Its my understanding that if you pull the banjo bolt off the top of the PRV and fuel comes out while the truck is running at idle... its bad. Mine is currently doing this. I've also recently been told that this is ok and its just a "myth" that fuel shouldn't leak from it. It would make sense that no fuel should pass the PRV at idle pressures. Who is right?? I just want it correct.
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Fuel Rail PRV leaking...is it supposed too??
- Thread starter TSPowell
- Start Date
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You should have no fuel leaking from the PRV at idle. The pop pressure on the PRV is 26. 5k psi, if it is leaking at idle of 6500 psi it is bad.
The caveat is there will always be fule in the PRV well because it is ties into the injector return line. You need to isolate the line you pulled off the top so it can't leak fuel into the well, and, clean and dry the well before testing for leaks.
The caveat is there will always be fule in the PRV well because it is ties into the injector return line. You need to isolate the line you pulled off the top so it can't leak fuel into the well, and, clean and dry the well before testing for leaks.
Im just trying to understand whats going on mechanically, but it seems like this test would diagnose problems with the FCA. Can you explain more...
TC you've got some of us confused. Wasn't the procedure you described for testing the FCA and not the PRV?
No, by unplugging the FCA, you max rail pressure, needed to actuate a bad rail pressure relief valve... .
Yes, that is expected, but, he is giving the same instructions he posted for testing for a bad FCA, the recover to normal idle time specs. The PRV leaking will generally not cause idle problems.
Now you can add to that confusion with income tax discussion thrown in. :-laf:-laf Mod your FICA carefully or the IRS will throw exceptions your way.
ok lets try again you did the correct thing with the bag. now that it is still leaking there is only two things it can be. the most likely the prv is bad however there is a slim chance the rail pressure is higher than 26,000 lbs at idle where it should be 5,000 there is two main things that cause this and one rare thing. tc was trying to give you a way to further isolate it. i take a slightly different approach, if the prv is operated very many times it ruins it and will leak at idle or pop off at lower pressure. the most common cause of the rail pressure peaking above the 26. 5k is the fca sticking intermittently. if you just change the prv you only have about 50-50 chance you have fixed the problem if it was something else that caused the peak's it will eventually ruin the new prv. by unpluging the fca the rail pressure will peg a 30,000 gauge causing the prv to open most times but not all. for you i would go to genosgarage.com and get the complete rail with prv and sensor for $299 and a auto meter rail pressure gauge for $149. 95 change the prv and rail sensor and mount the gauge on the steering wheel collum with velcro leave the light off of it. now start it up, i have found the auto meter gauges are not real accurate so readings may very by as much as 20% but will do for what we want. at idle you should see about 5,000 lbs should peak around 22,000 if you have a intermittent problem you will see the gauge go full scale, feel a surge in power and a rattle if the fca is sticking it may only last a few seconds and go back to running normal try running 1 quart 2 cycle oil and 1 quart dextron iii oil. this will fix a lot of them.
Thanks for answering my question Todd. Now if I can only remember all this when it comes time to use it. . :-laf
Ok gotcha, didn't know or maybe forgot... about the other posting. Yes you are correct about PRV not causing idle problems unless really leaking bad or stuck open from debris.
I'm not sure I agree with your statement. A good PLV should never pop off below it's rated pressure. When you shut down the engine the pressure should not peak, and certainly not higher than the rated PLV pressure. The valve is only good for a limited number of pop offs, so from what you said, every valve would fail in a very short time. The 6. 7's have a counter that counts the number of times the valve pops, and it must be replaced when it hits the limit. Without looking it up I believe it is about 50 times.
This is the correct way to test a PLV.
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I am deleting every Possible post ,Pictures everything Possible... I will be asking Robin or Brandon to delete every Post I have made Here at the TDR... I am tried of being call a lair by the so-called experts. Bob the valve always has fuel in it... So what happens to the water thats in even a small amount of fuel... Thats right its always at the bottom... So what do You think is going to happen to the Valve... Hmmmmmm If any Members wants picture to Prove this ,call or email I will send them to You. You Can post them But be prepare some will just dis-credit and call you a lair and try to bring You down to their Level. I think some get a Personal High off of taring down, that way they can think big of themselves.
TC, I didn't mean to offend you, and I see you have offered and helped many members on TDR over the years.
That being said, I think I can safely say I have attended more Cummins diesel factory training than anyone on this forum. I have gained the knowledge of the operation of Cummins engine and fuel systems from some of the best Chrysler and Cummins instructors and engineers. I back up my information with factory service information.
So when I see something that goes against the things I have learned personally from Cummins and Chrysler I make my best effort to provide the members here with factual information that is available to those Dealer professionals that repair the Cummins we all love.
At times we may not agree, but that does not mean I discount all the things you have done for the good of the other members here. It is up to them to decide what information is correct for their situation, but me sitting back and ignoring posts that do not make sense to what I have leaned over my 32 years in this business is also a disservice to them.
