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The Definitive Injector Swap HOW TO

317K views 690 replies 151 participants last post by  Billyjoebob007 
#1 · (Edited)
The Definitive Injector Swap HOW-TO

DISCLAIMER: This swap ONLY applies to the 1993 thru 1998 Jeep Grand Cherokee "ZJ". Although many other vehicles have included the 4.0 and 5.2/5.9; there is NO guarantee that this swap will benefit or even work on a different vehicle; because there have been many different varying injector sizes, connectors, and engine/fuel management systems on vehicles with these engines. Do your research on your particular vehicle, paying close attention to stock injector specs vs new injector specs, before you attempt this on a different vehicle.

So I think its time there was a write-up that defeated all the misconceptions, conflicting information, and myths about the infamous injector swap mod. I will try to do it as completely and accurately as possible, please comment so I can correct the post :)

There are two sets of steps, one for the 4.0, and one for the 5.2/5.9 found below courtesy of 1SASjeepster.

Theory:

The injectors used for the swap are the EV6 injector design as opposed to the stock EV1 injector design. The 4-hole pintle of the EV6 leads to better atomization of fuel, thus a more complete burn, with the same flow rate as the stock 1-hole EV1 design. You can see this easily in this video: .

The performance/economy advantages are:
-Engine idle becomes smoother
-Small increase in throttle response
-Small increase in fuel economy

Parts needed:

The injectors you need depend on the year and engine of your ZJ You will need an injector with the proper Jetronic/Minitimer connector or an adapter that will plug into your ZJ's harness. I have collected information from Jeepers that have done this swap to determine the best injectors for each model year. You can use the information below to select the best injector for your jeep

Stock Model numbers & Pressures:

Stock 4.0 Injector (93-95): Siemens 53030343; 22.4lb/hr @ 39psi
Stock 4.0 Injector (96-98): Siemens 53030778; 23.7lb/hr @ 49psi

Stock 5.2 Injector (93-94): Siemens 53007809; 18.4lb/hr @ 39psi
Stock 5.2 Injector (95onl): Siemens 53030262; 24.6lb/hr @ 39psi
Stock 5.2 Injector (96-98): Siemens 53030778; 23.7lb/hr @ 49psi
Stock 5.9 Injector (98onl): Siemens 53030778; 23.7lb/hr @ 49psi

Injectors Recommended:
Bosch 0280155703; 21.8lb/hr @ 39psi & 24.4lb/hr @ 49psi
Bosch 0280155710; 17.3lb/hr @ 39psi & 19.4lb/hr @ 49psi

Alternates, as reported by a few people in other posts. These injectors have been reported with mixed results, you can read for yourself in the thread. I have posted their specs here for easy reference:
Bosch 0280155784; 20.2lb/hr @ 39psi & 22.6lb/hr @ 49psi (slightly less flow than the 703s. You will need a Jetronic/Minitimer adapter for the electrical connector.)
Bosch 0280155789; 19.9lb/hr @ 39psi & 22.3lb/hr @ 49psi (slightly less flow than the 703s. Also needs a Jetronic/Minitimer adapter for the electrical connector.)
Bosch 0280155715; 21.3lb/hr @ 39psi & 23.8lb/hr @ 49psi (very close to the 703s flow. Users have reported mixed results with new/tested injectors. No adapter needed)

Injector Recommendations:
93-95 4.0 w/703s: CONFIRMED (zander21510, 93zjbums, ahoyt653)
96-98 4.0 w/703s: CONFIRMED (MaintMech, melk, moggie99, johnt671, torchd, DickDickle)
93-94 5.2 w/710s: CONFIRMED (General_Jeep, soopaghetto, ozzy_2_me, Proph2010)
1995 5.2 w/ 703s: CONFIRMED (extrememarine, dnuccio, jetjr91)
96-98 5.2 w/703s: CONFIRMED (1SASjeepster, zturn13,Mity White 96)
1998 5.9 w/ 703s: CONFIRMED (nickszj, NYCXJ90, hm_dart)
*Please help me improve this post by posting your success so that I can add your data!

