I have searched so many places and maybe haven’t searched in the right places but I’m about to light the car on fire and let it burn. So I thank everyone in advance for any help.


Ok I have recently bought a 1990 ls400. I bought it and it was running a bit rough. I noticed the pass. dizzy cap had cracks and was creating a misfire. So I replace that cap, all the plugs and wires.
Ran great ever since then, so I start dailying the car.
Every now and then it would cut out for a split second while driving then run fine for many days at a time. Also had cut off 1 time but would immediately restart. Never had a cel. and would run great with cold a/c.

A day last month I was driving like usual on my day off and bam it cut off on me. I go to restart the car but it just cranks and I’m stuck in the middle lane. After getting to a safe place I notice with ignition on***I have all my dash lights except my check engine light. My fuel pump wasn’t priming either.
I really need help finding an ecu plug diagram so I can check power and grounds to the ecu and any suggestions because I really don’t know what to do first. I had a similar problem in my Nissan 240sx where I was driving and bam it cut off. After diagnosis I found a capacitor blown in my ecu, changed the capacitor to one that would work and bam car runs great.

things I know

-I inspected the inside of the ecu and it looks spotless, no leaks that I could see.
-I can jump the fuel pump relay to get the fuel pump to run but still no start or stumble.
1-0 gauge wire to starter.
2- a wire goes from the battery to the alt fuse.
3-0 gauge wire from block to battery.
4- 4 gauge wire goes from negative battery to strut stud.
(not certain if 1-4 is an okay set up, I got the car like that)
-after getting it home I notice the crank sensor bolt was almost all the way backed out and covered in gunk. I cleaned and reinstalled assuming it’s not related.
-efi relay clicks when it’s installed with ignition on.
-when jumping te1 to e1 for cel diagnostic I get nothing. No light.
-when jump te1 to w I got the cel but no start so I believe that just tests the gauge cluster lights.
-I’ve got a multi meter and have tested EFI Relay and fp relay. Both had power.


I know I’m missing a lot of info, if you’d like exact numbers I can get you everything. When it comes to electrical I don’t know my a** from my hand so I don’t exactly know what to test but I can follow instructions. Please if anyone could help me try and figure this out. I don’t want to go buy another piece of crap right now. Thank you
-Justin

Thank you @fixmiester,

I apologize I said acc. on, I meant ignition on. I have edited my post to fix this issue.
I did leave out that I had sprayed starter fluid into the intake and nothing but healthy crank. Also like I said I jumped the fuel pump relay and got life to the fuel pump but still no cel at ignition on so I’d suspect no spark also. Also the car just cranked with the fuel pump relay jumped. Anyone have any ideas? Relay or fuses that might directly control power or ground to the ecu? Clearly my issue has something to do with ecu signal right? Idk fresh ideas please