Fuel injector harness question

[mobiusinfinitus]

Are the wiring harnesses between a '94Q and a '97Q interchangeable or am I just wishful thinking. I need a harness to troubleshoot an open on injector 5 which I can't ohm w/o removing the plenum, but can obtain a 97 harness. Will this work? Dennis

[elwesso]

Why would getting a 97 harness work? You can OHM it on the harness side, iwthout removing the plenum. SOMEONE hasnt been reading on Q45.org!!

http://www.q45.org/ohminjectors.html

[mobiusinfinitus]

I have ohmed it from the harness side and it shows an open. I am trying to isolate whether it is a wiring or an injector issue. Thanks for the response, but I'll probably be looking at a partial plenum removal anyway. Just don't want to invest in a new injector and still have the same problem!

Dennis

[elwesso]

Ahh ok.. I understand now..... Sorry

The last time i looked the harnesses were fairly cheap... Less than $50 from Joe if memory serves...... However if the harness is bad, it should throw a code.. I havent heard too many harness failures but i wouldnt rule it out.

You could probably unbolt the plenum and move it around to verify the integrity of the harness...

[mobiusinfinitus]

No apology necessary! I had no idea the harness would be so cheap, but have always been a little leary of troubleshooting with my checkbook when I can avoid it. It's a daily driver (so far) so may have to wait till week-end to do anything further. I am curious. Does the computer sense a faulty injector and stop feeding it raw gas, or am I accumulating gas in my crankcase past the rings if the cylinder isn't firing. Thanks

Dennis

[elwesso]

Its hard to say..... Generally, when the injector is open, its not stuck OPEN all the way, as you would easily hydrolock it.. I understand about checkbook troublehsooting, but if you do indeed go under the plenum to do the injector, if your iffy, id replace the harness.....

The ECU does not detect a faulty injector and stop feeding it fuel. There would be no way for an injector to stop pumping gas if indeed it is "stuck"

Generally though, the ECU can detect if the harness is bad by a short circuit or something...

[mobiusinfinitus]

Thanks again, elwesso. No reply necessary. Need some sleep so I can go in and work the 9 p.m. to 5:30 a.m. 'vampire shift'. Just hope I'm driving and not walking!

Dennis

[DAEDALUS]

The CEL will be flagged by an "abnormal" resistance in the injector. What is abnormal to the ECU, I don't know, but I have measured over 200 ohms across the harness contacts once, and the CEL was not lit. Not sure how the harness could be anything but open or closed. Reported it, but didn't have the time to pull the plenum.

[mobiusinfinitus]

Many thanks,Daedalus. I've read several of your posts and replies, and have the utmost respect for your mechanical acumen. Maybe I should rig up a stethoscope to #5 and see if I hear any sounds of activity? Most injectors are in spec except for 5 and 6, the most inaccesible ones, of course. A '94 is primitive in its diagnostic codes at best, but I'm getting a 34,51. Knock sensors and inspect fuel injection. I still don't understand how the harness could have continuity and show open, but I'm not well-versed in such things. Car ran great for 2 months, and then cel reared its ugly head. Some vibration when under load, and poor economy and performance, but guess I'll live with it till I get it figured out. You guys have been great, and someday I hope to be able to give some constructive input to those in need. Again, thanks!

Dennis

[DAEDALUS]

I still don't understand how the harness could have continuity and show open

Both 5 and 6 read open? You should have more than a slight stumble on acceleration. Reminiscent of a 66 big block with hipo cams if that were the case, aside from the noise.

Reading through the harness tells you the health of the entire circuit, not just the harness, so it could be either at fault...or neither if the harness were disconnected for whatever reason.

Auto stethocopes are cheap but effective. They have a long probe for reaching into deep tight quarters. Still, the values and the symptoms don't seem to jive.

[mobiusinfinitus]

I guess I didn't do a very good job of explaining. #5 is reading open, #6 is reading 184, and the rest are within specs. I still have a sneaky feeling it might be a continuity problem within the harness. Seems mighty strange that the vehicle could make such a rapid downturn in performance and economy! 165k on motor; doesn't burn oil, but maybe it's time to do some maintenance and further investigation. Not too excited about diving into that motor(used to twin sidedraught Webers in a Lancia Montecarlo) I shouldn't be intimidated by it all, but the motor seems pretty complex. Anyhow, thanks again and I'll keep posting when I come up with some solution.

Dennis