Quit running not starting

thermorex · **Posted:** Sat Mar 04, 2017 7:16 pm

flash7210 wrote:

I've had the limp mode and random dying issues.

Most of the time random dying is a fuel supply problem but it can also be electrical.
Unplugging and firmly reconnecting all four injector connections might fix that. I actually had to remove the rubber seal inside the connectors to get a good firm connection.

For me, limp mode was caused by problems at the fuel rail pressure sensor and the fuel quantity solenoid.
One time it went into limp mode and then died and would not restart. The only way I could get it to run was by unplugging the fuel quantity solenoid but then it would run in limp mode.

After replacing the pressure sensor and FQS and still having problems, I replaced the wire harness connectors. Since then I have had no more fuel system problems.

If you wind up replacing the pressure sensor connector I recommend also installing a Auto Meter fuel rail pressure gauge. It has been a valuable diagnostic tool for me.

LM, sorry for the off topic, I'd like to ask flash how did he connect the autometer gauge? Flash, did you connect to the vehicle wires, or you installed a sensor that is used by the autometer gauge?

LMWatBullRun · **Posted:** Sat Mar 04, 2017 7:19 pm

WolverineFW wrote:

Make sure you are using a fitting rated for 30,000 psi...

Sent from my SM-N910W8 using Tapatalk

Yes, HP fuel can be lethal, but a properly designed, fabbed and installed fitting ought not be a problem.
As those who have read the ARP stud thread know, I am a thorough engineer, and I don't plan
on getting sloppy for this. I don't do stuff that doesn't work, but it is worth noting to those who may not
know better that HP diesel fuel can kill you.

So, gents, my thanks for the cautions. Anyone know why the CRD limps? Is it simply intermittent connections?

flash7210 · **Posted:** Sat Mar 04, 2017 8:25 pm

thermorex wrote:

flash7210 wrote:

I've had the limp mode and random dying issues.

Most of the time random dying is a fuel supply problem but it can also be electrical.
Unplugging and firmly reconnecting all four injector connections might fix that. I actually had to remove the rubber seal inside the connectors to get a good firm connection.

For me, limp mode was caused by problems at the fuel rail pressure sensor and the fuel quantity solenoid.
One time it went into limp mode and then died and would not restart. The only way I could get it to run was by unplugging the fuel quantity solenoid but then it would run in limp mode.

After replacing the pressure sensor and FQS and still having problems, I replaced the wire harness connectors. Since then I have had no more fuel system problems.

If you wind up replacing the pressure sensor connector I recommend also installing a Auto Meter fuel rail pressure gauge. It has been a valuable diagnostic tool for me.

LM, sorry for the off topic, I'd like to ask flash how did he connect the autometer gauge? Flash, did you connect to the vehicle wires, or you installed a sensor that is used by the autometer gauge?

The gauge wiring splices into the rail pressure sensor.
Instructions are included with the gauge.

flash7210 · **Posted:** Sat Mar 04, 2017 8:26 pm

LMWatBullRun wrote:

WolverineFW wrote:

Make sure you are using a fitting rated for 30,000 psi...

Sent from my SM-N910W8 using Tapatalk

Yes, HP fuel can be lethal, but a properly designed, fabbed and installed fitting ought not be a problem.
As those who have read the ARP stud thread know, I am a thorough engineer, and I don't plan
on getting sloppy for this. I don't do stuff that doesn't work, but it is worth noting to those who may not
know better that HP diesel fuel can kill you.

So, gents, my thanks for the cautions. Anyone know why the CRD limps? Is it simply intermittent connections?

Open circuits, whether intermittent or perpetual, will cause limp mode.

thermorex · **Posted:** Sat Mar 04, 2017 8:27 pm

flash7210 wrote:

thermorex wrote:

flash7210 wrote:

I've had the limp mode and random dying issues.

Most of the time random dying is a fuel supply problem but it can also be electrical.
Unplugging and firmly reconnecting all four injector connections might fix that. I actually had to remove the rubber seal inside the connectors to get a good firm connection.

For me, limp mode was caused by problems at the fuel rail pressure sensor and the fuel quantity solenoid.
One time it went into limp mode and then died and would not restart. The only way I could get it to run was by unplugging the fuel quantity solenoid but then it would run in limp mode.

After replacing the pressure sensor and FQS and still having problems, I replaced the wire harness connectors. Since then I have had no more fuel system problems.

If you wind up replacing the pressure sensor connector I recommend also installing a Auto Meter fuel rail pressure gauge. It has been a valuable diagnostic tool for me.

