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Discussion Starter #1
Hey y'all,

I'm a 34 yr-old environmental engineer in Atlanta and this is my first Jeep! I'm no mechanic, but I work on older trucks, boats, and bikes on the side in addition to renovating old house.

I picked up this Commander two months ago and have loved it... when I haven't been working on it. This forum has been a big help so far with the issues I've had though!

The truck is in good shape and looks great. I bought it mainly to tow my boats around and it pulls nicely. It stops surprising well, which I learned when a car pulled out in front of my while I was pulling my boat - I was amazed it stopped as fast as it did because I was sure I was about to plow right into them with my new (to me) Jeep and new (to me) boat!

So far, I've replaced a leaking water pump (good think because it had the wrong coolant in it!), repaired a broken quick connect on the fuel line (after taping it together on the side of the road to get home), and now I'm working on a crank, no start issue that is caused by fuel pump not pumping. I've searched the threads thoroughly and they have helped me in troubleshooting and ruling out a number of things. I'll make a separate post about this issue in hopes y'all can help me.

Really apprecaite that y'all have such a nice and well-organized forum with helpful and nice folks!
Cheers,
Jake
 

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Discussion Starter #2
Well, I just went to start a new thread about my fuel pump problem, and I wasn't allowed to start a new thread! Did I miss something in the rules? This is what was indicated:

you do not have permission to access this page. This could be due to one of several reasons:

Your user account may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.
 

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Discussion Starter #3 (Edited)
I guess I'll just describe the problem here, and we can move it to a new thread when I'm able to create one. I just needed to get all of this out for my own sake...

Background:
A few days ago, I went to start my truck and it cranked and cranked, but wouldn't even try to run. Seemed like a "no fuel" problem to me. I checked the fuel pump fuse and relay. I disconnected by new quick connect in the fuel line and turned the key to "ON" to see if it would squirt some fuel out at me. Nope. So I rightfully concluded the fuel pump wasn't pumping. Got it towed to my house.

I left my code reader at a friend's house 100 miles away last week, so I learned and did the "key dance" (thanks for the stickies!) to read my codes on my dash:
P0627 - Fuel Pump A Control Circuit /Open
P0522 - Engine Oil Pressure Sensor/Switch Low Voltage

Ok. I had read on this forum that the Oil Sensor switch is a common problem. It's $15 a the parts store, so I just replaced it. Still no start.

So, I wanted to just see if the fuel pump was getting power. Dropped the tank, voltage to fuel pump is 0.5v lower than battery. That's right at the threshold of a problem, from what I've read, but it is still over 12V with a fully charged battery.

Ran a jumper from the hot side of the fuel pump relay to the fuel pump, used on of the grounds from the fuel pump harness that plugs into the fuel pump. I opened the fuel qucik connect again and watched the gas dump out of it when I connected the jumper. So the fuel pump works. I reconnected my fuel line and connected the jumper again for a few seconds, to see if it would pressurize my fuel system enough to start. Then I plugged the harness back into the fuel pump and tried to crank it - and it started! Idled down. Ran and sounded completely normal for about 45 seconds, then promptly ran out of gas. So, the fuel pump works. (Which I knew was likely anyway...)

Now I figured I really need to look hard into the 7000 page service manual PDF I have. I searched P0627 and got a troubleshoot process for it. Step 1-3 were fine. Step 4 and I've already got an issue:

I plugged a 12v test light into the indicated (top) spot at the relay plug. No light with key turned to "ON". Note: I do get a light when I plug into the bottom of the 3 signal spots on the relay, but not in the top one that is indicated in Step 4.

Since I didn't get a 12v test light to come on in Step 4, the manual instruct me to
"Repair the open or short to ground in the (F942) Fused Ignition Switch Output circuit. Inspect the related fuse and repair as necessary"
It took my a some searching to conclude (perhaps incorrectly) that F942 goes through the #10 fuse in the interior (under dash) fuse box. The owners manual indicates that this "Ignition Run Only Out (R/O)". Fuse was good. I used by 12v test light in the supply to the fuse. It was off with the key off, and ON with the key on. Assuming I found the right fuse, there seems to be an open circuit between the the Ignition Run Only R/O fuse under the dash and the fuel pump relay. So, I'm at a wall on the P0627 / fuel pump issue. Unless it's being caused by the P0522 Oil sensor issue:

I've read in this forum that the Oil Pressure Sensor can cause a no start situation, presumably by cutting the fuel pump. So I recognize that this could be the ultimate problem here...




