Exploded view of a Common Rail...?

[fkovalski]

Does anyone have an image of an exploded view or cut-away view of the actual common rail. I am interested in looking at the stuff inside this one:

http://www.genosgarage.com/CUMMINS-4929618-FUEL-INJECTION-RAIL-03-07-59L/productinfo/4929618/

 

[AH64ID]

T&C diesel may have some photos on his website, but otherwise I haven't ever seen one.

 

[sag2]

Their really isn't anything inside to look at. It is just a hollow manifold that holds a volume of fuel, kind of acting like a small pressure stabilizing tank to feed the injectors without pressure pulses. It has inlet, outlet and pressure sensor ports.
Think of it as a high strength lawn sprinkler valve manifold where the valves are the injectors. It is as simple as that.

 

[fkovalski]

The reason I ask is that I would like to know if there some sort of check ball that acts as some sort of check valve inside it?

 

[LHirshman]

Aside from the connections to the six injectors on the rail, there is the pressure sensor and an over pressure pop-off valve. This valve has a burst disk inside it that bursts when a pressure pulse that is too high occurs. It is a one time use item and needs to be replaced when it opens. One symptom is long cranking times to start the engine when cold.

 

[sag2]

The reason I ask is that I would like to know if there some sort of check ball that acts as some sort of check valve inside it?

Nothing inside, it is just a manifold.

 

[Joseph Donnelly]

If all you want is an empty manifold, I have one a lot cheaper than the one you saw with the sensors etc. on it.

 

[fkovalski]

Aside from the connections to the six injectors on the rail, there is the pressure sensor and an over pressure pop-off valve. This valve has a burst disk inside it that bursts when a pressure pulse that is too high occurs. It is a one time use item and needs to be replaced when it opens. One symptom is long cranking times to start the engine when cold.

If this "pop-off" valve burst, are there other symptoms from what you describe? Will there be a smell of diesel? Starting on my truck is fine as long as the heater grid cycles fully.



Bear with me... I am still trying to diagnose some issues on my truck and a local shop mentioned that a ball-type check valve could be causing the synonyms. I see in the latest Genos catalog that there is a fuel return check valve that is a separate component. If this component goes bad, what are the symptoms? Will it affect performance?

 

[LHirshman]

Let me relay the full story. I had put a rail pressure box on my truck. After one full throttle acceleration getting onto a highway the pressure spike must have burst the pop-off valve. I did not notice anything until I tried to start the truck the next day, it took about 15 seconds of cranking before it would start. When cold, below 40ºF, it would not start at all unless I plugged in the engine block heater. Also my fuel mileage dropped by about 3MPG. This went on for about a year and a half. I read many posts here on the TDR which ultimately lead me to the problem. As they say here, you are your own warranty station if you change your truck.

There are no outwardly visible signs that this valve is open. On the top of this valve is a Banjo fitting with a hollow bolt that returns bypassed fuel to the tank if the valve is open. You can remove this bolt and look to see if it is wet with fuel or dry. It should be dry. If it is wet, you need a new valve. I have not used the pressure box since.

 

[AH64ID]

The way I understand it is the valve regulates on a regular basis when you shut the truck down, especially on a cold motor. The pressure goes from 6-7K to 26K plus when shutting a cold motor down, that is enough to crack the HPRV, so wet is not always an indication of bad.

 

[cerberusiam]

The pressure goes from 6-7K to 26K plus when shutting a cold motor down, that is enough to crack the HPRV, so wet is not always an indication of bad.

Exactly. The are called a PRV for a reason, the insane spikes that the rail can see at shutdown or liffting off the throttle quickly. Reportedly, spikes on a stock fueling curve can easily hit 30k psi. You don't want to know what they can hit with a programmer.

 

[fkovalski]

OK... I will get more to the point, IF this PRV is bad, will I get a rattling that sounds like detonation upon acceleration?





Furthermore...

... I am still trying to diagnose some issues on my truck and a local shop mentioned that a ball-type check valve could be causing the synonyms. I see in the latest Genos catalog that there is a fuel return check valve that is a separate component. If this component goes bad, what are the symptoms? Will it affect performance?

This check valve component of which I mention... if it is defective, will I get a rattling that sounds like detonation upon acceleration?



I am trying to try and figure out what sounds like detonation as described IN THIS THREAD.



I have had dealers acknowledge the pinging sound but stating that it is normal. NO, it is not normal. I was never this way and low and behold there happened to be a used truck on the lot exactly as mine right down to the same manual transmission when 2 were offered on this year. It sounded and performed the way mine used to before these drivability issues.



