1991 Ls400 Starts For Split-second And Then Dies!

[TheOneChen]

Hello everyone, I just finished replacing the fuel pump on my 1991 LS400. However, I am still having a problem starting my car. I know the fuel pump works because I can hear the fuel surging under the hood every time I turn the key to crank the motor. I even bridged the B+ and FP pins in the diagnostic port under the hood to make sure the fuel pump is working, and that I am getting fuel into the engine. However, the engine will not stay running. Whenever I crank the motor, it will come on for a split-second, rev to around 2000 RPM and then die. Could someone please tell me what could be causing this?

 

[TheOneChen]

Ok, today I worked on the car a little bit more. The engine will now occasionally run for a little bit longer, more like around 3 to 5 seconds, and then it will die again. This happens every time I use the deflooding procedure, by cranking the car a few times with the gas pedal all the way down on the floor. I also did some diagnosis, and I got code 13 from the check engine light, which has to do with "RPM signal 2." Could someone please help me with this problem?

 

[Lextreme II]

I just had that issue. Code 13 is your cams or crank sensor. You can test them out using a volt meter and they should be around 930-1,250 ohm. Double check the connection also.

 

[TheOneChen]

Where exactly are the cam sensors and the crank sensors?

 

[Lextreme II]

http://lextreme.com/pdf/cam-crank-sensor-testing.pdf

 

[TheOneChen]

I don't know if this will help, but I also want to add that stepping on the gas pedal doesn't keep the engine running at all. Sometimes, it seems like stepping on the gas pedal actually kills the engine even faster.

 

[Lextreme II]

Double check your MAF plug... it might be unplug...

 

[TheOneChen]

I tried starting the car with the MAF sensor unplugged, and then with the MAF sensor plugged in, and during both times the engine would still shut off immediately after it started. Also, code 13 seems to come up intermittently. Every time I clear the codes, code 13 doesn't come up immediately.

 

[Lextreme II]

So,

If unplugging the MAF doesnt make a different. What does it mean? Test you MAF to see if it is still good and double check if your timing belt/marks are off or not.

 

[TheOneChen]

How do I test if the MAF sensor is good, and where are the marks on the timing belt located? Thank you so much for the advice!

 

[Lextreme II]

Do a search. There are few articles about this in our forum. If you cant find them. Let us know.

 

[TheOneChen]

Ok, I pulled the relay under the hood labeled "Main Engine Relay," tried to start the car without it, and it did the exact same thing. I was wondering, since the car displayed the same symptoms without this relay, if this might be the problem and the relay is bad. Also, the EFI relay (not the fuse) seems to get pretty hot whenever I try to start the car. Is this normal?

 

[TheOneChen]

I was also wondering if the problem could be a bad alternator? Every time I try to start the LS400, it has been by jumping it with my other car, because the battery in the LS400 is dead. The guy from whom I bought the car said the battery was new, but it has been dead since when he first showed me the car. Would a bad alternator cause the symptoms that I have described previously?

 

[attis]

Hi!

I'm no expert, I'm just thinking this. Sry for bad english I'm from europe.

I'm just having some problems with my timing belt installation, so I checked the cam/crank sensors (getting rpm signal 13, car starts, but runs rough when in Drive).

The crank sensor is near the crankshaft pulley, it can be easily disconnected, if you can go under the car.
The two cam sensors are near the camshaft pulleys... the wiring of the sensors are fixed to the plastic housing of the pulleys, you can follow the wires...

If one these sensors are disconnected, the car will produce the symptoms you mentioned (i guess it tries to start, but it can't because it cannot detect the correct timing for the ignition - due to the sensor error - )