Engine won't start

[MariaAZ]

I'm working on a '73 240Z with round top carbs that my husband & I bought as a non-running project car last year. We were actually able to get it started & drive it home, but it ran VERY rough.

We haven't been able to get it started again. I've checked the plugs & wires, gapped the points, swapped out the fuel pump with no effect. The engine turns but doesn't "catch."

I've read in other threads that the ballast resistor can keep the motor from running, but it seems in these cases the engine was revving. Any input would be greatly appreciated!

[Fun_in_my_z]

im not positive on this

dad had an old datsun truck with a 6 in it it only ran till he got it home

we tested everythang and the head gasket was blown i would try thatnext good luck to you hope you get it going

[1975yellowBSPZ]

have you set the valves and checked the timing?

do the plugs seem to be getting spark?

have you checked the vacum system for leaks?

just some things to check

[MariaAZ]

I suspect a blown head gasket. It was blowing white smoke, and a quick check of compression shows the following numbers; 160, 150, 130, 0,140, 175. Not being very knowledgeable about engines, I would think this justifies removing the head (something I've never done & have some anxiety about doing)

[Fun_in_my_z]

white smoke hummm

it realy does sound like the head gasket its not hard to change just time consuming

[1975yellowBSPZ]

There is a lot on info in the search on doing this, read it first. If you don't use something like a wedge to hold the timing chain tight against the chain tensioner you'll have to take the whole front of the motor apart.

[Fun_in_my_z]

yeah thats a pain we went through all that with that old truck

gopod luck to you hope you get it figured out

[MariaAZ]

This site has some awesome information, and I've made note of the excellent article in the tech forum. I've never done actual engine work though. Guess I just have to "feel the fear and do it anyways!" Fortunately we don't depend on this vehicle for transportation :eek:

[Daniel]

You may wish to start by pulling the valve cover and make sure you dont have a stuck valve or loose rocker arm. That could cause the "0" also. Then maybe just retorqueing the head to its proper values as a test.

[billcapp]

If the gasket is blown..you should see oil in the radiator or water in the oil pan.

Radiator is an easy check. Checking for water in the oil requires draining the oil and catching some of it in a glass jar. Let it sit for a while or overnight...the water will be at the bottom of the jar.

Doing a head gasket is not very hard to do if you leave the intake manifold on (just disconnect the fuel line, water line to the manifold and the linkage.) If you DO pull the head it's a good idea to replace the head bolts with new ones.

[2ManyZs]

I'm with Daniel on this one, before you start taking anything apart, pull the valve cover and verify the condition of the valve train first. Then dump oil and have a look to see if it may be contaminated.

The rest of the cylinders look pretty good as far as compression, a little low on a couple, but it could be due to valve train problems.

While you have the valve cover off, turn the motor over by hand and double check that the timing is correct as well. Check the cam chain for any slack too...

As to why it won't fire off, it could be ignition related, as in coil, cap and rotor, ballast resistor, or one of a few other things. The main thing is right now to find out why you are getting a 0 reading on number 4.

If after removing the valve cover and if the rockers are all in place with nothing missing or too loose, I'm thinking it a head gasket problem is a good possibility, as the cylinders loose compression the closer they are to number 4. If you notice, 1&6 have the highest reading, 2&5 are lower and 3&4 are the lowest of all.

After you pull the valve cover and check the valve train, just for the heck of it, re-torque the head bolts, lay the valve cover back on(so you don't shoot oil all over), and re-do the compression check. If the compression in number 4 comes up, and also in 3&5, you'll know right away you have a head gasket or head problem.

[Daniel]

The ballast resistor seems to be the new carb. Meaning it gets a lot of blame it doesn't deserve. If it was bad the car would run with the key in start mode and die when released. Its just a strip of metal. You can jump across it as a test.