Hey everyone. I'm new here, was googling to find out whats wrong with my car and stumbled on this site. Hope someone can help me out.

I have a 99 jag XJR that was running great up until a couple of days ago. The car won't start. It will turn over but just doesn't fire up. I plugged in my scanner, and the only code that shows up is one for my MAF sensor. I've read all over that a common problem with the symptoms I'm having is a fuel pump, but when i turn the key to the on position, I can hear the fuel pumps in the rear humming. ANyone have any suggestions? Any known common problems that I can be facing.
Cheers.

 

Fuel injection systems measure out the fuel at the injectors by varying the pulse width which switches each injector on based on readings from sensors. The two main sensor inputs are (1) Mass Air Flow (MAF), and (2) engine coolant temperature. Values from each of these are then compared to a digital "map" in the ECU for each possible value. The other sensors are for trimming purposes, or to detect sudden throttle movement for acceleration/deceleration. So your "only" fault code is actually referring to one of the two main inputs to the fuel controller. If this detects no flow, then no fuel is supplied, and hence no start !

 

Fraser's answer sounds better than what I'm going to say, but... I've had one instance where my '98 would crank just fine, but refused to actually start. So I'll share what solved my problem. Did you, perchance, drive it just a few feet the last time you turned it on? In my case, I moved it from the driveway into the garage. Apparently, my car does not have the latest ECU firmware and it flooded when I tried to start it up since it didn't get warm the last time it ran. After some quick googling, I was able to start the car by cranking the engine and repeatedly pressing the accelerator pedal to the floor and releasing it.

My google search also revealed that an alternative solution is to reset the ECU by turning the key to position II and leaving it there for 15-20 minutes before trying to start the car.

 

THanks for the tips. I tried keeping the key in the on position for a little over 20 minutes, but no luck. The problem arose after I did my daily commute (20miles), and starting it later that day, so no short driving.

Frasier, you were very informative, but i am still unclear as to what you think the problem may be. From past experiences, I know that a MAF sensor will cause the car to run rough, but it should start. I don't think this is what you were saying though. I believe it is getting fuel, I have good fuel pressure and I can hear the pumps humming. Also, I do get spark and the motor has good compression.

 

In reading you post I am not sure if your starter is turning you engine over when you attempt to start the car. If it does you may want to read this short checklist and procedure. http://www.gusglikas.com/AutoRepairNoStart.htm I hope it helps!

 

The trouble is cars just keep getting more complex !! I am only an old duffer experienced with cars that had the early EFI systems, not the avionics-type stuff we have now. No diaganostics with the old stuff, you just had to trace wires and volts.

As you have said, the diagnostic code points to the MAF, so that must be where to start the search for a fault; you have no other fault codes. These things can be as simple as a bad connection. Did you or anybody else do any work in or around the engine compartment just before the fault started ? Any other events, or did it just let go ?

You might care to check battery voltage too. Sometimes fuel injection systems can be sensitive to having only the correct voltage when cranking the car. A battery on the way out will suffer a large voltage drop when cranking the car, and this could affect the fuel system. I had this problem last UK winter, (very cold like Russia), and I had a car start failure that a new battery cured, (a Rover 75 V6). However, now it's summer.

All I can say is come back, carburettors, all is forgiven !!

 

Check the MAF sensor connection to make sure all is well. I do not believe they have a fuse for just the sensor. The MAF can just fail. I have had a no start condition with one car when it did.

 

What code are you actually getting?

Jim

 

Yes check the MAFS and any other codes you are getting but keep in the back of your mind that at times a low battery and the continued cranking will give you false readings and you will be chasing a ghost as many have. Use good common sense as you proceed and whatever you do keep us informed and we will try to help.

 

I don't have a jag specific code reader, just a universal one so I'm not so sure how helpful that can be. The code I am getting is P1000.

I charged the battery overnight last night, and it still isn't starting. Now, I just went to the fuel schraeder valve, and it does have pressure, but I'm not quite sure how much pressure is neccessary. I put a little screw driver into the valve and it squirts some gas out. When i crank it over, and check the pressure again, it gives another little squirt of gas. I'm not quite sure if the gas should be shooting out like BP's pipe, or if this is how it actually should be. I'm going to try to jump the fuel pump relay and see if that helps.

All my connections are good, nobody was tinkering around with the car before this happened. And the starter is engaging. I thought maybe the engine was flooded, so I attempted to crank it. One of my tries allowed me to rev it to 3k rpms but then it died.

 

The fuel pressure should be around 42 PSI +/- a few and you can get a pressure gauge from AutoZone as a loaner. The last time when you got the car started did you just move it or was it a short trip?

The P1000 you got is a System check not complete since last memory clear. Kinda like junk mail!

 

Hey Guys. So I went ahead and tried starting the car again after switching the fuel pump relays. THat did me no good. I then went ahead and cranked the motor for a good 20 seconds at a time with a 2 minute break in between. After the 4th try, i got my scanner and reset the codes, and it started!!!!

It idled on it's own, i let the car run for 20 minutes. I turned it off, and it wouldn't turn on again, until i reset the codes once again and it started. Now, I am getting a code of p1230 and the car seems like it has a rev limited at just below 3k rpms.

I did notice that my seal for the intake elbow is completely shot, and heard a pretty big vacuum leak from there. Do you think this would be my culprit? I'm going to change it tomorrow, but just for peace of mind, wanted to see if this $20 fix will bring my car back to life.


Again, thank you guys so much for your help.

 

you may just cure it with the seal. There's a rev limiter of 3000rpm for safety reasons. It will not rev over this in park.

p1230 = throttle position sensor/switch a circuit high input

 

A large leak in the intake will certainly cause all kinds of problems with the cars computer. You can not diagnose any of the issues properly without fixing the intake. Even if the engine was able to run -- a small leak could cause the computer to think something was up with the position sensor and/or the MAF.

Fix the leaks first

 

Try pushing the accelerator clear to the floor, hold it, and crank the car for about 20 secs. If it flooded that is the only way it will start.

 

sorry, didn't see the second page!

 

TPS issues can sometimes be cleared up by cleaning the throttle body. I was having similar problems and found the directions for cleaning in the forum somewhere (thanks to the original poster). Might want to give it a shot.

 

Thanks for all the great advice here; I was able to get my XJ-6 started. As previously mentioned I had just started the car to move it out of the garage and then shut it off. When I went to drive it next time it would not start. I turned the ignition while holding down the gas pedal and after 20 seconds it caught