Getting desperate, no ignition.

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

WWDiesel wrote:

Question? Is the starter motor itself failing or is it the starter solenoid on top the the starter motor?
Need to determine if the problem is electrical or mechanical. Have you load tested your battery? Low battery voltage or a weak battery cell will cause slow starter speeds and impede starter power.

You definitely need to connect a voltmeter to the positive lug on the starter and see how low the voltage is dropping to when the starter motor is engaged.
Amps go up exponentially as battery voltage drops, so a low voltage situation could be killing your starter.

As the battery voltage drops, it’s internal resistance increases due to chemical actions of the battery plates. This battery resistance increase limits the available battery current and reduces the amount of power delivered to the starter motor. Now the starter motor is not getting the voltage that it is designed for, so it starts dragging (arcing across the armature windings) and repeated occurrences will shorten the life of the starter motor very quickly. Weak batteries will destroy starter motors over time because of the excessive current draw and armature arcing due to low cranking voltage. The wires going from the battery to the starter motor also have resistance that adds to the impedance of current flow in low voltage situations.

Have you tested the starter relay in the Power Management Center under the hood? Try swapping relays say with one of the like size relays.
High-amperage feed circuit that feeds the starter motor (700 amperes - diesel engine)

See Section 8F - page 32 STARTING SYSTEM KJ in the online 2005 FSM (Factory Service Manual)

FSM wrote:

STARTER MOTOR - DIAGNOSIS AND TESTING, starting on page 39
2005JeepKJServiceManual.pdf

Ah, forgot to tell sorry.
I pulled the solenoid, put it under load and it was dead. So I replaced that.
Meanwhile I hooked my battery up on a charger as I declined it must be near flat.
Then I tried starting and it eventually did! But it took way too long.
So, thinking compression or pressure.
Why? Because my scanner readings indicate benchmark pressure isn't met by just a hair.
Now, I'm not a real mechanic so winging it here.
I tried posting an image of my scanner readings but was successful. Instead I posted a link.
But that's when my thoughts also turned to the starter motor.
If it was sluggish/worn it could be the culprit.

You are right so pointing out that the battery must be ok.
I load tested it and it was.
Thanks for your elaborate answer, especially on the starter motor. I will do the voltage checks.
I think I did check the starter relay but done so many checks I'm not sure anymore. So will do again.
Thanks again and will go through the fsm.

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

Hmm, fsm only covers gas starter motors...

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

Quick update.
Sweet talked a local garage into lending me their special amp meter clamp thingy.
(Sorry, forgot what it's called)
Hooked it up my starter motor and got the following readings:

Soon as it's cranked it drops to 9.1 V instantly and proceeds/ends ('cause it ain't starting) to 8.8 V

Amps:
Upon start I read 310 A which slowly dropped to 280 A

This puzzles me because, if I understood correctly, a faulty starter would show a higher Amp (>700 A) draw with a dropping Voltage.
But I could be wrong as this is not my strong suit and some might have been lost on me as English isn't my first language.

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

At a total loss here.
Proceeded to replace starter motor and fuel head.
Some improvement, it now starts when mildly warm.
:roll:

Ideas?

WWDiesel · **Posted:** Sat Mar 04, 2023 10:30 pm

Anytime the voltage drops below 9v while cranking the OBC can get real iffy about allowing the engine to start. :dead:

Even with a good new starter, I still would still be real suspect if the battery voltage drops too low during cranking. (<9v)
I have a volt meter in mine, and during cranking, it drops to around ~11 volts while the starter is engaged starting the engine even in real cold temperature conditions. .
But I do have a very high (1070a CCA) group 65 AGM battery... :wink:

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

WWDiesel wrote:

Anytime the voltage drops below 9v while cranking the OBC can get real iffy about allowing the engine to start. :dead:

Even with a good new starter, I still would still be real suspect if the battery voltage drops too low during cranking. (<9v)
I have a volt meter in mine, and during cranking, it drops to around ~11 volts while the starter is engaged starting the engine even in real cold temperature conditions. .
But I do have a very high (1070a CCA) group 65 AGM battery... :wink:

Ok, gonna check, thanks.
What's the OBC?
Could it be a compression problem?