EDIT: I was using the troubleshooting guide for the 5.7. Everything below this is not valid for the 4.7, so I will have to start this troubleshooting guide over over.



I started the troubleshooting process for P0522. One step is to check the voltage on at the harness going into the oil presure sensor. It's supposed to be 5V, but mine i 12V! It's getting battery voltage. I would like to take the next step in troubleshooting which is:

Turn the ignition off.
Disconnect the C2 PCM harness connector.
CAUTION: Do not probe the PCM harness connectors. Probing the
PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #881 to perform diagnostics. Measure the resistance of the (F855) 5-volt Supply circuit from the Engine Oil Pressure Sensor harness connector to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
However, I do not know which PCM harness is C2 (there are five harnesses going into the PCM and they look identical). I also don't have the special tool.
Any ideas on where to go from here?
 

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Hey y'all,

I'm a 34 yr-old environmental engineer in Atlanta and this is my first Jeep! I'm no mechanic, but I work on older trucks, boats, and bikes on the side in addition to renovating old house.

I picked up this Commander two months ago and have loved it... when I haven't been working on it. This forum has been a big help so far with the issues I've had though!

The truck is in good shape and looks great. I bought it mainly to tow my boats around and it pulls nicely. It stops surprising well, which I learned when a car pulled out in front of my while I was pulling my boat - I was amazed it stopped as fast as it did because I was sure I was about to plow right into them with my new (to me) Jeep and new (to me) boat!

So far, I've replaced a leaking water pump (good think because it had the wrong coolant in it!), repaired a broken quick connect on the fuel line (after taping it together on the side of the road to get home), and now I'm working on a crank, no start issue that is caused by fuel pump not pumping. I've searched the threads thoroughly and they have helped me in troubleshooting and ruling out a number of things. I'll make a separate post about this issue in hopes y'all can help me.

Really apprecaite that y'all have such a nice and well-organized forum with helpful and nice folks!
Cheers,
Jake

@jcatl;

Welcome to the forum; Post some pics of your Commander when you can; Here are some links to help you out with future repairs and/or upgrades to your XK;

Chrysler/Jeep Factory Parts: http://www.factorychryslerparts.com/...ukey_make=1064

Cheapest factory Parts: Find OEM BMW, Fiat, Ford, GM, Mopar, Nissan, Subaru & Toyota Parts & Accessories

JeepinByAl: JBAoffroad.com

JustforJeeps.com - http://www.justforjeeps.com/?gclid=C...9i0hoCSS7w_wcB

Rough County lift kits - Suspension Lift Kits, Body Lifts, Leveling Kit, 4x4, Jeep, Chevy, Dodge, Ford, Off-road Truck | Rough Country Suspension Systems®

AFE: Advanced FLOW Engineering | Engineered Adrenaline

CARiD.com - http://www.carid.com/?gclid=CjwKEAjw...NrrxoCEBbw_wcB

Bilstein shocks & struts - Home

The Steel Armadillo - Jeep Commander (XK/HK) 2006-2010

WAM Custom Bumpers - https://wambumpers.com/

4WheelParts.com - Truck Parts & Jeep Parts - Lift Kits, Winches, Tonneau Covers, Tires, Wheels, Bumpers, Performance ? 4 Wheel Parts

RockAuto - http://www.rockauto.com/en/catalog/j...catalog%2Fjeep

Also, please read this if you haven't done so already - lots of good information in here;

REQUIRED READING!!! New Member Introduction post & other important new member info.

Thanks and again, welcome aboard.
 

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I guess I'll just describe the problem here, and we can move it to a new thread when I'm able to create one. I just needed to get all of this out for my own sake...

