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Old 03-21-2015, 03:08 AM   #1
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Default 2003 NB Injector Installation

After reading and reading on how to replace the fuel injectors on a NB Miata, I figured it took around 30 mins for the average Miata mechanic, so I budgeted 3 hours.

The instructions tell you to remove the upper intake manifold then unbolt three bolts holding the fuel rail. They then say you can pull the rail out, but this isn't the case at all. My rail is stuck to a wiring harness that isn't so easily removed. On one end, the one closest to the firewall, 2 wire plugs need to be undone. On that same side, a nut needs to be unscrewed to remove a ground wire. Since this side is inaccessible, I'm deciding not to touch these wires and to just disconnect the one that will give me just enough room to move the fuel rail once its disconnected.

Second, I've removed the wiring from near the front of the engine and have that part loose. But, now I'm stuck on removing the actual fuel line itself. Its a metal line that is stuck inside a plastic conduit like thing. The plastic thing twists but doesn't budge. I'm now reading that the fuel line requires a tool to remove it? Is there anyway around this?

I've attached pictures... I'm not sure why the tutorials make it out to be around three steps.

How do you guys go about doing this procedure?

Can I just disconnect the wiring harness from the injector rail without unplugging it all? There's a hard plastic piece that doesn't allow the wiring harness to move.. Should I just wedge this thing out?

http://imgur.com/157HOn0,L6IRzCF,Ablu2St#0
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Old 03-21-2015, 06:19 AM   #2
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If you only need to change injectors, no need to disconect fuel lines, you should have enough play to do it.

If you wat to do it, you need this kind of tool
Amazon.com: Lisle 37000 Air Conditioning/Fuel Line Disconnect Tool Set: Automotive Amazon.com: Lisle 37000 Air Conditioning/Fuel Line Disconnect Tool Set: Automotive

Available at every parts store for cheap.
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Old 03-21-2015, 08:38 AM   #3
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Just like joyrider said, you should be able to leave the fuel lines connected and same goes for the wiring (as well as I can remember). You only need to raise the fuel rail about an inch (2.5cm) to get the injectors out.

I think "Pull the rail out" in the instruction was meant to be read as "out of the head" not "out of the engine bay".
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Old 03-21-2015, 09:35 AM   #4
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Don't forget to remove your gas cap before disconnecting fuel lines or injector, will spill way less. Get some rags and be ready.
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Old 03-21-2015, 11:16 AM   #5
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It's so much easier to change out the injectors with out the harness attached and connected.

The harness is usually cable tied to the fuel rail so once you disconnect the front connector(s) you can cut the ties and the harness will pull away from the rail.

Then, when you unbolt the rail it gives you some room to get your fingers in so you don't loose the black plastic spacers (if you do, good luck finding new ones...).

The front fuel line gets disconnected by sliding the tool over the line and sliding UP into the connector. put a little lube on it when reassembling and it goes together easier.

Put a lot of lube on the o-ring when pushing the injectors into the rail and make sure they seat all the way in. Helps when your trying to get them seated and lined up with the injector holes in the head.

You should download the FM instructions here; https://www.flyinmiata.com/support/i...all_turbos.pdf

And go to page 38 for the instructions.

Helpful hint on reassembly... Epoxy the spacers to the fuel rail. It makes it easier to put together without worrying about loosing them.
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Old 03-21-2015, 11:58 AM   #6
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Do the injectors just twist out?!

Thanks for all the help guys. Going into the garage for round 2 once I get my o rings and fuel disconnect.
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Old 03-21-2015, 12:23 PM   #7
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Quote:
Originally Posted by Chowcow View Post
Do the injectors just twist out?!

Thanks for all the help guys. Going into the garage for round 2 once I get my o rings and fuel disconnect.
Yes, usually just pull them out. It's easy to tear an o-ring so make sure to use lube on assembly but don't get the lube inside the injector.

They will just lift out with the fuel rail as an assembly. Then you can replace them one at a time then reassemble.
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Old 03-21-2015, 06:19 PM   #8
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MSMjohn from CR.net has a brilliant (ie. lots of pics) write-up on injector installation: Mazdaspeed mx5 Denso 321cc 23250-74050 injector info - ClubRoadster.net
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