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1994 Chevrolet 1500 5.7 Liter TBI

tk4076 tk4076
New User | Posts: 1 | Joined: 10/08
Posted: 10/23/08
08:16 AM

Vehicle will start and run approximately 20 seconds and then the fuel is cut off to the injectors and vehicle will not start again until you take the negative battery cable off. Already have replaced PCM, PROM, and throttle body and injectors and gaskets, fuel cutoff relay, fuel pump. Any suggestions to what my problem may be?  

waynep712 waynep712
Enthusiast | Posts: 651 | Joined: 10/08
Posted: 10/23/08
05:34 PM

just curious.....

throttle body injectors have a constant switched power to the Positive side...

the computer switches the other side to ground  to make the injector work????

were you able to verify that the power side is not cutting out .????
have you looked at the ecm side of the injector with a digital volt meter...  to see if the signal drops out first... the pulse width goes to 0 .. before the engine stops turning..

(digital volt meters... automotive ones.. measure not just  ohms, volts, amps.. but dwell, miliseconds, pulsewidth, hertz, this lets you see what the various sensors are doing... and then you can compare them to what the scan tool displays..)

can you pull the cap and rotor... take a bright flashlight..  look straight down the shaft.. see if the magnet that is barely visable is cracked... if so... that might be a place to start looking...

do you have a scan tool that can look at the live data...???

does this truck have a resistor in the ignition key??? like a camaro or corvette?? and a bunch of other cars... does the security light come on when it dies???????

it is possible  that the ignition switch is going bad???  electrical part of the switch...  

have you removed the ign module... taken it to a parts store.. many have the ability to test them... have them test it 6 times in a row...  this lets the module heat up...   sometimes they only fail hot...  be sure to use silicone dielectric tune up grease under the module..  or it will fail.. there is a lot of heat build up....  

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