Hey everyone, I just installed a new CPS after my last post. I'm seeing an Ohms reading of 210.7 at engine off but still 0.0v when cranking the engine. The old one had either sporadic or 0 ohms when reading. The engine does not start, it just cranks like the past few days so I'm feeling a little defeated. I rechecked for sparks again and I'm not seeing sparks. The battery has 12.26v at engine off. When I turn the key, all gauges move. Unfortunately I don't have a tachometer, I have that large fuel gauge. The temp goes all the way up for some reason. Then the car just cranks and cranks and cranks. Not sure where else to go. Any ideas?

 

Can you get a resistance reading between the "B" terminal of the TPS connector (vehicle side) and the negative terminal of the battery?

 

Are you thinking G101 ground? I unplugged everything here yesterday and cleaned it and put it back in. This was after finding out the cranking issue. I did clean all obvious grounds in or around the engine bay.

I can get a reading tomorrow and get back to you!

 

The sensor circuit gets its ground from the ECM, on the D3 pin. The ECM gets its ground from the dipstick, on the B11 and B12 pin. The sensor ground is just the farthest point from ground, so a good indication if there is a ground problem. With an '87 the C101 can be a concern but also splices in line.

 

I gotcha, so a good clean of C101 and then if it starts, then that's the issue...

I found this article: https://budgetgarage.net/2017/09/16/c101-delete/

 

Well, I'm actually thinking it could be something disturbed by the work on the oil filter, so not necessarily the C101. Since you can't "see" acceptable ground readings, an actual reading with a meter is the best place to start.

 

Thanks dmoe69, im a little intimidated by electrical work. So you're saying I connect to B pin on TPS, then negative on battery and show resistance. What should I be expecting?

I'm assuming if high resistance above 2 ohms would indicate a bad ground of the ecm?

 

Cruiser's tips say, "as close to 0 as possible". If I recall correctly, he wanted to see < .6 Ohms. While you are doing the resistance check agitate the wiring harness at the back of the engine where it tees into the bigger harness on the firewall. Also agitate the wiring harness up near the C101 connector. While you're wiggling the harnesses, watch the meter and see if there are any changes in resistance.

 

Thank you, I will give that a shot. The other only thing that I could have possibly agitated during the oil change is those large engine grounds. I verified this morning that the contact looks good but the wrapping of the cables is pretty frayed.

As a side note, I did find this yellow cable which is a ground that wraps around the engine bay and is screwed on the driver side of the radiator. The cable was torn below the coolant reservoir and I found a crimp of sorts that joined 2 yellow cables. I just popped that back in there but I don't know what that is. Any idea?

I'll report back with the resistance reading on the TPS and will wiggle those connectors and harnesses.

 

Just a side note when using any digital multimeter...they are Very Sensitive. They will find the inherent resistance in your test leads themselves. Directly connect red to black and see what that resistance is. My Fluke 115 reads anywhere from 0.2 to 0.6 ohm.....so if your looking for tiny numbers, the meter lead resistance is your relative ZERO.

 

Hey, just got around to doing this. Resistance is 1.4 when connecting to B on the flat wire connector of the TPS and the negative battery terminal. Given that the multimeter has a 0.4 resistance by default, this brings me within threshold of Cruisers tips so no adjustments needed to the TPS or it's grounds.

I've now gone through 2 different CPS that read correctly for resistance per Cruisers thresholds but they both show 0.0v AC when cranking the engine. Is it just not detecting the flywheel? Is the flywheel not spinning?

I'm at a loss right now as to how to proceed. The grounds look iffy and corroded but that doesn't seem to be an issue per the TPS test? I wiggled all harnesses and resistance did not change.

I may start a newer thread later today to bring it up to the top but I just don't know how to proceed from here.

 

Agreed, fairly decent resistance reading on the ground. Did this XJ ever run for you?

 

Yes prior to the oil filter change it was running fine. A little rough if I didn't let it warm up but upon flooring the gas it caught up fine.

I checked the ECU and that looks fine too, picture down below. I did see the ground cables to the engine block very frayed and corroded, picture also below.

I messed something up during the oil filter change and I have no clue what. Everything looks fine. There are no frayed cables around that area that I can see. I also went ahead and checked 2 fuses under the hood, those are fine (alternator and starter). I checked the fuses under the dash, they are all fine.

No idea what else to try. Maybe get a picoscope and see if I can detect the flywheel? I've never used one of those.

 

RENIX ECM needs to see about 300 RPM + during cranking. It would be a good idea to replace that battery ground. You might want to try another one of cruiser's tips at the bottom of Renix CPS Testing and Adjusting | cruiser54 he suggests drilling out the mounting hole on the CPS so that it can be positioned slightly closer to the flywheel/flex plate.

 

I'll try that later today or tomorrow. Thank you for sticking with me.
I just put a 5/16th drill bit into the holes of the old CPS and it exactly fits. I'll take out the new one and do the same.

I want to make my own cables I stead of buying those kits, they are a little above budget. Just some lugs, a crimp, heat shrink plastic wrap, and 2 awg cable is enough, correct? Should be easy enough to fashion a new one.