Robert88

Hi everyone, Long story short: I inherited a 1988 cherokee 4.0. Love it! Needed some work. Injectors were leaking, needed some sensors, plugs wires etc.. I went crazy with the volt meter. Replaced injectors with injectors that were made for a mustang with the 4 ports. Started running very rich and just blasting the cylinders with fuel.. So, I replaced the fuel regulator. It's a lot better now, I was only getting like 9 MPG now it's normal.. like 16 or 17MPG.. This was about a month ago and now it's starting to misbehave again. Floods at start up and idle, and I spend about 10 minutes blowing the fuel out of the cylinders until it clears.. Should I find some stock injectors and just put them back in? Oh yea, the IAC, TPS, CPS, CTS, MAP are all new so, my thought is that it has to be the injectors that is causing this. I also tested the ICM and coil. I really would appreciate some feedback from jeep guys, that's why I joined this thread. Thanks!

Radi

I'd put stock injectors back. Did you use the orange 19# 5.0 injectors? Looks like the earlier XJ's (like yours) were 18.6#

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

DFlintstone

X2^ I just noticed....the 19 lb > (Part no. FMS-M9593-C302)> might be fine, (for the 18.6 lb Renix), but the 24lb and higher..no no. My 21?-22 lb...are OK warm, running with the 02 sensor operating (I THINK), but before that running in "default" it might be pretty rich, slowing warmup.

I'm curious, I suppose that number is right on the injector. (or one of the other two Ford numbers in the link)

Robert88

I did put the number 19 Mustang injectors in. do you have any idea where i could get the stock injectors? i don't know if this will make i difference but mine is a Laredo. Thank you for your input.

DFlintstone

I started searching, than realized no-one in there right mind would install stock injectors. They just have one hole, like a squirt gun! The 4 hole available now is a big improvement. I'm quite sure functioning 19 Lb injectors will be fine. If the tube from the inside of the tb to the map up there on the firewall isn't perfect, (no cracks, not plugged it will run pig rich) Did you double check that? You should be able to pull it off the MAP and feel good vacuum with your finger. Also a faulty IAT (incoming air temp, on the manifold), or CTS, coolant temp, down on the block, could make it rich.

I see the sensors are new, still...that map tube comes up ALLOT. Also another member had a booger of a time with his coolant temp sensor.

You might double check fuel pressure, and be sure the regulator is getting good manifold vacuum.

AND if you insist, and the #'s match, PM ME. I might buy those FMS-M9593-C302! (also I have 703's, that allot of guys use)

Robert88

WOW! Thank you for the info..When I changed out the MAP I did a visual of the little hose that runs to the TB but did not check for suction so, I'll do that first. I never did test the IAT so I can do that. The CTS is new but you never know, I can test that again if I can get up in there, I had a difficult time replacing that without a lift and it's pretty tight. I'll definitely let you know if I go back to stock as a last resort!

Robert88

Update: I pulled off the tube that runs from the MAP to the tb and it shut down immediately, so I couldnt check the suction. Also, I just checked the part # on the injectors it is: Bosch 280 155 710 which is supposed to be comparable to the stock injectors in terms of Lb's per hour (19). I just have feeling it's not the right injectors, what are your thoughts on that?

DFlintstone

Just got back from a town trip...I'm here (with celery potato's and Nice $7/lb shrimp!. (on the floor) I'd like to know the # on those yellow fords...the difference between 18.6 and 19 won't matter.

Yea, I found the CTS a hassel > CPT! that waz the guy...had to run with his CTS unplugged till he found.....something.

I just wouldn't blame 19 as opposed to 18.6....something else is up.

An "open" on the temp sensors, will tell the ECU you are in Fargo! It "connects" to lower resistance 200 ohms? (CTS) and higher for the IAT. .....Idk if the impedance of cheap meters is a factor there or not...(my CTS neatly cycles with the T-stat, bottoming at #'~ 100 ohms over spec)

Gad, that's not easy to understand. If the resistance doesn't drop, it will think it's cold and make it rich. Meaning a broken, or discinnected wire, might, (or might not ) do that. (make it rich). CPT! where are you!!!

Robert88

Got it ( I think) LOL! I have a date with a volt meter tomorrow. Runs great on the highway when it's using up the fuel it's dumping. Maybe it thinks it's cold, logical. I'll give it a shot and let you know. Much appreciated- enjoy the shrimp! CPT, thanks, wherever you are! HA!

DFlintstone

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

OK if you want to be sure, again here are the stats on the ford..

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)

I can't say for sure, but if in tiny, almost imposable to read #'s, on your injectors are FMS-M9593-C302, the injector is probably not your problem. If it is one of the other numbers, maybe that IS your problem. It's not rare that people, with good intentions, don't get that Renix IS different, more AMC, and not Chrysler.

Looking again, the only difference is the A, B. or C.

Maybe one of us should rattle Programbo, or notop for more info. anyway Absolutely verifying those numbers might be a big help.

And thanks, no, beans and tortillas tonight...some of the shrimp will be bait for Red Tail Perch, and some hopefully bait for something with better curves....

Robert88

AH.. Let me back up a little. Just to clarify: The injectors I installed are the Bosch
280 155 710. They are rated at 18.25 Lb's per/hr @ 43.5 PSI. Ebay said they were compatible but, they are also trying to sell their injectors.

DFlintstone

OK Rob. Lets back up a bit. I sort of jumped in and missed a few crucial basics. In the link in my signature has a number of writeups by Cruiser54. You might stop, regroup, and take a good look. Getting that C-101 connector dealt with might be something to just DO. There's the ground refresh and sensor ground test. Trying to diagnose a problem, without having things connected right might be just chasing your tail. For instance if the map isn't grounded right, BINGO, there is ONE of the possible explanations. All time well spent. Even it it turns out you have injectors flooding it, having this stuff done will be good preventative maintenance.

Robert88

Sorry about post#4. I remembered the injectors did come off a Mustang but I was able to get a visual on the part # yesterday. One of Programbo's write ups that you sent me states that a regulator upgrade is needed for these bosch injectors. (49PSI). I have a new regulator but it's stock. I think this might be the culprit, I'll have to research that a little more. Checking all the grounds is a great idea, I'm sure the injectors themselves are grounded as well. Thanks for taking the time and I'll keep you posted.

cruiser54

Do this before proceeding any further.

Cruiser’s Renix Sensor Ground Test
　
This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.
Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.
You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well.
Revised 06/12/2012

cruiser54

Since it's an 88, do this, too:

Renix Jeep C101 Connector Refreshing
　
The C101 connector on 1987 and 1988 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and increased resistance over a period of almost 25 years. The C101 connector needs to be cleaned at least once in the lifetime of your vehicle. Chances are it’s never been done before.

Almost every critical signal between the engine sensors, injectors, ECU, and some to the TCU, travel this path through the C101 connector.
The C101 connector is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time.
Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth.
If you have a small pick or dental tool, tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter before bolting both halves back together.
　
Revised 07-17-2012