WolverineFW · **Posted:** Sun Mar 05, 2023 1:08 pm

You need to check your cables from your battery to your starter for poor connections, corrosion, and damage. Also your grounds.

Sent from my SM-S906W using Tapatalk

WWDiesel · **Posted:** Sun Mar 05, 2023 2:10 pm

roamer wrote:

WWDiesel wrote:

Anytime the voltage drops below 9v while cranking the OBC can get real iffy about allowing the engine to start. :dead:

Even with a good new starter, I still would still be real suspect if the battery voltage drops too low during cranking. (<9v)
I have a volt meter in mine, and during cranking, it drops to around ~11 volts while the starter is engaged starting the engine even in real cold temperature conditions. . But I do have a very high (1070a CCA) group 65 AGM battery... :wink:

Ok, gonna check, thanks.
What's the OBC? Could it be a compression problem?

OBC = On Board Computer aka ECM (Electronic Control Module) Also sometimes referred to as a PCM (Power Control Module) :wink:

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

WWDiesel wrote:

roamer wrote:

WWDiesel wrote:

Anytime the voltage drops below 9v while cranking the OBC can get real iffy about allowing the engine to start. :dead:

Even with a good new starter, I still would still be real suspect if the battery voltage drops too low during cranking. (<9v)
I have a volt meter in mine, and during cranking, it drops to around ~11 volts while the starter is engaged starting the engine even in real cold temperature conditions. . But I do have a very high (1070a CCA) group 65 AGM battery... :wink:

Ok, gonna check, thanks.
What's the OBC? Could it be a compression problem?

OBC = On Board Computer aka ECM (Electronic Control Module) Also sometimes referred to as a PCM (Power Control Module) :wink:

So.. I investigated further.
Before I went on with your suggestion I wanted to follow up on my compression thought train.
I detached the return hose from the rail solenoid and what do ya know fuel came out.
But the solenoid is new. Defective out of the box?
One thing is certain, there's the low pressure problem.
Hooked up the scanner and it showed a pressure of approx. 54000 kPa or ~7832 psi. That's way too high.
I measured cranking and non cracking situation. The numbers stayed the same.
What did change was the voltage, resp. ~5V and ~0.5V.
So I ordered a new pressure sensor.

To be continued...

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

Moving on...
Installed the new sensor and read 34.000kPa which is ~4931 psi, so that's good.
Warm start, easy peasy. The car runs noticeably smoother.
Cold start... Same!
Pulled the solenoid return hose and it's still dumping fuel when cranking!
Now, I did some reading on the thing and found 3 sources.
One says the solenoid is open when not charged. The other two say it should be closed.
What I gathered is that the solenoid is spring loaded (so shut) at a certain rating.
When cranking the spring gets help by an electro magnet so it stays shut no matter what because you need that pressure for starting/igniting.
Am I correct?
If so it seems to me that the solenoid is faulty straight from the box.

Could anybody enlighten me?

WWDiesel · **Posted:** Fri Mar 10, 2023 4:16 pm

Hope this helps some?
FUEL PRESSURE SOLENOID ON END OF FUEL RAIL

DESCRIPTION
Fuel Pressure Solenoid (on end of fuel rail) aka: Fuel Rail Pressure Control Valve.
The Fuel Pressure Solenoid valve is screwed into the rear of the fuel rail. The solenoid controls and maintains constant rail pressure by a pulse-width modulated control current transmitted by the (ECM).
The tip-end of the FPS uses a knife-edge type high-pressure seal. The knife edge actually deforms the metal in the fuel rail in order to seal the surfaces.
The FPS must be replaced if it is removed from the rail - each replacement must establish the knife-edge seal to prevent leaks at 1600bar (23206psia).

