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-   -   94 YJ 4.0 electrical problems (https://www.wranglerforum.com/f218/94-yj-4-0-electrical-problems-2380739.html)

Kim57 10-27-2019 01:17 PM

94 YJ 4.0 electrical problems
 
Hi Guys
Helping a neighbor work on his Jeep and have run into a problem.
Going from a 93 2.5 to a 94 4.0.
Have the swap all installed. Used a donor vehicle so we got the harness and computer along with trans and transfer case.
Engine cranks fine but no spark. Throws an engine code of 54 which is "no cam position sensor signal".
We have changed the crank position sensor along with the ignition coil and the distributor off of his 2.5 which was running when we pulled it out with no luck.
Have cleared the code each time and it always comes back the same.
Have not traced all the wires but the harness looks to be in good shape.
Is their something simple we are missing?
Thanks for any help you guys can give.
Kim

Got it at last 10-27-2019 02:47 PM

At the bottom of my signature below there is a dropbox link with most of the FSM's of the various YJ years, look in the one that most appropriately fits the donor and scroll through the troubleshooting section for no spark diagnosis. I have no computers so an of little help other than offering up a few resource manuals. Good Luck.

sequel 10-27-2019 03:00 PM

Are you using the 4.0 distributor? And the sync (cam) sensor from the 4.0? Also are you using the any bit of the 2.5l harness?

Luckymac 10-27-2019 04:03 PM

Quote:

Originally Posted by Kim57 (Post 34562511)
Hi Guys
We have changed the crank position sensor along with the ignition coil and the distributor off of his 2.5 which was running when we pulled it out with no luck.
Thanks for any help you guys can give.
Kim

If I read this correctly, you're using the CPS, the coil and the 2.5 distributor.
Is that right?

Good Luck, L.M.

Kim57 10-27-2019 04:38 PM

Quote:

Originally Posted by sequel (Post 34562557)
Are you using the 4.0 distributor? And the sync (cam) sensor from the 4.0? Also are you using the any bit of the 2.5l harness?

Started with the 4.0 Distributor until the diagnostic code. Got a new dis from AutoZone and had same problem. Was told AutoZone Dis was probably junk so got a reman from NAPA that had the same part number as the 2.5 so decided to use that one as that engine ran fine. Used a new cap and rotor in it.
No part of the 2.5 harness was used. Unplugged everything and left the harness intact on each engine as we pulled them.
All connections were made on the install of the 4.0.

Quote:

Originally Posted by Luckymac (Post 34562651)
If I read this correctly, you're using the CPS, the coil and the 2.5 distributor.
Is that right?

Good Luck, L.M.

CPS and 2.5 distributor.
Plugged the 2.5 coil in to see if that would eliminate the problem but it didn't so we are still using the 4.0 coil.
2.5 and 4.0 distributor have the same part number at NAPA.
Seems the only difference is the cap.
Rotor is also the same.

Kind of leaning toward a bad ECU but as this is the first time doing this maybe we missed something simple. Unfortunately he didn't hear the 4.0 run before he bought the donor vehicle.

Thanks for the help.
Kim

Kim57 10-27-2019 04:59 PM

Also have checked all fuses and relays in engine compartment.
Is there a fuse anywhere else that could be the problem?
Kim

sequel 10-27-2019 05:32 PM

Just looked it up on rock auto and the cam sensor is the same for 4.0 and 2.5. So I guess you are good. I’d trace the wire. Unplug the cam sensor and pcm. Check continuity to make sure the cam sensors wires to the correct pins on the pcm.

Kim57 10-27-2019 06:29 PM

Quote:

Originally Posted by sequel (Post 34562735)
Just looked it up on rock auto and the cam sensor is the same for 4.0 and 2.5. So I guess you are good. Iíd trace the wire. Unplug the cam sensor and pcm. Check continuity to make sure the cam sensors wires to the correct pins on the pcm.

I'm going to assume it does as we got the computer from the donor vehicle along with the harness.
Thanks again.
Kim

sequel 10-27-2019 07:09 PM

Quote:

Originally Posted by Kim57 (Post 34562785)
I'm going to assume it does as we got the computer from the donor vehicle along with the harness.
Thanks again.
Kim

I think that is a bad assumption to make, especially when your next step is replacing the pcm. The engine and wiring harness is a donor so you donít know the full story. The wiring harness is 25 years old. It has been moved more in the last month than the previous 24 years. Also the pcm recognizes that something is wrong with the cam sensor. A small break in a wire will cause your code.

