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Old 07-23-13, 07:36 PM   #16
BobSmith00
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Originally Posted by Yamae View Post
I suggest you to bypass the "Circuit Opening Relay " indicated in the circuit diagram here.

The "Circuit Opening Relay " works when the ECU detects something unusual and stops the fuel pump to work. Bypassing it can be done by shot-circuiting the terminal "5" and "3" and this enables the fuel pump to keep running and the engine might runs longer than before.

This is just to check whether the ECU is inhibiting to continue to run the engine or not. So don't bypass the terminal "5" and "3" for too long. The purpose of the bypassing is just to check and confirm that the ECU is detecting something unusual and stops the engine. If the engine keeps running after the bypassing, it simply means that the ECU disables the fuel pump to run.

I wrote the link above when a 98 LS400 was behaving the same symptom as yours. That LS400 caused the problem when the MAF sensor was not connected. Yours is not a 98 and the ECU is different but the fuel pump circuits are just the same. Also the conditions to stop the fuel pump are a bit different.

Anyway try the bypassing and inform me the result.
I used a piece of wire to shortcircuit terminal "5" and "3" on the Circuit Opening Relay.
The Result was the same as before, starts, then dies. I didn't see any change. In fact was same as in the video I posted.

I also while out confirmed the car Still will run on an alternate fuel source, Such as Starting fluid in the intake until the alternate fuel source is used up, then car dies.
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Old 07-23-13, 07:43 PM   #17
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I know you're probably going to say my issue is my capacitors, but just humor me Cowboy!
I don't always say it is capacitors, but in a lot of the weird confounding cases that make no sense, it often is capacitors!

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The car will do this intermittently. Temperature doesn't seem to effect it, its not bad or old gas, or specific gas because I have put fuel from 3 different stations in it always using 93. I have checked the MAF, coil, CTS, and alternator with a multimeter according to the FSM and all seem to be properly working. For what its worth the car is only running 13.42 volts while idle. My friends told me it should be running at least 14,
13.42 is fine at idle

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but we tested the alternator and it is putting out 95 amps (rated 100). The car will do this completely randomly if at all. I haven't driven it too much after the 5spd swap, but for what its worth it was not doing it prior to being parked. I have no check engine light or codes, and the last time I got it to do the issue I let it idle waiting for my buddy to come by to check it out, and it randomly stopped doing it and revved fine. Above 3k the car seems to be fine, though my friend Ben said that's because he thinks the car goes into closed loop. I've ran seafoam through it, changed the fuel filter, car has all new fluids, and there are no vacuum leaks. Any ideas?
most issues caused by a bad sensor or a broken wire or a failed component will generate a code - with no codes and running this poorly, the chance that it really is capacitors is greatly increased!

ECU capacitors are one of the very rare situations where the car can run terribly with no codes generated, the ECU didn't do such a good job of monitoring itself, back in those days
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Old 07-23-13, 07:45 PM   #18
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Originally Posted by LScowboyLS View Post
no, it sounds like someone who knows very little about the LS400


listen to Yamae - he is the world-class expert on LS400

My words were in reference to:

Quote:
Amedee,We found the problem! WinkYou led us to the culprit. We pulled covers and found the right side camshaft was off 2 teeth!Found out what caused the problem was that the tensioner failed.So,we replaced the belt,tensioner,both guide pulleys which was a kit for replacing the timing belt.Before we put the belt on I cleaned and inspected cam&crank sprockets Found the crank sprocket had some dings in it as well as the left side cam sprocket,and we carefully removed them with a jewelers file and some 600 grit sandpaper.Then,put it all back together and it fired up and stayed running.Customer said it runs better than ever. So thanks Amedee for your help and we will no doubt need your help again. Skip J.
I saw you mention something about checking timing belts and that came up, and combined with that human's original complaint about the "We have a 96' Lexus LS400 It will start then in 2 sec. it dies" Sounded sorta similar to my issue.
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Old 07-23-13, 07:50 PM   #19
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I also while out confirmed the car Still will run on an alternate fuel source, Such as Starting fluid in the intake until the alternate fuel source is used up, then car dies.
see if you can get it to run for like a full minute on alternate fuel source, if so, the we know it is for sure fuel delivery issue, which could be several causes besides the circuit opening relay Yamae mentions, such as the fuel pump, fuel pump relay, fuel pump ECU if equipped, fuel pressure regulator, completely clogged fuel filter or fuel line (rare), or ECU and there may be a couple of more fuel delivery situations Yamae can add to this

