QuestionQUESTION: I recently replaced the head gasket on this vehicle after it overheated and died on the highway. I cannot get it to restart, I suspect the starter relay,(i have fuel flowing and spark at the plug) is there any way to test a relay out of the car? I am contemplating pulling one out of the junkyard. Thanks!
ANSWER: Hi Tim,
The larger metal can relay on the firewall is the starter relay and it can be tested with a 12v battery and a test light or volt meter.
Connect your (+) test lead to "C-2" and your test light to "C-4"
Connect a 12v battery (+) to "W-1"
Touch the (-) battery lead to "W-2"
You should hear a "Click"
and when you hear the "Click" you should see your test light light up.
Howard
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QUESTION: I replaced the starter relay (new one) still no start. Cranks and every once in a while it slightly speeds up like it wants to go but nothing. Have spark and fuel. Checked compression cold and its low, one cylinder has only 5# others range from 89 to 30. I've moved distributor back and forth doesn't seem to help. I am open to any ideas. Thanks.
ANSWER: Tim, there is something very wrong with your compression test. Run it again and this time be sure the throttle is wide open and you get at least 4 to 5 revolutions on each cylinder. Write down the readings and then do a "Wet" compression test. That is where you put at least a teaspoon of engine oil in the cylinder before each test. The second "Wet" test will be higher than the first "Dry" test but it should only be about 10% to 15% higher. If the "Wet" test is more than that, you have collapsed rings from the overheating. Valve springs will also have suffered.
Most piston engines will not run at 100 PSI and below.
Let me know,
Howard
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QUESTION: I rechecked the compression as you suggested. FYI, #1 51 dry 110 wet, #2 10 dry, 49 wet, #3 38 dry, 80 wet, #4, 80 dry, 91 wet, #5 50 dry, 109 wet, and #6 61 dry, 90 wet. Obviously I need new rings. When I replaced the head gasket, I had the head resurfaced and replaced a valve, cleaned them up and reseated them. They all closed very tightly so is it safe to assume the springs are good? One other dumb question, since the engine has not run since replacement of the head gasket, do you think I could reuse it or should I get a new one after all these repairs?
Thanks so much for your patience with this novice mechanic!!
AnswerSorry Tim, your readings indicate you have both ring and valve problems. No, on the springs being good. When you strongly overheat an engine the exhaust valve springs go weak first then the rings and intake valve springs go next. That engine should have 150+ PSI on a dry test.
I would never try to reuse a head gasket on a Jag because it is so much work to remove it again. I have done it on small 4 cylinder engines by coating the gasket on one side with "Copper Coat" but have never tried it on a Jag.
You do know that when you install the cams, they must be installed "In Time" and you can not rotate either cam when they are in the head and you can NOT set the head down on a flat surface because the weight of the head will bend a valve. The only way you can set the valve clearance is to do all the intakes with the exhaust cam removed and vice versa. Valve keepers MUST not be mixed, they MUST be kept in pairs. Stem seals only go on the intakes.
To test for valve leakage, set the head on it's side and pour about a half cup of something like diesel fuel in each port before the cams are installed and look for seepage. I use .011" to .014" valve clearance. If the seats or valves are reground I try to stay closer to .014" as they tend to seat in when run a while.
Be sure to retorque the head and check valve clearance and upper chain adjustment after a few hundred miles. Also change oil and filter. You should also add a anti electrolysis additive to the coolant since the head studs go down into the coolant and bottom of the block. It is available at Diesel truck supply stores as they have the same need.
Howard
