New owner of a LS400 that won’t start
05-27-18, 06:37 AM
#1
Driver School Candidate
Thread Starter
New owner of a LS400 that won’t start
Hey everyone! I recently acquired a 1990 LS400 for a good deal as it won’t start. He bought it recently when it ran fine. However about a month after he owned it, it quit running. He couldn’t figure it out and has moved on to something else. I bought it as something fun to tinker with.
Car cranks over fine, here is what I’ve found out so far
-I do not hear the fuel pump prime when key is turned on. Maybe a Toyota thing? But I’ve always heard cars prime for 1-2seconds before start.
-No voltage to fuel pump when key on-engine off. Measured at pump. Should it be 12volts there? There is 12volts there once I start cranking engine over however. But I do not hear fuel pump coming on.
-Jumpered B+ and F with jumper wire and got fuel pump to run with key on-engine off. However vehicle did still not start when engine was cranked over.
-I did check continuity of fuel pump relay, circuit opening relay with Ohmmeter. I did NOt apply 12volts to these relays and check continuity with voltage applied yet. as I don’t have tools to do so yet. Relays checked out ok so far.
That’s where I’m at so far. Prior owner stated that they did get car to fire up briefly when shot with starting fluid so they thought fuel pump was bad, replaced it but still didn’t fix issue.
So that’s where I’m at. Looking for direction of possible next steps. Thanks everyone!
Car cranks over fine, here is what I’ve found out so far
-I do not hear the fuel pump prime when key is turned on. Maybe a Toyota thing? But I’ve always heard cars prime for 1-2seconds before start.
-No voltage to fuel pump when key on-engine off. Measured at pump. Should it be 12volts there? There is 12volts there once I start cranking engine over however. But I do not hear fuel pump coming on.
-Jumpered B+ and F with jumper wire and got fuel pump to run with key on-engine off. However vehicle did still not start when engine was cranked over.
-I did check continuity of fuel pump relay, circuit opening relay with Ohmmeter. I did NOt apply 12volts to these relays and check continuity with voltage applied yet. as I don’t have tools to do so yet. Relays checked out ok so far.
That’s where I’m at so far. Prior owner stated that they did get car to fire up briefly when shot with starting fluid so they thought fuel pump was bad, replaced it but still didn’t fix issue.
So that’s where I’m at. Looking for direction of possible next steps. Thanks everyone!
05-27-18, 07:19 AM
#2
Spray aerostart in throttle. Make sure it fires. If not you have an ignition problem. Check fuel pressure. If pump running but low pressure, get a new pump. If pressure is good, you have a spark problem.
Check your timing also.
Check the circuit opening relay. It's on the ecu.
Mine wouldn't start, needed a fuel pump and afm.
Check your timing also.
Check the circuit opening relay. It's on the ecu.
Mine wouldn't start, needed a fuel pump and afm.
05-27-18, 07:29 AM
#3
Driver School Candidate
Thread Starter
How do you check fuel pressure on these? I don’t see the traditional Schrader valve like on most cars from this time period unless I’m missing something
05-29-18, 03:15 PM
#4
Just look for the photo I posted on this site. If you can't find it complain to the folks that would not give me a special sticky area to post all my pictures and fix it things.
05-29-18, 05:49 PM
#6
...
-I do not hear the fuel pump prime when key is turned on. Maybe a Toyota thing? But I’ve always heard cars prime for 1-2seconds before start.
It should prime for 2 seconds like on all cars (well, maybe not electric cars or those with mechanical fuel pumps).
-No voltage to fuel pump when key on-engine off. Measured at pump. Should it be 12volts there? There is 12volts there once I start cranking engine over however. But I do not hear fuel pump coming on.
Key ON, engine off, after the initial 2-seconds prime, and not starting, there should NOT be 12 V at the pump.
When key is to START, yes, you should get 12V at the pump. If you get 12V at the pump, and the pump is not running, well that is a problem right there to look into. Wiring issue or bad pump (new, I know).
...
It should prime for 2 seconds like on all cars (well, maybe not electric cars or those with mechanical fuel pumps).
-No voltage to fuel pump when key on-engine off. Measured at pump. Should it be 12volts there? There is 12volts there once I start cranking engine over however. But I do not hear fuel pump coming on.
Key ON, engine off, after the initial 2-seconds prime, and not starting, there should NOT be 12 V at the pump.
When key is to START, yes, you should get 12V at the pump. If you get 12V at the pump, and the pump is not running, well that is a problem right there to look into. Wiring issue or bad pump (new, I know).
...
https://www.clublexus.com/forums/ls-...ml#post9777959
09-23-18, 07:17 PM
#7
Driver School Candidate
Thread Starter
Just an update on this. I FIGURED IT OUT! The car runs now yay!
I did some basic fuel and spark testing and realized it was spark that I did not have, not fuel.
Tested the igniters and got spark at the coil wires from both sides.
It dawned on me maybe I should check and see by chance, if there’s any stored codes. Sure enough, code 12 and 24
code 12 is no crank shaft signal. Which started to be my suspicion the last month or so. I decided to check the resistance and sure enough the resistance was through the roof(bad)
Autozone had one in the area so I decided to pick one up and try it out (fingers crossed)
the original sensor was seized in there and i ended up destroying what was left of it getting it out. I actually had to drill the metal portion out.
I put the replacement in, and DAMN SHE STARTED RIGHT UP! Ran just as a Billion Dollar Car should.
Just as an FYI for anyone struggling with no-start issues. Typically if the crankshaft position sensor is not working, the car WILL NOT start at all. If camshaft sensors are faulty it will still run but in some sort of “limp mode” at least this is how GM is and after this ordeal I’m certain TOYOTA/LEXUS is the same.
I did some basic fuel and spark testing and realized it was spark that I did not have, not fuel.
Tested the igniters and got spark at the coil wires from both sides.
It dawned on me maybe I should check and see by chance, if there’s any stored codes. Sure enough, code 12 and 24
code 12 is no crank shaft signal. Which started to be my suspicion the last month or so. I decided to check the resistance and sure enough the resistance was through the roof(bad)
Autozone had one in the area so I decided to pick one up and try it out (fingers crossed)
the original sensor was seized in there and i ended up destroying what was left of it getting it out. I actually had to drill the metal portion out.
I put the replacement in, and DAMN SHE STARTED RIGHT UP! Ran just as a Billion Dollar Car should.
Just as an FYI for anyone struggling with no-start issues. Typically if the crankshaft position sensor is not working, the car WILL NOT start at all. If camshaft sensors are faulty it will still run but in some sort of “limp mode” at least this is how GM is and after this ordeal I’m certain TOYOTA/LEXUS is the same.
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09-23-18, 08:23 PM
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