I am assuming you have double checked ALL fuses in the car, especially the underhood ones with a test lamp
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Old 07-23-13, 07:56 PM   #20
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Originally Posted by LScowboyLS View Post
ECU capacitors are one of the very rare situations where the car can run terribly with no codes generated, the ECU didn't do such a good job of monitoring itself, back in those days
Yeah, makes sense. Well its only 10 bucks so I'll just do it anyway. Problem is I don't trust myself to solder the caps in. Anyone wanna do it for some us currency?
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Old 07-23-13, 08:00 PM   #21
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Originally Posted by BobSmith00 View Post
I saw you mention something about checking timing belts and that came up, and combined with that human's original complaint about the "We have a 96' Lexus LS400 It will start then in 2 sec. it dies" Sounded sorta similar to my issue.
if the timing belt were jumped, the car would not run fine with alternate fuel source over an extended time frame like 1 minute
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Old 07-23-13, 08:13 PM   #22
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Originally Posted by LScowboyLS View Post
see if you can get it to run for like a full minute on alternate fuel source, if so, the we know it is for sure fuel delivery issue, which could be several causes besides the circuit opening relay Yamae mentions, such as the fuel pump, fuel pump relay, fuel pump ECU if equipped, fuel pressure regulator, completely clogged fuel filter or fuel line (rare), or ECU and there may be a couple of more fuel delivery situations Yamae can add to this

I am assuming you have double checked ALL fuses in the car, especially the underhood ones with a test lamp
I have tested all the fuses 3 times, so triple checked with a test light.

I was told by the mechanic friend I have, using starting fluid is not a safe thing for an extended period of time. That it burns at a higher temp, and can cause failures.

I can not try the alternate fuel method for a longer time period tonight because it is now too dark, but I should be able to rig up something tomorrow.




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if the timing belt were jumped, the car would not run fine with alternate fuel source over an extended time frame like 1 minute
Well I think the longest I've had it going off of alternative fuel source, is maybe 7 to 8 seconds.
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Old 07-23-13, 08:32 PM   #23
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I was told by the mechanic friend I have, using starting fluid is not a safe thing for an extended period of time. That it burns at a higher temp, and can cause failures.
well I did not mean make a habit of it, we are just trying to rule out electrical issues and timing, 30 seconds to 1 minute is not long enough to overheat anything, but it will tell us that the electrical is not being cut off and the timing has not jumped.

I have used starting fluid for as long as a minute on my 96 with no ill effects - just do it for 40 seconds if that is more comfortable to you.

A fuel pressure gauge is always the preferable tool, but starting fluid is safe for the MAF beginning on the 95 models

you could also use your gas soaked rag as the primary fuel source and spray an occasional shot of starting fluid to keep it going for the 40 seconds

Last edited by LScowboyLS; 07-23-13 at 08:42 PM..
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Old 07-23-13, 08:37 PM   #24
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I can not try the alternate fuel method for a longer time period tonight because it is now too dark, but I should be able to rig up something tomorrow.
Well I think the longest I've had it going off of alternative fuel source, is maybe 7 to 8 seconds.
I suggest you to check the "Fuel Pump Resistor".
If you cannot check it easily, try to bypass the "Fuel Pump Relay" short-circuiting pin "4" and "3". The "Fuel Pump Relay" is located next the the "Circuit Opening Relay" and it may be easier to try for you now. This enables the fuel pump to continue to run with the fuel pressure a bit too high but don't worry if it is within a minutes or so.

After the engine is started, the "Fuel Pump Resistor" is not bypassed by the "Fuel Pump Relay" because higher pressure is not needed anymore. But when the "Fuel Pump Resistor" is open, the fuel pump cannot work and the engine stops. I imagine your problem could be caused by the open resistor.

As you see the red lines, the "Fuel Pump" is getting the 12V supply via the "Fuel Pump Resistor" after the engine is started. If it is open, there is no supply of the 12V and the fuel is not supplied to injectors. Then the engine has no idea to run anymore. It only can run while the "Fuel Pump Resistor" is bypassed by the Fuel Pump Relay". Bypassing too long time is not OK for the pump but I would say, up to 3 minute would be quite OK.
Click the image to open in full size.

