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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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#2 ·
Great technical work! I recommend this for sticky. I dont want to come off as a critic, but the only thing I see that is missing is to disconnect the battery and use compressed air to clean around the injectors prior to removal. The battery disconnect is not only for safety, but to also learn the new injector pulsing.
 
#4 ·
Very nice job! Well thought out with good pics.

As a side note: When I did mine I didn't pull the fuel line off, just moved the rail out of the way. Had to pull each injector one at a time. Didn't pull the trans/throttle cables, just unbolted the bracket to have some more room. As I pulled each injector I had my shop vac running and kept it on the injector to suck the crud. Also when cleaning before installing the new ones had the vac running to keep it clean.

2X on lubing the O-rings, I tore one doing it dry and had to hit NAPA for new ones. I used white lithium spray grease on my finger then applied to the O-rings.

Used a rubber mallet (lightly on the rail!) to firmly seat the new injectors, I was surprised how loose they were even with the rail bolted up.

The only really noticeable change for me was how much more responsive it was under light throttle.

Watch the clips on the rail/injectors! My Jeep was hungry and ate the one from #6. Had to run to pick a part for replacements!

'96 GC 4.0
 
#8 ·
Disconnecting the battery isn't going to make the computer "learn" the new injectors, fuel injection doesn't work like that.

The PCM has static values calibrated into it called injector data. This houses data regarding the injector size, pulse widths, minimum pulse width, and flow values based on voltage and vacuum change.
 
#9 ·
The FSM doesn't support what you are saying. This fuel injection does work like that. It adjusts the pulse width based on O2 sensor output to obtain 14.7 -1 air/fuel ratio. I really dont want to start an argument about it because the article is about changing the injectors, not how they work. The battery needs to be disconnected anyway.

Happy Ho Ho
 
#10 ·
Something I am curious about is the different resistances listed... 12 ohm and 14 ohm... Wouldn't it be prudent to use injectors that match the factory resistance?

(could be impedance as well, but not sure.)
 
#11 ·
+1 for sticky. Thanks Zander for making this how to, I've been wanting to swap the injectors for a while, but haven't seen a decent write up on it til now.

Stealing your idea with painting the fuel rail, just btw.

One last thing, where'd you get the k&n filter for your valve cover?
 
#13 ·
+1 for sticky. Thanks Zander for making this how to, I've been wanting to swap the injectors for a while, but haven't seen a decent write up on it til now.

Stealing your idea with painting the fuel rail, just btw.

One last thing, where'd you get the k&n filter for your valve cover?
Well you will have to ask and thank melk, its his engine bay :D he took good pictures and didn't take pictures when I did it lol.
 
#17 ·
No worries, I updated the wording to be accurate. That is what I wanted it to be, accurate lol. So people can not only do the swap, but understand why it is a benefit and why they are doing what they are doing.
 
#19 ·
The 703s were a piece of cake, 2 bolts off the chrysler cars and they're out. IIRC I read that some of the ford engines are in such a way where its a real PITA to get to them. But I didn't really look at ford injectors. I would say whatever you can find first lol. As long as they are all of the same type!
 
#25 ·
Stratus / Breeze / Cirrus

I pulled 12 injectors today at a local pick'n'pull yard. The Dodge Stratus / Plymouth Breeze / Chrysler Cirrus with the 2.4L were definitely the easiest to pull - as stated - 2 bolts, pry the fuel rail out, unplug the harness and twist them out of the fuel rail. By the third car, it took less than 4-5 mins.

Thanks for putting the time and effort into a detailed write up on this.
 
#21 ·
Here are the procedures for the injector swap on a 5.2/5.9 courtesy of 1SASjeepster:

The job will take about two hours. You will smell like gasoline when you are finished, so keep that in mind with clothes and safety glasses. Also ONLY DO THIS UPGRADE WITH A COLD ENGINE!
REPLACING THE FUEL INJECTORS

FIRST, disconnect the negative battery cable and tuck it down on the side of the battery with a rag keeping it there. This job will have gasoline fumes throughout the engine compartment. You must make sure that the battery cable cannot touch the negative post whatsoever. Remember sparks ignite gasoline fumes easily.

