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Weird Starting problem, anyone help?

 
Old 07-24-12, 01:13 PM
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Default Weird Starting problem, anyone help?

So riddle me this batma....errr clublexus. So in the morning at about 8AM I try to start my 93 sc300. It turns over for about half a second (hits 1k rpm's) then immediatly turns off. Tried to start it about 25 times yesterday morning and this morning, each day. Same exact problem.

Now the weird part is that on both days I get home from work at 5(yesterday, 3 today), walk over to the car and it starts right up the first time. Plugs are new, battery is relatively new, ECU is about two weeks old. The ONLY check engine light is the knock sensor which has been on for much longer than this problem. I drove it around the block both days, no problem at all with driving, no stutter or anything. I can walk outside any time during the day and start her right up. But first thing in the morning it wont start and I have to keep riding the motorcycle to work. What the hell??

I know the knock sensor needs to be replaced I'm just waiting for it to come in. There is no way that the knock sensor is causing this very time specific problem is there?

Last edited by Piratse; 07-26-12 at 08:39 AM.
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Old 07-24-12, 10:58 PM
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Has it ever turned off while your diving the car?
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Old 07-25-12, 06:08 AM
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Originally Posted by sc300lexii View Post
Has it ever turned off while your diving the car?
Not since I replaced the ECU about 2 weeks ago.
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Old 07-25-12, 04:48 PM
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Originally Posted by Piratse View Post
Not since I replaced the ECU about 2 weeks ago.
this happened too me, what ecu did you replace?
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Old 07-25-12, 05:14 PM
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Originally Posted by sc300lexii View Post
this happened too me, what ecu did you replace?
The main ecu (ecm). I think (with most of the help of my mechanic friend Dane out of Houston) that we have figured it out. It SHOULD be the fuel pump ecu that is causing this problem. I am going to order a new one and see if that solves this. Possibly the high heat in the afternoon is keeping the voltage from dropping and the cooler air in the morning allows that hard voltage drop which keeps it from starting.


Anyone have a pic of the fuel pump ecu so I can see the easiest way to remove it? I have the below pic just wanted an actual pic.


AS ALWAYS I WILL LEAVE MY ORIGINAL QUESTIONS IN CASE SOMEONE NEEDS THIS IN THE FUTURE

I THINK this will fix the problem (oddly enough I found the link through a different forum as search pulled up nothing for me on here)
https://www.clublexus.com/forums/per...tures-faq.html

This did not fix my problem but the link could work for others.

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Old 07-25-12, 06:46 PM
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So I got in there and someone had already bypassed the ecu, BUT they cut two extra wires, so I tied those back in. I guess I will find out tomorrow if that worked.
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Old 07-26-12, 12:13 AM
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Originally Posted by Piratse View Post
So I got in there and someone had already bypassed the ecu, BUT they cut two extra wires, so I tied those back in. I guess I will find out tomorrow if that worked.
i think its probably the fuel pump too, did you check if it was working properly ? it could also be a dirty fuel filter. The 12v mod should work ! good luck dude let me know what happens so i can do it too my sc
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Old 07-26-12, 08:42 AM
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Originally Posted by sc300lexii View Post
i think its probably the fuel pump too, did you check if it was working properly ? it could also be a dirty fuel filter. The 12v mod should work ! good luck dude let me know what happens so i can do it too my sc
that was not the issues. Same problem this morn. We have now moved on to the next theory which is that the heat from the afternoon is causing pressure in the tank allowing the car to start. When it cools off over night the pressure drops and it won't start. Going to test later today by opening gas cap and seeing if it will start (once it is hot outside). Could be carbon canister or a couple other things. I will update this tread as I (and Dane, the true mastermind) figure this out.
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Old 07-26-12, 05:13 PM
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Well the pressure in the tank was not the problem either. Got home, opened the gas cap and released all the pressure. Started right up......This is a weird and very frustrating problem. Anyone have any more idea?
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Old 01-09-13, 03:09 PM
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did you ever get this fixed? My car is doing the same thing.
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Old 01-14-13, 09:46 AM
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Originally Posted by GS300CMO View Post
did you ever get this fixed? My car is doing the same thing.
sc300lexii was correct about the issue. The fuel pump was working but not enough pressure. I replaced it and the ECU ( main ecu, NOT fuel ecu, was causing some weird problems) and never had the issue again. Fuel pump wasn't too bad to do, just don't have big hands like me.
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Old 01-14-13, 09:56 AM
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Have the SAME EXACT issue down to the T. Had to do the 12V mod a while back when the fuel pump ecu went. my knock sensor is also bad, but as you confirmed it is not the knock sensor.

So all you did was change the fuel pump, and presto, problem solved?
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Old 01-21-13, 08:27 AM
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Originally Posted by Candela View Post
Have the SAME EXACT issue down to the T. Had to do the 12V mod a while back when the fuel pump ecu went. my knock sensor is also bad, but as you confirmed it is not the knock sensor.

So all you did was change the fuel pump, and presto, problem solved?
That and the main ECU. It was like $200 to have it repaired. But the fuel pump was the main cause. The pump is like $200 but is easy to replace, it is behind the rear seat (remove the seats), remove the circle plate and bolts you will see, pull the pump out (will need good skinny pliers to disconnect fuel lines), put in new pump, and try that. Best thing is that if it doesn't work you can take the pump back and get your money back. Took me about 45 min to do it.
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