Background:
A few days ago, I went to start my truck and it cranked and cranked, but wouldn't even try to run. Seemed like a "no fuel" problem to me. I checked the fuel pump fuse and relay. I disconnected by new quick connect in the fuel line and turned the key to "ON" to see if it would squirt some fuel out at me. Nope. So I rightfully concluded the fuel pump wasn't pumping. Got it towed to my house.

I left my code reader at a friend's house 100 miles away last week, so I learned and did the "key dance" (thanks for the stickies!) to read my codes on my dash:
P0627 - Fuel Pump A Control Circuit /Open
P0522 - Engine Oil Pressure Sensor/Switch Low Voltage

Ok. I had read on this forum that the Oil Sensor switch is a common problem. It's $15 a the parts store, so I just replaced it. Still no start.

So, I wanted to just see if the fuel pump was getting power. Dropped the tank, voltage to fuel pump is 0.5v lower than battery. That's right at the threshold of a problem, from what I've read, but it is still over 12V with a fully charged battery.

Ran a jumper from the hot side of the fuel pump relay to the fuel pump, used on of the grounds from the fuel pump harness that plugs into the fuel pump. I opened the fuel qucik connect again and watched the gas dump out of it when I connected the jumper. So the fuel pump works. I reconnected my fuel line and connected the jumper again for a few seconds, to see if it would pressurize my fuel system enough to start. Then I plugged the harness back into the fuel pump and tried to crank it - and it started! Idled down. Ran and sounded completely normal for about 45 seconds, then promptly ran out of gas. So, the fuel pump works. (Which I knew was likely anyway...)

Now I figured I really need to look hard into the 7000 page service manual PDF I have. I searched P0627 and got a troubleshoot process for it. Step 1-3 were fine. Step 4 and I've already got an issue:

I plugged a 12v test light into the indicated (top) spot at the relay plug. No light with key turned to "ON". Note: I do get a light when I plug into the bottom of the 3 signal spots on the relay, but not in the top one that is indicated in Step 4.

Since I didn't get a 12v test light to come on in Step 4, the manual instruct me to It took my a some searching to conclude (perhaps incorrectly) that F942 goes through the #10 fuse in the interior (under dash) fuse box. The owners manual indicates that this "Ignition Run Only Out (R/O)". Fuse was good. I used by 12v test light in the supply to the fuse. It was off with the key off, and ON with the key on. Assuming I found the right fuse, there seems to be an open circuit between the the Ignition Run Only R/O fuse under the dash and the fuel pump relay. So, I'm at a wall on the P0627 / fuel pump issue. Unless it's being caused by the P0522 Oil sensor issue:

I've read in this forum that the Oil Pressure Sensor can cause a no start situation, presumably by cutting the fuel pump. So I recognize that this could be the ultimate problem here...




EDIT: I was using the troubleshooting guide for the 5.7. Everything below this is not valid for the 4.7, so I will have to start this troubleshooting guide over over.



I started the troubleshooting process for P0522. One step is to check the voltage on at the harness going into the oil presure sensor. It's supposed to be 5V, but mine i 12V! It's getting battery voltage. I would like to take the next step in troubleshooting which is:

However, I do not know which PCM harness is C2 (there are five harnesses going into the PCM and they look identical). I also don't have the special tool.
Any ideas on where to go from here?
I think you will find this thread very useful to possibly help you diagnose your issues;

https://www.jeepcommander.com/forums/10-electronics-nav-discussion/55657-junction-block-explained.html
 

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Discussion Starter #6
Thanks for the replies, Big Blue!



I understand why I can't post in another subforum now. I will get my post count up!



Regarding the thread you linked me to - thanks!

I have noted the Junction Box and checked what I believe to be the relevant circuit for the fuel pump. Fuse is intact and I get 12V when the key is turned on. I have no reason to think the problem is in the junction box at this point.



I'm trying to figure out:


1. my oil sensor problem (P0522)
2. whether my oil sensor problem is causing my fuel pump problem; I've read in some threads here that an oil sensor problem can cause a no start


However, I'm getting ~11.5v at the fuel pump wiring harness when I turn the key on (with batter at 12v), which makes me think I might have too much of a voltage leak somewhere in the fuel pump circuit. I'm going back to troubleshoot more tomorrow and will update.


