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Did some work on a 2011 Ford Taurus (head gaskets, water pump, oil pump, tensioners, guides) and decided to throw the top end back together just to see if she'd start up. Here's the overall state upon start up: Overall setup at start up

Tried starting the engine twice. Each time it sounded like the engine would potentially start up. This was also accompanied by gurgling, which I presumed was the oil pump, as well as a little bit of smoke, which I presume is a result of not having any exhaust manifolds on. But after the second cranking, I decided to check out the timing chain to see if it was still tight. I found that the answer was yes and no.

Between the cam sprocket and upper guide there's a little slack: slack between cam sprocket and upper guide

However, between the crank timing sprocket and the lower guide, the chain feels rock hard, no tension even if I push on it as hard as I can with my finger: tight between crank and lower guide

Any ideas what could cause this situation to occur after only cranking for a few seconds twice?

Keep in mind that:

  • air box not installed
  • timing cover, and thus engine mount, not installed
  • exhaust manifolds not installed
  • no coolant
  • no metal on metal noise on cranks
  • intake variable valve timing
  • initial symptoms before job: milky oil, poor compression
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  • Does this engine normally turn clockwise when running? If so, what you're showing doesn't make much sense to me, either. Unless the chain guide under that side is keeping it really tight (taking up all the slack). Commented Apr 22, 2022 at 20:47
  • Yup, it's a clockwise engine. Update: took valve covers off and started turning crank by ratchet. Wanted to see if anything felt weird. Everything felt fine. I also noticed that the slack would move depending on where in the revolution you were. But then somewhere on the 3rd revolution, I was pleasantly shocked to see that all timing marks lined up. Based off this, it seems to me that when you fire up an engine with a new oil pump, it perhaps takes a while for slack in the chain to be taken up.
    – TLex
    Commented Apr 22, 2022 at 22:12

1 Answer 1

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Oil pump is going to have nothing to do with it since the chain does not drive the pump nor visa-versa. The pump runs directly off the crankshaft. Thinking about it, I'd bet there is no problem. I'm thinking this has to do with valve timing and how it will pull the chain tight when one of the valves close at the proper time. As long as the timing marks line up, the guides are in good shape, and any type of tensioner is adjusted correctly, it should be just fine. Part of it may stem from the VVT (whatever Ford calls it) pulling it tight before it gets oil to it. Again, I don't think there is a real issue here.

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  • As it turns out, it seems you're right. I was able to start the engine, several times, despite the amount of slack in the chain. I think I was just surprised because I was always under the impression that the timing chain is supposed to be very taught to be in time. I guess that's not necessarily true.
    – TLex
    Commented Apr 26, 2022 at 8:57
  • @TLex - I'm not completely familiar with your engine, so I cannot be "for sure" in my answer. It just seems like what is logical. It could be the chain is stretched somewhat, which provides the extra slack. IIRC, Ford uses long chains on their engines, which might exacerbate what's going on. If it seems like there is more slack in there than you like, you might want to consider putting a new one on it at some time. Commented Apr 26, 2022 at 10:51
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    Yea, I was considering replacing the chain, but it measured 31.75" long, which is the exact length of a new chain. From what I hear, a chain would have to be measurably longer to make a difference.
    – TLex
    Commented Apr 27, 2022 at 0:12

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