LM, sorry for the off topic, I'd like to ask flash how did he connect the autometer gauge? Flash, did you connect to the vehicle wires, or you installed a sensor that is used by the autometer gauge?

The gauge wiring splices into the rail pressure sensor.
Instructions are included with the gauge.

Cool, thanks flash!

flash7210 · **Posted:** Sat Mar 18, 2017 9:22 pm

Any update?
Did you get it fixed?

LMWatBullRun · **Posted:** Sun Mar 19, 2017 8:39 pm

geordi · **Posted:** Mon Mar 20, 2017 12:15 am

If you are having intermittent limp mode but all else seems OK - and no codes - check the wires and the connections to the little Mercedes Logo Sensor on the side of the airbox. Those wires get pinched a lot and break right by the connector, and then all manner of stupid things start to happen in the computer. Mine would put me into limp mode randomly, but ONLY after moderate (not hard) acceleration, or hitting bumps in certain ways.

You'll see on the CRD you bought from me that I replaced that plug with another from another harness - sorry about the wiring job, I always meant to make that better.

Once I replaced that plug, the limp mode went away.

LMWatBullRun · **Posted:** Sat Apr 01, 2017 12:20 pm

going after plugs and connector replacement today- will advise.

LMWatBullRun · **Posted:** Sat Apr 01, 2017 2:19 pm

OK. I did check the airbox 3 wire plug, and it was OK.

Jeep started just fine. Ran great for about 15 minutes; gouged on it going up a steep incline and it leapt up the hill. Alas, after the third trip around the block the limp mode gradually eases in. Cold, the thing runs like a champ, but hot it goes into limp mode after about 20 minutes run time. On restart it takes about a minute or so after it is warm and goes into limp mode. Finally, I was trying to accelerate up a hill, and it quit. Just like that, just like before. So I restarted and came home. CEL was on. MAF varies from 9.6 to 16.5 at idle so I think the MAF is bad. It reads 2.4 when the engine is off.

Not getting the injector codes as I was before.
So I am wondering, can this be a bad rail pressure sensor? I've replaced the Cam PS AND the Crank Sensor, and I have swapped the FQS at the CP3 pump with another one, and it's still doing the same stuff, so I think it has to be either the rail pressure sensor or the relevant connector.

Suggestions on replacing the connector?

LMW

WolverineFW · **Posted:** Sat Apr 01, 2017 3:25 pm

You obviously have a bad sensor somewhere that is exhibiting a resistance change when it is exposed to heat and causing problems. Does not sound like a connector or wire problem although that is still a slight possibility.

Maybe take the cold resistance reading of the sensor. Then take it again immediately after it goes in to limp mode. I believe that sensor should be controlled by varying the voltage to it and resistance should stay the same.

Did you ensure that none of the connector pins have been pushed back at all? They will cause problems if not seated correctly.

Sent from my SM-N910W8 using Tapatalk

LMWatBullRun · **Posted:** Sun Apr 02, 2017 9:34 am

taking a multimeter with me on the test drive is an idea I have had, Wolverine, and I may just do that. I did change the connection to the rail sensor, and no joy. Still does the exact same predictable splah after 20 minutes of warmup.

I keep getting the "leak detected" code, not getting any others since I cleaned the connections at the ECU.

Haven't done a detailed inspection of the rail pressure sensor pins but will do that today. Doubt that this would show a gradual predictable fault progression, but will check. I know the MAP can induce limp mode, and I cleaned the sensor again, which was slightly sooty but otherwise fine. No change.

Very strongly suspect the rail pressure sensor, and am tempted to swap it for another, but not sure about leaks. I think this sensor has a one-time crush washer, IIRC.

WWDiesel · **Posted:** Sun Apr 02, 2017 10:19 am

LMWatBullRun wrote:

OK. I did check the airbox 3 wire plug, and it was OK.
Jeep started just fine. Ran great for about 15 minutes; gouged on it going up a steep incline and it leapt up the hill. Alas, after the third trip around the block the limp mode gradually eases in. Cold, the thing runs like a champ, but hot it goes into limp mode after about 20 minutes run time. On restart it takes about a minute or so after it is warm and goes into limp mode. Finally, I was trying to accelerate up a hill, and it quit. Just like that, just like before. So I restarted and came home. CEL was on. MAF varies from 9.6 to 16.5 at idle so I think the MAF is bad. It reads 2.4 when the engine is off.
Not getting the injector codes as I was before.
So I am wondering, can this be a bad rail pressure sensor? I've replaced the Cam PS AND the Crank Sensor, and I have swapped the FQS at the CP3 pump with another one, and it's still doing the same stuff, so I think it has to be either the rail pressure sensor or the relevant connector.
Suggestions on replacing the connector?LMW