And while I'm at it, this first section is straight from the Chrysler student training manual concerning the PLV. The second section is straight from the factory service information (2006 MY) for the proper testing of the PLV.
Figure 34 Fuel Rail Pressure Limiting Valve
The fuel rail pressure limiting valve uses a knife-edge seal and is threaded into the front of the
common rail. It is a dual stage, mechanical relief valve. The first stage relieves fuel rail pressure if
pressure exceeds 1,950 bar (28,282 psi). The second stage of the valve maintains pressure at 900
bar (13,053 psi).
The PCM can detect a fuel limiting event based on data from the fuel rail pressure sensor. The PCM
counts any fuel limiting events that occur and stores the data in memory. The wiTECH™ can display
the PCM fuel limiting counter data.
The valve can be replaced, but it must be inspected for leaks under operating pressures.
PRESSURE LIMITING VALVE
--------------------------------------------------------------------------------
1. Using the scan tool, measure the rail pressure and determine if the rail pressure is excessive (above 185,000 kpa/26,831 psi), if it is, troubleshoot for excessive rail pressure first.
2. Remove the banjo bolt from the pressure-limiting valve on the fuel rail.
3. Install fuel system test fitting ( 9013 ) into the pressure-limiting valve.
4. Attach one end of a fuel hose to the fuel fitting and put the other end of the fuel hose into a container.
5. Perform the tests listed below to determine if the pressure-limiting valve is leaking.
6. a. Operate the engine at idle and watch for fuel flow into the fuel container.
7. b. Operate the engine at idle and actuate the high pressure safety valve test with the scan tool. Watch for fuel flow into the fuel container.
8. If fuel flows into the fuel container, replace the pressure-limiting valve. If fuel does not leak from the pressure-limiting valve, the test is complete.
9. NOTE: do not drive the vehicle with any portion of this test kit installed.
The photo I posted that was removed earlier tonight showed this procedure being performed in an actual Chrysler training class. I'm sorry if you disagree with the factory diagnostic information, but I feel compelled to provide the members here with the information the engineers that designed it determined was the proper repair information.
That being said, I think I can safely say I have attended more Cummins diesel factory training than anyone on this forum. I have gained the knowledge of the operation of Cummins engine and fuel systems from some of the best Chrysler and Cummins instructors and engineers. I back up my information with factory service information.
So when I see something that goes against the things I have learned personally from Cummins and Chrysler I make my best effort to provide the members here with factual information that is available to those Dealer professionals that repair the Cummins we all love.
At times we may not agree, but that does not mean I discount all the things you have done for the good of the other members here. It is up to them to decide what information is correct for their situation, but me sitting back and ignoring posts that do not make sense to what I have leaned over my 32 years in this business is also a disservice to them.
And while I'm at it, this first section is straight from the Chrysler student training manual concerning the PLV. The second section is straight from the factory service information (2006 MY) for the proper testing of the PLV.
Figure 34 Fuel Rail Pressure Limiting Valve
The fuel rail pressure limiting valve uses a knife-edge seal and is threaded into the front of the
common rail. It is a dual stage, mechanical relief valve. The first stage relieves fuel rail pressure if
pressure exceeds 1,950 bar (28,282 psi). The second stage of the valve maintains pressure at 900
bar (13,053 psi).
The PCM can detect a fuel limiting event based on data from the fuel rail pressure sensor. The PCM
counts any fuel limiting events that occur and stores the data in memory. The wiTECH™ can display
the PCM fuel limiting counter data.
The valve can be replaced, but it must be inspected for leaks under operating pressures.
PRESSURE LIMITING VALVE
--------------------------------------------------------------------------------
1. Using the scan tool, measure the rail pressure and determine if the rail pressure is excessive (above 185,000 kpa/26,831 psi), if it is, troubleshoot for excessive rail pressure first.
2. Remove the banjo bolt from the pressure-limiting valve on the fuel rail.
3. Install fuel system test fitting ( 9013 ) into the pressure-limiting valve.
4. Attach one end of a fuel hose to the fuel fitting and put the other end of the fuel hose into a container.
5. Perform the tests listed below to determine if the pressure-limiting valve is leaking.
6. a. Operate the engine at idle and watch for fuel flow into the fuel container.
7. b. Operate the engine at idle and actuate the high pressure safety valve test with the scan tool. Watch for fuel flow into the fuel container.
8. If fuel flows into the fuel container, replace the pressure-limiting valve. If fuel does not leak from the pressure-limiting valve, the test is complete.
9. NOTE: do not drive the vehicle with any portion of this test kit installed.
The photo I posted that was removed earlier tonight showed this procedure being performed in an actual Chrysler training class. I'm sorry if you disagree with the factory diagnostic information, but I feel compelled to provide the members here with the information the engineers that designed it determined was the proper repair information.
Nice post sag. A genuine effort to restore the dignity of all, not to mention the always excellent info you provide.
Thank you.- Status
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