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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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#77 ·
Ok so my injectors of the 5.8 is the wrong numbers...its of a 95 anyways. However I have injectors off a 97 5.4 ad the only numbers are. Fote-d5a Which according to google are 028 -015-0943...so I can't use these either right? Cause mine need to be replaced and id rather use what I have you know. I'm sorry fo the questions. I'm a painter not a mechanic, trying to learn.
 
#78 · (Edited)
96 up flows at 49psi pressure (15% more fuel flow than 39psi)
I find it interesting that the jeep used the same 778 injectors that doge used when they switched to 49psi fuel pumps only jeep uses them with a 39psi pump so they push less fuel...and doge used a smaller injector with the 39psi pump on the 94-95 rams... Maybe I have been misinformed?
 
#83 ·
I'm on my phone so I can't see signatures, but it seems like a lot of the people having issues appear to have dodge trucks... Is anyone having issues with their JEEP after having installed the 703s? Specifically the 5.9 JEEP motor? Also, what techniques have you all been using to clean the injectors?
 
#84 ·
Well the way I understand it the 5.9 is just a 5.2 with a bigger bore so it shouldn't be a big problem

Just wipe off the outside with a rag, make sure you get the kit in the OP and finally run a bottle of techron or seafoam in your gas tank
 
#87 ·
Normally bigger bore also means more gas flow but in this case they are close enough... The issue is everyone in this thread that is running 703's and a magnum engine also seems to be driving a 95 or old 5.2 liter with only 39psi fuel pressure...once you up that to 96 or newer fuel pump thats 49psi and 15% more flow your pushing through those injectors... It need to be determined for sure if jeep changed their fuel pumps to 49psi ones in 96 like dodge did... I if you look at the places that sell aftermarket or upgraded injectors for these engines you'll see they all offer different injectors for the 95 and old than they offer for the 96 up models... the pcm is setup with preprogrammed fuel tables the truck relys on for proper AF ratio until its gets warm enough to pay attention to the 02 sensor and make adjustments... so even if it does work of in WOT conditions it may run pig rich during warmup every time...
my fuel trim is at -33 when in open loop warming up and goes al the way to +30 when fully warmed up... talk about something being out of whack..
 
#85 ·
Sounds good, I have the kit from the OP. Any special tools required?
 
#86 ·
My 2 cents.
I decided to burn e85 in the V8. Good or bad idea, that is not the question here.
With origin injectors, it seemed to me that the engine was running poor when putting the right pedal down.
I've read somewhere that you need 30% e85 more than gaz for the same energy.

So I put 30% bigger injectors, Ford Racing red one.
Wow, then engine runs very fine at all speeds.
But, it was too rich when burning gaz.
One day, I found an inexpensive air intake. Magic ! the engine was not rich anymore.

The ZJ PCM is GREAT. It allows a lot of changes in the input chain. You can test new injectors with no fear: they will work !
(I am not mechanic, just a guy who tries, make mistakes and sometime is lucky !)
 
#93 ·
DO NOT RUN E85 ON VEHICLES ITS NOT MEANT FOR

The e85 will eat at all the o rings and seals it moves through. Not to mention the incorrect input at senors to the comp. It might run fine now, but not for long.
 
#88 ·
Just got back from the JY, dug around for a while, got some injectors out of a Tbird. Upon closer inspection they seem to be 700's. Can I use these? Connectors look the same, it was a 97 Tbird V8 I believe.
All the Crown Vics had the different style electrical connectors, no joy there.
Didn't see any of the correct numbers on the Chrysler/ Dodge side either.

Did find a new glove box light assembly.......
 
#91 ·
sammyb123 said:
If I wanted to get new injectors from let's say AutoZone what would I tell the guy at the counter I called them this afternoon and the guy on the phone was oblivious
Use the full model number found in the original post...just give him the number and don't confuse him by telling him it's for your jeep. If he asks just say you are sure its that model number
 
#92 ·
So can someone verify if this works for the 5.9 or not? And which injectors to use? I have mine out to change the intake and I'd rather swap the injectors now if it makes sense.
 
#94 · (Edited)
I can tell you they would not work in my 96 5.9l dodge ram...it ran way too rich and fouled out my plugs and 02 sensors...I have switched back to stock and everything is running great now.... No one here seems to know if the 96-99 jeeps use the same pcm program and 49psi fuel pump as the 96-99 dodges do...they say they work great for the 95 and older models but those used totally different obd1 computers and different fuel pressure... as far as the doges go all the 95 and older magnums used DIFFERENT injectors than the 96 up... the first page of this thread says that jeep was using the 778 injectors right from the start which has me totally confused ..especially since the fuel pressure changed in 96 and altered the flow 15%..
I may throw some of them in the 4.0 wrangler..
 
