When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
I should add, when it comes up on compression everything seems to be fine so I hadn't considered it. Just under cursory examination with VC off the valves shut when they should. It could be off but not by a ton IMO... i will definitely check it though.
I was more thinking along the lines of the ckp reading tdc 1 in the wrong place because of a faulty tone ring possibly
So I got a scope reading this afternoon on it. I'm pretty nonplussed right now... instead of three groups of four inside and three groups of four outside the cam window, I have three groups of 20 each... so that's a crank sensor malfunction right?
yeah crazy weird. But there's the big window at the end of each go round so I can pretty well confirm its reading 20 per cylinder... I'll toss a couple other crank sensors in to check I suppose and go from there.
Just got back in from testing one of the JY crank sensors and it does the same thing... You might be onto something though. I'll take a look at how the transmission is bolted up since I hadn't checked any of that yet.
Looking at everything today, and pulling out/reinstalling the ckp yet again, I'd say the flex plate seems to be where it should be. The ckp goes behind the ring gear and is snugly placed in the plastic ckp sensor surround in the bell housing.
How about a bad ground? That could make the sensor go haywire right? I'm pretty lost.
I would expose both ground and power all the way back to their respective sources. There's a lot of heat down there so perhaps there's a near-short. After that I'd put in 2 new wires from CKS to fresh ground and ECU. Bypass the connector too.
If that don't help seems to me there'd be only one thing left.
I did a little thinking this morning and I think I'm on to something here.
First, why the engine seems flooded and is smoking when it does run - injectors are firing 5x too often. Same reason for p0340 code, it thinks cam sensor is only working every 5 rpm. In fact, cam sensor signal is good.
So now to the real problem and possible solution. In my mind it's unlikely either the ground or 5v reference is bad because they're all directly connected on ckp and cmp and the cmp signal is good. And it can't be reading flexplate because it has a clear window between cylinders and is lined up good to the cmp window. But the ckp to ecu signal wire is reading too many pulses.
This pretty much has to mean that there's a near-short in that wire alone that shorts under load, or somehow there's a short in the ecu causing it to feed back into the ckp wire. Unlikely but possible if I eliminate the wire to the pcm.
so tonight after work I will de-pin that wire and run the exact same scope test to see if that changes the signal. If it does change the signal I can plug that wire back in and de-pin it at the ecu connector and run again to isolate the problem.
Ok so I just unplugged the signal wire from the ckp and the wire by itself coming from the ecu disconnected from the sensor has 5v while cranking. That's wrong, isn't it? Shouldn't it read nothing without input from the ckp?
That could be normal if the ECU might has a pull-up resistor on it. It's at zero volts with the CPS plugged in though, right?
Good point, I guess I don't know what the 5v reference signal the cam and crank sensor share is for in that case. So maybe the ecu gives a 5v signal and the ckp just pulls it down? So then what in the world could cause it to make 20 pulses per cylinder? I'm pretty stumped
04-08-2022, 10:55 AM