Kim57 10-27-2019 11:34 PM

Quote:

Originally Posted by sequel (Post 34562831)
I think that is a bad assumption to make, especially when your next step is replacing the pcm. The engine and wiring harness is a donor so you donít know the full story. The wiring harness is 25 years old. It has been moved more in the last month than the previous 24 years. Also the pcm recognizes that something is wrong with the cam sensor. A small break in a wire will cause your code.

Very good point.
Will trace the wires just to be sure.
Kim

Luckymac 10-28-2019 12:44 AM

Is a 4 cyl distributor actually supposed to work in a 6 cyl engine?

Good Luck, L.M.

Kim57 10-28-2019 09:00 AM

Quote:

Originally Posted by Luckymac (Post 34563177)
Is a 4 cyl distributor actually supposed to work in a 6 cyl engine?

Good Luck, L.M.

They have the same part number when you go to replace them.
Only difference is the cap.
Kim

sequel 10-28-2019 10:10 AM

One thing that would also be worth checking is the 8v power feed coming to the Cam sensor. When you unplug the cam sensor and check on the harness side connector. There should be an orange wire coming in. Check for 8V on that pin. You can even check for 8v by putting read lead on that orange wire pin and black lead on wire that is black/light blue stripe. Key needs to be on.

Luckymac 10-28-2019 12:21 PM

Quote:

Originally Posted by Kim57 (Post 34563311)
They have the same part number when you go to replace them.
Only difference is the cap.
Kim

When I first started working on cars in 1960, all gasoline powered cars had points & condensers in the distributor. A 4 cyl distributor shaft would have a 4 lobe cam to open and close the points. A 6 cyl distributor shaft would have a 6 lobe cam to open and close the points.

With that in mind, I would have never considered attempting using a 4 cyl distributor in place of a 6 cyl distributor.
I looked on the NAPA and Rock Auto sites and indeed, the re-man distributors have the same part number. When you scroll down the NAPA page with the re-man 4 cyl distributor it states it's for a 6 cyl.
Both NAPA and Rock Auto have new OE distributors and they have different part numbers.

I don't dispute that a 4 cyl and a 6 cyl distributor can be interchanged because I just don't know enough about the innards of electronic distributors.
For peace of mind, I'd examine the area on each distributor shaft that activates the sensor. If they're the same, well, carry on. If they're different, be sure to reinstall the 6 cyl distributor.

In any case, I would carefully determine the compression stroke of #1 cylinder. Some home mechanics put a piece of tissue paper in #1 spark plug hole and crank the engine over. As the tissue paper blows out, that should be #1 compression stroke. I prefer to remove the valve cover and watch for #1 cylinder intake valve to actuate as I crank the engine over by hand. Only then would I look for #1 cylinder TDC on the crankshaft pulley and install whichever distributor that would work best. Bear in mind that the rotor points in a different location after installing the distributor than it points to just before you drop it into place because of the angle of gear at the bottom of the distributor shaft.
Once the distributor is in place, make sure that the rotor points to #1 spark plug wire. Your service manual will have a picture of what it's supposed to look like with the distributor properly installed.

Did you actually hear the 6 cyl engine run when it was in the donor vehicle?
If so, did it run well?

Keep us posted, I think you're close to getting this thing running. I'll bet it's something that'll be an easy fix once it's discovered.

Good Luck, L.M.

Kim57 10-29-2019 10:23 AM

Quote:

Originally Posted by Luckymac (Post 34563563)
When I first started working on cars in 1960, all gasoline powered cars had points & condensers in the distributor. A 4 cyl distributor shaft would have a 4 lobe cam to open and close the points. A 6 cyl distributor shaft would have a 6 lobe cam to open and close the points.

With that in mind, I would have never considered attempting using a 4 cyl distributor in place of a 6 cyl distributor.
I looked on the NAPA and Rock Auto sites and indeed, the re-man distributors have the same part number. When you scroll down the NAPA page with the re-man 4 cyl distributor it states it's for a 6 cyl.
Both NAPA and Rock Auto have new OE distributors and they have different part numbers.

