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Ls400 Slow Starting Problem


Kamana
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Hi folks,

I have run into an issue in which my car (90 LS) would take around 5 seconds to start when the engine is cold like in the mornings. When the engine is warm, the car starts quick. Also it starts quick if I turn the ignition key twice to start like let it crank once then turn the ignition off, then crank it again. My mechanic checked the Fuel Pressure Regulator and it was fine. After talking to an electric guy, he suggested the problem is with the Fuel Pump Relay and Circuit Opening Relay both will cost around $100 each from the dealer. Could someone give me an advice?

This problem started showing up after the starter was replaced. I don't know if this could have anything to do with the problem.

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Hi folks,

I have run into an issue in which my car (90 LS) would take around 5 seconds to start when the engine is cold like in the mornings. When the engine is warm, the car starts quick. Also it starts quick if I turn the ignition key twice to start like let it crank once then turn the ignition off, then crank it again. My mechanic checked the Fuel Regulator and it was fine. After talking to an electric guy, he suggested the problem is with the Fuel Pump Relay and Circuit Opening Relay both will cost around $100 each from the dealer. Could someone give me an advice?

This problem started showing up after the starter was replaced. I don't know if this could have anything to do with the problem.

Could you provide a little more info on the cars history, mileage, last time plugs and battery were changed etc. If it starts fine when warm then I think that pretty much eliminates the relays as the problem. Are you starting outdoors? 5 seconds doesn't seem to long to me if its really cold.

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Try this and let us know how it goes:

First turn the ignition to "ON" position and hold it there for 5-10 seconds, then crank the engine. It should start up in less than 2 seconds. I was told this from another friend on this forum, if I remember correctly this allows the fuel pump to "prime" the engine before you actually try to start it.

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hi there

did you fix the problem.

i just bought used LS430 model 2001 and have the same problem. the electrician thinks maybe fuel pump and relay sensors.

he will check it next week

i will come back to you if it is sorted out, hioefuly.

let me know if you solved it so i can benefit

many thanks

<_<

Hi folks,

I have run into an issue in which my car (90 LS) would take around 5 seconds to start when the engine is cold like in the mornings. When the engine is warm, the car starts quick. Also it starts quick if I turn the ignition key twice to start like let it crank once then turn the ignition off, then crank it again. My mechanic checked the Fuel Pressure Regulator and it was fine. After talking to an electric guy, he suggested the problem is with the Fuel Pump Relay and Circuit Opening Relay both will cost around $100 each from the dealer. Could someone give me an advice?

This problem started showing up after the starter was replaced. I don't know if this could have anything to do with the problem.

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Hi folks,

I send the test procedure (from Lexus repair manual) to the mechanic for the following three items as he suspected them to be the cause of the problem:

1) Fuel Pump Relay 28380-30010

2) Fuel Pump Resistor 23285-50010

3) Circuit Opening Relay (next to ECU) 85910-22040

(Part numbers are for 90 Ls400)

After testing them with OHM meter, all three parts were fried.

Called Park Lexus and prices are $60, $98 and $133 respectively.

Mechanic suggested to find the parts at a junk yard and he can test them to make sure they are working to save a few bucks.

Let you know if they solve the problem but most likely they will come through.

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Hi folks,

I send the test procedure (from Lexus repair manual) to the mechanic for the following three items as he suspected them to be the cause of the problem:

1) Fuel Pump Relay 28380-30010

2) Fuel Pump Resistor 23285-50010

3) Circuit Opening Relay (next to ECU) 85910-22040

(Part numbers are for 90 Ls400)

After testing them with OHM meter, all three parts were fried.

Called Park Lexus and prices are $60, $98 and $133 respectively.

Mechanic suggested to find the parts at a junk yard and he can test them to make sure they are working to save a few bucks.

Let you know if they solve the problem but most likely they will come through.

Something still does not seem right. If these parts are "fried", why would it start at all? It is highly unlikely that all three are bad.

I would be looking for a leak-down issue somewhere or a fuel pump problem. It sounds like when warm, the fuel system is pressurized and the fuel pump has

no problem keeping up. But when it sits for a period, the fuel system pressure leaks down and the pump takes a few seconds to re-pressurize.

Perhaps the pump itself is getting weak? Or something in the system is allowing the pressure to bleed off more than normal.

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What grade of oil are you running? Also, since you've replaced the starter, check the ground connection to make sure it's clean and secure. A dirty connection is going to provide greater resistance especially in colder weather with reduced cranking power from the battery.

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landar, I spoke about your comment to the mechanic and I'll try to explain to the best of my understanding. He says once these parts are fried then the power to energize the fuel pump comes from ignition while in crankcase. In normal situation, the order of operation when the ignition is placed in the On position is, from Circuit Opening Relay (commanded by ECU) to the Fuel Pump Resistor and eventually the Fuel Pump Relay energizes the Fuel Pump. Therefore, by the time the ignition reaches crankcase the fuel pump is energized and ready to send fuel.

If only power is coming to fuel pump while in crankcase then it takes a while to energize the fuel pump hence taking too long to start.

eatingupblacktop, my mechanic checked the wirings earlier and everything was correct. I also though that the problem had to do with the new Starter exchange. Grade of oil is 5W-30 synthetic.

I can seek more answers if need be.

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Well oil is ok. If the starter wiring checks out, next on my list would be the cold start injector. Also check the power going to the injector. Like Flanker was suggesting, until you get that checked out, save the wear on your new starter by cranking for 1 sec then release until you hear the fuel pump stop. Then turn it off and try starting again. Should shorten your cranking time.

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  • 2 weeks later...
  • 2 weeks later...
landar, I spoke about your comment to the mechanic and I'll try to explain to the best of my understanding. He says once these parts are fried then the power to energize the fuel pump comes from ignition while in crankcase. In normal situation, the order of operation when the ignition is placed in the On position is, from Circuit Opening Relay (commanded by ECU) to the Fuel Pump Resistor and eventually the Fuel Pump Relay energizes the Fuel Pump. Therefore, by the time the ignition reaches crankcase the fuel pump is energized and ready to send fuel.

If only power is coming to fuel pump while in crankcase then it takes a while to energize the fuel pump hence taking too long to start.

eatingupblacktop, my mechanic checked the wirings earlier and everything was correct. I also though that the problem had to do with the new Starter exchange. Grade of oil is 5W-30 synthetic.

I can seek more answers if need be.

FYI, try a 0w-20 instead of 5w30. Mus better in synthetic land.

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