QuestionQUESTION: Hello,
I just got a 1981 XJ6 Series III. She starts fine when she is cold, starts right up and keeps going. As the weather here in Northern Calif began warming up, we noticed that she would just die, as though she had a vapor lock. After talking with a friend that owns a BMW repair shop (BMW also had problems), I tried wrapping the fuel rail lines with metal backed foam (safe to 300*F). This seemed to help for a while. Now it is really getting hot outside, runs fine, but when you shut her off, after 20-30 minutes she will not start. If you wait for several hours, she starts right back up.
I replaced the fuel pressure regulator, all the fuel lines and installed a fuel pressure regulator heat sensor. Looking through the internet, someone indicated a 2 pound check valve going into the charcoal canister and another posting mentioned that there was some modification done to the later series III, but I can't find what the modification was.
Any help would be greatly appreciated,
Bob
ANSWER: Hi Bob,
All gasoline engines operate the same and when one dies it has lost one or more of only three items. Compression, Fire or Fuel.
Compression ---- If an engine looses compression when running it will not usually return so for now you can skip that.
Fire (Spark) ---- Electrics can over heat and stop working so you need to run a fairly simple test to see if "Fire" is lost at the time of the engine dies. Don't waste time trying to insulate items from the heat until you know for sure what died.
Connect a timing light up to a plug wire and tape the trigger down and run the wires out from under the hood and place the light under a wiper arm so you can see the flash of the light as you drive. If it is bright sun light you may need to tape a small piece of cardboard on the windshield so as to shade the light end so you can see it in the sun light. Drive the car until it dies and quickly look at the flash of the timing light to see if the light flashes all the way to a stop of the engine or does the flash go out first. This clearly established if it is "Fire" or "Fuel" related.
Fuel ---- Fuel must always be tested LAST. Since the engine is dead for several hours there is a simple test to establish fuel as the cause. Try to start the engine and when it will not start, spray a little starting fluid into the intake horn and try to start it. If it starts and you can keep spraying a little starter fluid into the intake and keep it running with the spray can, it for sure is fuel related. So you then need to start testing the injection system.
However, ALL you tests MUST be done while the engine is in it's failed mode (not running)
First is fuel pressure at the fuel rail. 42 PSI (engine not running)
Second is Injection pulse signal at the injection wires. (wire plugged into a "Noid" light. Available at most any auto parts store and not expensive.)
Give me all these test results and I will give you the next set of tests.
Howard
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QUESTION: Hi Howard,
Here are the results:
When we first got the car, I checked the compression at that time and it was 150 psi. This is when it was missing.
I think I confused you. It is not dying when I am running her. It is only when she is not running and hot that she won't start. I can restart her when she is hot after 5 minutes, after 10 minutes, after 15 minutes and then when I hit 20 minutes after I have shut her off that she will not start. I can spray a little starting fluid and the she fires off. This pretty well seems to indicate that it is fuel related.
Does this help? I really appreciate the time you are taking,
Bob
ANSWER: Try this, do your run to operating temp and shut it down and do your 5,10,& 15 minute wait and when you get to the "no start" condition and it will not start instead of spraying in starting fluid hold the throttle all the way wide open and try to start it. Don't pump the throttle as that does nothing just hold the throttle all the way to the floor. If it starts don't let it rev too high so be ready to drop the throttle. Let me know if it started.
Also, weather it started or not start it up (with starting fluid if necessary) and run it to operating temp again and do the 5,10,15 minute test starts and when you arrive at the "no start" again. Test the two wires with a 12v test light (still plugged in) on the Thermo-time switch while the key is in the "start" position. The Thermo-time switch is the large one in the coolant rail on the intake manifold and usually the front one. The two wires are white w/green tracer and a white w/purple tracer. Let me know what the results of that 12v test is.
Now make up a jumper with a male flat spade connector on one end and unplug the wires from the thermo-time switch and plug the jumper into the white w/green tracer wire and then remove the larger (12 ga) wire (White w/red tracer) from the starter relay (larger metal can relay on the firewall next to the fuel pump, main relay and the red diode pack)
Now, have someone hold the key in the "Start" position. All you should hear is a relay click. Now with the key in the start position listen and feel by placing a finger on the cold start injector, scratch the test lead you made across a ground. Don't connect it to ground only touch and scratch the ground with the test lead. You should feel and maybe hear the cold start injector operate.
If so, connect up the white w/red tracer wire back on to the starter relay and have someone try to start the car and while it is spinning over touch the test jumper to ground. If the engine starts, you may need to get another thermo-time switch.
The job of the thermo-time switch is to ground the cold start injector but only if the coolant is cooled off and only for a few start attempts. Even if the coolant is cool it will disconnect the cold start injector if too many failed attempts are made.
In the dealership we didn't have time to experiment or play with the system but I do believe many thermo-time switches got replaced that could have been saved with a resistor added to the White w/purple wire to delay the cut off time when failed attempts were made to start an engine.
There is a test of the time and temperature that the thermo-time switch is suppose to operate and if you want to do the test, let me know and I will post it for you. You would need a pan of water, something fabricated to suspend the thero-time switch in the water and a good thermometer and a stop watch and test leads with an ohm meter.
Other things can affect the system like a high alternator charge rate and poor engine to battery ground connections. These are easily tested and should be tested anyway on any series III car as they are prone to problems in this area. Put a volt meter across the battery post and read battery voltage and then start the engine and set the RPM at about 1500 RPM and read battery voltage (13.8v to 14.5v) Now with the engine running put the voltmeter on a low volt scale and put the negative post of the meter on the negative post of the battery and put the positive post of the meter on the engine itself and read the voltage. It should stay well below .5 volt. Now, leave the meter connected and turn off the engine and have someone hit the starter and watch the voltage. If you see over .5 v you should add or correct the engine to body to battery ground connections.
let me know,
Howard
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QUESTION: Hi Howard,
In the interest of time, I was just going to order a new Thermo Time switch. However, even though I could find it on a number of web sites, no one has it in stock here in America. Is there a web site you could direct me to where I could order it from England? Or any place that they may have this darn thing.
You are right though - as I am remembering - when I just put the throttle on the floor it did re-start, when I pumped it - it did not!!!!!!!!!!!!!!!!
I just cannot thank you enough. Have a great week and let me know, if you can, where I can buy one of these switches.
Bob
AnswerHi Bob,
Pumping the throttle does absolutely nothing but holding the throttle wide open does open the airflow meter flap further thus telling the ECU to make the injection pulse longer.
You need to test it first so you don't buy a part not needed and not the problem. I have two series three cars and just last month I had a cold start injector fail.
But if the Thero-time switch is bad, you might try Engel Imports, Moss Motors, John's Cars to name a few but most any Jag dealer should be able to get the part. These three I have bought parts from and they are reputable companies. They each have a web site and toll free numbers to talk to live people.
Howard