SECOND, remove the air cleaner assembly. Since I don't have a stock one, you have to do this on your own.

THIRD, remove the "A" bracket at the rear of the air compressor. All you have to do is loosen it so that it can pivot out of the way. Remove the top "A" bolt and the lower right corner "A" bolt... from the perspective of looking directly at it with your knees leaning on the front bumper. Loosen the lower left corner. Now pivot the bracket towards the passenger side as far as it will go. That's it. It prevents you from getting full access to the driver's side fuel rail.

FOURTH, unplug the three sensor plugs on the throttle body. There is one in front, one on the driver's side and one at the rear. All three plugs are removed by gently pressing down the tabs while pulling. These plugs get very brittle. BE GENTLE. You do not want to damage them.

FIFTH, unbolt the throttle body. Do not remove or disconnect any of the throttle cables are linkages. It is not necessary. All that has to be done is that the throttle body needs to swing out of the way of each fuel fuel rail as you are lifting it. There are four bolts on top of the throttle body that hold it to the intake manifold. Remove these bolts and be careful lifting up the throttle body because you don't want to damage the thin gasket underneath it.

SIXTH, release the fuel line pressure at the driver's side fuel rail. The fuel line pressure port is at the midpoint of the rail, next to the throttle body. It has a cap on it. (If your vehicle does not have this "pressure port" you need to find out how to relieve the pressure before you do anything.) I just used a small baby food jar and put it under the port. With my safety glasses on and my baseball hat, I used a large Phillips screwdriver and pressed down on the nipple. The gas flowed out of the nipple into the jar. When it stops flowing, you're done, but remember there is more fuel in the line, just not under pressure. (Whenever I suspect gasoline might "shoot out" I wear safety glasses and a baseball hat. I have had gas in my eyes before. It isn't pleasant.)

SEVENTH, now remove the driver's side fuel rail, BUT BEFORE YOU DO... you need to realize a few things. (1) There is a vinyl/ plastic tube connecting both fuel rails which runs around the rear of the throttle body. DO NOT KINK THIS LINE, DO NOT DAMAGE THIS LINE. DO NOT PUT HOSE CLAMPS ON THIS LINE. This is considered a "non serviceable" item. If you damage it, it has to be replaced in its entirety. It is OK because you have just enough clearance to get the injectors out. Just be careful. (2) There is a fuel line connecting to the driver's side fuel rail. (This is the "feed line" coming from the gas tank.) You do not have to remove this. Just be careful when you start handling the fuel rail. (3) Remaining gasoline will run out of the rail every time you pull out an injector. Have rags ready to wipe this up.
The fuel rails are held onto the intake manifold by two bolts. Remove the two bolts on the driver's side fuel rail. Now grab the fuel rail and gently move the rail left and right, and to and fro. The idea is to do this gently. Once loose, pull the rail straight up. The injectors are vertical. Pull straight up. (Now, the rear of the fuel rails will not pull far up because of the vinyl fuel line connecting both rails. That is OK. You will have more than enough clearance. If you can't pull them straight up, use a large, flat bladed screwdriver and pry up. Be careful what you rest the screwdriver on before you pry. You can break things like this, so be careful and think it through.
Once the fuel rail is up, you have four injectors connected to the fuel rail by thin sheet metal clips. Use a flat bladed screwdriver to remove the clip. The clip is shaped like a "square U" so work it off and then the injector pulls out. Notice how the clips come out because that is how you need to put them back during installation. The fuel injector holes in the intake manifold are tapered and mine were very clean.

EIGHTH, Remove all of the injectors from the driver's side rail. Put them aside and get four of the replacement injectors. Use some oil to lubricate both "O" rings on the injector. This makes is a lot easier to get the injectors back in.

