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Jeep Fuel Injector Tech
Not much has changed with fuel injectors over the last twenty years. However fuel injector swaps for our Jeeps have changed quite a bit. All the go to swaps (eg Neon injectors etc) are now for vehicles that old, and less common, so the parts are pricey. So I'd figure I'd throw together a quick guide on newer options, and picking out injectors.

Flow Rates

First, keep in mind:
  • Fuel Pressure for a YJ is 39 PSI
  • Fuel Pressure for a TJ is 49 PSI
Fuel injector flow rates are specified at a specific fuel pressure. Adjusting the fuel pressure will change the injector flow rate (see the image below). On the YJ, well any 91-95 4.0, you can pickup an adjustable fuel pressure regulator. See my writeup here. If you need to adjust the fuel pressure on a TJ, you must use a fuel pressure regulator delete kit, and run an external pressure regulator.
Injectors flow rates vs Fuel Pressure



Next when looking at injectors, I almost universally found sets of 8 where cheaper. I could get Neon Injectors for $160 each or I could get a set of 8 Mustang injectors for $225*. The asterisk is because they will need an adapter which costs more, discussed later. No matter what injectors you use, Mustang, Camaro, etc, you will likely be better off looking for a set, and will likely end up with a couple extra.


When looking at injectors you may find the a very limited selection of the old EV1 style injectors (Minitimer or Jetronic connector). Worse yet the options you do find will generally be pretty expensive. The solution is just use the EV6 injectors (USCAR connector). EV6 are newer and more common. You will need an adapter to plug them in though. There are many different types of adapter harnesses readily available for this purpose, from short pigtails, to little clip styles. I recommend using the adapters over splicing your harness, this way it is reversible if you ever wanted to go back.
Here is an image of the injectors:
EV1 vs EV6 Injectors

Here is an image of an adapter:
EV1 vs EV6 Injector Adpater



If you've been looking for replacement injectors I'm sure you've seen references to 4-hole, 6-hole, etc. This is just the number of holes in the bottom of the fuel injector for fuel to come out. In general more holes is better. It produces a finer spray to help better atomize the fuel as it comes out of the injector. That being said I wouldn't let this entirely guide your decision. I also wouldn't swap injectors just to "upgrade" from stock injectors to 4 or 6 holes injectors. You won't notice a difference, assuming your injectors were in good condition to begin with.
For reference here is an image of my old Ford 4-hole injectors, and my new 6-hole Ford injectors:
4 Hole Injector vs 6 Hole Injector


Choosing Injectors

For my Jeep, this time around I ended up using a set of Ford Performance M-9593-LU24A. These are rated at 24 pounds at 39 PSI. Rather than find a vehicle with the injectors I wanted, I was able to go to the Ford Performance site, look through their injector list, find the ones I wanted, then quickly verify that they would work (EV6, etc). Then it was just a matter of checking prices through the regular vendors. Most manufacturers actually let you search in a rather generic manner like this. Interested in Accel or Holley fuel injectors, their website lets you search and sort injectors by flow rate, connector, etc. Then take these part numbers over to Summit, Jegs, Amazon, etc and double check pricing. Don't forget adapters if necessary if converting over to a EV6 style injector. You'll likely find this method of searching for fuel injectors much easier than endlessly trying different vehicles in the part store websites.

Why would you upgrade your injectors

Generally you're only going to upgrade your fuel injectors for a modified motor. Otherwise stock injectors are fine. Now if your stock injectors are bad, it's not to say you can't use some of this same information to find "better" replacement injectors. As some of the stock injectors form parts stores are expensive now.
Related Topics: | 91-95 Jeep 4.0 Adjustable Fuel Pressure Regulator |
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