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injector wiring question

345 Views 13 Replies 6 Participants Last post by  Hybrid77Z
does it matter which injector connector goes to which injector? This is on a 1982 280zx Turbo
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Are you asking, can you take the one plugged into say 2 and exchange it with the injector wire in 1? Injectors are fired based on the intake valve being open, so yes it matters.
Well, actually, aren't they 'batch fired'? The way I understand it, they are triggered by the coil and fired in batches of three simultaneously, then the other three. With that scenario, you could conceivably switch leads around among the same batch. Thing is, I don't know if the batches are 1-3/4-6 or odds-evens or what. And anyway, why take a chance? Why would you want to change them anyway?
firing order for a Z I think is 153624. Anyway a detailed explanation is available at

http://www.motec.com/definitions.htm#Injection Timing

My link for some reason is not working.
I understand the firing order, but the Z cars don't have sequential fuel injection, so the injectors don't fire in order, they fire all at once. I still don't quite understand the batch-fire thing completely, but for a spirited discussion of it, go to this archive:


After re-reading posts from Tony, Wayne Monteath and others, I now believe that Surf really could mix and match the injector connectors any way he wants and it wouldn't matter. Still don't understand WHY he would want to do this, but theoretically, it would work. Unless I STILL don't get it.
No, it does not matter which injector lead goes to which injector.

The injectors are not timed with the intake valve being open. They all fire at the same time.

FYI, this is number 10 on the Megasquirt most common mistakes list....

HIM does not know the EFI system.
It DOES NOT matter since they are batched fired. They fired with the intake valve open and when it is closed.

The wires should "lay" where they were plugged in for teh last 20 years, but if they don't, it's not a problem. As long as they are connected, they will work just fine.

Him makem big mistake as the post pointed out. Wire as you please as posted twice. Batch fired do not care.


PS I guess this is a payback for the crate engine reply ha?

Post Edited (Nov 18, 8:10am)
not payback at all, just answering as forcefully with the correct answer to counter the authoratatively stated incorrect one. Nicer corrections from JR did not seem to do it.
See ya,
My link described different FI types. JR's then provided a link after mine, and his link specifically discussed Datsun. JR's link was not questioned, and the discussion ended. JR's link lead this thread to Tony's post that CLEARLY explained the Datsun FI.

Your reply was the third uncontested answer, I guess that serves a purpose. Thanks again for the clarification.

'HIM does not know the EFI system.' I don't read as clarification, but as payback. Yes as I said I made a big mistake? I should have known early Datsun's are batch. Live and learn. I guess this won't be forgotten, but that is nothing I control.

This is typical of here. I was tempted to let it slide, but you will simply carry this into another post so I chose to address it here.

Nothing is wrong in having too many good answers to a question.
Give the wrong answer in a tech forum and it will be pointed out.

I agree, and in an effort to increase the number of ‘good’ answers to this question I provide.

The injectors in an early Datsun Z are batched fired NOT sequentially fired. Therefore, the injectors opening are triggered based on the first cylinder to fire on startup, and NOT to any valve position.

The possible order based for random first to fire for a Datsun 6 cylinder are:
153624, 536241, 362415, 624153, 241536, and 415362.

And as was pointed out clearly by Tony D in:

Tony explained that injectors are fired every third spark firing. First fire is determined randomly. The first to fire is based on which cylinder the engine last fired when it was turned off (the engine of course will fire the next in order when restarted). Any of the above are possible.

The injection will occur after every third cylinder fires. The number of cylinder fires is based on the number of cylinders in the engine divided by two for a 4 cycle engine. This sequence is started based on the first cylinder to fire when the engine is started. Therefore, all cylinders over time tend to cause fuel injectors to perform their function.

Pairs from above are therefore, (1,6) (5,2) (3,4) or (6,1) (2,5) (4,3). Ignoring ordering within the pairs, either set of three are the possible sequence for injectors on a 6 cylinder with 153624 as it’s firing order.

Injected (1,6) when either cylinder 1 or 6 fires first
Injected (5,2) when either cylinder 2 or 5 fires first
Injected (3,4) when either cylinder 3 or 4 fires first
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Thought you said paycheck...

"Payback, I thought you said PAYCHECK!" Nevermind. NK.
OK, HIM knows his EFI ;-)
Very good post!
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