Can any1 tell me what would be exceptable differences in ohms of resistance between fuel injectors?? I have 5 @ 14.3 and 1 @ 15.4.... I just want to know if this difference would be enough to warrant replacement.

 

Not to change the suibject but why is it when you ask a service tech. about checking them they just say they don't need it. The question is why after 70,000 on one truck and 160,000 on my car. Why not worrey about it.


Now go back and help the person that ask the 1st question. I am sure he would like to hear from you on this.

 

I did some checking and yes the difference in ohms on the #3 cyl means it is bad and stuck in the open position.

 

Where did you hear this?

Usually if the resistance b/t the injector terminals is between 13-16 ohms, then they test out OK.

Are you getting a misfire, or do you have another reason to think that the #3 cylinder is having trouble?

 

I replaced the injector that was at 15.4 and all is well. The engine miss is gone and it runs better and stronger than it has since I bought it.

 

How did you test them? I would like to just check mine out, how do you go about it?
If you listen to the exhaust, it has a couple of burps in it, and somtimes backfires.

 

Peter, get a 12v test lamp, pull the harness connector off each injector, stick each end of the test lamp into the two pins on the connectors, and crank the engine. The test lamp should blink clearly and regularly for each connector.

Then you want to measure the resitance between the two terminals on the inector itself. The resistance should be between 13-16 ohms; however, you really don't want more than a 10% difference among them, which is probably why Freddie's injector was causing problems, since the testing indicated that it was approaching that kind of descrepancy from the others.

 

i wonder if its possible to get at them without taking off the upper intake manifold. Sounds fairly simple. I just dont want to rip half the engine apart to test them. it would kinda be neat if this is why my gas mileage is only like 14.6 city and 18 highway, with all the mods i've done, it should be like 18 city and 22 highway. However, i did notice, after putting in the diablo chip, my town gas mileage is almost always 14.6xx no matter how hard i push it. and on a trip where the most i could get was 17.7, i got 18.59x with a 750 lb fourwheeler in the back. gotta love that chip, you could barley tell the fourwheeler was there.

 

I can tell you that on my '98 4.0L, there is no way I can check the injectors without pulling off the upper intake manifold assembly. Probably much the same thing on your '94.

 

Yeah, when i checked my FPR, i remember seeing them imbedded in there, i wonder if there is a wire that is haging out in the open i can check somewhere, like, from the injector on its way to the computer, i can just tap in, or somthing, but i suppose that would effect my resistance readings.

 

Checking the wire(s) like that would be the same thing as checking the circuit and the signal from the PCM to the injectors. That's what in fact makes the test lamp blink when plugged into the harness connectors. So if you could find those same wires somewhere else and tap into them, then you could still do the same test, since resistance in such case would be negligible since we are talking about 12 volts. Now in all honestly, I've never heard of it being done that way though before, and to me it sounds kind of complicated.

The resistance that you are testing for involves the fuel injector itself, so you probe between the injector terminals. This resistance test is independant of the circuit or signal from the PCM.

 

Since I recently had the opportunity to take a closer look at the fuel injectors on my own 4.0L, I figured I'd update this thread with a little more feedback.

Over the past month or so I was getting a stumbling at higher rpms that slowly got worse until the CEL finally came on. I pulled the codes and got a P0304 (misfire on cylinder # 4). Naturally, along with the ignition system, one of the things I focused on was the fuel delivery system. Fuel pressure checked out fine, the fuel filter is new, and so after doing a full compression test (wanted to make sure cylinder # 4 was OK), I swapped the fuel injectors around to see if the problem followed the suspect injector. What ended up happening is that the misfire did seem to follow the injector, but I also got an additional misfire from another cylinder. So I then decided to pull all the injectors and have them professionally cleaned.

Well, it turns out my injectors (130k) were pretty darn dirty, and a professional cleaning of them was a very good call. Overall, it resulted in an average of over 12% increase in fuel flow rate. That’s quite an improvement if you think about it. Moreover, the spray pattern of the injectors is also much improved as a result of the process, resulting in better fuel atomization and therefore more complete combustion.

One of the injectors measured over 5% deviation in volume of fuel delivery from the others after being cleaned, so I had it replaced with a new one.

Click Here to View the Injector Test Results.

Long story short, I reinstalled the injectors, buttoned up the engine, and after clearing up a spark plug gap issue, I fired up my 4.0L and it started purring like a kitten. Problem has been solved! And to top it off, my 4.0L is running better than ever! I really can feel a difference in performance, especially when under load. It just seems like I don’t have to give it as much throttle to maintain speeds. Acceleration is as smooth as silk. I fully expect to be getting much better gas mileage, and I’ll be keeping an eye on that.

I’m very happy with my nice clean injectors.

P.S. For those of you who are wondering, I run a bottle of fuel inejctor cleaner through my fuel system about every oil change...

 

if you dont mind me asking, about how much did the tests run? like 100$ or less? My truck just seems to run worse and worse every day. At idle it burps and doesnt idle smoothly like it should. like its kinda running rich. No CEL or anything, but the last fill, it got about 13.6 in town, driving it nicely, with 3.27 gears. It should get better than that. Especially on HWY. last trip it maxed out at about 18.5. This was a 600 mile round trip, and i think the average was about 18.67 or somthing like that. With 3.27 gears, crusing at about 60 mph, it should at least be in the 20's.

 

$23.75 per injector, which includes cleaning, testing, and new O-rings.

http://www.injector.com/

Service and communication were excellent

BTW, the new injector only cost me $48 which is the best price I could find anywhere for my application.