The root of most problems people have had with this swap is leaky, old injectors untested from the junkyard. Exposed to the elements, these injectors are highly prone to decay. If you find your Jeep to be spewing white smoke or running rough, or if you just want to take the precautions and test the injectors first, here is an easy way to do it:

I had very similar experience when I first installed the 703's. I did not take the time to rig up a way to pressure test them. I had 3 that were dumping fuel; I found this by taking a clear piece of tubing and a children's cough syrup syringe and made a tester. I put some carb cleaner in the tubing, slide it on the injector, and pushed the plunger down to pressurize the fluid. Sure enough, droplets would form on the motor side of the injector. Swapped those three out and all was fine the second go round.
Also, I strongly recommend you get a rebuild kit. It's very easy to rebuild the injector with basic tools. I used to have a link to an online retailer but they no longer sell the kit. You can find the kit on eBay from various sellers. Pre-made eBay search: here

Cars where the injectors can be found:

Bosch 0280155703:

97 Dodge Caravan Base 2.4L
97 Dodge Caravan SE 2.4L
97 Plymouth Voyager Base 2.4L
97 Plymouth Voyager SE 2.4L
97 Chrysler Sebring JXi 2.4L
96-97 Chrysler Sebring JX 2.4L
96 Plymouth Breeze Base 2.0L
97 Chrysler Cirrus LXi 2.4L
95-97 Chrysler Cirrus LX 2.4L
95-97 Dodge Neon Base 2.0L
95-97 Dodge Neon High Line 2.0L
95-97 Dodge Neon Sport 2.0L
95 Dodge Stratus Base 2.0L
95-97 Dodge Stratus Base 2.4L
95 Dodge Stratus ES 2.0L
95-97 Dodge Stratus ES 2.4L
95-97 Plymouth Neon Base 2.0L
95-97 Plymouth Neon High Line 2.0L
95-96 Plymouth Neon Sport 2.0L
Bosch 0280155710

Proph2010 said:
1994-97 Mercury Cougar 4.6L V8
98 Ford Crown Victoria/Mercury Grand Marquis/ 4.6L V8
97-99 Ford E-350 6.8L 10-cyl
96-98 Ford Explorer 5.0L V8
99 Ford F-250-550 6.8L 10-cyl
97-98 Mercury Mountaineer 5.0L V8
94-97 Ford Thunderbird 4.6L V8
94-98 Lincoln Town Car 4.6L V8
Remember there are TWO numbers on each injector, one of them will be some number you won't recognize, the other one is the model number. As long as one side matches the numbers above, it is that injector model.

Tools & supplies needed:
-Ratchet kit to unbolt fuel rail
-Pie pan or small, shallow container to catch fuel
-A little clean motor oil or lubricant oil
-Some rags

Steps: This was performed on a 95 ZJ with a 4.0. I used 703 injectors. (5.2 and 5.9 procedure click HERE)

1. First, if you have used injectors, perform the rebuild. Be very careful not to damage the pintle on the injectors. If you have extra parts, they are extra, don't try to add them to the injectors. You can remove the old filters by using a screw, screwing it into the old filter, and pulling out with pliers. The old pintle cap can be removed by carefully using a blade to cut the cap down the side and pull off. (I stabbed myself when i did this...not fun...cut AWAY from yourself...)Install all the new stuff!

2. Disconnect the battery. DON'T IGNORE! Not just because of the safety aspect, but as you are working it will reset the PCM and allow it to "learn" the new fuel trims needed to operate efficiently. The PCM will return to its factory values, and as you drive it will adjust the injector pulse rate to accommodate the different injector design. This is vital if you want to notice any benefits quickly. Also, if you have the equipment, blow some compressed air around the injectors prior to removal. This will prevent dust and pieces of who knows what from getting into the combustion chamber.

