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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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#38 ·
I fitted mine yesterday and they seem to work nicely apart from the fact that instead of starting instantly (as the old ones did), the engine turns on the starter for an extra 1-2 seconds before catching. Anyone have any ideas?
 
#43 ·
Can I suggest an addition to the how-to? Before you start the engine after doing the swap, turn the key to Run, leave it for a few seconds, then off, then repeat a few times. This will allow the pump to build up fuel pressure in the rail. Then go out and check the fuel rail area for leaks. If all is good, start the engine.
 
#44 ·
I have just recently swapped the 703 injectors into my 5.9l in my 96 ram (rebuild ones) and its smoking and running very rich after resetting the pcm? my long term fuel trim is now at -33.6 as well as my short term fuel trim once it reaches temp and goes to closed loop operation?.(according to the torque app monitoring everythingin real time )... and the engine is smoking from all the fuel.
I dont see anyone mentioning the fact that the 5.2 and 5.9 was designed so the stock injector actually sprayed fuel onto the back of the closed hot valve to cause the fuel to vaporize and then enter the combustion chamber.... so ideally the feul timing has to be retarded about 4 degrees to work properly and take advantage of the wider spray pattern and atomized fuel?

On a side note I miss my cj7 and my wrangler...they were so much more reliable than my dodge till they rotted to pieces :( !.... I am looking for a TJ for the girlfriend now...
 
#45 ·
running rich and smoking

This may or may not apply to your situation - but i had a set of 703's that I installed before I tested them thoroughly. When I started the truck, I had black smoke and it was idling on 5-6 cylinders. It would smooth out some if I rev'd the motor, but it was not right. So I pulled them; and when I got around to testing them, I found 3 that were leaking under pressure. So I assume the smoke and miss fire at idle was from the bad injectors dumping fuel into the cylinder(s).

I just got a complete set installed last Thursday. The truck fired right up, a little rough on idle at first, but after 200 miles, it is running smooth. I have the Mopar Performance Intake (from Kolak), and these injectors seem to be working very well with it. MPG is up, and the truck pulls harder in the mid and upper range now according to the butt-dyno.

I have just recently swapped the 703 injectors into my 5.9l in my 96 ram (rebuild ones) and its smoking and running very rich after resetting the pcm? my long term fuel trim is now at -33.6 as well as my short term fuel trim once it reaches temp and goes to closed loop operation?.(according to the torque app monitoring everythingin real time )... and the engine is smoking from all the fuel.
I dont see anyone mentioning the fact that the 5.2 and 5.9 was designed so the stock injector actually sprayed fuel onto the back of the closed hot valve to cause the fuel to vaporize and then enter the combustion chamber.... so ideally the feul timing has to be retarded about 4 degrees to work properly and take advantage of the wider spray pattern and atomized fuel?
 
#47 ·
the ohms load could effect how the computer control's the duty cycle (the timing and duration of fuel pulses) that being said there's a lot of people like Five-o selling injectors with completely wrong specs posted on there site and they seem to work...(the red ones he offered for 5.2 and 5.9 "upgrade actually tested over 16ohms with a meter) and the feul flow is much higher at the 49psi that the 5.2 and 5.9 use between 96 and 01...this causes most engines to run very rich with those injectors... in 94-95 they only used 39psi.. and different injectors.
I'm not sure what the fuel pressure is in the different jeeps but that matters a lot in fuel flow.. and the fuel sync should be readjusted to really take advantage of the gen 3 design... the guys I spoke to who did it said it made a huge difference... also the aluminum on the inside of the kegger of the magnum engines around the injector hole should in some cases be trimmed for the wider spray pattern of these 703 injectors...
 
#48 ·
I modded my kegger by cleaning up and smoothing out the runners and injector bosses.

I with that info of possibly too high of a fuel rate running the 715s, I think I will just stick with the Chrysler 703s. With the extra holes and slightly higher flow rates will work just fine for my mildly modded 5.2.
I need some mpgs (14 right now mix hwy/city) with this being a trail rig/family camping rig. Jumping the fuel rate up that much with the 715s would most likely drop my mpg numbers.
 
#49 ·
I just tried the 703 injector swap in my 95 V8. All I got for my efforts was a massive cloud of white smoke. :(

I am guessing that I got a leaky injector or two, and they just dumped fuel into the combustion chamber. No external leaks or anything, and I did ohm them out prior to installing them. All were just a hair over 12 ohm. Put the old injectors back in, and within about 10 minutes the Jeep cleared back up.
 
