Car won't start, weird compression results!

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Chezedik
Posts: 4726
Joined: Tue Dec 17, 2002 8:35 pm
Car: 1991 Nissan 240sx

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Alright, here is the deal. I have been trying to get this motor started and have gotten to this point. I have spark and am almost certain I have dizzy timing right (although it wouldn't matter, read on). Fuel is running through the rail and the injectors are pulsing. With all of the cranking the oil smells like fuel, so it is probably getting that. Here is what is really disturbing, compression test results were as follows:

1 - 1512 - 1503 - 1504 - 210

These results were gotten on a cold, never ran rebuilt engine. The head was milled .009'' and the cyl walls were deglazed but not honed. These are chrome-moly rings.

The motor is a rebuild, and I know it needs a new intake cam gear, but surely that cannot explain the result for number four, can it? Anyway, it sputters a little and backfires on starting fluid. I get a little smoke in the timing cover, but that is just blowby I would assume. Any Q's just ask, please help!


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rogoman
Posts: 848
Joined: Fri Feb 17, 2006 5:44 pm
Car: 1991 240SX FB
2012 Altima 2.5 S

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Chezedik wrote:These results were gotten on a cold, never ran rebuilt engine. The head was milled .009'' and the cyl walls were deglazed but not honed. These are chrome-moly rings.
Were the cylinders checked for out-of-round ond taper limits. If not, the limits may have been exceeded; the cylinders probably should have been at least honed if not reborded.

That could account for the weird compression reading on #4.

As far as the motor unable to start condition, check the ignition timing; if that's OK, then check the cam timing.

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Chezedik
Posts: 4726
Joined: Tue Dec 17, 2002 8:35 pm
Car: 1991 Nissan 240sx

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No, I did not check for out of round condition, but they looked right (for what that is worth, I know... nothing). I did check ring gap though, and it was at less than 1.5mm, which seems still really high, but I believe it is in spec. I believe cam timing may be an issue and have bought another gear. I would love more sug's, but will let you know how the gear works out on Sat.

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Chezedik
Posts: 4726
Joined: Tue Dec 17, 2002 8:35 pm
Car: 1991 Nissan 240sx

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Here is an update:Last night I reset the timing to stock, turns out I was a little off. I don't think I banged up any valves though since I always rolled the engine over by hand before making an attempt to start it, and no valve clearance issues. The compression test results are looking a little lower, but more consistant. The new results are:

1 - 1052 - 1353 - 1224 - 145

I know that is out of spec, but a few drops of oil gives me:

1 - 2202 - 2103 - 2104 - 225

If not for number four, it would meet spec for total deviation. Now here are the new questions:

1. Does this indicate anything to anyone? (the engine has never been ran, and the test was done cold, so I know ring clearance is obvious, but anything else?)

2. Am I putting too much stock in these numbers for an engine that has never ran, and the test done cold?

Any new input would be great, and thank you all for the help so far.


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