Interesting findings after Dyno Days - Pressure Relief Valve Failures

[strokerschmoker]

On the top end the smoke didnt seem to change alot, there was some variation but not an ample amount. On low end it would get pregressively smokey'er according to how much I turned up the ramifier until the turbo spooled.

 

[JVolpe]

Not only the Pressure relief on the Common Rail but the Cascade inside the CP3 are sometimes not functioning within spec.

I kept getting low boost and lower power then what others where and I always had heated fuel in the tank... super heated from being pressurized and sent back to the tank because of these items being out of spec.

Superduty showed me how he did a by pass between the supply and return on the CP3 to maintain fuel supply... this is what lead me to finding a solution to my problem. Not only can a properly functioning pressure box make the symptoms worse, so can too high of pressure from an aftermarket lift pump.



I was testing an Essex pump and started at 20 psi at idle thinking I was getting lots of fuel... it was working against me... I lowered it to 15 and learned over time that the volume is what is needed, not a bunch of pressure and too much volume can make the out of spec parts show their problem even more.



The by pass that Superduty came up with makes sense because if your sending fuel back to the tank and the lift pump is working overtime to supply the demand for the engine, it now can take fuel from the by pass instead of trying to draw it all from the tank... heated. Heating fuel over and over can and will diminish its quality too.

The other way around applies too. If the lift pump is supplying too much pressure and/or fuel, it can dump through the by pass and return to the tank before it gets pressurized and heated.



Perhaps pressure boxes and/or high pressure pumps can cause this but I feel that the specs of the cascade and the pop off are weak in a lot of these trucks from new and the add on components although doing a good job at what they do are working against these issues.



Scotty

That is a very interesting post. I really dont think I have popped the rail pressure relief valve, but I do believe that I have a problem with fuel pressure and drive pressure. I can feel/see more potential power than I can acutally sustain. I will have to learn more about how to diagnose the issue. Of course $8,000-$10,000 worth of diagnostic equipment would help, but there are always more than one way to skin a cat.

 

[Tomeygun]

On the top end the smoke didnt seem to change alot, there was some variation but not an ample amount. On low end it would get pregressively smokey'er according to how much I turned up the ramifier until the turbo spooled.

what TST program? and what tires did you use when you dyno'ed? and lastly what kind of dyno?

 

[scotty1]

That is a very interesting post. I really dont think I have popped the rail pressure relief valve, but I do believe that I have a problem with fuel pressure and drive pressure. I can feel/see more potential power than I can acutally sustain. I will have to learn more about how to diagnose the issue. Of course $8,000-$10,000 worth of diagnostic equipment would help, but there are always more than one way to skin a cat.

Let me know if you learn more. I am sharing what I have encountered and so far the 'theory' makes sense and is working. I wonder if this by pass would work on helping the high HP rigs keep fuel in the rail? Isn't somewhere near 70% of the fuel returned to the tank? The by pass would enable the CP3 to take it from there? thinking out loud or... in text.



Scotty

 

[robertyoke]

Let me know if you learn more. I am sharing what I have encountered and so far the 'theory' makes sense and is working. I wonder if this by pass would work on helping the high HP rigs keep fuel in the rail? Isn't somewhere near 70% of the fuel returned to the tank? The by pass would enable the CP3 to take it from there? thinking out loud or... in text.



Scotty

I dont think that the problem lies in fuel getting to the cp3 it seems to be fuel going through the cp3 to the rail. some people are moding the cp3 to flow more fuel, from what i gather the passages from the internal transfer pump to the pistions is the flow restrictor. man I wish I had some pictures of the internals of the cp3..... santa are you listening.

-robert

 

[steved]

Now school me on this... am I reading this right: that only trucks that are running boxes that add pressure to the rail are being affected?? So basically a stock truck should be fine?



steved

 

[scotty1]

I dont think that the problem lies in fuel getting to the cp3 it seems to be fuel going through the cp3 to the rail. some people are moding the cp3 to flow more fuel, from what i gather the passages from the internal transfer pump to the pistions is the flow restrictor. man I wish I had some pictures of the internals of the cp3..... santa are you listening.

