Hard to find noise -- clinking and clanking

layback40 · **Posted:** Sun Sep 17, 2023 7:54 pm

WWDiesel wrote:

Do you have any codes set or stored relating to fuel pressure?

Code is for large fuel leak.

Maybe some of this will be of some help to you?
It explains how this device operates. If you are having low fuel rail pressure problems, it can be caused by quite a few different things including the fuel rail pressure sensor, fuel rail pressure solenoid, Cascade overflow valve on top of CP3, and Fuel Quantity Solenoid on back of CP3 injection pump.

Fuel rail pressure solenoid replaced.
The new one gave a slightly higher output signal & allowed starting without starter fluid. Need over 1v to start. At idle it has about 1.5v, best seen is just over 2v. I dont see a drop in output voltage leading to the engine cutting out & CEL/code.
Fuel Quantity solenoid replaced
CP3 replaced & so the cascade valve.
Cam sensor replaced
Crank sensor replaced
injectors replaced

Lack of adequate fuel flow to the CP3 can also cause improper fuel rail pressure. If the CP3 cannot get the required amount of fuel, it cannot build the fuel rail pressure as needed.

Electric pump fitted just before filter.
New element in filter.
Clear fuel lines fitted & no air visible.

A bad fuel injector, leaking, can also cause low pressure problems.

New injectors not overflowing excessively

Everything thing must be ruled out one at a time to find the problem. Either you are not getting enough fuel or something is dumping (losing) the fuel rail pressure. It could also be an electronic control issue causing it? This is not an easy one to diagnose unfortunately! :cry:

Quote:

Fuel Rail Pressure Too Low

For a test: You could disconnect the hose from the fuel return line plastic block and see how much fuel is being returned to the fuel tank. If it is a lot of fuel, then you must determine by disconnecting each item one at a time and find out if it is coming from the fuel pressure solenoid, the CP3, or a fuel injector.

Have covered the strainer cap of the fuel pressure solenoid so absolutely no fuel flows through it. Injectors not leaking.

Watch this video testing the Fuel Rail Pressure Solenoid (regulator): https://www.youtube.com/watch?v=tqW1dNp ... Automotive

Will look at.

When it gets me down :banghead:

, I just walk away from it for a while until the weather is nice.

WWDiesel · **Posted:** Sun Sep 17, 2023 10:16 pm

Thats a tough one, looks like you have covered most all the bases. :shock:

Could end up being an ECM problem? :cry:

layback40 · **Posted:** Mon Sep 18, 2023 5:33 am

WWDiesel wrote:

Thats a tough one, looks like you have covered most all the bases. :shock:

Could end up being an ECM problem? :cry:

Not given up just yet! That would be letting us both down!
Have 12.3v at the solenoid plug on the rail when unplugged & ignition on. I did see about 2v on the other wire. Dont know if that is ok, expected 0v. Maybe its an electronic thing in the ECM.
Want to look at the fuel quantity solenoid & see what I see there.
Will probably look at the GP control box & see if its producing a pulse signal.
That was the start of my problems ~ failed GP's. I initially had to put 7v ones in, replaced them with 5v ones when they arrived.
I know Bosch here in Australia offer a ECM check & repair service. Its not cheap though.
I want to make sure its not a jammed cascade valve. The low rail pressure with 2 different CP3's has me a little stumped.
Diesel fuel in Australia now is mainly imported & blended with biodiesel. Dont know if there is an issue with it.

WWDiesel · **Posted:** Mon Sep 18, 2023 1:39 pm

layback40 wrote:

I want to make sure its not a jammed cascade valve. The low rail pressure with 2 different CP3's has me a little stumped.
Diesel fuel in Australia now is mainly imported & blended with biodiesel. Dont know if there is an issue with it.

With two different CP3's it is highly doubtful that both would have a cascade overflow valve problem. Not impossible, but highly improbable.
Also, if it is the cascade overflow valve issue, you should be getting a lot of fuel return through the return system block going back to the fuel tank.
How much fuel is being returned via the fuel return block??? (KEY)

The scope waveform I posted above shows that the voltage modulates by the ECM, so you certainly may get a small voltage reading using a voltmeter as it would not be fast enough to capture the modulations of the pulse width.

Don't believe biodiesel has anything to do with the problem.

Quote:

Cascade/Overflow Valve (on top of CP3)
Regulates lubrication to internal parts of the injection pump and regulates the fuel pressure to the fuel quantity solenoid valve on the back of CP3 injection pump. Also, controls the amount of fuel being returned to the fuel tank via the fuel return line.

CaptainDean · **Joined:** Thu Oct 05, 2017 2:22 am **Posts:** 673

layback40 wrote:

Hi Dean,
Hope your health is improving!

Have you ever had a look at the signal going to the solenoid at the end of the rail with a CRO? Or the solenoid on the CP3?
I have no signal showing on the rail (quality) solenoid at idle. If I unplug the solenoid the engine cuts out. I am using a proper CRO.
I have seen a good app that has a CRO through the audio socket on a smart phone.
I remember you played with the rail solenoid once.
There is a PDF about the fuel system that shows a signal on a screen of a DBR scanner.
WW may wish to comment.
I am still having trouble with the fuel system on mine.
Thinking there may be an issue with the ECU. Probably the pulse signals is switched by a FET in there.
It looked like you took the cover off your original ECU. The sealant on mine has it stuck on very tight.
Any comments always appreciated.

Thanks layback40 for asking about my health. I'm basically healed now with only 1 issue to overcome -- a weak stream at the urinal. Going to the Urologist tomorrow (Tue 9/19/2023). My biggest concern was my eyesight - I could only see close up. Turns out nature gave us lenses in our eye filled with sugar/glucose. It's real clear, real clear. With high blood glucose, the lens fills more and inflates causing the lens to get fat - and only focusing on close up things. Keeping my blood glucose low allowed the lens to normalize again. Amazing!

