Stumped with no start engine

ruston

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Jun 27, 2021
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Well at this point I'm fairly certain I've bent valves. I redid the timing perfectly. Much better than before (cam locking bar goes in perfectly with crank at TDC). I put the spark plugs back in cranked it over and still zero compression at the compression tester gauge. I cranked the engine for at least a minute in total so I would think that would have cleared the flooding if there was any, but maybe there's not enough compression to push the fluids out the exhaust? The engine still cranks fast, and there is an audible whistling in the engine bay as it cranks, and if I put my head near the back of the engine I can feel pressure on my face so I think compression is leaking out somewhere it's not supposed to.. Should I keep trying to deflood or just start pulling the heads..?
 
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Sounds like bent valves. As trav said pull rocker covers and check the height of the valve tops with camshafts removed. If the a valve is bent it will sit low
 

ruston

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Just pulled the cams, the intake valve was lower than the exhaust valve on every cylinder except #4. I put a straight edge on exhaust valve and put a feeler gauge under on intake valve. The difference ranged from 0.65mm up to 0.88mm. I'm not sure how high the intake or exhaust is supposed to be sitting, but that's what I found. Will pull the heads and hopefully only see bent intake valves.
 
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With any luck the pistons are okay, make sure the crank pulley still has its pin and is in good shape, some of these engines V6 had a habit of breaking it.
 
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This is a picture of a damaged pulley, I don't know how relevant it is to your engine but it is probably worth a look.


audi_vw_crankshaft_pulley_jpg.jpg
 
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Well, trust me, you need compression for an engine to start, so that's your focus.
The valves are probably opening at the wrong time, or all bent by now.
 

ruston

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So I finally got the heads off, and inspected the valves. So I’m not the best judge as I don’t have a lot of engine internal experience, but everything looks good to me. I tested for leaks by pouring acetone on top of the valves and by shining light on them and found nothing. Not sure of how else to test them for leaks. Only thing I could think of is the timing still somehow being off or bad rings. I will check the crank timing gear for that thanks. Also I’ve attached pictures of the heads.
 

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ruston

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Inspected the pistons more closely and noticed a crescent shaped imprint into the carbon on the pistons. The imprints are lined up right with the exhaust ports so it must be the exhaust valves that are bent. I guess they're not bent enough to be noticeable, but bent just enough to leak compression..
 
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The pictures definitely help paint the picture of this engine. It looks to me like this engine has been burning a considerable amount of oil for some time. It looks like it’s in need of a rebuild at this point.
 

RAR

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My experience with a BMW 330xi a few years ago might help here…

My brother’s car - he had a repair he did (don’t remember what exactly), and he couldn’t restart the car. Fast crank, good battery and starter, but it would never catch. Starting fluid wouldn’t even take. So I went to the BMW owner’s forums and did some searching.

Turns out what was going on was the repeated start attempts would wash down the cylinders and prevent good compression. The fix? Pull the spark plugs. Put some sort of oil (not a lot!) into each cylinder, replace the spark plugs, then try to start.

It worked on that car, and it wasn’t worse for wear. We did change the oil soon after, what with all the gasoline that was likely in it.

Worth a try… 😎
 
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