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Old 03-06-2018, 05:19 PM
 
2 posts, read 11,753 times
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I have an '02 Town Car. On my way to work yesterday morning, I pulled off the highway and it died at a light. It was NOT overheating and had been running seemingly fine right up to that point. It would not crank after that. Mechanic says I have lost compression on several cylinders and is low on others. What gives? How does it not overheat and still have that loss?
I asked him those same questions and his answer was to repeat "no compression, you need a new car". Part of me says to get a second opinion before I just write it off as dead.
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Old 03-06-2018, 05:28 PM
 
Location: San Antonio, TX USA
5,251 posts, read 14,121,230 times
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I am sure he offered to buy if from you too.

Get a second opinion
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Old 03-06-2018, 05:30 PM
 
1,139 posts, read 1,364,296 times
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Why wouldn't it crank? If there were no compression i would think it would crank easier than normal.

I guess if its not cranking, your mechanic would technically be correct that there wouldn't be any compression, though.
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Old 03-06-2018, 05:31 PM
 
Location: Eastern Washington
17,106 posts, read 56,712,890 times
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This sounds like a broken or jumped timing chain to me. That will give you very little compression in most cylinders because at least one valve is open in that cylinder.

If there is no air moving out the tail pipe, and no suction at the intake, when you crank it, this is your answer.
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Old 03-06-2018, 05:37 PM
 
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That's what's bugging me, why wouldn't it crank. If the rings were getting worn, wouldn't it have been missing? Yeah, I really need a second opinion. It is a 4.6 V8, for what it's worth.
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Old 03-06-2018, 06:38 PM
 
Location: Eastern Washington
17,106 posts, read 56,712,890 times
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I don't think this is ring or valve wear. I think more likely your timing chain has jumped or broken, if it jumps it puts the cam(s) out of phase with the crank and the engine won't run, or will hardly run. If the chain breaks outright, the cams don't turn at all.

I have seen this with other Ford V-8 engines, but have not seen it on a 4.6. But I don't see why the 4.6 would be immune.
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Old 03-06-2018, 07:52 PM
 
Location: Texas
5,717 posts, read 18,763,719 times
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The Ford modulars are notorious for dying just like yours. It won't start because there's not enough compression left to start the engine- the gas from the injectors won't pop because of lack of compression. They will all of a sudden just give up. My personal opinion it's due to the low tension ring packs. Once they have worn, it seems like they will no longer expand to seal against the cylinder walls and when it says she's done- she's done. Usually though the modulars like your 4.6 will generally go 200,000+ miles before they crater. Should you decide to put a junkyard engine in it, look for a 2004 or newer 4.6 2V engine. It will have the newer head design that eliminates the bad spark plug threads in the soft aluminum heads and has more power. It's a plug and play bolt in. Should you decide to rebuild the existing engine, make sure they replace the oil pump or expect a complete catastrophic failure. Oil pumps on these engines are another known failure.
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Old 03-06-2018, 08:43 PM
 
Location: Raleigh
8,168 posts, read 8,454,098 times
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Usually when people say "IT WON'T CRANK" they mean that the engine will not turn over when they turn the key. Is that what is happening to you? Or does it turn over and spin but not start. Since the mechanic apparently has done a compression check it does crank but it does not start?
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Old 03-06-2018, 10:08 PM
 
Location: moved
13,565 posts, read 9,570,895 times
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The Ford modular 4.6L V8 is evidently an interference-engine. This means that if the valves are improperly actuated (because the timing chain broke, or skipped), [some] pistons could crash into [some] valves. If that happens, then besides major engine damage, the engine may no longer crank-over. But as others have said, if a compression-test was done, then engine must have cranked over. Perhaps the compression-test itself exacerbated the damage?
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Old 03-06-2018, 11:40 PM
 
Location: Here and there, you decide.
12,908 posts, read 27,860,829 times
Reputation: 5050
Quote:
Originally Posted by Crashj007 View Post
Usually when people say "IT WON'T CRANK" they mean that the engine will not turn over when they turn the key. Is that what is happening to you? Or does it turn over and spin but not start. Since the mechanic apparently has done a compression check it does crank but it does not start?
see trapperLs post, he is correct. you need a new car
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