-robert

That would be nice to have. I wonder if the internal Cascade would limit the supply to the rail if its messed up? Its a theory for me, nothing tangible other then real world driving with a mildly modified truck.



I know when I ran stock my truck ran well but still felt weak compared to other stock trucks... it just seemed to be sluggish and I would get an intermittant 'burp' that would not trip the CEL.

With a pressure box [any brand] and higher pressure lift pump... I would get the CEL... now and then. Plus I always would have super heated fuel in the tank.

I started wondering about the fuel on a spring day this year when I was at about 1/4 tank, I opened the fuel cap and I saw steam come rushing out.

Instead of filling I went and got the infra red and had a temp at the tank of 179F after a run down the highway for about 20 miles.

The lower the fuel the hotter it got which leads me to think that if its getting recirculated and sent back over and over, it would compound the result and with less fuel to help dissipate the heat... well, you get the idea.



just sharing what I have stumbled across.



I agree, the next thing that restricts these trucks is the CP3's ability to supply the rail. And that brings me back to the Cascade, if its out of spec, its only going to show a problem sooner. Maybe the high HP trucks will be more prone to this and the stock supply will never be enough but having something out of spec can and will amplify the problems. Make sense?



More coffee needed



Scotty

 

[strokerschmoker]

I was using the standard tst program that they used when I bought it about a year ago. As for the tires, I was on the factory set that came on the truck when I bought it. The dyno was a dyno-jet (model 248 i think).

 

[Tomeygun]

I was using the standard tst program that they used when I bought it about a year ago. As for the tires, I was on the factory set that came on the truck when I bought it. The dyno was a dyno-jet (model 248 i think).

All I can think of is that a DYNOjet can be funky to get correct number off of - Do you know what you HP was with the TST at 0/0 - and the ramifier off?



I hit 196 I think, You should be close to the same with your SO - Heck the SO motors seem to be the easiest to get to 500



I am stumped, you have a pusher pump, so thats good...

hmmmmm... ... . All thses trucks with different HP, wierd

 

[robertyoke]

That would be nice to have. I wonder if the internal Cascade would limit the supply to the rail if its messed up? Its a theory for me, nothing tangible other then real world driving with a mildly modified truck.



I know when I ran stock my truck ran well but still felt weak compared to other stock trucks... it just seemed to be sluggish and I would get an intermittant 'burp' that would not trip the CEL.

With a pressure box [any brand] and higher pressure lift pump... I would get the CEL... now and then. Plus I always would have super heated fuel in the tank.

I started wondering about the fuel on a spring day this year when I was at about 1/4 tank, I opened the fuel cap and I saw steam come rushing out.

Instead of filling I went and got the infra red and had a temp at the tank of 179F after a run down the highway for about 20 miles.

The lower the fuel the hotter it got which leads me to think that if its getting recirculated and sent back over and over, it would compound the result and with less fuel to help dissipate the heat... well, you get the idea.



just sharing what I have stumbled across.



I agree, the next thing that restricts these trucks is the CP3's ability to supply the rail. And that brings me back to the Cascade, if its out of spec, its only going to show a problem sooner. Maybe the high HP trucks will be more prone to this and the stock supply will never be enough but having something out of spec can and will amplify the problems. Make sense?



More coffee needed



Scotty

after reading that, that does not sound right, I think you are returning fuel from the the rail for it to be that high temp. bad pressure limit valve or bad injector or connector tube???



the cp3 returns fuel to the tank via the cascade (over flow valve) before it enters the high pressure end of the pump( through the fuel control actuator). fuel that makes it to the rail is for injection and does not return to tank unless the pressure relief valve opens, or aleast that is how I understand it, but I could be wrong .

the fuel that lubes the pump would get hot and then it would make it back to the tank but it is a very small amount, and I dont know were it goes anyway it may go to the high pressure side?? and be used. if the cascade is weak it may return more fuel to the tank than is necessary?? and starve the pump?

I wish that there was more info on the internals on that pump.





steved, I dont run a pressure box on my truck just a tst box. I cant run all that box can deliver without running the rail down on a long pull. short term dyno run or drag race, the pressure box would give me more hp but untill I mod the cp3 I am not going to bother. and yea stock truck should be fine.