Just curious, what was the DTC (CEL)? :?:

LMWatBullRun · **Posted:** Sun Apr 02, 2017 10:38 am

WWDiesel wrote:

Just curious, what was the DTC (CEL)? :?:

0093 (fuel leak)
0734 (fuel pressure)

WWDiesel · **Posted:** Sun Apr 02, 2017 12:23 pm

LMWatBullRun wrote:

WWDiesel wrote:

Just curious, what was the DTC (CEL)? :?:

0093 (fuel leak)
0734 (fuel pressure)

Yep, looks like computer is sensing low fuel pressure at times on fuel rail for some reason.... :roll:

rankom · **Posted:** Sun Apr 02, 2017 1:28 pm

i say if i was testing rail pressure solenoid , i would cap plastic fuel manifold , and run clear tubing from rail into fuel container on passenger floor , also i would hook up some gauges to monitor return fuel flow ,

LMWatBullRun · **Posted:** Sun Apr 02, 2017 3:04 pm

So, I asked the DW to ride shotgun to read the pressure on Torque while I put the Libby through her paces.
what we found was that the engine cycles between about 5k psi and about 15-19k psi when it was accelerating ( at 2k rpm or better.)

The jeep would go into limp mode and when the accelerator was pressed, pow- pressure dropped to 180psi and the motor would shut off.
Restart reset the engine, no limp mode, and then same thing would happen. If I ran the jeep without pressing the accelerator too hard, it continued to run in limp mode.

Just went out and checked the resistance of the sensor it is about 25,000 ohms from one side to the other, but I get nothing at the center pin. infinite resistance. so how does the computer know what the resistance/pressure is?

rankom · **Posted:** Sun Apr 02, 2017 3:46 pm

how about go back to step one , get fuel container on pass floor and run fuel line direct to engine (WITH INLINE FITER) so that would by pass fuel tank , and run that hill again , LOL i like the old fashion testing , we had lots of luck testing old motors , and it worked , but i guess we have to trust electronics testing equipment these days , me ,, i don't trust them all the time .some time LOL

LMWatBullRun · **Posted:** Sun Apr 02, 2017 4:16 pm

So, I changed the fuel pressure sensor after I put a multimeter on the replacement and found the same thing WRt resistance.
about 23 k from side to side but again infinite at the middle. Took it out for a test drive, and did not wait for limp mode, but put the peddle down and pushed hard. Whap! Engine quit. Restart, no problem. Jeep did not go into limp mode. It is not the rail pressure sensor; the rail pressure is dropping virtually instantly and it is doing so when I press the throttle.

So what would make the fuel pressure drop like that, so fast?

If there was an intermittent in the FQS at CP3, the pressure would go UP.
I changed the FPS mid rail AND the connector.
The only thing left I can think of is the fuel pressure solenoid at the back of the rail, OR the connector to same.
A momentary intermittent there WOULD dump the rail pressure, and once that dropped the ECU would not permit it to continue running, but would immediately restart as long as the intermittent was gone.

I'm going to go play with the wiring for that connector and maybe give the solenoid a few taps..........

flash7210 · **Posted:** Sun Apr 02, 2017 4:37 pm

LMWatBullRun wrote:

So, I asked the DW to ride shotgun to read the pressure on Torque while I put the Libby through her paces.
what we found was that the engine cycles between about 5k psi and about 15-19k psi when it was accelerating ( at 2k rpm or better.)

The jeep would go into limp mode and when the accelerator was pressed, pow- pressure dropped to 180psi and the motor would shut off.
Restart reset the engine, no limp mode, and then same thing would happen. If I ran the jeep without pressing the accelerator too hard, it continued to run in limp mode.

Just went out and checked the resistance of the sensor it is about 25,000 ohms from one side to the other, but I get nothing at the center pin. infinite resistance. so how does the computer know what the resistance/pressure is?

Next test.
With the engine idling and in park, watch Torque while wiggling the wire connector at the fuel quantity solenoid. If you see a similar drop in fuel pressure or the engine sputters and stumbles, replace the connector for the FQS.
Then, do the same test at the fuel pressure sensor.
And again at the fuel rail pressure solenoid.

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