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Hey this is my first time using the forum to ask for help directly rather the getting clues from other threads. I have a 1990 LS400 with less than 200,000 miles. I can’t give the exact miles because the odometer stopped working with a previous owner.
When I first got it I noticed the start times were a little longer than I expected, but with this being my first older car I thought nothing of it.
One day my car started misfiring if I was too quick with the pedal and I could only operate it by slowly and gradually pushing the pedal down which limited any misfires. As the car got up to speed past 45-60 mph it would misfire less if at all while accelerating. But it was most prominent at lower neighborhood speeds.
Along with the misfire and longer start time my car began to have a rough idle but it would never stall on me!
I tried fixing this by replacing sparks and wires but my problem persisted.
Later on my car had intermittent starting issues for 3 days, my car would crank but not start.
Id have to leave my car and come start it in the morning to get it running.The last day of that 3 day period I was driving it home and then for the first time it shut of on me while I was driving. A shop fixed it saying that it was a timing belt issue I believe they changed my cam position sensors as well.
After I got my car back it was running but the misfire symptoms persisted so I stayed sensitive with the pedal and drove it seeing that it’s my only mode of transportation and I’m in college commuting.
Time goes on and the rough idle gets a little lower and I had to be even more careful with the pedal from a stop to get the car moving without much misfire or any at all might I add.
Last month I was driving it and then pedal went limp completely unresponsive, but unlike the first time my car went unresponsive, I still had power. So I sent it to the shop and by the time the looked at it the car started right up for them. This was about a 4-6 day period.
I drove it home misfire and all but this time I was way more hesitant to drive it around since I didn’t want to get stranded anywhere.
Coming home from the skatepark one night I was low on gas and admittedly it wasn’t the first time I’d done it (driving low on gas) I filled up what I could afford at the time $20 worth and drove it 3-5 minutes home. I only use premium btw never anything else.
Little did I know, after that night my car would not start again. Just cranking and has been doing so ever since.
This time I started checking electronics. I checked my ecu because I heard about the caps going bad yet I had no damage or leaking coming from them. Not a single bulged top either and I confirmed all of this with an electronic repair tech today.
Irresponsibly, I’ve taken out the ecu without disconnecting the battery a couple of times before today maybe 3 or 4. I thought I should add that.
So my only other thought is my fuel pump because as I stated before I had longer than usual start times and misfires. I can also confirm it hasn’t been replaced I’ve asked the previous owner.
I learned a while back in the beginning of my ls400 that if a car has a longer start time you can cycle the key a few times (2-3) and pressure should build up to start it right up and in the past that actually worked but I stopped doing it because I heard it could damage the pump or something I think.
Needless to say that doesn’t work right now because the car cranks with no start and I can’t hear my pump prime from in the driver seat, the backseat, nor from putting my ear up to the the gas cap (open ofc as well).
So here’s where I’m stuck.
Trying to check codes with a wire doesn’t work for me because my cel won’t light up even when I swap a bulb that works on it. For some reason I can get the trac light to blink when checking but not the od light for the trans ALTHOUGH the od light did start blinking recently when the car was running recently. But the car ran and shifted fine besides the misfire.
With the electric tech saying everything checks out fine on my caps, but having wire jumping problems, and me not being able to hear my fuel pump prime and it’s lack previous replacement I don’t know what I should do.
Im leaning towards the fuel pump since all that’s happened, besides cel failure, can come from the fuel pump I feel like that’s the problem, but I don’t know and I’m looking for guidance here. One thing I can note is that, although I don’t hear my pump prime whatsoever, when turning the key back to the off position I do hear a single click that comes from the back of the car, but I don’t really know what that is.
Someone, ANYONE, SOS :’(
If you know anyone in the Houston area that work on these I will gladly give them business.