-robert

 

[steved]

steved, I dont run a pressure box on my truck just a tst box. I cant run all that box can deliver without running the rail down on a long pull. short term dyno run or drag race, the pressure box would give me more hp but untill I mod the cp3 I am not going to bother. and yea stock truck should be fine.

-robert

Robert:



Thank you for that clarification... I was wondering if this was something I might have need to check on mine once in a while since you can't actually tell when it is happening.



Thanks

steved

 

[SRadke]

I hit 196 I think, You should be close to the same with your SO - Heck the SO motors seem to be the easiest to get to 500

I hit 212hp stock on a Mustang and 250hp on a dynojet with 40 hp injectors.

 

[scotty1]

after reading that, that does not sound right, I think you are returning fuel from the the rail for it to be that high temp. bad pressure limit valve or bad injector or connector tube???



the cp3 returns fuel to the tank via the cascade (over flow valve) before it enters the high pressure end of the pump( through the fuel control actuator). fuel that makes it to the rail is for injection and does not return to tank unless the pressure relief valve opens, or aleast that is how I understand it, but I could be wrong .

the fuel that lubes the pump would get hot and then it would make it back to the tank but it is a very small amount, and I dont know were it goes anyway it may go to the high pressure side?? and be used. if the cascade is weak it may return more fuel to the tank than is necessary?? and starve the pump?

I wish that there was more info on the internals on that pump.





steved, I dont run a pressure box on my truck just a tst box. I cant run all that box can deliver without running the rail down on a long pull. short term dyno run or drag race, the pressure box would give me more hp but untill I mod the cp3 I am not going to bother. and yea stock truck should be fine.

-robert

Yeah, I follow exactly what your are saying.

What got me to thinking about the Cascade is the 'dealer' changed my pop off even though they said it was fine. We also tested the injectors, fuel volume from factory lift pump and all was within spec.

What is not clear for me is if that is all within spec, why the hot fuel and lower power?

Its something that has been on my mind during many a trip and if I/we could learn more about the CP3, perhaps we could determine more.



I should add that when they checked the fuel pressure values with the DRBIII

[I think thats what they used] The pressures where out of whack[lower then what was asked for], pointing towards something like the pop off. New pop off netted similar readings on the diagnostics. I will take the truck back there with the by pass and run another couple of tests with their gear. Maybe that will unveil something. Of course good ole DC says no code/no problem/no repair. I did have codes but once I took off the pressure box... no codes.

Running stock... I get the 'burp' and with the BDDL on Perf setting I get the 'burp' more often. Fuel tank is often warm even in the winter up here.

Not blaming the pressure box but I bet it amplfied the problem.



Dealer agrees there is something amiss and will test it with the by pass and help to narrow down the issue.



Like I said... its a theory and as we all know, theory's need to be proven or discredited and so far anyone that is in the 'know' is not devulging any info.

Whether its because they do not know or they do not want me to know... who knows? LOL



Scotty

 

[Tomeygun]

Yeah, I follow exactly what your are saying.

What got me to thinking about the Cascade is the 'dealer' changed my pop off even though they said it was fine. We also tested the injectors, fuel volume from factory lift pump and all was within spec.

What is not clear for me is if that is all within spec, why the hot fuel and lower power?

Its something that has been on my mind during many a trip and if I/we could learn more about the CP3, perhaps we could determine more.



I should add that when they checked the fuel pressure values with the DRBIII

[I think thats what they used] The pressures where out of whack[lower then what was asked for], pointing towards something like the pop off. New pop off netted similar readings on the diagnostics. I will take the truck back there with the by pass and run another couple of tests with their gear. Maybe that will unveil something. Of course good ole DC says no code/no problem/no repair. I did have codes but once I took off the pressure box... no codes.

Running stock... I get the 'burp' and with the BDDL on Perf setting I get the 'burp' more often. Fuel tank is often warm even in the winter up here.

Not blaming the pressure box but I bet it amplfied the problem.



Dealer agrees there is something amiss and will test it with the by pass and help to narrow down the issue.



