1991 LS400 no start issues "Heeellp" - ClubLexus - Lexus Forum Discussion


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1991 LS400 no start issues "Heeellp"

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Old 07-29-14, 10:21 AM   #1
mercedes84
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Default 1991 LS400 no start issues "Heeellp"

My 1991 LS400 needed a starter so I let it sit for maybe a year or more disassembled. Finally put it together but it won't start (cranks over fine). I'm getting 12v from the coil pack, low to no reading on the underhood diagnostic ports,cel doesn't come on when key in the on position, no fuel in rails, fuel pump not engaging. I'm wondering could the heat build up have caused the ecu to malfunction (capacitors). I went to school for electronics so I do know multimeter testing so for the coils to have 12v but all else pretty much dead or low voltage. especially the diagnostic ports and no cel i'm thinking ecu. Any help would be appreciated. Thanx in advance
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Old 07-29-14, 01:56 PM   #2
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Old 07-29-14, 05:03 PM   #3
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guessing bad fuel pump.
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Old 08-02-14, 12:29 PM   #4
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Today I did some test light and vom testing. Result, 12v at coils, 12v at injectors. With key on, no voltage at fuel pump, no volts at sensors, 1 to 2 volts at b+ rest of diagnostic ports interior and exterior 0 to .5 volts...Changed out known working ecm and same results. No cel on dash all other dash lights on. could this be a security issue or a body control issue
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Old 08-03-14, 08:00 AM   #5
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I ran a wire from battery to b+ in the diagnostic port and my cel came alive, the car ran briefly with starter fluid spray, another wire to fuel pump relay activated the fuel pump. So do I have a short, security issue or what is going on here, thanx
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Old 08-03-14, 04:58 PM   #6
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Quote:
Originally Posted by mercedes84 View Post
I ran a wire from battery to b+ in the diagnostic port and my cel came alive, the car ran briefly with starter fluid spray, another wire to fuel pump relay activated the fuel pump. So do I have a short, security issue or what is going on here, thanx
The +B in the diagnostic port is connected to the battery via the EFI fuse and the main relay with wires and connectors. I assume that you forgot to reconnect or incorrectly connect the EFI related wire or connector.

It should not be difficult for a guy who went to school for electronics to trace the line and find out what is causing the problem if you'd have a circuit diagram.
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Old 08-23-15, 05:35 PM   #7
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After letting my car sit for more than a year, today I jumped out B+ and fuel pump to the battery. The car started, smoked a little briefly but ran extremely rough. Do you think the issue could be he fusable link in the main and/or efi
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Old 08-23-15, 05:55 PM   #8
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http://us.lexusownersclub.com/forums...lectric/page-2

Go down to post #27 at the bottom of the page, there is a wire diagram of the B+ and fuel pump.
Now you can see what Yamae was talking about, he's always pretty much right on when it comes to the electrical system in these cars.
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