I don't dispute that a 4 cyl and a 6 cyl distributor can be interchanged because I just don't know enough about the innards of electronic distributors.
For peace of mind, I'd examine the area on each distributor shaft that activates the sensor. If they're the same, well, carry on. If they're different, be sure to reinstall the 6 cyl distributor.

In any case, I would carefully determine the compression stroke of #1 cylinder. Some home mechanics put a piece of tissue paper in #1 spark plug hole and crank the engine over. As the tissue paper blows out, that should be #1 compression stroke. I prefer to remove the valve cover and watch for #1 cylinder intake valve to actuate as I crank the engine over by hand. Only then would I look for #1 cylinder TDC on the crankshaft pulley and install whichever distributor that would work best. Bear in mind that the rotor points in a different location after installing the distributor than it points to just before you drop it into place because of the angle of gear at the bottom of the distributor shaft.
Once the distributor is in place, make sure that the rotor points to #1 spark plug wire. Your service manual will have a picture of what it's supposed to look like with the distributor properly installed.

Did you actually hear the 6 cyl engine run when it was in the donor vehicle?
If so, did it run well?

Keep us posted, I think you're close to getting this thing running. I'll bet it's something that'll be an easy fix once it's discovered.

Good Luck, L.M.

Thanks
Made sure each time I removed the dis it was at no. 1 cylinder.
Unfortunately he didn't hear engine run before he bought donor as there was no gas tank installed.
I have inspected the wires and can't find any breaks yet.
I'm leaning toward the ECU which he may have to change anyway as we're in Ca. and from the number on the ECU it may not be Ca. compliant for smog.
Thanks again.
Kim

MILOJ 10-29-2019 07:52 PM

Quote:

Originally Posted by Kim57 (Post 34562511)
Hi Guys
Helping a neighbor work on his Jeep and have run into a problem.
Going from a 93 2.5 to a 94 4.0.
Have the swap all installed. Used a donor vehicle so we got the harness and computer along with trans and transfer case.
Engine cranks fine but no spark. Throws an engine code of 54 which is "no cam position sensor signal".
We have changed the crank position sensor along with the ignition coil and the distributor off of his 2.5 which was running when we pulled it out with no luck.
Have cleared the code each time and it always comes back the same.
Have not traced all the wires but the harness looks to be in good shape.
Is their something simple we are missing?
Thanks for any help you guys can give.
Kim


You had a code for a cam sensor and replaced the crank sensor? How about replacing the cam sensor that has show a code

Kim57 10-30-2019 01:05 PM

Quote:

Originally Posted by MILOJ (Post 34565663)
You had a code for a cam sensor and replaced the crank sensor? How about replacing the cam sensor that has show a code

Replaced the distributor with one we know works.
Cam sensor as far as I understand is in it. If not I couldn't find where else one is.
Kim

Kim57 10-30-2019 01:21 PM

Quote:

Originally Posted by sequel (Post 34563403)
One thing that would also be worth checking is the 8v power feed coming to the Cam sensor. When you unplug the cam sensor and check on the harness side connector. There should be an orange wire coming in. Check for 8V on that pin. You can even check for 8v by putting read lead on that orange wire pin and black lead on wire that is black/light blue stripe. Key needs to be on.

Did this and not getting 8v as far as I can tell.
Didn't crank engine but looks to be a problem with the electrical supply.
Kim

MannyN 10-30-2019 01:32 PM

Quote:

Originally Posted by Kim57 (Post 34566593)
Did this and not getting 8v as far as I can tell.
Didn't crank engine but looks to be a problem with the electrical supply.
Kim

Camshaft position sensor determines which cylinder is firing. Then it uses that information to sync the injectors with the ignition. The CPS is one of two sensors that if they fail, your Jeep will not fire the spark plugs or cycle the fuel injectors. Pretty much leaving your Jeep Wrangler sitting dead.

Where is the CPS Sensor located?

In the Jeep Wrangler YJ & Cherokee XJ, it is located inside the distributor on both the 2.5L & 4.0L.

