Upgrade your OEM injectors to 19# or 24# FoMoCo injectors.

Leaking fuel injectors can turn your XJ into an instant rolling bar-b-que so why not save that bag of marshmallows for when ya can stand around a fire drinkin' a beer (or twelve) instead of looking like a fool running around in circles while your rig burns to the ground at the mall?

A set of fuel injectors from a Ford 5.0L V-8 are a plug & play replacement that will solve your injector leaks, poor spray pattern, clogged tips and/or leaking o-rings for less than the cost of 2 aftermarket oem injectors from your local auto parts store! Just be sure to choose the correct rating injector for your particular engine.

Ford 19# Injectors

Great for lightly modified 4.0L engines.

These are all ya need for most applications. Commonly found on factory performance package Ford Mustangs. (No - I don't know which packages had them... but there are more than one type / rating Ford OEM injector for the 5.0L engines.)

Ford MotorSports 24# Injectors

These are for HIGHLY modified 4.0L motors or strokers ONLY!
*** 'Take offs' are a great way to get some inexpensive and very slightly used injectors that were removed from 'new' engines by car customizers who buy & build up new cars for street & race use. These are literally used only long enough to get the car from the factory to the customizer's build shop.

Be sure to check out eBay as they OFTEN have fantastic deals on injectors if you can stand the bidding process!

Choosing an injector size.

Stock, or nearly stock 4.0L engines do NOT need 24# injectors!

If you have a stock motor and think ya just absolutely gotta have 24# injectors... You're wrong! A basic rule of thumb is ONLY consider getting 24# injectors for stroker & built 4.0L engines (w/ hi-compression & big cams). Sure, your engine -will- run with 24# injectors but you'll encounter issues that you'd be much better off avoiding. Check out Jeeps Unlimited and do a search for username 'Dino'. He's posted a lot if information on injector size especially in the "Speed Freaks" forum. Read his posts and check out his website before ya buy.

EZ - Fuel injector size calculations.

8-Cyl. engines:

6-Cyl engines:

4-cyl engines:

Horsepower / 16 = Injector size Horsepower / 12 = Injector size Horsepower / 8 = Injector size


A 300 horsepower 6 cylinder would need 25# fuel injectors.
300 / 12 = 25

What to get? Where to get them?

Ya can buy a new set of Accel injectors from Summit Racing made for the Ford 5.0L for around $215 shipped. You'll get a set of 8 so you'll have two left over when you're finished.

There are companies online that have used injectors and here's a link to one to get ya started. 5-0 MotorSports will sell ya six for about $125.

KarKraft sold me a set of eight standard 19# injectors for $89 plus a few bucks shipping. These weren't the fancy racing units but I used these on my stock Renix 4.0L and was real happy with them. It helped that the price for 8 injectors is less than 3 stock replacements from local aftermarket parts houses! Note! - KarKraft no longer lists these on their site... dunno if they offer them now.

A friend scored a set of 19# injectors on EBAY for under $50 so keep an eye peeled there. I scored my 24# Ford Motor Sports injectors for about $95 shipped! (Details on Stroker page). The only pain is bidding against some bidding-crazed crackhead in Pokemon, MA who's buying the set you want just to get one for his modified racing lawn chair.

Local boneyards may not know their heads from a hole in the ground on injector types so if you go that route do your research first and give them a range of Makes & Models w/ the injector yer looking for. Yeah, they can cross reference them... if you get someone on the phone who can work the computer. I didn't.

My injectors from KarKraft came with perfect o-rings allready on them. If they're not PERFECT... REPLACE THEM! If your o-rings are damaged in ANY WAY... REPLACE THEM! (Engine fires suck!) Heck, just REPLACE THEM!

UPDATE!: A contributor to a tech forum thread reported that 1994 Crown Vic's with the 4.6L's have 19# 4 hole injectors!
(This likely means that the 4-hole injectors can be found on other 4.6L FoMoCo engines as well.)

Installed 19# FoMoCo injectors on Renix (non-HO) engine

There isn't much to the job other than to TAKE YOUR TIME! The fuel rail can be bent if you are not careful. The injector connectors have small, sliding clips (visible in above picture) that you must slide off connector to slip it loose from injector body. There is also a different style clip at the fuel rail that is pretty much a slip on / slip off affair. Just look at your injectors and you'll see what I mean.

Fuel rail outlined in yellow.
The injectors come off very easily once you unbolt the rail, undo the clips & GENTLY AND SLOWLY ease the rail from them. You may have to move the rail from end to end (rocking VERY SLIGHTLY) by only 1/8" or so at a time just to break loose the injector o-rings.
Um... you did buy some new o-rings didn't you?... DO NOT REASSEMBLE WITH THE OLD O-RINGS! My "new" injectors had nearly new o-rings ('take-offs') so I was able to use those but do NOT reuse your old XJ o-rings. Replace them - they're cheap insurance

The oem RENIX fuel pressure regulator is non-adjustable so don't go poking it with a stick trying to modify it... you can't adjust it. Period.
HESCO does carry an adjustable model IF you have modified your engine to a certain point. 99.9% of you do NOT need anything more than the stock regulator! If you "think" you need one - You don't. But if your engine builder calculated your fuel curve and recommends a certain injector size coupled with a particular flow rate and THAT rate is outside the stock regulator's parameters... THEN contact HESCO, have your engine specs handy and they'll fix you right up.

If you have pics of your own repairs or can suggest other methods - please contribute your ideas (and pictures) to this article!

Revised on: November 28, 2007

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