1996 Ls400 Will Not Start

[Tom130]

i have a 1996 ls400,, when to wal-mart,,, running fine,,, came out and it will not start. it spends over just fine,, has plenty of gas,,, had a computer put in about 2 months ago,, after a while, with in the last 2 months, the tack started reading 1/2 of what it should,, speedometer stopped, hit dash and it came back on lol,, had to car towed to a mechanic, he said he thought the computer was bad, i bought one,, and now when you try to start it,, it backfires and suptters, but still want start.

computer it had was a 89661-50303, i replaced it with a 89661-50341, 95-97, the 341 is for a 97. do they have to be programed or something ?? or and do ls400 ever jump time when you turn them off? it has almost 300,000 miles on it,, dont use a drop of oil,,, but does suck the power steering fluid out. i know the valve on the pump is bad, and will replace it,, but what is the best guess of why it will not start,, i even waited till the next day and tryed to start it,,, but no luck,, spends over great,, but now,, after replacing the comuter,, is that what is cause it to now back fire ??

[VBdenny]

For whatever reason, the LS400 engine need a LOT of juice to start and run properly. A slightly bad battery can cause all kinds of problems. Consider having that checked. Regarding the computer, very well could be causing problems. Hopefully you still have the old computer.

Good luck over there in "The Greenest State in the Land of the Free"

Denny

[Tom130]

It is not the battery, the battery is really hot,,, spends the engine really good,,, installed the new, (used) computer and now it just backfires ,, trys to start but want,, reinstall the old computer,, and now it will not hit a lick :(

the computer it had in it was a 89661-50303 replaced it with a 89661-50341 95 to 97 the 50303 is for a 96,, the 50341 is for a 97,,

[landar]

Tom, you should never drive a Lexus to Walmart. Too classy. ^_^

I just want to point out that you said it was running fine when you shut it off then when you came out, it would crank but not start. I would not fixate on the computer at this point because it may very well be something else like ignition or fuel delivery. With 300k miles it could be a lot of things. And depending upon when the last timing belt was done, I suppose it is possible the belt jumped. Not likely but possible. So, I would focus on checking fuel and spark. Could be as simple as distributor caps/rotors. Ignition coils also go out after a lot of mileage. Maybe fuel pump is shot. Try to isolate between fuel and spark.

You also mention hitting the dash and getting the gauges working again. Bad connection(s) on the circuit board and you will have to remove it and examine.

[Exhaustgases]

Was the battery disconnected when changing the ecu? The dash gauge deal is the cluster itself not the engine ecu.

Yes can jump time and also mess up some valves too.

Do what landar says and check compression too.

[billydpowell]

reason it out, it takes fuel & fire at the proper time under combustion to run, what is missing..

[Tom130]

has fule,, (had fire) ( but seam to be at the wrong time) when i put another computer in the car,,,,,,,,,, i put the old one back in and i had NO fire,, duh,, i guess i got a bad computer,,, but did not think it would make it back fire,

p.s. i know no one on here knows me on here,, but ,,, in my life,,, i have built every thing from briggs engines to some that you can walking around in LOL,,, but i do thank you for your reply... :)

[billydpowell]

IF it jumped time, you could have some bent valves, run a compression test... that could also make it "backfire"

[Exhaustgases]

has fule,, (had fire) ( but seam to be at the wrong time) when i put another computer in the car,,,,,,,,,, i put the old one back in and i had NO fire,, duh,, i guess i got a bad computer,,, but did not think it would make it back fire,

p.s. i know no one on here knows me on here,, but ,,, in my life,,, i have built every thing from briggs engines to some that you can walking around in LOL,,, but i do thank you for your reply... :)

Me too, but not any Sulzers etc.

Did you disconnect the battery before disconnecting the ecu's? If not that can cause problems.

So you did check for fuel pressure? And spark? There is an igniter test procedure on youtube. But if your swapping ecu's hot then you could be causing problems. Its not like the old Briggs points days. And your sure its spinning against compression. I would pull the LH cover and check the belt.

[billydpowell]

tom, any report??

[Tom130]

Ok,, bought a nother ecu,,, 89661-50303, does it have to be programed ? the 303 is what the car calls for .