You can try this, short B+ -FP in the diag connector and crack a fuel line
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Are you telling me to jump B+ (idrk what that is) to -FP (still never heard of it) in the hood diagnostic port with a wire..too crack a fuel line? Or did you want me to crack the fuel line literally (I doubt it) XD
Jumpering those pins forces the fuel pump to run, "cracking open" a fuel line is to verify fuel pressure/flow. Be careful such a thing is hazardous to you and obviously a fire risk.
there should be a diagnosis box by your intake plenum drivers side, mine is a 96 so it's a bit different. I don't think you will have to loosen a fitting(crack a line) just feel the return fuel hose and you will be able to tell if there is fuel pressure. will look something like this under the cap....B+ is battery positive and FP is fuel pump.
One day my car started misfiring if I was too quick with the pedal and I could only operate it by slowly and gradually pushing the pedal down which limited any misfires. As the car got up to speed past 45-60 mph it would misfire less if at all while accelerating. But it was most prominent at lower neighborhood speeds.
Along with the misfire and longer start time my car began to have a rough idle but it would never stall on me!
I tried fixing this by replacing sparks and wires but my problem persisted.
This time I started checking electronics. I checked my ecu because I heard about the caps going bad yet I had no damage or leaking coming from them. Not a single bulged top either and I confirmed all of this with an electronic repair tech today.
With the electric tech saying everything checks out fine on my caps, but having wire jumping problems, and me not being able to hear my fuel pump prime and it’s lack previous replacement I don’t know what I should do..
Sounds like the ECU to me cuz of the different problems you have. I have the same symptoms plus more and my ECU is bad. Except mine hasn't stalled yet. As for the caps in the ECU, ya can't see if they are bad just by looking at them. What kind of "electronics tech" did you have look at it, and what did he use to test it? I'm sure you've seen the ECU thread here https://www.clublexus.com/forums/ls-...capacitor.html
As for the fuel pump I thought we were able to hear it prime at one point but I was mistaken, ya can't hear it from the drivers seat.
What I did to test it is, I turned the key to on, (not start) then under the hood I jumped the +B and Fp in the diagnostic port and watched the screw on top of the fuel pressure damper. If it jumps then ya got pressure. It'll only jump the one time.
Are you saying your engine light doesn't come on even when you start the car or only when you check for codes using Te1 and E1 in the diagnostic port? If it works when you turn the key but not when checking codes it means there's no communication from the ECU and it's bad.
Sounds like the ECU to me cuz of the different problems you have. I have the same symptoms plus more and my ECU is bad. Except mine hasn't stalled yet. As for the caps in the ECU, ya can't see if they are bad just by looking at them. What kind of "electronics tech" did you have look at it, and what did he use to test it? I'm sure you've seen the ECU thread here https://www.clublexus.com/forums/ls-...capacitor.html
As for the fuel pump I thought we were able to hear it prime at one point but I was mistaken, ya can't hear it from the drivers seat.
What I did to test it is, I turned the key to on, (not start) then under the hood I jumped the +B and Fp in the diagnostic port and watched the screw on top of the fuel pressure damper. If it jumps then ya got pressure. It'll only jump the one time.
Are you saying your engine light doesn't come on even when you start the car or only when you check for codes using Te1 and E1 in the diagnostic port? If it works when you turn the key but not when checking codes it means there's no communication from the ECU and it's bad.
Well my car won’t start, but I’m saying that it doesn’t come on with all the rest of the lights on the dash, and it also won’t come on when checking for codes. I took one bulb from a working light next to it and plugged it in but still no luck!
Oh yea and he works any motherboard repair but he didn’t hook it up to anything jus visually checked the caps. Maybe it’s good to send my ecu off anyways just so I don’t have to worry in the future.
there should be a diagnosis box by your intake plenum drivers side, mine is a 96 so it's a bit different. I don't think you will have to loosen a fitting(crack a line) just feel the return fuel hose and you will be able to tell if there is fuel pressure. will look something like this under the cap....B+ is battery positive and FP is fuel pump.
Ok gotcha I’m gonna go try. Are you saying it’d force it on in the scenario it’s actually broken? Or if the ecu is cause it not work.(if that’s even possible)
This puts power directly to the fuel pump bypassing the COR aka circuit opening relay. Which is another term for fuel pump relay. If the ECU is bad engine won't run it still needs injector pulse, spark etc.
07-13-22, 10:12 AM
1990 LS400 crank no start
