1984 ,911 wont start some help

[hyperkinesis]

I used the car about 2 weeks ago, and works perfect
now i try to used today but it crancks but wont startup, it have 1/2 tank of gas, I check the battery and was low so I use a jumper from my other car, and again it crancks but don`t startup, I used an battery jumper 750 crancking power, but again
wont start

some help please, what I need to check?

[brujo65]

ck main relay, under driver seat next to the ECU

[hyperkinesis]

I check and I don`t have spark on spark plugs, but I do have spark in the coil

[911obgyn]

Rotor, Cap, Plug wires, coil wire, Spark plugs. I had magnecore wires come apart at the plug connectors.

[Luccia at Pelican Parts]

When's the last time you replaced your ignition components? One of the most common problems with the older cars is that owners don't change the ignition components often enough. Some more info here: Porsche 911 Ignition Tune-Up | 911 (1965-89) - 930 Turbo (1975-89) | Pelican Parts DIY Maintenance Article. Good luck! Hope you get it figured out quickly.

[JTL]

If no spark check the flywheel sensors. I'll bet one of those has given up the ghost.