#54 ·
sebian said:
I just tried the 703 injector swap in my 95 V8. All I got for my efforts was a massive cloud of white smoke. :(

I am guessing that I got a leaky injector or two, and they just dumped fuel into the combustion chamber. No external leaks or anything, and I did ohm them out prior to installing them. All were just a hair over 12 ohm. Put the old injectors back in, and within about 10 minutes the Jeep cleared back up.
I don't know for sure about the magnums in Jeeps but I do know the 5.2 and 5.9 liters in the 94-95 dodges used different injectors and less (39 vs49psi) fuel pressure which effects flow.
 
#56 ·
That was my other thought to, that the flow rate might be too high, and my PCM was not able to compensate for the higher flow, resulting in an extremely rich running condition.
 
#55 ·
Clean for normal parts is not clean for a micro small orifice part like injectors must be inside. I have my 703's to clean still and parts kit on the way. I plan to clean the outside gunk off first using rubber gloves to cover both ends. This will get the outsides clean and then all cleaning fluid from then on will be new and I will think super clean like a wafer fab clean room. I hope they work for me. Kinda a fun 100$ project. 7$ each x8 at JY and 15$ for the kit. I hear the 703 usually have a flow within 5% of each other and rarely are found to be bad.
 
#58 ·
I believe they will work for the 94 since the PSI is lower than a 96+ you should have a slightly lower rating with the 703's maybe 21.5?
 
#60 ·
It doesn't work this way... The injector on off times (=duty cycles) are varied by the electronics that use the Upstream and downstream O2 sensors as well as possibly various other data to run the correct fuel to air mixture.
I have my 703s to install once the kits comes in for my 93 5.2.
The main benefit is maybe better atomization and thus cleaner burning which might raise the mileage a tiny amount most likely not measurable.
Some claim to have better pep. I am doing it because I might have a leaky injector.
As far as 12 vs 14 ohm...check out ohms law... lower ohms means higher current for a certain voltage.
http://en.wikipedia.org/wiki/Ohm's_law
 
#61 ·
What does higher current mean for the system and how would that effect the computer?
I'm only asking, no need to try and talk down to others.

If the injector flows 22lbs/hr @ 39psi and if swapped with different ones that flow 22.5lbs/hr @ 42psi. At the stock 39psi wouldn't the new injector flow less then stated? I wanna learn, show me how to correctly understand this...
 
#62 ·
Don't worry about the impedance too much. Just know that anything 12 and up is what you want. For the people the bought 703's from me, I tried to match everyone up in terms of impedance
 
#64 ·
I didn't mean to talk down to you.. and let it be know I just have been on this site reading voraciously for 2 weeks. I do have a good understanding of this sort of stuff. Pressures, flows, currents, control circuits. A 14 ohm compared to a 12 ohm just means what 15% more or less current.. THer is probably only very small power required to open an injector so I gather this difference is not a problem for the wiring or control circuit. Using the 703's sounds like it is so close to the factory flow rate in the 93-95 to original that the circuitry and control loopcan handle them. Just imagine a super clogged air filter runs ok and how much more gas is needed at sea level compared to 14k in Colorado. when 18,ooo ft altitude has half the O2 as sea level and these things can run tells you something.

impedance is just= 1/R think of it in terms of what size hose the current can flow through . larger ohms and smaller flow of electrons.at a given voltage.. voltage is like the pressure in a air line... higher means more flow. current is how much flow..

I really dont thnk the gas milage is going to be a big thing??? I hope It is .. my 93 5.2 jeep has been pretty much a 16 mpg for its whole life of mixed driving..
 
#68 ·
That is simplistic genius! Great idea, I will have to rig up a simlar device and test the ones that I have. Maybe of the 10 I have, I can salvage 8 of them to reinstall in my Jeep.
 
#70 ·
Yes there are injector deals all over the net... I found one person who will sell you 8 ohmed and cleaned and tested for matching flow rates within 5% for 120$ OF course this was after I paid 20$ for my kit and 8 x 6=60$ at the JY for mine.
I think some of these guys got them for free at junkyards and have built up a testing rig where they can actually make sure the flowrates are matching within 5%. Some guys have ultrasonic tanks.. These parts have a very small orifice so you need to be real careful what gets under the screen.
 
#71 ·
I have ford 24s I get 13 mpg city and that's with a blown plenum gasket

Besides that I can defineitly say i see way better idle and throttle response but I also I've mods that all go to gether
 
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