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tech3

Must Prime To Start

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Hello all. First of all I am a new member and want to thank all of you for your post they have been most helpful.

Now I could use some help with my LS 400. It will not start in the mornings unless you crank on the starter for a long time or in cold weather you actually have to shoot starter fluid into the intake and she starts right up. Once it starts for the first time she will start all day but left over night you get the hard start issue again. I am a High Horse Power Diesel Engine Tech for Komatsu America. When I see this issue in Diesel engines it is usually the fuel pump or the fuel system is sucking air or there is an inlet fuel restriction but they will have power complaints. Anyway my Lexus will run fine after you let her warm up. I did notice that when it first starts in the morning if you hit the throttle right away it will stall like it is running out of gas but let it run 2-3 min and it responds just fine. She has 194k miles and the wife loves the car I just need to get her up to par! The car that is not the wife LOL :chairshot:

Any help with this will be greatly appreciated.

Thanks.

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Hi, tech3... Welcome aboard.

I haven't had the same experience you describe, but have read of some generally similar problems from a bad O-ring on the gas cap. Have also seen references to replacing the gas cap to correct the problem. Just my #0.02.

I notice you are in my favorite city, but don't see your year model in the profile. Helps to identify year and mileage.

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Hi, tech3... Welcome aboard.

I haven't had the same experience you describe, but have read of some generally similar problems from a bad O-ring on the gas cap. Have also seen references to replacing the gas cap to correct the problem. Just my #0.02.

I notice you are in my favorite city, but don't see your year model in the profile. Helps to identify year and mileage.

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I will check on the cap now. I asume by all the post I have read that there should be presure in the tank at all times?

Also I will see if I can find how to add more details to my profile. Being new to this site I am not sure I am doing this rite so thanks for your reply.

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Also check coolant temp sensor and intake air temp sensors. Maybe engine ECU is getting false engine block/air temperature reading and thinks its warm when it isn't. As a result it isn't using a cold start EFI fuel map in its computations. Open circuit sensor means -40 degrees C, shorted sensor means 140 degrees C for coolant sensor.

Does car accelerate fine once warmed up? If so fuel delivery system probably OK (injectors, fuel pump, pressure regulator,...).

Welcome, your background should add a lot to the discussion here.

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Also check coolant temp sensor and intake air temp sensors. Maybe engine ECU is getting false engine block/air temperature reading and thinks its warm when it isn't. As a result it isn't using a cold start EFI fuel map in its computations. Open circuit sensor means -40 degrees C, shorted sensor means 140 degrees C for coolant sensor.

Does car accelerate fine once warmed up? If so fuel delivery system probably OK (injectors, fuel pump, pressure regulator,...).

Welcome, your background should add a lot to the discussion here.

I just checked and found a sensor broken under the spark plug wire cross over plastic bracket / chanel. I thick it is the temp sensor but not sure. It is just to the left and on the front of the intake manifold. It is a green 2 wire plug and the wires are red with blue stripe and a brown wire. Yes the car runs just fine after it warms up.

As for back ground we had the intake manifold gaskets change and shortly after this problem started. I was out of the country so I did not over see the work done. Guess if you want things done rite you got to do it your self. mad.gif

So if this is the coolant temp sensor why does the dash gauage show temp to run ok?

I will order the sensor and post the results here. Let me know if this is a temp sensor or what you think it may be.

Thanks so much for your help.

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Two different sensors. The 2pin sensor is for the ECU to measure temperature, the single pin sender is for the gauge. A bad coolant temp sensor would give a faulty signal, so I'd replace it for certain. you might also have a very small vacuum leak from the intake being apart, the gaskets are steel multi-use but a piece of grit or debris could be sitting under one.

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Two different sensors. The 2pin sensor is for the ECU to measure temperature, the single pin sender is for the gauge. A bad coolant temp sensor would give a faulty signal, so I'd replace it for certain. you might also have a very small vacuum leak from the intake being apart, the gaskets are steel multi-use but a piece of grit or debris could be sitting under one.

Ok thanks. I found the sensor on line for 26 dollars I will order and let you know how things go. as for vacume test I did a leak test and found no leaks so I think this broken sensor will do it but I will let ya know.

Thanks for all the help guys.

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I believe the ECU and dash gauge are two different sensors. Maybe your ECU sesnor is the dead one... Its quite inexpensive so you may have a quick fix in your reach.

this may help

...http://us.lexusownersclub.com/forums/index.php?showtopic=36954

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Coolant temp sensor can be bad and still read on the dash , doesn't mean it is any good , just working.

You problem is fuel as the spark and timing seem to be working fine once fluid is added.

Get some seafoam for the oil and a full can for 1/2 tank of gas , google for ways to do it .

It sounds to be injector related and I think you car has a cold start injector in the intake which may not be working.

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