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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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#245 ·
ok so all went well with all the help from my gf and everyone on here and my trusty service manual.

My gf loves taking pictures so i have included some that she took

The hardest part was the driver side font two wouldn't hardly get out or go back in the rest was a cake walk



turning the injector makes it a lot easier to take off the clip



the comparison between the new and old injectors



my service manual said to oil the o-ring with some engine oil and boy did that make things easier



Sensitive content, not recommended for those under 18
Show Content


having it backwards to put the clip on makes thing easier also



and there we have it they are on when i turned the key to the on spot and waited about 45 seconds then off and on few more times then stared it and it and she ran really rough for the first few seconds and then started running smoother and now she runs great idles smother and throttle responds way better so i can confirm it works on a 98 jeep grand cherokee 5.2 v8 :)
 
#253 ·
can anyone tell me what size head is on the bolts that hold the 710s in to the fords? dont want to have to make a return trip to pick n pull...
 
#254 ·
ok, i went to the junkyard today and found some 710 injectors to try out this swap to see what all the fuss is about. to answer dpshoup's question it's a 8mm deep socket. and bring a flat screwdriver with you. that's all you need. I was luckey enough to find a set of 710 injectors that look practicly bran new. when i pulled them out they where like super clean. when i got back home i switched them out, turned the key on and off a couple times and left the key on and then went to check to see if there was any fuel leaks. all was good so i started it up and started a litttle rough then smoothed out. like really smooth out. this is the smoothest idle i have very seen/heard from this jeep. i let it idle for about 15 minutes and while it was idling i was still looking for any fuel leaks. still couldn't see any. i guess it is good thing. after that i shut it off restarted and took it for a spin. i can report that it has better thottle response and as for any increase i gas mileage it is to early to tell. i will report back in a couple days of driving. the one thing i think that is lacking so far in this thread is a vehicle list for the 710 injectors. i totally forgot which vehicle it was that i got mine from other then it like a grand marqui or lincoln ....something like that the year was like around 96 or maybe 97. if some can chim in and maybe provide a list i think that would greatly help this thread and all the guy's and gals out there with the 5.2 that want to try the 710's out. thanks again for this thread. other then the lacking info on the 710's it was a weath of info.
 
#255 ·
I did this swap just before I retired, so I'm not driving as much as I was, put still drive in the area. Driving up the mountain and going to work, my average MPG always showed 15.6 or 15.7. The trip home always showed 16.6 or .7. My over all average was 16.7.

The five days I drove to work after the swap it never went below 16.3, And the trip home showed 17. or 4 or 3. The first tank showed 17.3 and the second tank showed 17.4. So my net gain so far is between .6 and .7 MPG.
 
#256 ·
Any gains,or losses for that matter cannot be trusted totally by looking at the overhead display. The pulse width of the injector may be different which the pcm may alter as it learns the new injectors. To get a somewhat accurate mpg figure do it the old fashioned way, miles driven and fuel used.
 
#257 ·
I started the rebuild process for my 703s today that I picked up like 2 months ago from the JY. I've got them soaking in carb cleaner right now to loosen up any sort of debris. I'm not going to power them up and attempt to clean up the insides. I'm making sure the pintle is clean as well as changing the O rings and screens. I hope this all goes well...
 
#259 ·
I got the 703s in today. So far the only thing I've been able to notice is the incredibly smooth idle. It feels like it may have slightly better throttle response than it had before, but that could be because I completely tore down the 703s and rebuilt them. It could also be psychological. I will comment after a couple tanks of gas about the mileage differences.

This is another success story for a 96-98 (97) 5.2L with 703s. :D
 
#263 ·
My gas mileage seems to have slightly increased by about 1.5 mpg. I used to sit around 12-13 mpg and now I'm averaging between 13-14.5 mpg, sometimes a little better than that. Now, the true test will be to see if my leaky plenum fix helps any.
 
#260 ·
ozzy_2_me said:
ok, i went to the junkyard today and found some 710 injectors to try out this swap to see what all the fuss is about. to answer dpshoup's question it's a 8mm deep socket. and bring a flat screwdriver with you. that's all you need. I was luckey enough to find a set of 710 injectors that look practicly bran new. when i pulled them out they where like super clean. when i got back home i switched them out, turned the key on and off a couple times and left the key on and then went to check to see if there was any fuel leaks. all was good so i started it up and started a litttle rough then smoothed out. like really smooth out. this is the smoothest idle i have very seen/heard from this jeep. i let it idle for about 15 minutes and while it was idling i was still looking for any fuel leaks. still couldn't see any. i guess it is good thing. after that i shut it off restarted and took it for a spin. i can report that it has better thottle response and as for any increase i gas mileage it is to early to tell. i will report back in a couple days of driving. the one thing i think that is lacking so far in this thread is a vehicle list for the 710 injectors. i totally forgot which vehicle it was that i got mine from other then it like a grand marqui or lincoln ....something like that the year was like around 96 or maybe 97. if some can chim in and maybe provide a list i think that would greatly help this thread and all the guy's and gals out there with the 5.2 that want to try the 710's out. thanks again for this thread. other then the lacking info on the 710's it was a weath of info.
I also would like a list of 710 donors as well as 784 donors, for the 98+ guys...

I will be going to the JY this weekend. So maybe I can start a list of what I find
 
#261 ·
Add Me To The List - CONFIRMED

Yesterday I installed my "703" injectors on my 98 4.SLOW.

They hooked up w/o any problems. First start after priming them a couple of times car ran a little rough, but that was b/c yesterday I installed my injectors, a new header and a WJ intake..

My impressions.. Idle is sooooo much smoother, acceleration is great, but then again that might be bc of the header and intake I did at the same time..

All in all, worked PERFECTLY for me!!!
 
#265 ·
I don't know much about the WJ injectors. I'd imagine they have single hole pintles like the ZJ injectors. If that's the case, the main purpose to going to the 703s is for the 4 hole pintle design to allow for better atomization of the fuel.
 
#267 ·
Yes the WJ fuel injectors are just like the ZJ injectors; they both have the single hole for the spray.


You don't want that, the "703" injectors have the 4 holes for the spray
 
#268 ·
KyBoy1991 said:
Would it still be advisable to change to the 703 injectors in my 4.0 after changing to a new 2001 intake that came with fuel rail and injectors? Or, are the new injectors better to keep or will they even work?
IIRC don't wj injectors have the different connector anyways? I seem to remember looking at a wj in the jy and it had the different connectors
 
#269 ·
I honestly haven't looked at them close enough. I bought the thing for the intake...and it came with a power steering pump, bracket, fuel rail, injectors, throttle body....IMO it was a steal of a deal for $100 shipped.

So I just wanted to know if what I needed to still get or reuse before putting it on.
 
#270 ·
I pulled my injectors from a 97 neon. I cant seem to get the filters out on them.. Am I doing something wrong? Should I just not worry about the filters and replace the o-rings? Did I get the wrong injectors?
 
#273 ·
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