Jaguar Repair: Engine dies after driving, fuel pressure gauge, temp gauge

Question
Howard,

I have a 1985 XJ6 and it starts and runs well but has an issue when I have driven about 15 to 20 miles. It will start spitting and sputtering when I try to accelerate. If I come to a stop it will die. I leave it sit for about 10 minutes (with hood up) it starts back up and acts OK. The temp gauge shows the engine is not hot. Could I be getting vapor lock? I know the fuel is supposed to be cooled and my air is not working right now. You have helped me many times in the past.  Any ideas would be appreciated.

Thanks,

Kim

Answer
Hi Kim,
Even though there are a thousand things that can make a car quit after driving, there are methods to find what is wrong.

All engines only require 3 items to run and when an engine dies one or more of the three is missing. So it is just a matter of finding which of the three has went away.

The three items are compression, fire and fuel with conditions on each.

Compression will not usually come back it it were to go away so you can skip that for now.

"Fire" (ignition) can do that so you need a method to "See" ignition while it is in the failed mode (not start) This is easily done with a timing light but must be tested either while driving or right away when it quits and won't start.

An easy and sure way is to connect up a timing light and tape the trigger down so it flashes a light all the time and connect it up and run the cable out from under the hood and place the light under a wiper arm so you can see it while driving. Note the flash as the car dies to see if the light went away causing the car to quit.

"Fuel" is not as easy since it requires a fuel pressure gauge in a "T" fitting in the fuel line and a long hose and gauge under a wiper arm. Instead you can just purchase a spray can of starter fluid from any auto parts store and when it dies and will not start just spray a little fluid into the intake and if it starts up and runs for just a second or two and will only keep running if you keep spraying then you know it is a fuel problem.

These two tests only tell you in what area the problem is in, not exactly what is wrong so it then requires more tests after you pinpoint the area.

One other test that can be run is a vacuum test. Here you connect a vacuum gauge to the intake manifold vacuum and run the hose out from under the hood and drive the car to the time it quits and read the vacuum as you drive and let me know the results on the gauge.

Howard