1988 Chevy 2500 4x4 with 5.7 A/T
Engine died while driving no spark no fuel pulse. I can make the fuel pump
run by jumpering fuel pump relay but without spark- no run. If ignition
module goes will it also kill fuel pump control? The Green wire at fuel pump
relay has no voltage when key is turned on or when engine is cranking. I
have checked all the fuses all are good. Any ideas greatly appreciated!!!
When cranking, the PCM must receive reference pulses from the module before
it will pulse the injectors.
It doesn't matter if you jump the fuel pump....no spark, no fuel from the
You need to test for spark with a spark tester or inductive timing light.
Ok that did answer my question. I did check for spark but had no spark
tester handy so I just grabbed the coil wire as I suspected no spark anyway.
It does kind of look like it is gonna be the module bad but as you can tell
from my sig-- I am an Acura tech and have thrown everything out the window I
remembered from GM school. I have checked G107 and G108 both of which are
good and I do have voltage at the ECM where I should have it. I am probably
just overthinking this thing and I should just go out and get an ignition
module for it and just fix the damn thing!!! Thanks for the help!!!
anyway. I remember another post about something to do with the control module
needing a pulse from an oil sending unit ... to protect from low oil pressure?
not sure but if ign module doesnt work it may be worth looking into...really not
sure...but thouhgt Id bring up just incase it helps...
I think you were reading an abominable message about the oil pressure
The oil pressure switch only provides another vote for the pump to run.
Disconnecting it will not stop the pump providing the balance of the system
is working properly.
So, from memory, the pump will run under any of the following conditions....
1: For two seconds after the ignition switch is turned to the run position
provided that it was just off for at least ten seconds
2: Any time the ignition switch is in the crank/start position
3: Any time the ignition switch is in the run position AND reference pulses
are being received
4: Any time the oil pressure is 4 psi or higher
There is also a test port in the obd connector to bypass the relay and run
the pump provided the relay is not arced/welded closed.
If I left any off, please add to the list.
while your at it, you might want to pull the dist. out and put a new
pick up in it. the pick up coil is useally corrodedand no signal from
the pick up will give no pulse or spark.
better that 60% of the time the module MAY give spark OR pulse but the
pick up will give you nothing at all.
If it is the switch it is not expensive to replace if you do it
yourself and the ingition switch itself snaps on to base of housing
key goes into so you can replace it easily without replacing
everything. I am not convinced it is the cause here though.
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