OPERATION
In de-energized state, the FPS valve is closed as spring tension forces the ball into the
ball-seat - spring tension limits minimum rail pressure to 100 Bar 1445psi. When the engine is started, the solenoid valve is additionally held closed by electro-magnetic force. When running, fuel pressure counteracts the magnetic force of the coil and spring tension, opening the valve. When the engine is running, the valve is always open to a varying degree, controlled by the ECM.
The ECM senses actual operating fuel rail pressure by the signal received from the fuel rail pressure sensor.
High pressure fuel in the rail flows to the ball-seat of the solenoid valve. The specified rail pressure required by the system is set by the FPS - the ECM sends a controlled current thru the solenoid, building up a magnetic force which corresponds to this specific pressure. This magnetic force equals a specific cross-sectional outlet at the ball-seat of the valve, which allows excess fuel to flow through.
Rail pressure is altered as a result of the controlled quantity of fuel which flows out the return.
The controlled excess fuel then flows back through the return-fuel line, into the tank.
*By reducing fuel at the inlet to the high-pressure pump with the Fuel Quality Solenoid valve, which reduces excess fuel through FPS valve without reducing rail pressure, the ECM can control in-tank fuel temperatures.

Leaking fuel pressure solenoid:
There should be no fuel coming out of the solenoid return line while cranking the engine. Perform the fuel rail pressure solenoid leak quantity test to determine if it is faulty. If the injectors check good, the fuel pressure solenoid should hold 870-1450 psi during engine cranking.

THE ENGINE WILL NOT START IF THE FUEL PRESSURE SOLENOID HAS FAILED!

Testing the Fuel Rail Pressure control Solenoid:
Multimeter – Test internal resistance of solenoid valve windings, typical value is approximately 3.6 ohms.
Diagnostic Scanner – Check for DTC’s and monitor fuel rail pressure during all operating conditions.
Oscilloscope – Test supply voltage and earth (ground) switching signal from ECM (PWM – “Pulse Width Modulation”) Test stability of waveform.

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

WWDiesel wrote:

Hope this helps some?
FUEL PRESSURE SOLENOID ON END OF FUEL RAIL

DESCRIPTION
Fuel Pressure Solenoid (on end of fuel rail) aka: Fuel Rail Pressure Control Valve.
The Fuel Pressure Solenoid valve is screwed into the rear of the fuel rail. The solenoid controls and maintains constant rail pressure by a pulse-width modulated control current transmitted by the (ECM).
The tip-end of the FPS uses a knife-edge type high-pressure seal. The knife edge actually deforms the metal in the fuel rail in order to seal the surfaces.
The FPS must be replaced if it is removed from the rail - each replacement must establish the knife-edge seal to prevent leaks at 1600bar (23206psia).

OPERATION
In de-energized state, the FPS valve is closed as spring tension forces the ball into the
ball-seat - spring tension limits minimum rail pressure to 100 Bar 1445psi. When the engine is started, the solenoid valve is additionally held closed by electro-magnetic force. When running, fuel pressure counteracts the magnetic force of the coil and spring tension, opening the valve. When the engine is running, the valve is always open to a varying degree, controlled by the ECM.
The ECM senses actual operating fuel rail pressure by the signal received from the fuel rail pressure sensor.
High pressure fuel in the rail flows to the ball-seat of the solenoid valve. The specified rail pressure required by the system is set by the FPS - the ECM sends a controlled current thru the solenoid, building up a magnetic force which corresponds to this specific pressure. This magnetic force equals a specific cross-sectional outlet at the ball-seat of the valve, which allows excess fuel to flow through.
Rail pressure is altered as a result of the controlled quantity of fuel which flows out the return.
The controlled excess fuel then flows back through the return-fuel line, into the tank.
*By reducing fuel at the inlet to the high-pressure pump with the Fuel Quality Solenoid valve, which reduces excess fuel through FPS valve without reducing rail pressure, the ECM can control in-tank fuel temperatures.

Leaking fuel pressure solenoid:
There should be no fuel coming out of the solenoid return line while cranking the engine. Perform the fuel rail pressure solenoid leak quantity test to determine if it is faulty. If the injectors check good, the fuel pressure solenoid should hold 870-1450 psi during engine cranking.

