No crank w/starter connected to harness

[DailySX]

Hey guys I am having some weird issues starting the car. The car will not crank when the starter connector plug (thinner cable) is connected to the harness. The thick cable bolted in gets constant 12V.

I've looked at:

> (With the starter cable plug disconnected) 12V gets to the connector when "starting" the car with the key. Tells me clutch switch seems to be ok and relay works. Tested blue interlock relay independently with 12V power + continuity tester and seems good.
https://i.imgur.com/GbHKWqr.png?1

> (With the starter cable plug disconnected) Starter works and can crank the engine if I bridge the starter end of the connector directly to the battery.
https://i.imgur.com/fxfN5Q7.png?1

> With the starter cable plug connected, the starter sees 0V (DMM) when I try key starting it.
https://i.imgur.com/C2XYYK5.png?1

> I suspected bad connection between the plugs so with the plugs disconnected, I bridged both ends of the plug with a cable, ensuring the cable ends make good contact with the plug contacts.
https://i.imgur.com/9bvmtZA.png?1

Any ideas what else I can do, short of buying parts and replacing things willy-nilly? I've searched, but couldn't find anything specific to this issue. I feel like I'm close, but I'm at a loss.

[thegr8one013]

just to make sure, was this an auto converted to manual?

if not, your ignition switch is probably finally worn out. at the ingition switch connector check resistance between pin 4 and 1 while the key is in the start position. it probably has very high resistance (most likely worn/dirty contact inside) so when the starter soleniod plug is disconnected its putting out 12v and when you reconnect it and it doesnt have enough current to complete the circuit.

[DailySX]

just to make sure, was this an auto converted to manual?

if not, your ignition switch is probably finally worn out. at the ingition switch connector check resistance between pin 4 and 1 while the key is in the start position. it probably has very high resistance (most likely worn/dirty contact inside) so when the starter soleniod plug is disconnected its putting out 12v and when you reconnect it and it doesnt have enough current to complete the circuit.

This car is originally manual. Sounds plausible! I will definitely check that next. Thanks!

[DailySX]

Quick updated: Fixed. it was a faulty interlock relay. Replaced it and engine fires up.

I checked the ignition switch (checked for continuity and resistances at different positions). During ignition start, i noticed connection between pin 1 and 3 was intermittent so I replaced the switch. Engine still doesn't crank even with new switch.

I replaced the interlock relay because why not (ordered it the same time as the ignition switch) and engine starts right up. The original relay probably couldn't handle high current under load due to age. Even though i checked it manually, albeit under no load conditions.

Now onto fixing my current issue: car idles above 2k-2.5k. i'm thinking vacuum leak from when i disconnected hoses and crap to change the belts. anyways.

Thanks!