QuestionQUESTION: 1984 XJS HE V12 car suddenly wont start idles from 0-500 a few times then stalls sometimes wont idle at all has newer fuel pres regs and new tune up seems to have had this problem b4 i found some tell tail signs that someone has checked a few things just picked up the car today. car also backfires sligtliy if i give it a lot of fuel to try to get it to run is reminds me of a noise a bad aif flow meter makes when it does not get enough air it also has a very strange smell when trying to run a bitter smell. THE CAR WAS RUNNING PERFECTLY
ANSWER: Hi Michael,
It does sound lean but it does not have an air flow meter. You need to be sure between ignition or fuel and you can do that just like a carburetor car by spraying a fuel like WD-40 or such in the intake of each side to see if runing improves. If you can improve the running by supplying outside fuel then you need to first check fuel pressure. (32 to 34 PSI as I remember) If pressure is OK make some preliminary tests. Put your fingers on each injector as you spin the engine over to feel them clicking (or use a stethoscope) If any are not clicking check for power to each from the resistor pack. (ECU grounds in groups of three at a time) That can be tested with a test light or VOM. There were three versions of that injection system depending on the Vin number but you can eliminate one by looking at the 02 sensor. The later system had heated 02 sensors thus three wires. The two earlier systems had one wire 02 sensors. Another preliminary test you can run is the throttle potentiometer under the throttle bell crank. It has three wires and you can check with an ohm meter between the red wire and the green and work the throttle and see the resistance move up and down smoothly, then check between the red and the Yellow and see the reverse resistance go up and down. Don't worry about the actual values just that the resistance changes.
Let me know up to that point and I will give you more.
Howard
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QUESTION: ALL OF THE INJECTORS ARE CLICKING FUEL PRESSURE SEEMS FINE IN AND OUT OF THE FILTER IN THE REAR, FUEL DOES NOT HELP IN THE THROTLE BODIE, CAR RAN FINE A LITTLE WHILE AFTER THE TOW LAST NIGHT FOR A MINIUTE, NOW TODAY ITS DOING THE SAME THING BUT AT LEAST ITS IN THE DRIVEWAY
ANSWER: Keep in mind that any test you run needs to be done while the engine is in it's failed mode. What do you mean fuel pressure SEEMS to be ok in and out of the filter? fuel pressure needs to be tested close to the injectors and while the car is running poorly.
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QUESTION: the fuel pressure going into the rail after the little press reg is 100 on a brand new gage and 80 when crancking so i checked it coming out of the filter it was 100. Is that not extreemly high or can a pump go bad the oppisite way higher instead of lower
AnswerIt should only be in the 30s unless you dead headed it to a gauge which is useless info. You need to test it with a "T" in the line so you can see what it is regulated to.
A pump can't go bad that way but a regulator can. But you need to be testing from a "T" in the line.