THE ENGINE WILL NOT START IF THE FUEL PRESSURE SOLENOID HAS FAILED!

Testing the Fuel Rail Pressure control Solenoid:
Multimeter – Test internal resistance of solenoid valve windings, typical value is approximately 3.6 ohms.
Diagnostic Scanner – Check for DTC’s and monitor fuel rail pressure during all operating conditions.
Oscilloscope – Test supply voltage and earth (ground) switching signal from ECM (PWM – “Pulse Width Modulation”) Test stability of waveform.

It does!
Thanks!

DieselJeepLuvr · **Posted:** Sat Mar 11, 2023 1:59 am

Oh and when you change it, remove the common rail, put it in a vise and make sure to torque down the COLLAR ONLY! Don't allow the solenoid valve to rotate!

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

DieselJeepLuvr wrote:

Oh and when you change it, remove the common rail, put it in a vise and make sure to torque down the COLLAR ONLY! Don't allow the solenoid valve to rotate!

Thanks for the advice.

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

Today I took a closer look at the solenoid.
Didn't have time to remove so did a few tests.
I measured the voltage and it starts of with 12V and drops to 8V while cranking. (Scan tool)
Is that correct?
The thing still dumps fuel when cranking.
How is this possible?
It's new outta the box, the connector delivers a full 12V (measured with multimeter)

Checked the pins on the ECM and they look like new!
Pressure reads about 4600 psi so that's a lot less then it was before and tells me the pressure sensor replacement made a difference.

How do I stop the solenoid from dumping fuel?
Am I overseeing some?
Only thing I can think of it's defective from new.

Help!

WWDiesel · **Posted:** Sat Mar 11, 2023 2:33 pm

12v while cranking is correct, ECM is commanding it shut while starting the engine to try and build fuel rail pressure.
If it is still dumping fuel while the ECM commands it closed, it is leaking by or not getting the correct voltage to hold it shut.

What is your battery voltage doing when starting the engine?
If your battery voltage is dropping to low, it can cause starting issues.
The ECM is not very happy below 9v.
What are the starter amps? Maybe a bad starter or bad cell in the battery? :juggle:

WolverineFW · **Posted:** Sat Mar 11, 2023 3:22 pm

Have you checked any of this yet? Bad connections cause resistance and therefore voltage drop.

WolverineFW wrote:

You need to check your cables from your battery to your starter for poor connections, corrosion, and damage. Also your grounds.

Sent from my SM-S906W using Tapatalk

Sent from my SM-S906W using Tapatalk

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

WWDiesel wrote:

12v while cranking is correct, ECM is commanding it shut while starting the engine to try and build fuel rail pressure.
If it is still dumping fuel while the ECM commands it closed, it is leaking by or not getting the correct voltage to hold it shut.

What is your battery voltage doing when starting the engine?
If your battery voltage is dropping to low, it can cause starting issues.
The ECM is not very happy below 9v.
What are the starter amps? Maybe a bad starter or bad cell in the battery? :juggle:

The voltage drops to about 8V. (Solenoid)
According to your info that causes issues with both the solenoid and the ECM.
Gonna have to hook up a new battery and start measuring various cables, grounds and what not.
Thanks.

roamer · **Joined:** Tue Jul 31, 2018 3:49 pm **Posts:** 28

WolverineFW wrote:

Have you checked any of this yet? Bad connections cause resistance and therefore voltage drop.

WolverineFW wrote:

You need to check your cables from your battery to your starter for poor connections, corrosion, and damage. Also your grounds.

Sent from my SM-S906W using Tapatalk

Sent from my SM-S906W using Tapatalk

I did but gonna do again

Billybob · **Posted:** Sun Mar 12, 2023 12:08 pm

Take a thick cable such as is used in jump-starting the Jeep.

Clamp one end onto the Battery negative terminal.
Clamp the other end directly on to the Starter Motor body.

This should override any bad-earthing problems to the Starter Motor! :wink:

Getting desperate, no ignition.

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