67 GMC

OK-Well, I don't have the Volvo injectors yet and mine were leaking so bad I thought I was going to have a fireball so I changed 4 of the 6 out to JY injectors (they're orange coloured bodies-stock were metal and black). When I had the rail off, I also took the throttle body off and cleaned it and the IAC with TB cleaner and replaced the gasket. Put it all back together, recalibrated TPS and voila, started up and ran fine. Idle screw has not been tampered with-still has aluminum cap on it.


That was 1 week ago. I wish this was the end of the post.


Intermittent long cranking but will start. Today, I cranked and cranked and after maybe 5 minutes or off and on ignition switch, it finally started up.

I think the idle is rougher than before but strangely enough, the Jeep has more power when you hit the pedal. Anyway, I bought an old MT2500 a year ago and it is showing a lot of data that I don't understand.


Looks like it's going out of closed loop and back into open loop while idling. In OPEN:
RPM=910, O2Volts=2.42, STFuel Trim=128, LTfuelTrim=103, Map Sen=1.5V, MAP=39kPa, Man Vac=63, exhaust=Lean


In CLOSED:
RPM=600-800-900, O2Volts=3.4, STFuel Trim=64 (erratic), LTfuelTrim=103, Map Sen=2.5V, MAP=50kPa, Man Vac=63, exhaust=rich


Could this be a bad EGR or O2 sens? I haven't done that yet. TPS is maybe 2 years old as is CPS. Fuel pump around that time too. Fuel Press is 39.


Thanks in advance. Wife needs this for work so just worried about the weird cranks but won't run.

DFlintstone

When my 02 sensor was stone dead, (not grounding the feed at all), my idle would fluctuate about every 20 secs. Fine for a bit, slow, nearly die, rev slightly, repeat. Wonder if that Snap-On has a deal to watch the voltage (5v feed) from the ECU to the 02. My dead one stayed right on 5 when it should have been fluctuating, around 2.5 IIRC.

Anyway, I wonder if those JY injectors could be flooding it.

Edit. Excuse me, I see now you posted 02 volts. (3.4). See what others have to say.... see here> http://www.naxja.org/forum/showthrea...ht=sensor+test

67 GMC

When my 02 sensor was stone dead, (not grounding the feed at all), my idle would fluctuate about every 20 secs. Fine for a bit, slow, nearly die, rev slightly, repeat. Wonder if that Snap-On has a deal to watch the voltage (5v feed) from the ECU to the 02. My dead one stayed right on 5 when it should have been fluctuating, around 2.5 IIRC.


Yes-Mine is doing that fluctuation. Sounds like it's going to die at idle but does recover by going into OPEN loop. The O2 voltage is displayed by the MT2500 and it's less than 5 volts so it looks like it's working. I checked the AC voltage on the CPS as well and it was putting out 0.27 Volts which I think is ok.


That link to the NAXJA forum was information too-Thanks for that.

DFlintstone

That just might be backwards! I'm quite sure .35 AC volts from the unplugged CPS, cranking, is bare minim. Below that will likely cause problems. Up near .5 and above is more like it. See Cruisers tips...you might just move your CPS closer to the torque plate and save some $.

I guess I'd see if the 02 sensor voltage oscillates around 2.5, warmed up running at about 2000 RPM. 3.4 might be a little high...but that was idleing...Idk.

My idle smoothed out after I changed my 02 sensor Btw. (I didn't expect that) Seems I stumbled on to something!

67 GMC

Now I'm thinking CPS. Cruiser's tips say 0.5 V AC at least. Mine never got that high. I have a new STANDARD PC87 I can put in. $28 from Rock Auto. I'm going to do that and see what voltage it puts out (once the rain tapers off a little).


Thank you.

cruiser54

O2 sensor needs to fluctuate from 1 to 5 volts RAPIDLY.

DFlintstone

I've "borrowed" another IR temp gun to add a second reference to your 208* figure so I could second you on the FSM being incorrect. A little brandy and a randy girl made me loose, actually the IR gun.

So the DRB displays 1 to 5 ? Or not? My cheap, (high impedance) analogue bobs around closer to 2.5....One to five seems a little meaningless,.....Of course it's between grounded and not. I'm wondering ,from what you said , if the DRB-II has a sample rate that works well there? Learning partly from Pete...1 to 5 is not a "reading"(here). Or is it?

67 GMC

I'll have to re-scan to see how the values were changing. Do you mean it should be jumping around showing largely different values every second or couple of seconds? I don't think it was doing that-I think it was like 2.34, 2.4, 1.95 etc but not 2.3, 4.6, 1.9 etc.

cruiser54

It should be going from 1 to 5 rather quickly.

67 GMC

Do you think the 0.27VAC on the CPS is too low? I'm having some intermittent no-starts when the Jeep is warm but it starts fine first thing when cold. I have another CPS to put in so I think I'll do that before I look at the O2 Sensor. Those O2 sensors are kind of expensive.

DFlintstone

I do. After Cruiser turned me on to that test a few years ago, I started watching mine. Around the time my cheap-o-meter started flashing .2 something, instead of .3 something my crank time was too long. (even for a Renix, that needs more then a full rev, and 300 cranking RPM)(to start spark and injector pulse)..

The Echlyn CSS980 from Napa brought it up to .4 something and all's good, mostly. One hot no-start, (this July), .....it started after un/re-pluging the CPS. The Standard brand PC307 I gather is the high altitude, (advanced) CPS, that Cruiser mentioned, and I bought...28$? to carry as a spare.

More PC307 guinea-pigs are welcome! In a Renix with a functioning knock sensor, my only concern is I don't know exactly what the ECU does with the timing when it scenes a knock. In a "perfect world", it would just adjust the timing right. In the "real world" it might default to a retarded timing then work back forward at some rate. If it does that supper fast all is well, if it needs to seek and cycle....I just don't for sure know.

About every time I did a tuneup on a points engine, I'd road test/set the timing for a "ghost of a ping". Proper, advanced timing rocks! Every engine is different. The timing light is just a convenience for shop people. (and advance curves)

67 GMC

From the pictures on Rock Auto, the PC87 and the PC307 look identical except for the 307 being moved a little along the arc (which advances the timing). If it isn't any better, I guess I can always try the mod of moving the head along by force. I haven't done the distributor re-indexing yet (which is another way to advance the timing I suppose).


Just need the time to do it!

cruiser54

Get the 307 and do my drill mod.

67 GMC

With the new 746 injectors, the long cranking time is now shorter and it's more consistently starting. I changed the CPS (although still a Standard brand CPS). The voltage was only about 0.3VAC. The 20 second cycling is what's leading me to think O2 sensor or knock sensor. At any constant speed, it seems to stumble every 15-20 seconds. It feels like a change in timing as there is almost no noticeable change in RPM. It will last for maybe 4 seconds, then it's back to normal for about 20 seconds. It is going from OPEN to CLOSED loop and back to OPEN while driving. So, on the highway at 50 MPH, constant throttle, this is happening so it's not a transmission issue.

I don't mind buying an O2 Sensor but from my scan tool, it looks like this one is working. They are over $100 up here but I can get one at Rock Auto for around $60.
Let me know what you think it might be or what to test. Any chance I have a bad ECU?

cruiser54

What's the 20 second cycling?

That O2 should be going Rich-Lean so fast you can't hardly read it.