260z cranking trouble

[maton_acoustic]

Having trouble when cranking my 260. I turn the key and it'll turn over briefly before abruptly stopping like its locking up. Does the same thing every time.

I thought it could be a starter motor problem so I took it off and bench tested it, there was just over 1v volt drop while the motor was spinning which I've been told proves the starters fine?

It's a brand new battery. Engine turns over fine by hand.

Anyone got any ideas?

Thanks, Dave.

[buysell]

How is the ignition timing? Sounds like it's too advanced.

[Zed Head]

Give some information on the state of the system before the problem. Did it start and run right before or is this one of those "ran when parked ten years ago" projects?

In the mean-time I would pull the spark plugs, spin the engine, and see if any fluids come out. Gas, water, or oil can all cause hydraulic locking.

[buysell]

Is the firing order correct?

[zKars]

Simple things first. Often the ign switch is not getting full voltage to the trigger contact on the starter. Re-install it and short out the trigger contact (where black/yellow spade connector goes) to the main fat battery wire terminal on the starter. IF it spins nice and fast and normal, then its the ign switch or the connections between there and the starter. Start by replacing the spade connector on the end of the wire at the starter.

[maton_acoustic]

Is the firing order correct?

I assumed the engine would crank on the starter even if there was a ignition problem.

I'ts worth looking at timing issues then?

Has been sitting along time, I've been doing strictly body repair.

[maton_acoustic]

I'll try shorting out the switch and then look at timing. Thanks

[Zed Head]

Engine turns over fine by hand.

I missed this part. Good luck with it.

[Captain_Zeros]

If your timing is too advanced or you have your spark plug wires rearranged it'll act like that, a real simple check for that is to pull the low voltage power cable off the coil and see if the engine will crank over quickly with ignition out of the picture.

I've got a 280zx electronic distributor on my car and it doesn't have much mechanical advance so I have it pretty advanced at low rpm so everything will be happy up at RPM. It causes a bit of a hard start.

[Captain Obvious]

I assumed the engine would crank on the starter even if there was a ignition problem.

The reason people have suggested an ignition timing issue or plug wires on the wrong plugs is because if you get a spark too early as the piston is coming up, the explosion inside the cylinder will push back down on the piston and fight the starter. If this happens, the explosion will stop the starter spinning very abruptly like you described.

Pull the coil wire out of the center of the distributor cap and lay it against the engine. Then crank the engine over while that coil wire is removed and if the problem goes away, then you know it's some sort of ignition timing problem.

I took it off and bench tested it, there was just over 1v volt drop while the motor was spinning which I've been told proves the starters fine?

And I don't think your starter is the problem, but the above wouldn't tell you much anyway. Under a no load condition, I don't think you'd learn much from measuring the voltage drop across the starter. It's more of a current thing than a voltage thing.

[Captain_Zeros]

Pulling the high tension coil wire from the center of the distributor cap is not recommended. Pull the positive 12 volt power supply wire from the + terminal on the coil, it'll have the same effect without high voltage trying to hunt its way to ground willy nilly.

[maton_acoustic]

Yeah, thanks for the help all! It was infact advanced timing causing the trouble.

I'm learning.