Howler_GT

Time to replace injectors in my 94 Sport (4.0L HO)
#1 and #4 have recently got some leaks...not bad but will only get worse.

I have read on the net about using the #9 Mustang 5.0L injector (?)

Anyone ever tried this upgrade?

pros? cons?

MPG /
HP /



-OR-
Is it even worth the trouble?

Specific part numbers or engine/year search criteria?

Any input would be greatly appreciated

Howler_GT

BlueXJ

I used a set from a mid 90s 5.0L mustang. Bought them through Summit and have bought a set through eBay and they looked the same. I installed the eBay ones in my daughters Jeep. Thats all I remember except they were 19 pounds.

biztyke

i just did that this weekend to an 88, worked great. you can use any ford/bosch design 3 19lb injectors, you can get a set of 8 on ebay for $50. only thing to look out for is to make sure they have the right connectors. i got a set off a crown vic, but didnt realize how new it was. they had the EV6 connectors, where jeep(up to 98 or 99 i believe) used EV1 or EV3(not sure)......wasnt a big problem, just robbed 6 connectors at a j/y and swapped them out.

i dont think you will see any HP or MPG improvements, maybe minor ones. i did notice that it idles and runs a lot smoother.

it is definitely worth it if you need new injectors, as jeep oem replacements are quite a bit more expensive.

okcjeeper

RENIX jeeps use 19 pb 39 psi injectors...91-95 use 21 lb 39 psi injectors..So you can look for these ford motor sport part numbers.. FMS-M9593-A302 That's a 24lb 39 psi injector and it will work perfectly..Main think is 91-95 must be 39 psi injectors and 96+ are 49 psi..

Howler_GT

Everything I have read (from numerous sites) says to use the Ford Motorsport 19.0lb/hr @ 39psi (Part no. FMS-M9593-C302)

Now I am confused. I don't need to make ANOTHER costly mistake.
Guess its another day of research.

Howler_GT

Bouncy

Here are some facts without part numbers.

New injectors or even good used ones will work fine.
You could clean yours with some gumout cleaner and new seals.

The only difference between jeep injectors and mustang 19lbs injectors is the amount of holes that spray fuel. Jeep uses ONE hole and mustang's have FOUR holes usually.

Upgrading to 21 or even 24lbs injectors at 39PSI will use more fuel and worsen gas milage. It may improve performance very very little. Keep in mind, your sensors and computer will back off the amount of fuel being sprayed to compensate for your new bigger injectors (back to square one basically).

Next thing not to confuse. 39psi and 49psi. Make sure you have the proper injector for the job. If your system is 39psi, don't put a 49psi injector in the system.

A 49psi injector NEEDS the 49psi to pop and spray properly. If you put a 49psi injector in a 39psi system, the pressure will not open the injector properly and it will dribble past the injector. Reverse is true as well. A 39psi injector in a 49psi system will keep the injector OPEN leaking fuel since the injector can't close completely due to the pressure.

High impedance and Low impedance injectors. I believe ALL jeep injectors are low impedance. Using an ohm meter, check the resistance across the pins of your current injectors. I believe its in the 6-8 ohm range (but can't remember). I believe high impedance injectors are in the 75 ohm range.

Last but not least is the connector. I believe as mentioned there are a few different types of connectors. As I call them (Injectors) you have the short fat looking injector and the tall skinny ones. These come in all of the above mentioned variations. pressure, impedance, etc. The tall skinny injectors use the newer style connector, and the short fat ones use the older connector. I believe in 1999 they switched from short fat to tall skinny. (Verify all this info in this section. As I can't remember and am to lazy this morning to look it up.)

BlueXJ

Research can save you lots of money and except for your time it is free.

okcjeeper

I will tell you this much my 1991 uses these injectors from the factory....
91-93........33007127, ...Brown, .......39psi, .................21.0lb/hr

That's straight from the factor parts manual... On the renix parts manual I have they use 19 lb/hr injectors.. 94-95 should be 21 lb i39 psi njectors just a slightly different part number...In 96 they switched to the 49 psi injectors. If ya it cleared up go by your local jeep dealer have em look it up on their computer and they will tell you the stock factory specs...You don't want to goto a 24 lb injector is yours came with a 21lb injector but the gain in going to an identicle lb/hr and psi ford injector is going from a single spray hole to a 4 spray hole setup..The advantage is better atomization of fuel. Is it worth it I don't know haven't tried it but have read many things about it..

Bouncy

I don't know how accurate this info is but its close.

http://www.jeep4.0performance.4mg.com/tech_specs.html

Copied from link above.

Some of those specs that are hard to find in any workshop manual.

The following is a list of the injectors used on the 4.0L since 1987 along with their rated static flow:

Model Year, ...Part #, ......Colour, .....Fuel Pressure, ...Static Flow,
'87-'90, ........53003956, ...Black, ........39psi, .................18.6lb/hr
'91-'93, ........33007127, ...Brown, .......39psi, .................21.0lb/hr
'94-'95, ........53030343, ...Tan, ...........39psi, .................21.0lb/hr
'96-'99, ........53030778, ...Grey, .........49psi, .................23.2lb/hr
'00-'01, ........04854181, ...Blue tip, .....49psi, .................22.5lb/hr

The injector flow rate varies as the square root of the pressure drop across the injector. The stock '91-'95 4.0 injectors are rated at 22lb/hr @ 43psi fuel pressure, so at 39psi they flow ( sq. rt.(39/43) x 22.0 = 21.0 ).
For stock/modified 4.0 engines or stroker build-ups the following injectors can be installed. The flow rates are:

Ford Motorsport 19.0lb/hr @ 39psi (Part no. FMS-M9593-C302)
Ford Motorsport 24.0lb/hr @ 39psi (Part no. FMS-M9593-A302)
Ford Motorsport 30.0lb/hr @ 39psi (Part no. FMS-M9593-B302)
Chevy LT1 24.0lb/hr @ 43.5psi (Part no. 17124248)
Chevy LT4 28.0lb/hr @ 43.5psi (Part no. 17124251)
'98 Chevy LS1 25.2lb/hr @ 58.0psi (Part no. 12533952)
'99-'00 Chevy LS1 26.2lb/hr @ 58.0psi (Part no. 12456154)
'01-'02 Chevy LS1/LS6 28.6lb/hr @ 58.0psi (Part no. 12482704)
Accel 19.2lb/hr @ 44.1psi (ACC-150119)
Accel 21.1lb/hr @ 44.1psi (ACC-150121)
Accel 24.4lb/hr @ 44.1psi (ACC-150124)
Accel 25.6lb/hr @ 44.1psi (ACC-150126)
Accel 29.4lb/hr @ 44.1psi (ACC-150130)

The '95 Jeep 5.2 ZJ/Dodge 5.9 injectors (Part no. 53030262) are rated to flow 24.6lb/hr at 39psi.

The selection of injector size will depend on the estimated horsepower output, brake specific fuel consumption BSFC (assume 0.5), no. of cylinders, and the injector duty cycle (assume 80% or 0.8). The formula is:

Injector size (lb/hr) = (horsepower x 0.5)/(no.of cylinders x 0.8)

okcjeeper

The 91-93 matches what my factory parts manual states...

BlueXJ

Formula at the bottom is quite helpful.

COSXJFAN

I plan on doing this upgrade on my Waggy this winter!! Thanks for all the info!!