NINTH, Now the fun part... the only problem I had with this swap was getting the new injectors into the fuel rail. They were a PITA... but doable with patience. I found out that once you press the injector in a certain amount, that it just snaps in... but getting to that point is something else. I tried twisting them, pushing while twisting, etc., etc. If you find a great technique, LET ME KNOW!! Anyway, you will do better starting at the rear of the fuel rail. Once the injector is in, put the clip on. The clip fits in a thin groove cut into the injector body. It just presses on with finger pressure. Once you finish putting in the four injectors with their clips, start pushing down the fuel rail so the injectors go back into the holes in the intake manifold. You need to gently manipulate the injectors so each line up perfectly in the holes. You do not want to tear the "O" rings on the bottom. Once you have them in the holes, push the fuel rail down and they should center on their own. Now install the two bolts that hold the fuel rail to the intake manifold. You are now finished with one side. Go to the passenger's side and repeat.

TENTH, Once this is all done, hook up the "A" bracket to the air compressor again. Install the throttle body, install the plugs for the three throttle body sensors, put on the air cleaner assembly and make sure there are no puddles of gasoline on your engine, intake manifold, exhaust manifold, etc., etc., Reconnect the negative cable to your battery. Now turn the key "on" but don't start your engine yet. This will get the fuel pump to pressurize the fuel rails. (I gave it five seconds.) Now start the motor. My motor was idling rough at first, due to the fuel that was dumped into the holes in the intake manifold when I pulled the injectors. However, once the engine settled down, IT WAS GREAT!!! The computer had to "learn" again, so I took it for short run (20 minutes). There were no more sluggish response and the engine was running great. I was at 70 mph and punched it. Usually there is a sluggish response. Now it pulled unbelievably. I took my foot off the pedal at 90 mph, but I had plenty more to go. (Oh. please note... NOBODY WAS ON THE ROAD WITH ME ON THIS STRETCH OF HIGHWAY.) I drove it around some more on errands, and my starting problem was gone. It idles more smoother and the engine's response is so much better. My fuel consumption was 15 mpg. Now it is 21 mpg. This swap worked for me.
 
#22 ·
Question - I have 8 of the 703 injectors.. 0280155703... Some of them don't have the little caps from the tip. I was going to order the injector rebuild kit for the injectors, which have the o-rings and everything. Question is... is this the right kit? According to the bosch part # above, this is a EV6 type injector, but that kit is for a EV3 injector.
 
#23 ·
Zander,

Fantastic write up! Truly you have organized all of the data in one great thread. If anyone can't do it after your thread, they need to pay a mechanic!! Great job! I am sure it will help many jeepers.

Take care and have a safe New Years.
 
#24 ·
Yup I need to find me some "703" injectors and swap them in
 
#26 ·
I did this swap and it seemed to do wonders for my V8. I took the injectors out of a Crown vic i believe it was a 1995 I was just looking for the right connector type. I couldn't find any with the 703's or 715's but I believe this is due to elevation. I put in some yellow Injectors in place of the POS ones that were there. I have been enjoying my idle and more power ever since.
 
#27 ·
If anyone needs neon injectors for their Jeeps PM me, I raided all the yards around my house and have enough for at least 4 V8 vehicles I believe. I already OHMed them all out too and matched them impedance wise for consistency. Not trying to make a killing on these I just want to help Jeepers who are having a hard time finding these and don't want to spend a millions dollars online.
 
#29 ·
neonhomer said:
Question - I have 8 of the 703 injectors.. 0280155703... Some of them don't have the little caps from the tip. I was going to order the injector rebuild kit for the injectors, which have the o-rings and everything. Question is... is this the right kit? According to the bosch part # above, this is a EV6 type injector, but that kit is for a EV3 injector.
that is the correct kit, they fit on both.
 
#33 ·
How much for the injectors. Send me a PM please so we don't violate the board rules
 
#34 ·
when i did my 703 swap i already had one or 2 original injectors that were bad and just leaking in cylinder not spraying so my difference was huge. Mine starts like a normal jeep now not turn over for almost 8 secs before it catches and it idles a lot better and some of it smelling like unburnt gas out the tail pipe was gone
 
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