starts and dies, starts and dies. (1 Viewer)

[loquito]

1994 tlc
symptoms:
will start in normal time when key is turned. will rev right up to about 1400 rpm's just like when you start her when the engine is cold.
as soon as it gets to 1400 (less than a second) the engine just dies. This happenes again and again.
If I stomp the gas peddle the rpm's will go up to about 3500 and then she will just die.

What I have checked.
There is gas.
efi main
fuel pump relay
efi 15 amp fuse under hood
ign 7.5 fuse under dash
dry dizzy
no obvious cracks in intake hose or any obvious loose vacume hoses
the fuel filter is about 4 yrs old
this truck has never thrown a check engine light/code
all wires plugs dizzy cap and rotor are close to new
the check engine light DOES come on when the key is turned to on.

the truck ran fine and the next morning she started acting like this. I have searched and done the various checks I could find but no luck.
does anyone have and hints they would like to share, at this time I am at a loss.

Thank You
Steven

 

[jvazquez53]

You mentioned everything but the plugs. A friend of mine had a similar problem in her Suzuki Vitara and as soon as she had the plugs replaced the problem was gone. Also the fuel filter is about 4 years old, I would replace it. It could be clogged.

 

[landtank]

sounds li9ke a air flow sensor problem. I know on the later model terucks they act like that when the MAF sensor is unplugged.

 

[mp_cude]

I had the same exact problem on a 97 celica. Tested the MAF, replaced the computer, tested the wiring (obviously in a more economic order) individually tested each vaccume line, replaced the fuel filter,replaced the distributor, spark plugs, plug wires, tested the TPS sensor, tested the relays, and if I am forgetting anything, tested or replaced everything related to starting and running.....It turned out to be the fuel pump, my initial suspicion......my buddie was funding the project, and he would not listen to me

 

[Tenzig Norgay]

It could be a sensor going bad. Hook up a test light to the fuel pump, and start it up. If the light comes on at start up(it should), then goes off and the engine kills, the computer is shutting everything down.

I had this problem before, and it turned out to be the water temp sensor. You could probably just check the sensor though

 

[TRDCRUISER95]

sounds li9ke a air flow sensor problem. I know on the later model terucks they act like that when the MAF sensor is unplugged.

X2 my friend LC was doing the same problem 2 weeks ago.

 

[NerdNoise]

sounds li9ke a air flow sensor problem. I know on the later model terucks they act like that when the MAF sensor is unplugged.

agreed. Once you start sucking more air in the thing does not know what to do and it just gives up.

 

[gmadriz]

Check Fuel Pump resistor

Hi, first sorry about my bad english. My friend chek the fuel pump resistor, all 80´s efi pumps works with 2 voltge; 8volt for normal working and 12v for special work (like start engine), i will tray to explain. Wen we start the engine (key in "start" position) the relay works in the first position, bypassing the ressistor (12v), then, wen the engine starts (key in "on" position) the relay works in the second position using the ressistor to put down the voltage in 8Volt. If the resistor have any damage the fuel pump will not work in normal conditions (like ralenti RPM).

Check de voltage in the fuel pump conector to be shure, if de voltage < 8v the fuel pump will not work.

Esplico en español, para mejor detalle. Las bombas de gasolina de las 80´s efi, trabajan en dos voltajes, 12v para usos especiales (tales como el encendido del motor) y 8v para el funcionamiento normal del motor. Cuando giras la llave a la posicion "start" el rele de la bomba evita el paso de corriente por la resistencia, enviandole a la bomba de gasolina los 12v necesarios, una vez que el motor esta encendido y soltamos la llave esta retorna a la posicion "on" y el rele de la bomba cambia de posicion haciendo pasar la corriente por la resistencia, llegandole a la bomba de gasolina 8v. Cuando la resistencia falla, no existe paso de corriente por ella, dando asi la falla que describes. (Enciende el motor pero al segundo se apaga)

Chequea el voltaje en el conector de la bomba (debajo del asiento de pasajeros) deberias conseguir 12v al encender y 8v o 9v despues de encendido el motor.

 

[TrickyT]

gmadriz's suggestion about checking the fuel pump resistor is a good one. Also, when you checked the fuel pump relay, did you also test for continuity with the relay energized? It's a little more work, but definitely a possible cause of your problem.

 

[WristPin]

Air Flow Meter connection loose.

Its NOT a MAF. Simalar function but completely different design