3. Relieve the pressure on your fuel rail. Take a rag and and unscrew the plastic cap near the front of the rail. Push the little button inside and fuel should first squirt out and then eventually dribble. Hold the rag under it and keep it there until it stops squirting. You can then screw the plastic cap back on so you don't lose it.

4. Unplug the electric connectors from the fuel injectors. Pull them out of the way. It shouldn't be a problem, but if for some reason they are very loose or the wires aren't tied down, make sure you keep track of what plug goes to what injector.

4. There are 3 bolts to remove the fuel rail, and you need to remove the 3 throttle body cables and get them out of the way to make a clear path for the fuel rail to be pulled. You need to place the shallow container, or have a buddy hold the container, under the fuel rail, so that you can catch the excess fuel. Pull sharply on the rail in the direction of the injectors to remove. Usually the injectors will stay in the rail when you pull it from the intake. Remember you have a lot of fuel still in the rail.

5. Keep that container under the rail over as you remove each injector, because there is a lot of fuel in the rail (way more than you would think...).

6. Once you have everything disassembled, you can attach the new injectors to the fuel rail. Lube the O-rings with some motor oil or lubricating oil to make them easily slide into the fuel rail openings. Make sure they are oriented properly, the pintle holes should go into the intake. You can spin them when everything is attached to a point, but it might help if they are oriented with the connectors pointed up so you can connect the electrical connectors easily.

7. Lube the other ends of the injectors, and evenly push them into the holes in the intake manifold. You know they are in when you can line the fuel rail holes with the bolt holes.

8. Bolt everything up and reconnect the electric connectors.

9. If you made a mess with all the fuel, soak as much up as you can and give it an hour or so for it all to evaporate so you don't start a fire. Just in case, have a fire extinguisher handy (the C type).

9. Start her up! It may take 2 or 3 more seconds to turn over, the fuel rail has to regain pressure and squirt fuel into the cylinders.

10. Enjoy! There are a few pictures below for reference taken from the older threads courtesy of melk.

Old injectors vs the 703 injectors with new O-rings, filter, and pintle caps:


Fuel rail with old injectors:


Fuel rail with new injectors installed:
 
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#208 ·
I wouldnt!!! I bought 8 brand new 703 injectors off of ebay for $200 delivered and installed them in my 1998 5.9 and they run perfectly.... very smooth and mileage appears to be good too ( dont have a big enough sample to say for sure).

I say stick with the 703's, they are proven by me.
 
#214 ·
Lets just relax...this is a discussion every post contributes to making the original post more complete. I appreciate both of your contributions, augiedoggy made us all look at the possibility of problems with the magnum engines and I was able to improve the OP immensely from data he and others provided, along with ideas he presented.

Not to say you didn't help nickszj, being the only reported success with the 5.9 makes you a valuable contributor too! I think a lot of guys looking at this will be able to confidently do the swap to their 5.9 thanks to you.

Relax guys...we're all buddies here. Even if somebody owns a Dodge truck...;)
 
#215 ·
I was cleaning up around the shop the other day and found a set of injectors left over from an engine swap in an Explorer...

The numbers are 0280155735, they are completely red, 4 hole design. I can't find much information on these injectors. According to the Bosch injector chart, they only flow 18.25 lbs at 42.5 PSI... but I found a conflicting source saying they actually flow that much at 32 PSI. I'm thinking about throwing them into my ZJ, if anyone else can find some more information on them I'd appreciate it.
 
#220 ·
I don't know if this question has been asked or I just skipped over it.

Has anyone done the 99+ intake and done the 703 injector swap in a 4.0L I6 98 ZJ? Was there an issues? Was it worth it? Is there a better injector than the 703? Thanks
 
#221 ·
xbeakerx said:
I don't know if this question has been asked or I just skipped over it.

Has anyone done the 99+ intake and done the 703 injector swap in a 4.0L I6 98 ZJ? Was there an issues? Was it worth it? Is there a better injector than the 703? Thanks
I think based on the info in this thread that is the best setup for your motor, in terms of you intake manifold and injector selection.
 