Thanks layback40 and WWDiesel for all the fuel system troubleshooting information. My jeep is running good again and has not gone into near-limp-in mode for over a week. However, if it does become a problem again, I have a PicoScope and I will be able to test the ECM.

I do have a question about a couple acronyms: CRO and DBR. C? R? Oscilloscope?. Digital? B? R? Please explain.

Dean.

CaptainDean · **Joined:** Thu Oct 05, 2017 2:22 am **Posts:** 673

WWDiesel wrote:

Do you have any codes set or stored relating to fuel pressure?

Maybe some of this will be of some help to you?
It explains how this device operates. If you are having low fuel rail pressure problems, it can be caused by quite a few different things including the fuel rail pressure sensor, fuel rail pressure solenoid, Cascade overflow valve on top of CP3, and Fuel Quantity Solenoid on back of CP3 injection pump.
Lack of adequate fuel flow to the CP3 can also cause improper fuel rail pressure. If the CP3 cannot get the required amount of fuel, it cannot build the fuel rail pressure as needed.
A bad fuel injector,leaking, can also cause low pressure problems.
Everything thing must be ruled out one at a time to find the problem. Either you are not getting enough fuel or something is dumping (losing) the fuel rail pressure. It could also be an electronic control issue causing it? This is not an easy one to diagnose unfortunately! :cry:

Quote:

Fuel Rail Pressure Too Low

For a test: You could disconnect the hose from the fuel return line plastic block and see how much fuel is being returned to the fuel tank. If it is a lot of fuel, then you must determine by disconnecting each item one at a time and find out if it is coming from the fuel pressure solenoid, the CP3, or a fuel injector.

Watch this video testing the Fuel Rail Pressure Solenoid (regulator): https://www.youtube.com/watch?v=tqW1dNp ... Automotive

Thanks WWDiesel for all the artwork.

All these things collected together make the job far more interesting. Since there is a lot of intricate timing elements connected with fuel delivery, I suppose that the Fuel Pressure Regulator solenoid fires in between the injector firings.

Dean.

WWDiesel · **Posted:** Tue Sep 19, 2023 3:22 am

cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides accurate time and amplitude measurements of voltage signals
The CRO uses a cathode ray tube to display the waveform on the screen, while the DSO converts an analogue signal into a digital one, allowing it to store an image of the waveform.

DBR? Sure you don't mean DRB?

CaptainDean · **Joined:** Thu Oct 05, 2017 2:22 am **Posts:** 673

layback40 referred to "...a PDF about the fuel system that shows a signal on a screen of a DBR scanner..." I don't know if DBR is a typo or not.

So I Googled "DBR scanner" and found a link that provided a name as Diagnostic Reader Box.

This is all new to me. It seems to be a big brother to the OBDII code reader that can gain reading and writing access to the Transmission and Body control modules. That link also mentioned a price of $6000. Whew - may as well be part of the Space Shuttle.

Dean.

layback40 · **Posted:** Wed Sep 20, 2023 5:59 am

CaptainDean wrote:

layback40 referred to "...a PDF about the fuel system that shows a signal on a screen of a DBR scanner..." I don't know if DBR is a typo or not.

So I Googled "DBR scanner" and found a link that provided a name as Diagnostic Reader Box.

This is all new to me. It seems to be a big brother to the OBDII code reader that can gain reading and writing access to the Transmission and Body control modules. That link also mentioned a price of $6000. Whew - may as well be part of the Space Shuttle.

Dean.

Hi Dean,
For some reason, unknown to me, my post has gone.
The scanner I referred to is what Chrysler/Jeep dealers use.
The dealer nearest to me quoted me $250 to do a full scan with their scanner.
Its more like a tablet than the small handheld scanners most of us use.
It will look at all modules, even the ABS one.
They do have a small handheld version they use in their workshop.
The PDF I mention is a training presentation.
IIRC it gave information about the pressure control solenoid under different conditions like WOT under load.
The CRO I have has allowed me to look at the pulse signals. I was something I was able to get on a long term loan.
The app that WW has helped you get will probably do all that is needed. I was going to try an app that uses the audio input of a smart phone but the CRO was handed to me first. I had used one previously decades ago at University.
The signal to the pressure control solenoid for mine looks fine, next I am going to look at the quantity one on the CP3.
Probably will look at the GP pulse signal as well.
I am not getting high enough signal from the rail pressure solenoid. I have replaced it & got a small increase in the signal.
As my background is in process control & this probably dictates my approach.
Will keep you guys posted on what I find.

WWDiesel · **Posted:** Wed Sep 20, 2023 12:45 pm

FYI
There are some DRBIII Emulators available that runs on a laptop.
Much cheaper $ than the original Mopar tool itself and is supposed to be capable of doing everything the expensive Mopar DRBIII is capable of doing and then some.
I have not purchased the product, so I can attest to its validity. :wink:

AE Tools & Computers wrote:

DRB III Emulator
This is the exact scan tool software application used in Chrysler, Jeep, and Dodge dealerships to service non-CAN based vehicles from 1998-2007. The DRB III Emulator software application now runs on your personal computer and interfaces with the DRB III+ hardware device to enable all the functions of the original Chrysler DRB III Scan Tool and more. This software package even comes with non-powertrain ECU programming files to enable reflashing everything from BCMs to sliding door modules. Optional Multiplex Cable for Sprinter and Crossfire.

Hard to find noise -- clinking and clanking

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