Experienced Fuel Injector harness question

Stang_ROTY · 07-17-2001, 03:27 PM

My engine builder is a straight-up carb guy. He is just as scared of EFI and computers as I am waking up one day and finding an IROC in my driveway :-) I was wondering exactly how the injectors fire (after spark, randomly, etc) and if plugging the injector harness into the wrong injectors can do any damage? For example..say I took the number 4 cyl. plug and popped it into the number 8 injector by mistake...what could happen?? Could I bend a rod by injecting the cyl. on the wrong stroke?? We will be starting a fresh balanced and blueprinted 393 stroker Friday and were wondering if damage can be done by mistakingly plugging the wrong harness into an injector. Personally, I can't see how it could get screwed up b/c the harness is set up to only fit the sensors and injectors one way but I did notice that the injector plugs are not numbered. Thanks

------------------
Finally DONE!!
93 GT, 393 stroker, Dynamic Roller Mite C4, 8 pt cage,
Sothside Machine bars & Sub-frames, 3.73's,
'69 351W block w/SCAT crank.

ArtMan · 07-17-2001, 06:20 PM

Yes, plugging the harness plugs into the wrong injectors would be harmful. Don't do that. The correct plug is generally defined by the length of the wire needed to reach the injector. If you're struggling to get the plug to reach an injector, its the wrong one.

The injector firing is controlled by the computer and follows the firing order of the spark plugs. I believe the computer receives input from the Thick Film Module to determine which injector should squirt next, but I'm not certain.

In any case, plug the correct harness plugs onto the correct injectors.

Stang_ROTY · 07-18-2001, 06:25 AM

That's what I was thinking also. My engine builder keeps reminding me to "make sure" I put them into the right injectors. I told him you can't really screw it up b/c they each have their own length. Thanks

BlackFly · 07-18-2001, 11:48 PM

this should not hurt your engine , but performance and economy would suffer. the injector sprays in preset order and time according to engine load. spraying in bad time would result in the correct amount of fuel being delivered at the wrong time ,resulting in the fuel sitting, hopefully atomized still, waiting for the valve to open and suck it up, instead of spraying at the time of the valve opening.brand x ran batch fire injection on those slow irocs of the 80's, which fired pairs of injectors at once, resulting in the same situation, fuel sitting in the port waiting.

Stang_ROTY · 07-19-2001, 01:12 PM

But I still can't understand why he's worrying so much. It's not like you can screw it up. If you put the harness on the wrong way the temp and oil sensors wires won't attach to the sensors, right?

BlackFly · 07-19-2001, 11:46 PM

stangroty is right , it falls in place better than a cheap puzzle, as long as you have the correct harness, you really cant go wrong, if the other sensors dont land in the right place , the harness is on the wrong way, flip it over and all will be well. these things are easier to hook up than cars of old.

07-17-2001, 03:27 PM	#1
Stang_ROTY Registered Member Join Date: Feb 2001 Location: Berkshire County - Massachusetts Posts: 735	Experienced Fuel Injector harness question My engine builder is a straight-up carb guy. He is just as scared of EFI and computers as I am waking up one day and finding an IROC in my driveway :-) I was wondering exactly how the injectors fire (after spark, randomly, etc) and if plugging the injector harness into the wrong injectors can do any damage? For example..say I took the number 4 cyl. plug and popped it into the number 8 injector by mistake...what could happen?? Could I bend a rod by injecting the cyl. on the wrong stroke?? We will be starting a fresh balanced and blueprinted 393 stroker Friday and were wondering if damage can be done by mistakingly plugging the wrong harness into an injector. Personally, I can't see how it could get screwed up b/c the harness is set up to only fit the sensors and injectors one way but I did notice that the injector plugs are not numbered. Thanks ------------------ Finally DONE!! 93 GT, 393 stroker, Dynamic Roller Mite C4, 8 pt cage, Sothside Machine bars & Sub-frames, 3.73's, '69 351W block w/SCAT crank.

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07-17-2001, 06:20 PM	#2
ArtMan Registered Member Join Date: Dec 1998 Location: Scarsdale, NY Posts: 45	Yes, plugging the harness plugs into the wrong injectors would be harmful. Don't do that. The correct plug is generally defined by the length of the wire needed to reach the injector. If you're struggling to get the plug to reach an injector, its the wrong one. The injector firing is controlled by the computer and follows the firing order of the spark plugs. I believe the computer receives input from the Thick Film Module to determine which injector should squirt next, but I'm not certain. In any case, plug the correct harness plugs onto the correct injectors.

07-18-2001, 06:25 AM	#3
Stang_ROTY Registered Member Join Date: Feb 2001 Location: Berkshire County - Massachusetts Posts: 735	That's what I was thinking also. My engine builder keeps reminding me to "make sure" I put them into the right injectors. I told him you can't really screw it up b/c they each have their own length. Thanks

07-18-2001, 11:48 PM	#4
BlackFly Registered Member Join Date: Feb 2001 Location: winnipeg , manitoba , canada Posts: 83	this should not hurt your engine , but performance and economy would suffer. the injector sprays in preset order and time according to engine load. spraying in bad time would result in the correct amount of fuel being delivered at the wrong time ,resulting in the fuel sitting, hopefully atomized still, waiting for the valve to open and suck it up, instead of spraying at the time of the valve opening.brand x ran batch fire injection on those slow irocs of the 80's, which fired pairs of injectors at once, resulting in the same situation, fuel sitting in the port waiting.

07-19-2001, 01:12 PM	#5
Stang_ROTY Registered Member Join Date: Feb 2001 Location: Berkshire County - Massachusetts Posts: 735	But I still can't understand why he's worrying so much. It's not like you can screw it up. If you put the harness on the wrong way the temp and oil sensors wires won't attach to the sensors, right?

07-19-2001, 11:46 PM	#6
BlackFly Registered Member Join Date: Feb 2001 Location: winnipeg , manitoba , canada Posts: 83	stangroty is right , it falls in place better than a cheap puzzle, as long as you have the correct harness, you really cant go wrong, if the other sensors dont land in the right place , the harness is on the wrong way, flip it over and all will be well. these things are easier to hook up than cars of old.