Last edited by Yamae; 07-23-13 at 09:02 PM.. Reason: to add an additional explanation
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Old 07-23-13, 08:41 PM   #25
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listen to Yamae - he is the world-class expert on LS400
I am not that big, Cowboy.
The only thing I can say is that I live close to Toyota HQ and I have some connections with engineers there.
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Old 07-23-13, 08:56 PM   #26
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Originally Posted by Yamae View Post
I suggest you to check the "Fuel Pump Resistor".
If you cannot check it easily, try to bypass the "Fuel Pump Relay" short-circuiting pin "4" and "3". The "Fuel Pump Relay" is located next the the "Circuit Opening Relay" and it is easier to try for you now.

After the engine is started, the "Fuel Pump Resistor" is not bypassed by the "Fuel Pump Relay" because higher pressure is not needed anymore. But when the "Fuel Pump Resistor" is open, the fuel pump cannot work and the engine stops. I imagine your problem could be caused by the open resistor.

Alright, will attempt to shortcircuit pin 4 and 3. Will report back after doing so.
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Old 07-23-13, 08:58 PM   #27
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I am not that big, Cowboy.
The only thing I can say is that I live close to Toyota HQ and I have some connections with engineers there.
Club Lexus is the largest Lexus technical forum on planet Earth, and you are the strongest technical person on Club Lexus - so that is pretty BIG!!
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Old 07-23-13, 09:14 PM   #28
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Originally Posted by Yamae View Post
I suggest you to check the "Fuel Pump Resistor".
If you cannot check it easily, try to bypass the "Fuel Pump Relay" short-circuiting pin "4" and "3". The "Fuel Pump Relay" is located next the the "Circuit Opening Relay" and it may be easier to try for you now. This enables the fuel pump to continue to run with the fuel pressure a bit too high but don't worry if it is within a minutes or so.

After the engine is started, the "Fuel Pump Resistor" is not bypassed by the "Fuel Pump Relay" because higher pressure is not needed anymore. But when the "Fuel Pump Resistor" is open, the fuel pump cannot work and the engine stops. I imagine your problem could be caused by the open resistor.

As you see the red lines, the "Fuel Pump" is getting the 12V supply via the "Fuel Pump Resistor" after the engine is started. If it is open, there is no supply of the 12V and the fuel is not supplied to injectors. Then the engine has no idea to run anymore. It only can run while the "Fuel Pump Resistor" is bypassed by the Fuel Pump Relay". Bypassing too long time is not OK for the pump but I would say, up to 3 minute would be quite OK.
Click the image to open in full size.
I removed the Fuel Pump relay. I used a piece of wire to short circuit at 4 and 3. The wire felt warm as attempting to start car, as if current was passing through it.
Car started and died as shown in the youtube video I posted.
So I conclude from what I did by shorting 4 and 3, had no effect.

Much thanks for your help so far.
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Old 07-23-13, 09:31 PM   #29
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we will get to the bottom of it! - press on, troops!!
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Old 07-23-13, 09:33 PM   #30
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I removed the Fuel Pump relay. I used a piece of wire to short circuit at 4 and 3. The wire felt warm as attempting to start car, as if current was passing through it.
Car started and died as shown in the youtube video I posted.
So I conclude from what I did by shorting 4 and 3, had no effect.

Much thanks for your help so far.
Sorry that my suggestions were not effective but you are stepping to the conclusion one by one. Your efforts and the reports are about to catch the rat.
You already has confirmed that:
1, The "ECU" is not disabling the 12V supply to the fuel pump,
2, The "Fuel Pump Resistor" is not open,
3, The "Fuel Pump Relay" is supplying currents that may be a bit bigger than normal because the wire was warm when bypassed.

The 3rd item is quite important. Is it possible for you to measure the current by an ampere meter?
If not, bypass the "Fuel Pump Resistor" using a bulb for a brake light or equivalent instead of a wire to know the current level by the brightness. If any bulb is not available, try again using a wire again and feel the warmness and the change of it from the start to may be up to 10 seconds using your finger. I want you to inform me the result.

I am not good at speaking English but may be I can talk to you over the phone and let me give you some more. Inform me your phone number using the personal message to me, I will call you up. If it's too late for you, I will try tomorrow evening at your local time.

Last edited by Yamae; 07-23-13 at 09:52 PM..
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Old 07-23-13, 09:33 PM
 
 
 
 
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