#222 ·
FWIW I installed those Explorer injectors... It seems to run much better and the slight off idle hesitation is gone. It's hard to tell if it runs smoother because I replaced the motor mounts at the same time. I pulled a trailer 200 miles round trip without overdrive and averaged 12.5 mpg at 60-65 mph, which really isn't bad.
 
#223 ·
Proph2010 said:
I think based on the info in this thread that is the best setup for your motor, in terms of you intake manifold and injector selection.
Thank you, I just wanted to make sure before I buy the items and found out that there was a better setup.
 
#224 ·
I just did the 710 injector swap on my 93 5.2. Pulled them from a 4.6L V8 thunderbird

Everything went smoothly. Engine idles a tad lower but i like it; low rpm = less fuel used. seems like better throttle response as i used to apply more force on the skinny. Acceleration seems better. Since i just did it today, i dont know about MPG yet, but as soon as i started to drive it, the overhead started to climb above normal for me...

I have a pic for comparison. The o-ring positioning are at same length from top/bottom.



I am not sure on everthing as i just finished 1 hr ago. I know right now things could be placebo and since im running 39psi and the injectors only flow .5 lb more than stock, i dont foresee too much gain.

Mods:

2.5" cat back w/turn down before rear axel
50 mm bored throttle body
generic "CAI"
 
#237 ·
Those are the exact ones I purchased...they are perfect, very quick shipping, bacnd new injectors... what he is saying int he ad is that he buys them in bulk of 70 at a time.. he obivoulsy sells them individually... they all come with caps to protect the o-rings... buy them, they work perfectly.
 
#230 ·
I would say its fine to go for it there has been success and there is no reason we have figured out why it wouldn't work.

Did u see in the description where they only sell in bulk with 70 injectors per box? :D
 
#232 ·
I am pretty sure the seller is trying to state that there are no individual boxes. S/he probably bought them in bulk and they were all contained in 1 single box. So, you are purchasing them separately (hence the # sold up top), but you won't be getting them in individual boxes probably wrapped up in bubble wrap and shoved into a flat rate box or envelope.
 
#234 ·
I see a lot of ppl on here talking about buying them from ebay etc. I did a search on here and we have a member of this forum who sells the all the injectors. Im in the process of purchasing them from him as we speak. His user name is DezertXj88 and his classified thread is http://www.jeepforum.com/forum/f126/injector-upgrade-703s-784s-789s-ford-19lbs-24lbs-28lbs-1327630/

He sells sets of six and eight for much cheaper than what ive seen on ebay. He says he just cleans them well and installs new filters in them, i dont know about o rings etc, but he says he ensures working order before selling them. So even if you wanted to put new rings on them with the price tag he shipping them for its cheaper than ebay.
but these from ebay are new not used

I would say its fine to go for it there has been success and there is no reason we have figured out why it wouldn't work.

Did u see in the description where they only sell in bulk with 70 injectors per box? :D
thanks for the response and yes i did i messaged them and they said you can order as many as you want from them and its up to 70 per 1 box so if you order more then 70 it will be more then one box
 
#242 ·
Im in the same bout as you are, youre getting new plastic thats it IMO...maybe some piece of mind that its new...IF it was coming from a walk in business, the whole ebay thing has never sat to well with me with impression of quality goods for cheap...because in all reaity 25 dollars is super cheap than what advanced auto sells these puppies new for, the sell them for like 150 a piece... makes me wonder how "new" his are as well...

At any rate mine have been in my jeep since 1994 they work just fine, im sure newer injectors used, cleaned, with important components replaced new will work just fine.
 
#244 ·
zturn13 said:
well i got my new injectors they look great printed off the walk thru (have read it several times) is there any last minute advice I'm getting up early and doing this and hopefully will be done in time for work lol
Just take ur time and ull be fine! Good luck
 
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