 60 PSI easy. Everything the engine doesn't burn goes through the fuel pressure regulator (call it average 35 PSI, that's close enough) and back through a return hose to the tank. If you're seeing 45 or more at any point, you have a faulty fuel pressure regulator or a return line restriction. It happens, rarely.

Supply faults is another story. The biggest problem is hot restarts, when the outlet check valve on the pump fails and the residual fuel pressure quickly drops when the engine is shut off. No rail pressure + hot engine = vapor lock. Key on, pump relay activates, pressure hits (nominal) 35 PSI, pump relay opens, pump stops, pressure holds relatively steady: that's what you should see. If you have identified the pump relay correctly, and it is clicking on and off or continuing to allow pump operation with the engine not running, you are on the right path.

Check for fuel fail codes on the dash, I think you have another problem entirely. The exact fuel pressure varies with engine vacuum, but it has to be radically high or low to cause a significant performance fault.
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Old 04-06-2009, 10:42 AM
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Thanks JagTechOhio,

I am not getting any codes from the VCM. My repair manual says the pump relay is under the passenger's side dash liner. The diagram lists it as PI Pump Relay. Is that the one? This is what keeps clicking on and off, even when the engine is not running. If I listen near the fuel rail, I can hear fuel moving while this is clicking (sounded like fuel was still being injected or something like that). My fuel pressure readings were taken at the end of the fuel rail closest to the windshield.
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Old 04-06-2009, 03:15 PM
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The pump relay was on the right side underdash component panel on early cars, if I am mistaken and that is where yours is, fine. Start the engine and pull the relay, if you're looking at the right one then the engine will stall in 10 seconds or whatever. That relay functions as I described, if you have a problem, then you have a problem.
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Old 04-06-2009, 04:38 PM
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Thanks for the quick reply. I just pulled it and it acts as you described. However, when the engine is hot, it will click like mad after a stall. Is there a fuel pressure sensor or anything that controls this relay? I have switched the relay with a known working one, and same story.
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Old 04-06-2009, 04:56 PM
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So that's the correct relay, verified as good, doing something it shouldn't. Now you have to use your wiring diagram and find out why. You can also pull down the ECU and inpect the connections, as I believe you will find that the ground sigal to activate the pump relay originates from there.
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Old 04-07-2009, 03:45 PM
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Thanks for the help, im in the process of tracking down the problem, but so far, no success. There are two things that just occurred to me, but im not sure if they have anything to do with my problem. First, my coolant indicator light on the dash is always on. The person i bought it from says it happened when he had a new rack put in, and the coolant level is fine (verified). Is there any sort of shut-off if that light is on too long? Also, the exhaust smells REALLY strong, and stays visible, but not smoky, even if the car has been running for a while, and is warmed up. Should either of these indicate anything? I'm probably grasping at straws. Thanks again.
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Old 04-07-2009, 03:45 PM
 
 
 
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Tags
1990, change, check, code, crankshaft, filter, fuel, jagquar, jaguar, position, pressure, pump, regulator, sensor, xj40



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