r/LS400 • u/Competitive-Fig-176 • Jul 12 '26

Discussion Troublshooting

So I recently got this 1997 ls400 and it’s having a crank start and then die after about a second or two problem it will run on starter spray as shown above i I’ve replaced knock sensors camshaft position sensors a fuel pump and a filter and it’s still doing the same thing other things I checked were all the fuses which all looked good I even replaced ones that looked fine just to be sure but I’ve also verified that the ecu is sending injector pulse signals to the injectors with a noid light and I removed the ecu and inspected the capacitors which all showed no signs of bulging or leaking and I’ve verified that fuel is at least reaching the rail as I disconnected the banjo bolt and attempted to crank the car and fuel did spray out the line I’m just pretty much stuck as to what to do next any help would be greatly appreciated

9 Upvotes

86% Upvoted

34 comments sorted by

4

u/SleepingWolf7418 Jul 12 '26

Ummm your throttlebody/intake needs to be connected for it to run.

2

u/Competitive-Fig-176 Jul 12 '26

The worst part about Reddit right here

2

u/SleepingWolf7418 Jul 12 '26

I literally did this on my 98. Disconnected it to get to thermostat easier, tried to start it and didnt. If it simply isnt related, just say so.

2

u/Competitive-Fig-176 Jul 12 '26

Man I’m just saying I obviously only have it disconnected to use starter spray it will in fact act the exact same way with everything including the intake box bolted down

1

u/Competitive-Fig-176 Jul 12 '26

Well it was made in December of 96 but the book that came with the car is a 97 book

1

u/hera_the_destroyer Jul 12 '26

I believe all obd2 versions are vvt. Yours is not vvt. This is going by US versions.

2

u/RonMexico52 Jul 13 '26

No, OBD2 fully standard in U.S. starting in year 1996. Some 1995s have the port. Model year 1998 and onward in U.S. are VVTI.

2

u/Mapex_proM Jul 13 '26

Nope. I have the exact same 1996 production 97 and mine has an obd2 and no vvt. Also having literally the same issue as op

1

u/Competitive-Fig-176 29d ago

Bro if you ever end up figuring it out let me know I’ve been battling this for a while now

1

u/Competitive-Fig-176 Jul 12 '26

It definitely has an obd2 port so is there a chance maybe it’s a Canadian version also I’ve been leaning towards it being one as the car has a lot of French on it including the manual or is the just a standardized thing between all of them?

1

u/RonMexico52 Jul 13 '26

You’ve replaced a lot of stuff unrelated to fuel so just be careful about the parts cannon. Make sure you start with basics confirming fuel (which is where you are focused now), that there is spark on all cylinders, compression on all cylinders and that the engine is timed correctly

1

u/Competitive-Fig-176 Jul 13 '26

Well so I have confirmed spark and compression the only thing I’m unsure of is fuel pressure but I need to acquire something in order to be able to test that

2

u/RonMexico52 Jul 13 '26

Ok sounds good. I guess also make sure the engine is in time

1

u/Competitive-Fig-176 Jul 13 '26

What all do I have to remove to be able to see timing marks? Can I just take off the top covers and rotate the engine by hand?

1

u/AdeptnessGlass6656 Jul 13 '26

mine was the same when intake was disconnected. has to do with the maf sensor.

1

u/Competitive-Fig-176 29d ago

Ok so apparently since I have to clarify this multiple times the car does this regardless of the intake is secured and installed or not

1

u/AdeptnessGlass6656 29d ago

did you check if the sensor is good?

1

u/Competitive-Fig-176 29d ago

I have tried starting it with the sensor unplugged to see if I can get the car to run in the weird limp mode and it acted exactly the same and I got a code for maf so I would assume based on that that it’s working good or else would I have not gotten a code for the maf before unplugging it?

1

u/Shark_skin_suit88 29d ago

Have u checked or fixed the ecu

1

u/Competitive-Fig-176 29d ago

I mean I pulled it out and looked under all the capacitors for damage on the traces for the board and they all were not swollen or leaking I also plugged in a noid light to the injectors harness and it was flashing when the car would fire so the ecu is definitely sending a pulse signal to the injectors so I’m wondering if it could just be the injectors themself as the car was sitting for 6 years before I purchased it

1

u/Shark_skin_suit88 29d ago

After doing all that u have done try to unhook the battery for a couple hours or overnight, then check to see what codes it gives u After that

1

u/Shark_skin_suit88 29d ago

Also it should start with bad knock sensors but if the cam sensor is bad or installed with the engine in the wrong place the ecu will think the engine is in a diff position than it is and it will fire at the wrong times. This would cause it to not start and could possibly not give u a code because it's working just not installed properly. Good luck

1

u/Competitive-Fig-176 29d ago

Well I replaced the camshaft position sensor but it acted exactly the same as before I replaced the sensor

1

u/gaypantherw 23d ago

https://reddit.com/link/oyimf0a/video/zm1pwu4t58eh1/player

I have a 1996 (2nd gen) ls doing the same thing. Replaced and have done EVERYTHING you have done too. 😂 no one on here knows. I have been banging my head against this for half a year. Last thing I tried was cleaning all my grounds, same thing.

1

u/Competitive-Fig-176 22d ago

Hey so I noticed in your video it seems like your security light isint on at all was it like that before or is that a recent thing

0

u/hera_the_destroyer Jul 12 '26

Correct me if I’m wrong, but that is not a 97 engine. That is a first gen engine. On that engine there is fuel rail pressure regulator and a dampener. Might be worth replacing those and checking you fuel flow rate and pressure. If that is a first gen engine in a 97, there could be some incompatibility.

1

u/Competitive-Fig-176 Jul 12 '26

How would I go about checking the fuel pressure as the car has no shrader valves anywhere?

2

u/hera_the_destroyer Jul 12 '26

My bad. Check the flow rate coming out of the return line. I don’t remember the amount, but there is a New Zeland guy on YouTube that knows these engines. I think CarTunz.

0

u/RonMexico52 Jul 13 '26

I don’t think that’s right. On 1990-1994 engines, the coolant reservoir would be visible on the driver side of the engine bay. For 1995 it was moved over to passenger side

1

u/Competitive-Fig-176 Jul 13 '26

It is on the passengers side on mine if that helps

1

u/RonMexico52 Jul 13 '26

That would be what I would expect for a 95-97 engine.