4x4jeepmanthing

Hey all,

I was in the jeep idling for 20 minutes or so and then it died. I assume it's the crank sensor currently, its not the first one I have replaced. It still cranks very strong and I can smell fuel.

What I have tried:
.no melted wiring from visual inspection
.grounds are cleaned! and secure
.it cranks strong and I can hear the fuel pump prime from key on, I also tried jumping the fuel pump relay and still hear it running.
. i tested the ckp sensor for resistance and I am only getting an open loop. Based on this video:
,I'm thinking it's bad. Can someone please help me understand what he means when he suggests jumpering the 5v supply and signal wires, I have never heard of this in regards to crank position sensor testing? If I understand that correctly it would dump 5v feed into the signal, but the signal wire should recieve a pulse instead correct?
.I have tried looking for spark with a screw driver resting near the valve cover, I saw no spark with a couple attempts of positioning the screwdriver close enough I thought it should be visible.

I have not:
tested the cam sensor
Tested for actual fuel pressure
had the battery tested
ignition coil un tested



Am I missing anything that I have overlooked testing currently?

I'm currently checking all this solo in a parking lot so it's a little more difficult using the phone as my eyes while crank testing things. Thank you for any helpful direction you can give.

-1999 XJ Sport Auto 4.0, sorry I just realized none of this information was on my post.

4x4jeepmanthing

.49 psi confirmed at the rail
.cps ohm test terminal B and C is open loop
. with scanner and multimeter the cps is reading when manually turning crank.
. no cel
. 5v supply confirmed on both cam and crank sensor

does the ignition coil get a constant supply that I should be testing for?

Saudade

The primary side of the coil does get 12v through fuse 21 (20A) in the PDC on the DG/OR (dark green w/ orange tracer). It grounds at the PCM.

Do you have the FSM?

4x4jeepmanthing

I have sourced an online version for 1997s, most of the sections on the sensors say either refer to the powertrain diagnostic manual, or DRBIII scan tool.
There is a section on scanning the camshaft position sensor signal wire, which I have yet to do with my cheapo analog multimeter.

I have not tried swapping the ASD relay yet, would this relay allow the fuel pump to prime, but still not allow for spark? Ill try swapping that today if this is a reasonable thought?

4x4jeepmanthing

Well today I was able to tow the jeep home. I did try swapping the ASD with the fan relay before hand, no luck, the battery is getting a little weaker. Ill check the coil for power tomorrow, and the cam sensor. I saw another video of the cam sensor being tested, a fella tried continuity testing negative probe to terminal A, and then positive to B, then to C. If you did not get OL on both B and C, then he said the cam pickup sensor is bad. Can anyone confirm this? I have not seen any of the droves of threads talk about that manner of testing a cam sensor. If I have been read correctly, the PCM requires appropriate signals from both the Cam and Crank sensor, in order to send the ignition coil power. So while the crank sensor would communicate "where" in the engines rotation to send fuel and spark, the cam sensor would give the "when" for spark, and either could prevent the Ignition coil from firing. Does that sound accurate?

Once I check for a signal being sent to the ignition coil, if that is good, I'm a bit lost on where to go from there. Years ago I had a mess of a thread on here tracking a cam sensor issue, I had a cheapo scope for the lap top, Ill see if I still have that somewhere and if I can see what the crank and cam signal wires are putting out, it was with great effort from those on here that I was able to operate and attempt to test a signal, hopefully I can figure it out again if I still own this tool.

I would appreciate a little guidance on what else I should be checking, I'm happy to follow up with the findings once I know what else to look for. I am curious if the online manuals are the same as the Chrysler paper FSMs. I have never seen an online powertrain service manual posted anywhere. The digital FSM I have, quite frequently says to use this powertrain service manual, along with the DRB scan tool, I'm at odds there I suppose.

Thank you all,

4x4jeepmanthing

Today I had a minute to see that 10V is making it to the ignition coil. I did find my Hantek 6022BE oscilloscope and tried to take a sample the crank signal today. I need to learn how to choose a proper "sample rate, and voltage, and x1,x10,x100 option". I set the trigger to 0V and requested the program to track highest and lowest voltage. The signal did produce square wave at 4.8V. I attempted to crank with the cam signal back probed, but I didn't get it to a good visual with the "above specs". I took a still shot from a video, I don't recall how to keep what the scope was recording, so that I can go back and look at it. Yellow is crank, Green is the cam sensor. Ill try and see If I can get a better sample on the cam sensor tomorrow, when its warmer and the baby is sleeping. Feels likes there is never enough time in the day these days.

4x4jeepmanthing

Here is a crude photo of a signal, I need to figure out how to condense the waves In a smaller grouping. I appologize that the pictures aren't the greatest, I was struggling to get a picture from a video capture while our baby was sleeping.
I have checked all fuses and I am trying to find a diagram so that I can visually understand what I need to check for continuity from the Pcm and coil ground. I found pin A7 on the PCM side and the coil ground. Am I mistaken that I need to check this run of wire for continuity?

Dave51

Double check the test leads and circuit for the camshaft position sensor to insure you have a good signal, but IMO

Dave51

The 100ms is fine, you should have seen the CPS clearly (see my sample).

Dave51

FYI using push pins to insure you're getting a good signal:

Dave51

Because splicing together the 20ms waveforms reveals



and that's the signals you should be seeing.

Dave51

Also measure signals at the ECU. Maybe you have good signals that aren't getting to that.

If CPK/CPS is in fact OK then hook up the Hantek to each fuel injector, then each plug wire (use the attenuator switch on the probe for that cause that's a LOT of volts).

Yank plugs to see how they look (wet or dry). Might as well check compression while your in there.

Is the distributor where it should be? Nothing cracked or fried?

Reviewing old threads to look for clues:

https://www.cherokeeforum.com/f2/cam...254732/index4/

https://www.cherokeeforum.com/f2/99-...251947/index5/

Timing chain was a little sloppy. Maybe now it's a lot sloppy?

Moving the waveforms to confirm sync:

4x4jeepmanthing

Ok, I have acquired the push pins and I'll get ahold of a compression tester for good measure. Being that I can't Start the jeep to warm the engine, would it be wise to jump straight to adding a little oil into each cylinder?

For attenuating the scopes probes, there is a 1x or you can slide the switch to 10x. Which of these are appropriate for a plug wire? I am uncertain if my scope can measure this many Volts, if it can, I read that I can wrap some wire around the outside of the sparkplug wires and hook the probe up to that.

I'll dig for the PCM signal wires diagram and measure from these as suggested.

Dave51

Nah. If there's a problem it'll be massive. And whatever it is it's there now.

Looking that up now. Yours is

Mine is

and I use the HT-25 cable which has

I also have a 20:1 external attenuator. I don't think you have enough stuff to attenuate that down.
​​​​​​​

Dave51

HT-201 Hantek attenuator:

Oh well, can't worry about that now...