#95 ·
If someone can look at their post 96 v8 injectors I would like to correct my model numbers, I was under the Impression they all had the same injectors. Ill figure out the pressure ratings and such as compared to the 703's
 
#96 ·
I can varify that the 96-99 rams had the Siemens Deka "778" injectors with 49psi ... but the 94-95 rams did not they had different injectors and 39psi to go with them...thats what makes all this so confusing... I guess the 96-99 jeep could very well handle the injector flow differently than the dodges do?
as you can see here the flow changes quite a bit with different pressure...
http://www.csgnetwork.com/fiflowcalc.html
 
#99 ·
I found someone selling:

"6 Ford 24lbs hr fuel injectors. Blue tops as they are known"

thats what his add said anyways... Does anyone know what he is talking about and would thease be an upgrade for my I6?
 
#106 · (Edited)
It will run... will it run better or use less gas... NO just the opposite those 24lb injectors are way overkill for a 5.2 or a 5.9 without a cutom tune to trim back the fuel levels.
They will be dumping too much fuel until the truck goes closed loop and even then they will likely be spraying too much fuel...
You need to have your engine on a scanner or wideband meter while running these and you'll see exactly what I mean...
or run them and find out the hardway what kind of damage running rich can do... hell anyone whos running them now just pull your 02 sensor and look at it... I bet its sooty and black like the inside of your cat converter now vs tan in color...
EDIT I should clarify
If you are running the 24's in the older 5.9 jeeps with the 39psi they may be ok... the 93-95 dodge 5.9l used 24 lb injectors before they switched to 778 ones because of better flow at lower fuel pressures... however if you jeep had 778 injectors the pcm is likely setup for the 22lb injectors (flowing at 23.2lbs at 49psi)... the 93-95 5.2 l used smaller injectors and different leaner pcm tables... here is a flow chart..Jeep may have possibly changed this a bit I dont know.

Dodge Engine Years Flow rate in lb/hr
5.2 Magnum 92-95 18.2
5.2 Magnum 96-01 23.2
5.9 Magnum 93-95 24.5
5.9 Magnum 96-01 23.2
 
#108 ·
the yellow bosch generation 3 part # 0280155710 ones right? thats what I have here that the seller from ebay sent me to replace the 703's...I'm going to try them out as well... I believe they are found in mustangs.
the only downside I see to thse so far is there is no notches for clips to clip them to the fuel rail. Not that they dont work but you may want to double up the o rings using one in both lower positions so the injector can rest on the upper one to help hold it in position.
 
#109 ·
I think the ones I saw were 700's but yes, same idea...

Without the clip... will they go too far into the intake manifold bore? I dont know if there is a step there... that is the only direction they can go...
 
#110 ·
I think the ones I saw were 700's but yes, same idea...

Without the clip... will they go too far into the intake manifold bore? I dont know if there is a step there... that is the only direction they can go...
thats why I suggest the extra oring but the 700 injectors may have the notches for the clips... 710's would be better since they flow closer to stock but either should work I imagine... and Sean should have a good idea what works.
the 700,s are rated at 204cc at 43.5lbs pressure and stock is 234cc at 43.5... the 710's are rates at 210cc @ 43.5 and 221 at 49psi

702's have the notches and are right between the 700 and 710's as far as flow...
 
#111 ·
Actually - Sean believes the stock injectors are 19lbs... they just flow more a the higher pressures, that is why he recommends the 19lbs injectors.... its all so confusing.. :confused:
 
#112 ·
It's been awhile since I did the read, but I think catsplat had a major writeup on the 703s and the 96-98 4.0 at 49 psi. It was a long thread but they flowed at an acceptable rate if I am not imagining it. I think it was recommended to go with a adjustable regulator or something to that nature but I'm not sure.
 
#113 ·
So you are you guys saying now the original write up is inaccurate and the 703's/715's are not foot for the 4.0, 5.2, and 5.9's we have? Everyone who installed them seemed to be pleased with the direct results, and if fuel was running rich wouldn't it trip the cel? I was planning to get 703's with one of the next paychecks; I'm confused with the conflicting information... I have a '94 5.2
 
#114 ·
Dude... I am soooo confused too! My confusion has more to do with the 1998 5.9 and the 49 psi fuel pressure...

Based upon Auggiedogs experince, it doesnt sound like the 5.9 likes the 24lbs injectors... again, he has a dodge trucka dn a couple other guys have used them and seem to be ok... that is the confusing part..
 
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