Rojo

I don't know if this topic has been posted before but here I go. New to the forum and need help. I have a fault code 27 on my 94 Cherokee. The code is that the injectors are not reaching peak voltage. I can't find anything on trouble shooting this problem. My thought is the ECM may need to be replaced.

My symptons are in 4th gear at ~ 1500 rpm the engine feels like it is being starved and shakes violently. I can drop it into 3rd gear, the rpms increase and "normal" engine operation. The jeep also has a rough idle. Plugs wire cap & rotor has ~60K miles on them. I don't think it is a tune up issue.

Any help greatly appreciated!

claygrassmann

hey man you could need new injectors as far as testing take a multi meter to the elec plugs on both the injector and harness for the injector use the ohm setting the resistance i believe should be zero and im not sure on the other end. but if you want new injectors and an upgrade on your injectors i got some for sale for 50 bucks

Rojo

I will check it out. But if the injectors are bad, wouldn't I have the problem all through the operating range and not when it hits OD in 4th at 1500 rpm?

alpine.adrenaline

If your injectors are getting clogged they'll throw that voltage discrepancy code, you might run some seafoam through there first.

claygrassmann

no not always due to the difference in fuel pulse thru out the entire timing curve

Rojo

are the injectors $50 a piece or for all 6

Rojo

Seafoam? Please elaborate.

claygrassmann

its 50 for all six and seafoam is a type of engine and injector cleaner, i put 1/3 of a can in the oil, 1/3 thru the vacuum tube that comes off the intake and to the brake booster, and 1/3 into the gas tank, i used it and it made a difference in power but later down the road i still had to replace the injectors

alpine.adrenaline

http://www.seafoamsales.com/ Amazing stuff, you can find it at most auto stores. You want that white can third from left.

ThatDude114

Did you ever figure out the problem? Im having a similar problem with my 91.

Gryphon439

My 91 won't start and it's throwing the 27 code which for our control module means "Logic module fuel circuit internal problem of TBI injector does not respond properly to control signal"

I'm unclear on what the "Logic module" is. It ran great last night and got parked overnight. Wouldn't start the next morning. I have verified that the connectors for each injector are clean and that there are no breaks in the wires specifically. I did find a light green wire chafed at the back of my fuel injector heat shield. Could this be my problem?

Gryphon439

I did a mod today with Plasti-dip to cover the bare wires, the worst one(green wire) was only worn through 1/4 of the way so there is plenty of conductivity there.

After putting plasti-dip on the wires and letting it dry, I wrapped it tight with gaffers tape and added a flexi-conduit for heat shielding.

Last, I trimmed back the fiber-plastic heat shield provided by Chrystler about 3" so it won't chafe the wires anymore.








I ended up finding out that the problem I was having was that my CPS(Crank Position Sensor) was faulty and telling my computer that there was no need to spark. Swapped out the CPS and she fired up slow and rough, but smoothed out after 15 seconds or so.

Gryphon439

Ok, now that we have been on a road trip, it's been 3 years, and 13k miles my Code 27 is back... This time I have a ton of unburned fuel coming from Cylinder 1. I know this because I see a little weep of fuel coming through the header gasket and a ton of it passing through the tail pipe. I also have pulled the injector wire for cylinder 1 and noticed no difference in the rough idle.

This time I did my research and decided to replace my CPS, TPS, and O2 sensors with the authentic Mopar parts along with a full tune-up (plugs, wires, cap, and rotor). None of these have made a difference with my symptoms.

4.0
260k miles
Ran great until she sat for 3 months

Anyone have any idea what my problem could be?

Cummins93

If you are passing raw fuel through the combustion chamber either the injector is stuck wide open or the plug isn't firing the charge. If you disconnect the suspected injector and the unburnt fuel stops being produced from the exhaust then you found your issue. If it keeps producing raw fuel then multiple injectors maybe the issue or your injectors are fine and something is telling the ECU to add fuel.

Gryphon439

Thank you. I will test my injectors.