Like I said... its a theory and as we all know, theory's need to be proven or discredited and so far anyone that is in the 'know' is not devulging any info.

Whether its because they do not know or they do not want me to know... who knows? LOL



Scotty

I forget, does our trucks have a fuel heater on the filter housing?



Maybe it is stuck on? (just thinking out loud)

 

[steved]

The fuel heater is on the housing... it is thermostatically controlled by an external temperature sensor (up near the driver's side of the grill IIRC).



I was wondering how the CP3 could make a tank of diesel "steam" by itself, but I'll be the first to admit I don't know much about the fuel delivery system once it gets to the CP3.



steved

 

[jhyatt]

dbr3 ill take two

 

[scotty1]

I forget, does our trucks have a fuel heater on the filter housing?



Maybe it is stuck on? (just thinking out loud)

I will look at that as well.



I know of another guy in Edmonton that was upgrading from his 01 to an 03 when the 03 first came out. He took it for a test drive and bought it over the phone but by the time he got back to do the paperwork the next day he had the same thing happening with that truck, steam from the tank. The low fuel light was on when he took it so he went to dump some fuel in and encountered this.

So the salesman takes it for a drive, opens the cap and steam rolls out.

He passed on the deal and never did find out what was wrong and now owns an 05.



Scotty

 

[KevinO]

your selling me a little short Tom i made 491 that day :-laf

 

[TCluff]

after reading that, that does not sound right, I think you are returning fuel from the the rail for it to be that high temp. bad pressure limit valve or bad injector or connector tube???



the cp3 returns fuel to the tank via the cascade (over flow valve) before it enters the high pressure end of the pump( through the fuel control actuator). fuel that makes it to the rail is for injection and does not return to tank unless the pressure relief valve opens, or aleast that is how I understand it, but I could be wrong .

the fuel that lubes the pump would get hot and then it would make it back to the tank but it is a very small amount, and I dont know were it goes anyway it may go to the high pressure side?? and be used. if the cascade is weak it may return more fuel to the tank than is necessary?? and starve the pump?

I wish that there was more info on the internals on that pump.





steved, I dont run a pressure box on my truck just a tst box. I cant run all that box can deliver without running the rail down on a long pull. short term dyno run or drag race, the pressure box would give me more hp but untill I mod the cp3 I am not going to bother. and yea stock truck should be fine.

-robert

the injectors also have a return, any fuel that is not used is sent to a return line on the rear of the cylinder head through internal passages in the cylinder head, the injectors have a check ball in them, a faulty check ball will dump most of your rail pressure back to return, and the only way to repair it is with new injectors or injector if you can find it, i too have been on a quest to cure a hard start, low rail pressure problem, i am on my second cp3, 3rd set of injectors and 3rd rail relief valve, changing the rail reliefs, cascade and fca had very little affect on the problem i had, we found the problem to be a bad injector dumping my rail pressure back to tank and they were brand new, there was nothing wrong with the stock and 3rd set of injectors, hope this helps

 

[scotty1]

the injectors also have a return, any fuel that is not used is sent to a return line on the rear of the cylinder head through internal passages in the cylinder head, the injectors have a check ball in them, a faulty check ball will dump most of your rail pressure back to return, and the only way to repair it is with new injectors or injector if you can find it, i too have been on a quest to cure a hard start, low rail pressure problem, i am on my second cp3, 3rd set of injectors and 3rd rail relief valve, changing the rail reliefs, cascade and fca had very little affect on the problem i had, we found the problem to be a bad injector dumping my rail pressure back to tank and they were brand new, there was nothing wrong with the stock and 3rd set of injectors, hope this helps

That would be pressurized/heated fuel dumping back to the tank correct?

Did you solve it with aftermarket injectors because Dodge 'claims' mine are fine. :-laf

I wondered about one being bad but of course Dodge said the tests said all is fine.

Steam from the fuel tank must be normal. LOL



Thanks for the post as it was once what I thought was the cause.

Its like a big pressurized leak and would or could cause the lift pump to work overtime then even if one is a dud... makes a lot of sense to me. I bet the 'burp' I get is when the injector messes up.



Scotty