Dumb wiring q. Testing circuits

[Andy_]

Car wont start. Ive been following the recommendations from ?sons delorean wont start?, a covid lockdown chat on here.
With everything connected as normal, with the ignition switch off, and battery disconnected, the white/silver coil wire is grounded. (Checked with multimeter set to continuity, tested white/ silver to engine ground).

This wire should only be grounded with the ignition on? Switched by ignition ecu?
Using the multimeter i found it was grounded through the white wire on the ballast resistor. From here on i tested continuity from white at ballast to engine ground.
Eventually realised by removing fuses 1 and 5 stopped the continuity.
Fuse 1 was permanently grounded by the vac solenoid. I thought it could be wired either way around (doesnt matter which way around connector is). With battery and ignition set to run, lifting the throttle plate off the idle switch makes the vac solenoid click.

The green wire from fuse 5 is also grounded. I disconnected the green otterstat wire, and theres still continuity on white ballast to ground. Other items on the green (service counter, binnacle) i havent got too yet.

Exact resistance from ballast white to ground :
Just fuse 1 in : 24 ohm. Open circuit with vac solenoid disconnected.
Just fuse 5 in : 21 ohm.

Am i testing right? I may not know what im doing. Any help appreciated.

[Bitsyncmaster]

You really can't use an ohm meter testing circuits. That only works when your testing a component not wired to the circuit. Each ballast resistor is 0.5 ohms. The stock ignition coil primary is about 0.4 ohms. When measuring low resistance values, you short your meter leads and subtract that reading from the reading you get testing the component.

The stock ignition ECU will ground (not quite 0 volts) the ignition coil when the engine is not running and the key is on. Expect to see around 1 volt in that condition. The + side of the ignition coil will read around 3 to 4 volts with the key on.

[David T]

For a no-start you must first try to figure out if it is fuel or ignition. A quick test is to see if there is resistance when you push down on the air sensor plate. No resistance means no fuel pressure. The other test is to see if there is spark. Several ways to do that. Easiest is to pull a spark plug, plug it back into the wire, ground the shell and crank. No spark means an ignition problem. A no-start is very commonly a bad connection at the ballast resistor.

[iflights]

Let me ask a more basic question. Did this only recently start and was any work done between the last time the car started and now?

[Ron]

For a no-start you must first try to figure out if it is fuel or ignition. A quick test is to see if there is resistance when you push down on the air sensor plate. No resistance means no fuel pressure. The other test is to see if there is spark. Several ways to do that. Easiest is to pull a spark plug, plug it back into the wire, ground the shell and crank. No spark means an ignition problem. A no-start is very commonly a bad connection at the ballast resistor.

I agree, except it is much easer, and more informative, to spray some ether under the plate to eliminate fuel issues, imho.

[David T]

I agree, except it is much easer, and more informative, to spray some ether under the plate to eliminate fuel issues, imho.

You're right, that is another quick and easy thing to do but not everyone has a can of starting fluid around. A lot of the owners who have problems are mechanically challenged and don't have even basic tools let alone the knowledge of how to use them. When I give advice I try to use the simplest techniques assuming that the person asking for advice is asking because they don't have a lot of mechanical skills. Overusing starting fluid can be dangerous if you don't know what you are doing.