I'm supposed to have emissions done in 10 days, so need to get this fixed!
Thanks again!
 

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Thanks for the replies, Big Blue!

1. my oil sensor problem (P0522)
2. whether my oil sensor problem is causing my fuel pump problem; I've read in some threads here that an oil sensor problem can cause a no start

However, I'm getting ~11.5v at the fuel pump wiring harness when I turn the key on (with batter at 12v), which makes me think I might have too much of a voltage leak somewhere in the fuel pump circuit. I'm going back to troubleshoot more tomorrow and will update.

I'm supposed to have emissions done in 10 days, so need to get this fixed!
Thanks again!
P0522 - Oil Pressure Sensor Low; Oil pressure sensor input below acceptable voltage.

Jeep Grand Cherokee WJ - Diagnostic Trouble Codes
 

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<<2. whether my oil sensor problem is causing my fuel pump problem>>


I dont know about our jeeps but I have heard of other cars that shut down the fuel supply if there is no oil pressure. In order to save the engine from damage. Also, do out jeeps have the roll over switch that shuts down the fuel pump in care of roll over? i know from experience that a 2005 ford explorer sport trac does not have this feature. I could have sworn that my old xj did though. Might be another thing to look into.
 

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Discussion Starter #10
I haven't found any reference to a roll-over sensor.

Thanks, rblapham!
I've located them in the Service Manual now. That 7000 page beast isn't the most user friendly!

I disconnected the battery for an hour tonight and my P0522 code is now gone, so the new oil pressure sensor seems to have addressed that.

However, the truck still won't crank and I've still got the P0627 - fuel pump relay circuit

Going through the troubleshooting guide:
The manual says that the resistance of the fuel pump relay should be between 70 and 90 ohms. I'm reading 40 ohms, so SM say I should replace relay (which I'm going to). However, I tested the 3 other identical relays adjacent to the fuel pump relay (Started, A/C clutch, EATX) and they all show the same resistance 40ohm ... seems odd.

Also, as I mentioned above. Step 3 in the guide is ok. Step 4 is no good. The bottom signal circuit for the relay shows 12V when key is on, top shows 0v though.
Steps 3 and 4 can be seen at www . imgur . com /a/SINEBea (without the spaces of course. I still can't post photos or links until I get mt post count up, apparently) I typically wouldn't be so impatient, but I have to pass emissions by Oct 26...

All of this is complicated by the fact that I dropped the tank and found 11.5v at the fuel pump harness. Do I simply have a 0.5V voltage leak somewhere and the fuel pump just won't run on <12v??

Thanks for any help!!!
 

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Discussion Starter #11
Well, it's working. I'm not really sure exactly what did it, but it appears to have been a ground issue. I went through and check/cleaned all of the grounds I found. The big grounding strap near the transfer case (the one shaped like a "Y" with 3 connections) is broken on one leg of the Y. I'm ordering a new one as well as a new "NGC to engine" ground strap, which I think is the PCM grounding strap and will replace both. Adjusting and reconnecting grounds in the only real change I've made other than moving wires around and checking voltages. Whatever it was, my fuel pump is working again so I jacked my fuel tank back up and reconnected it. Put 10 miles on it so far... I missed my inspection and registration deadline but I'll do that when I'm back from a work trip week after next.



I was pleasantly surprised to see how easy it is to remove and install the fuel tank (other than the one bolt that is behind the drive shaft - a flex head ratcheting wrench made that one possible), considering there is no other way to access the fuel pump.



I'll replace these grounds and check/adjust all others and hope the problem doesn't come back! Now to trying to install my rough country 2" lift. My first attempt failed when I couldn't remove the notorious lower LCA-strut "clevis" bolt. I'm reading up on more strategies for that. I've read that Jeep says the bushing on the clevis bolt is not a serviceable part, but MOOG has a replacement that some people report using - part K200183 - $17 at Rock Auto, so I'm considering taking an approach that may destroy the original bushing. We'll see. I'll spray it down with more pb blaster for a few weeks first.


Thanks again for all the help y'all!
 
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