Questions and Answers

Nissan 240-SX Head Gasket Q. Dear Vince, I have a 1993 Nissan 240-SX, automatic transmission, 2.4 DOHC with 150,000 miles, that blew a head gasket. Since I was removing the head I decided to do a valve job as well. Once I removed the head I noticed the timing sprockets were worn and the tensioner was all the way out so I decided to replace the timing chains (2) and sprockets. The procedure I followed is as follows:

1. I set the #1 piston at TDC on the compression stroke prior to removing the cylinder head, distributor, old timing chains and sprockets etc.
2. I installed the new lower crankshaft sprocket and aligned the marks on the chain with the marks on the new idler sprocket.
3. I aligned the marks on the upper cam sprockets with the mark on the idler sprocket and installed the new upper cam chain.
4. Once I put it all back together, I made sure the distributor marks were lined up and pointing towards the #1 tower on the distributor cap etc. However, I can't get it to start? It cranks normally but just wont turn over.

I troubleshoot as follows:

1. I checked the fuel system and its getting fuel.
2. I checked for spark and I'm getting good spark.

Since I can't get it to start, I'm assuming the timing chain may be off somehow? I'm starting to doubt weather or not it was on the compression stroke?

1. Is there a definitive way to determine that the engine is on the compression stroke once the engine's been turned over other than putting my finger over the spark plug hole and feeling the air push out?
2. In addition, how can I know if the valve timing is correct? If I position the cam shafts with the #1 piston lobes pointing straight up, the marks on the timing sprockets and chain don't line up. They only line up when the intake cam lobe is laying on the left side pointing towards the intake manifold and the exhaust cam lobe laying on the right side pointing towards the exhaust manifold?

Please help, I'm dreading having to start over and tear down the front of the engine and realign everything.

I have to raise the engine 3" and lower the front suspension 3" to get the oil pan off so I can disconnect the oil strainer from the front lower timing cover since the oil pump is attached to the inside of the timing cover, not to mention removing the air compressor, alternator and power steering pump to get to the motor mounts! Any suggestions?

Sincerely,
Tom

A. There is an old saying Tom, it goes like this. "An ounce of prevention is better than a pound of cure."

Before you do anything like removing the cylinder head or timing chain, the first thing to do is to set the engine in the base timing position. This way if something happens, you reduce the chance of totally screwing up. And believe me, I learned that the hard way.

Base time is when the crankshaft pulley timing mark is on 0 °, the distributor rotor is facing number one tower of the distributor cap and the intake and exhaust lobes of the camshaft are pointing directly opposite of the valves, i.e. valves fully closed.

If you do this now, you will know where you stand. If the chain is on wrong one or two may line up, but not all three. If that is the case taking it apart to reset it will be the least of your worries. If it was put back together 180° out, you most likely bent the valves. If you hear a metallic ticking sound when you crank the engine, I would get 16 little coffins.

At this point I would try to set the base timing to see where we are, and go from there.