Kim57 10-30-2019 01:52 PM

Quote:

Originally Posted by MannyN (Post 34566609)
Camshaft position sensor determines which cylinder is firing. Then it uses that information to sync the injectors with the ignition. The CPS is one of two sensors that if they fail, your Jeep will not fire the spark plugs or cycle the fuel injectors. Pretty much leaving your Jeep Wrangler sitting dead.

Where is the CPS Sensor located?

In the Jeep Wrangler YJ & Cherokee XJ, it is located inside the distributor on both the 2.5L & 4.0L.

Used 3 different distributors and have the same problem.
Last one is out of the 2.5 which was running so pretty sure it's not that.
Kim

sequel 10-30-2019 02:08 PM

Quote:

Originally Posted by Kim57 (Post 34566593)
Did this and not getting 8v as far as I can tell.
Didn't crank engine but looks to be a problem with the electrical supply.
Kim

This is a good bit of info. Now find the pin out of the the PCM connector. Locate that 8v supply and see if the PCM is actually producing the 8v. You can check preferably by back probing the connector or by if you have to use a wire piercing probe.

Note that if you don't get 8v it could be a PCM issue but in your case you need to ensure you have the pin out diagram of the year PCM you have. Then also ensure that the wires are correctly putting it at the right pin of the cam sensor. Because they are donor engines and wiring harness, a little bit of skepticism that the years they gave you match what they told you they gave you.

Kim57 10-30-2019 02:26 PM

Quote:

Originally Posted by sequel (Post 34566643)
This is a good bit of info. Now find the pin out of the the PCM connector. Locate that 8v supply and see if the PCM is actually producing the 8v. You can check preferably by back probing the connector or by if you have to use a wire piercing probe.

Note that if you don't get 8v it could be a PCM issue but in your case you need to ensure you have the pin out diagram of the year PCM you have. Then also ensure that the wires are correctly putting it at the right pin of the cam sensor. Because they are donor engines and wiring harness, a little bit of skepticism that the years they gave you match what they told you they gave you.

Only thing I'm not sure of is the PCM.
Everything came out of the same donor vehicle together as we pulled it.
P.O. could have changed the PCM without letting my friend know.
He said the engine ran but without hearing it buyer beware.
Are the pin out diagrams on the net?
Thanks for your help.
Kim

Kim57 10-30-2019 03:05 PM

Found this diagram.
https://troubleshootmyvehicle.com/je...L/pcm-pin-outs
Only problem is the wire colors on mine are different colors than what he has listed, specifically #7 which is the 8v sensor wire. .
Going to check them anyways when I get a chance.
Kim

sequel 10-30-2019 03:35 PM

I have a '94 service manual on my home PC. I can send you or post the graphic later this evening.

This is the challenge. Always important to have accurate wiring diagrams. Details become big difference.

Kim57 10-30-2019 04:33 PM

Quote:

Originally Posted by sequel (Post 34566765)
I have a '94 service manual on my home PC. I can send you or post the graphic later this evening.

This is the challenge. Always important to have accurate wiring diagrams. Details become big difference.

That would be great.
Thanks
Kim

sequel 10-30-2019 09:16 PM

As promised:
https://uploads.tapatalk-cdn.com/201...8bfa4d4884.png

sequel 10-30-2019 09:22 PM

Here is the wiring diagram at the cam sensor. I would validate that you are seeing same wire colors and pins on both pcm and cam sensor connectors. If not you have something else at play.

https://uploads.tapatalk-cdn.com/201...8ae920f987.png

Kim57 10-31-2019 09:31 AM

Quote:

Originally Posted by sequel (Post 34567143)
Here is the wiring diagram at the cam sensor. I would validate that you are seeing same wire colors and pins on both pcm and cam sensor connectors. If not you have something else at play.

https://uploads.tapatalk-cdn.com/201...8ae920f987.png

Thanks for these.
Should be a big help.
Kim

Kim57 11-01-2019 07:26 PM

Probed the wire at the ECU and get 6.6 volts.
Probe the wire at the connection to the distributor and get nothing.
Thinking wire is broken somewhere unless it passes through another relay.
Can we just splice in a new wire between ECU and distributor or do we need to be looking for a new harness?
Thanks for any help.
Kim

Luckymac 11-01-2019 10:26 PM

Which wire did you probe, the tan/yellow or the orange one (looking at the schematic that Kim57 gave you)?

Good Luck, L.M.


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