PCM bad? cranks but no fuel or spark
09-17-2015, 06:32 AM
#1
PCM bad? cranks but no fuel or spark Im helping a friend getting his car back together after he had a oil pickup screen get plugged and ultimately had a couple rods go through the block. Putting a sbe ls1 in that i purchased from another member with 59cc patriot heads 231/237 .600/.600 112 fast 90/90 tsp 1 7/8 & tick stg II t56. Also installed a "direct replacement" walbro 255.
After checking all connections and hooking up the battery and turning the key to ACC. the hazard indicators light up as well as the bright indicator and seat belt light but no external lights are on. Turning the key to ON the cluster does no come on and stays the same as ACC. and odometer never comes on however doing that cycles the fuel pump for a half second and gives multiple sparks to #1 spark plug (only one i checked). Turning the headlight switch on shuts off the hazard and brights indicator and cluster lights up. Turning the key all the way forward to START the fuel pump has no power and no spark but cranks over and turning the key back to OFF the tach and speedo do a full sweep but the 4 other gauges are all wrong and never move. After trying to manually prime the fuel by crossing the relay found out we had to wire the pump backwards to have it pump fuel to the rails. My diagnoses is the pcm since i have never seen these issues before and he did unhook the pcm from the harness to look at it for whatever reason before new engine was installed.
Any help is appreciated. Thanks
After checking all connections and hooking up the battery and turning the key to ACC. the hazard indicators light up as well as the bright indicator and seat belt light but no external lights are on. Turning the key to ON the cluster does no come on and stays the same as ACC. and odometer never comes on however doing that cycles the fuel pump for a half second and gives multiple sparks to #1 spark plug (only one i checked). Turning the headlight switch on shuts off the hazard and brights indicator and cluster lights up. Turning the key all the way forward to START the fuel pump has no power and no spark but cranks over and turning the key back to OFF the tach and speedo do a full sweep but the 4 other gauges are all wrong and never move. After trying to manually prime the fuel by crossing the relay found out we had to wire the pump backwards to have it pump fuel to the rails. My diagnoses is the pcm since i have never seen these issues before and he did unhook the pcm from the harness to look at it for whatever reason before new engine was installed.
Any help is appreciated. Thanks
09-17-2015, 09:32 AM
#3
He made notes when he was taking everything apart and said only 2 grounds on the back of the head which I confirmed were there and the ground strap from driver side frame to block and main ground. Ill have him search again. Bad ground was my first thought but after checking and finding 4 good grounds and him mentioning removing the pcm I suspected that. Thanks for the quick response!
10-04-2015, 10:29 PM
#4
Update:
Found a ground he had bolted to a coil bracket that wasnt getting grounded and fixed some other wiring issues and that fixed the problem. Tuner was able to get 430whp out of it with 29.5* 12.5 afr using 91 & 180* engine temp even with some rusty tatlor spark plug wires he refuses to replace
Found a ground he had bolted to a coil bracket that wasnt getting grounded and fixed some other wiring issues and that fixed the problem. Tuner was able to get 430whp out of it with 29.5* 12.5 afr using 91 & 180* engine temp even with some rusty tatlor spark plug wires he refuses to replace