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Jaguar Repair/1984 XJ6 not starting


Jar of bad gasoline
Jar of bad gasoline  

About two months back, we discussed an issue I had with some fouled fuel and a no-start problem. The past two months have been the most trouble free since I have owned my XJ6 - starts first try every time, runs strong and smooth, etc - until last Saturday. On a short trip, it began losing power and barely made it home. The next day, it would not start at all. I checked spark and was good, fuel pressure was good, so I pumped some fuel in to a jar from the hose at the rear of the fuel rail and once again it is cloudy. I have put no additives in since draining and refilling tanks in November. I also changed the filter at that time, and as I said, it has been great ever since. I did take the tanks out in 2011 and have the re-lined, but the lining is dark red and I would think if it were failing, there would be a reddish tint to the gas. It is just foggy, and after several minutes sitting on my work bench, it even begins to separate. I have attached an image here. Have you ever seen or heard of such a thing? It seems uncanny for it to happen twice within months.

ANSWER: Hi Michael,

Any time a gosoline engine does not start you have to run the same tests even if it ran good two minutes ago and you had replaced a lot of parts. All engines require the same things to run. Compression, Fire and fuel. They MUST be tested in that order and NEVER try to guess what is wrong and never try to diagnosis by symptoms.

Even if it has been running great, test the compression. 135 PSI on EVERY cylinder or better.
(throttle open when testing)

If every cylinder don't have that or close to it then don't bother going to any other test because it will never run until the compression is close to correct.

Next test is easy because it will test both spark and fuel. Spray starting fluid into the intake while someone tries to start the engine. If it starts but will not keep running unless you keep spraying then you have a fuel problem. If it does not try to start then you have either no spark or the timing is off.

This will tell you which has failed and then you test that system (fire or fuel).

The only exception to that is the battery problem that the Jaguar ser III has. Even if the battery spins the engine over fast you still need to connect a known good battery to the car like you are jumping off a car with a dead battery. If that makes it start then you need a new "Deep Charge" battery. The old battery can usually be used in another brand car for some time.

let me know what these tests show.
The color of the gas don't mean anything.


---------- FOLLOW-UP ----------

QUESTION: I only asked if you had seen gas do that before. I know the no-start testing backwards and forwards. Neglected to mention it would start and run on starting fluid, so no need to test battery or compression. Since fuel pressure was strong, the only thing left is that the fuel itself won't burn. That had been well established, so I was only asking if you had ever seen gas turn bad. I figured it out though. Both times this has occurred after the car was outside in heavy rain. The gaskets under the fuel filler doors must be letting water that pools up there get in the fuel tank. The jar I took a photo of last night is clear tonight other than globules of clear heavy fluid resting at bottom. Water.

ANSWER: It can be a cap problem but there are drains in that cap area so that rain will drain and not raise to a level that might get past a set of bad rubber seals in the flip cap. Some use an old speedometer cable to run down the drains to clean them out and even some put the cable in a drill motor to use it like a roto rooter. Many gas stations don't keep their tanks cleaned out and you can pump some water into the fuel tank from a gas station.

When the system if working there is about 3 PSI pressure buld up in the fuel tanks. So even if the drains were stopped up and the rain filled the cap cavity no water could enter the tank due to the pressure in the tanks. This pressure it held by a plastic pressure valve in the vent line jsut behind the charcoal canister behind the right front head light. If your round rubber cap seals are cracked then there will not be any pressure build up in the tanks. And if the drain vents are clogged you could get water in there.


---------- FOLLOW-UP ----------

QUESTION: I drained the entire left tank, in to two containers, then reasoned that the water should settle in those, so poured all of container 2 and most of container 1 back in the left tank and it flowed clear and the car would start and run on that. I removed both filler caps from the vehicle and cleaned them, threw away the paper gaskets I made when I painted the car in 2012, and went with a silicone gasket-maker bead on each, just as one might for a valve cover, or oil pan. I also blew out the drain holes with air from compressor. I drained about a gallon off the right tank tonight, and it was foggy at first, but as soon as it ran clear, I reinstalled the plug. Having been 24 hours since the silicone job, I poured water over each closed cap and saw it pour out underneath. car ran on both tanks tonight and I netted a loss of about a gallon which I can use as driveway solvent - to loosen up oil stains, etc. What a mess, and a good lesson!

Thanks again Howard, I'm just glad I didn't get crazy and start accusing someone of vandalizing my car with sugar or something.

Sounds like you have it handled. Keep and eye on those round rubber seals in the caps because when they get cracks in them the TN emissions test will fail the car. They got me once. Rather then use the rubber ones from Jaguar I bought a small sheet of 1/8 inch Neoprene from Volunteer rubber and Gasket in Nashville and made my own.


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Howard M. Fitzcharles III


Jaguar from the XK 120 to XJ-6 ser. 3 1987


Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

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