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5.7L Mag

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cambric88

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anyone come across this. 1999 5.7L Mag, cylinders #3 and #5 have no injector pulse. Swapped ECM and injectors themselves. checked connectors, the ones that are working have pulse across connector, the ones not have no pulse
 
they are all normally driven by the same injector driver...

without knowing the details on your engine, its just a best guess on my part...lots of configuration changes occurred thur the late 90s as EFI was getting adopted on marine engines...
 
makomark said:
they are all normally driven by the same injector driver...

without knowing the details on your engine, its just a best guess on my part...lots of configuration changes occurred thur the late 90s as EFI was getting adopted on marine engines...
Click to expand...
@makomark - finally found a decent wiring diagram and I see what you mean. if there were a problem with the circuit to ECM then you would figure that there would be an issue on 2 & 8 as well.
 
That's the thought...assuming that where the issue is, which one works/doesn't work will de driven by how the wiring deterioratedfailedget damaged, etc...
 
Thank you. do you know how to determine which connector these drivers are in? two interesting issues that I now have come to:
A - there were preceding issues to the injectors going dead, that is 2,3,5 & 8 would carbon foul shortly after installing new plugs
B - the completely dead #3 & #5 did not start happening until i swapped ECMs - I wonder if I pushed back or bent a pin
 
best thing to do is figure out which ECU you have - either MEFI-2 or -3. For sure method is to get the GM number off the "back". the quick method is to just eyeball the connectors to the ECU. On the -1 and -2 units, the connectors are such that they are on opposites ends of the ECU and "push towards each other" to seat. on the -3 and -4 versions they connectors are parallel to each other and push into the ECU to seat. some prefer the description (for the -3 & -4) that the connect pins are parallel to the heat sink fins...

Once you know which version you have, a www search can provide you with the delphi manual covering the MEFI. That will get you 99% of what you need. the other 1% covers the details the specific software implementation has...
 
agree -3...crusader and marine power use that same part as well and I suspect VP is on the list as well.

You will see all of the engine harness info/diagrams and the troubleshooting charts per DTC and symptom as well...

I'd suggest they big thing to remember is not everything is monitored or controlled by the ECU...so an engine can run bad and no have any DTCs set.
 
yes, found a diagnostic manual for it. there are some conflicts on wire color (which is typical), other than that, seems like the real one. There are diagnostic charts. As I read through the steps, knowing the answers, it is pointing to a bad ECM ground. At least I have some steps to take. Thank you for all of the information. once I figure it out, I will post it.
 
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