will not start or intermitent start problem

[Michael F.]

this is on my tow truck, 93 5.7 1/2 ton chevy. driving down road less than mile from house truck shut off, tried to restart would not, later starter but stalled minute any gas given, disconnected timing bypass and went into limp mode to get home. Here is what I have done with no joy: tested and all met specs...temp coolant switch, throttle position sensor, egr valve, solenoid, vacuum good, coil replaced and checked good, ignition module under dist cap checked good at auto parts stores 6 times, pickup coil under cap good, fuel pump, filter and lastly today the ignition switch on lower steering column replaced and checked good, cranked it up and it ran 20 seconds and died then no restart or spark, seems to be an intermitent spark issue....so what I am missing or what do you suggest.

[Carl N.]

Re: will not start or intermitent start problem

looks like you have covered all the easy ones - next thing that comes to mind is timing chain - you did not state how many miles if you are at 100k+ that and/or the timing chain gear on the cam (I think they were plastic) could be the issue - other thing could be a plugged vapor recovery line to fuel tank, pull that line and block it off and see what happens - keep trying you will find it !

[Edward J.]

Re: will not start or intermitent start problem

Mike, do you see fuel coming from fuel injectors when cranking? If not try cracking the supply line fitting at throttle body(bigger line) and cycling the key on for a split sec. to see if there is any sort of pressure. put a old towel under the line to help trap the fuel. DO NOT CRANK ENGINE JUST CYLCE KEY ON, the fuel pump will run for about 3 sec. and the pump will shut off.

Some of the issues I have seen is the Distributor pick up, and also the shaft has a magnet that the pick-up uses to signal firing the injectors and ignition coil, sometimes what happens with the magnet is oil runs up the distributor shaft collects on the magnet and it loses it magnetic field. What I have seen is the truck will sometimes randomly stall, this is the first sign of this problem.

[Dick W.]

Re: will not start or intermitent start problem

Sounds like fuel supply. Pump, regulator, or plugged filterfilter

[Michael F.]

Re: will not start or intermitent start problem

here is what i did that fixed the problem: bought a new complete dist from autozone, dropped it in and runs great now...must have been a problem pickup coil or ignition module. I changed pump, filter, relay but didn't fix so went with new dist. thanks for help.