Hello!

1996 LS400, 218k miles.

Issue at hand: Car would not start when WARMED UP...SOMETIMES...will start up when i hold key and rock the car back and forward and will suddenly start to crank.

Replaced: Starter, coolant pipe gaskets, valve cover gaskets, full tune up, full timing belt kit, fuel filter and fuel pump. Car also got a brand new battery replaced since it sat for 3 months and wanted it fresh.
Issue at hand still remains....
I changed the coolant temp sensor, thinking the sensor that sends info to the ECU maybe thought the car was over heating and killed the starter off until it cooled.
for 2 days, i drove the car (and it actually ran better and idled better with the new sensor), and would start warm every time, did some short highway runs for about 20-30 min, floored it, got it to 95mph, everything working fine.
THEN, day 3....took the car for a much much longer drive (about 75 min, 70 miles almost all highway).
halfway along the drive, the CLUSTER started wigging out (but the car drove fine) and nothing else in the car was flickering, the headlights were not dimming or flickering, just the cluster would go dark and wig out, then come back on, then off again.
3/4 of the way along the drive, i noticed some very light cutting out like a slight misfire almost.
at destination, car would NOT crank, just do relay clicking rapidly, even when i tried to rock it back and forth.

I pulled the ECU, opened it up. i sent the pics to a rebuilder and found one capacitor and he informed me the one that is leaking slightly is along the fuel injector signal lines which explains the weird cutoff after a while. he did tell me that nothing he can see on the rest of the board is bad, or leaking, and will not cause the cars starting issues.

this video link shows how the car reacts to the NSS operating. when in a gear, no relay clicks. when in P or N, relay clicks rapidly but wont start


All of this only happens when the car is WARMED UP. there is without any hesitation it is consistent that the car only fails to crank and start when the engine is at operating temperature. even when its slightly warm it will restart, its always when its fully warmed up. as for the rocking back and forth, thats not always reliable, but its more consistently reliable if its been on shorter runs but at full operating temp.
It did this BEFORE and AFTER the new parts and work done. basically the existing problem that sparked changing the starter never got resolved. So im not thinking its any new parts issue. when everything was removed, it was basically all original parts from 96 (minus tuneup stuff and timing belt), nothing was loose, corroded, etc and everything reinstalled was triple checked. but again....this issue existed before any parts were changed.

So at this point, im at a real cross roads of what the problem really is. Anyone have any possible ideas?
while i do know the ECU needs to be redone for a different reason and just for general PM, I need to figure out this issue first before i start spending another dime on this car. its not so much about being cheap, its about being logical.
It needs a rear brake caliper, a PS pump (the vacuum valve replacement did not fix it, soo ill have to replace it now and wish i did it when i was there already), the ECU redone, new seat leather in the front, and wondering why the dash chose to start flipping out.

if this issue cannot be resolved, then theres no point in doing any more work to it as it will still be half a useless car if it cant be started when its at operating temp.

 

very odd, that the rocking causes the starter to fully engage! but w/o the rocking, you just get a clicking like it's trying to start - this leads me to believe you have a loose connection somewhere. start at the battery terminals, and wiggle them to make sure. also what is the condition of your battery? how old, what voltage is it at rest?

lastly i would check the shifter itself - there is a neutral safety switch that can get mucked with spilled drink. when cranking, try and jiggle the shifter instead of rocking the entire car to isolate! and yes the starter should NOT engage in any gear other than P or N!

 

i will try to jiggle shifter see if that makes a difference. it has never allowed the relay to click in any other position than P or N,
the battery is brand new, but this also happened with an older battery, weaker battery, and the new battery too. and the new battery has been tested 2x just to be sure. its def not a battery itself issue. even on a "weaker" battery, the relay clicking wouldnt be so rapid....even a weak battery will attempt to crank, or relay engage even if very slowly. battery terminals, at the battery itself, are secure.

 

have you tried to switch the starter relay with another relay, just to rule it out?

 

Is that your starter solenoid ~ motor clicking? Or the relay? If it starts pretty much every time when the engine is cold, its not a worn flywheel. Rocking it back and forth repositions the flywheel gear ring to allow the starter gear to catch on a favorable spot on the flywheel. If a starter solenoid ~ motor is weak it will be even weaker when its hot as engine heat radiates to the starter motor and solenoid making it harder to locate the ring gear well because heat is making weaker and there is an issue with the internals of the starter. Rocking the car helps a weak starter motor ~ solenoid find the favorable spot on the ring gear of the flywheel. Really no one knows what the problem is for sure yet but that's how my thinking is.

 

i have a feeling its something electronic causing it, it did it with the 30 year old starter and a brand new starter. especially since its so precise in terms of how it is being very consistent in its current habits if that makes sense.

 

i have not yet. i thought i had another relay around but i cannot find it. it was a a junkyard relay i got a while back, but since then i was working out of town, and moved lol.

 

Yes that makes sense, something electronically is "heating up" or causing a problem to power to the starter and not the starter itself, interesting problem though not a fun one, I know there are cases of bad or loose ground wires that can cause problems too not sure if thats a thing here though. This will be an interesting one to finally figure out.

 

I hope its just a relay, that would be a very easy fix !

 

swapped it today, no change. i drove it longer than a quick warm up and it wont start when rocking it either at the moment. something is telling the car not to crank when warm...its simply too consistent.

i also tried jiggling around the shifter and stuff, and no change either.

relay swap no changes....
now im truly baffled.

 

did you get the ECU caps replaced? also, cold solder joint cracks can also cause intermittent performance dependent on temperature.

 

i have not done the ECU yet. and mainly because I am at a cross roads. Spending more money at this point fixing the car, but still having the same issue....makes the money spent useless. im not against getting the ECU fixed, but need this issue solved before i spend another dime. however, im also wondering myself if it is the ECU causing this very predictable issue. it seems as if this specific condition my car is having no one has really experienced the same exact symptoms to confirm if it is ECU related or not.
then theres always just the gamble of spending the money on the ECU and hope for the best.

 

i understand. just double and triple check all your connections, especially at the battery terminals! what looks to be tight might not fully be!

also what i found interesting in your video is that the gas gauge DROPS to zero when cranking - this is not normal. it should just sit where the level is and fire up.

 

interesting, AND, it did not drop when it was in neutral and i tried to crank.

ok, im all ears if this means anything!!