I had a mechanic tell me that wrong injectors may have been installed in my truck by an aftermarket diesel injection service and injector rebuild shop. The mechanic told me that the symptoms of what I describe which include the pinging/ detonation sound, the lack of power upon accelerating (until speed builds up) and most significantly, NO smoke when accelerating! All of this he says could be to incorrect (too small) injectors being installed. He feels that there is not enough fuel being delivered which is causing the lack of power which cause a lack of turbo boost (until RPM comes up) and most importantly he states that having no smoke is not right especially at my altitude (9,300 feet. )



My truck even when new smoke pretty good at this altitude. Now it is not doing that now.



I am frustrated and p!ssed and after dishing out some $2,800 for the new injectors it is running worse than when before. The diesel service shop is telling me it is normal. Bu!!$#!t! The truck is running like crap and it is ******* me off because I know that it is not normal having owned it since new.



the diesel shop that did the injectors told me to run the truck with my camper on at 3,000 RPM while hauling the load to really heat up the engine to burn off any carbon that might be causing detonation. I am beginning to think it is not detonation because the "working" of the engine as described has made no difference. Adding a cetane additive makes no difference. Hence all my questions about the fuel delivery system questions.



The tech who suspects that too small injectors are the culprit says that this check valve external to the common rail can make noise if there is a programmer on an engine with stock size injectors. he thinks that perhaps I have normal pressure (I have no programmers or chips) but the normal pressure on too small injectors could cause this rattling sound along with all the performance symptoms I describe.



Apologies for the dissertation rant, but any truth to what I describe?

 

[AH64ID]

The pinging you are describing sounds like timing rattle, which is normal and common on your era of truck. It may come and go with ambient temp changes, and fuel quality. An increase in timing rattle is generally from too much rail pressure or timing (not too little pressure).

I don't think you can get too small of an injector, at least I have never heard of that possibility on a common rail.

Have you hooked up a scanner to check rail pressure?

I would guess that you have a MAP sensor or IAT sensor going out, they provide ambient pressure and temp, as well as intake temp and manifold pressure, to the ECM. If those are off the rail pressure and/or timing could be off and both of those are what causes the rattle to increase.

 

[LHirshman]

I would think if a MAP or IAT sensor is bad there would be a CEL. Fkovalski did not mention that, perhaps an oversight in his rant. I believe his symptoms sound like some of the posts about the FCA on the CP3 pump going bad. That would certainly limit fuel delivery. On that thought, could the fuel filter be plugged or the lift pump be bad. The CP3 is capable of drawing fuel from the tank with a bad lift pump. If there is no CEL the solution might be some thing simple.

 

[cerberusiam]

The only 2 check valves in the fuel system I am aware of are 1 in the CP-3 on the high pressure side to keep rail pressure from back feeding the high pressure circuit, and 1 in the back of the head to maintain a minimum pressure in the injector return circuit. The last one cannot in any way effect injection, the firts could but you should be able to see problems in the rail pressure in demanded vs actual. Since you have a newer CP-3 it is doubtful that is a problem but checking demanded vs actual across operating range should be done, with you camper and any other load also.

As AH46ID pointed out, MAP and IAT could be the source of the problem. Whne you have this low power in lower rpms have you mapped what boost and rail pressure are doing for a comparison? If there is an issue in the control systems for fuel or air you will almost always see something out of line there.

My truck has had timing rattle or whatever you want to call it from 50k on. It does not effect power so not sure we are hearing the same things, that rattle is hard to hear across the internet.

If you had it before you changed injectors then likely it is not the injectors causing it. However, if your power loss and lack of trubo spool started with the new injectors they might have put the wrong tips on them. Are they new or reman injectors? Every time these problems come up many of the issues can be traced directly back to the injectors. Unless you are buying Genuine Bosch new or certified reman there are so many potential problems nothing can ruled out.

Thaty help any or just confuse the issue?

 

[cerberusiam]

I would think if a MAP or IAT sensor is bad there would be a CEL.

FYI, neither of those sensors will trip a CEL or a DTC when they are not functioning correctly. Yes, if they short or go open you get DTC's but a lazy operation in their expected range or just wrong readings but still in the range will kill performance, casue ghost codes, and drive a person to drink.

 

[AH64ID]

I would think if a MAP or IAT sensor is bad there would be a CEL.

Only if they fail out of tolerance, and not just provide false readings.

If the rail pressure were too high or too low that would also set a CEL. To me it seems that the truck is doing what it thinks it should, but it's not what it should be doing.

 

[fkovalski]

Hey all, OP here. Thank you very much for constructive feedback! I am at the office and cannot reply in proper fashion... I will do so later today. But a couple of quick questions as far as terminology goes of which I am not familiar:

What is "DTC?"

What is "CEL"

BTW- dealer replaced the CP-3 and turbo at approx 70K miles(+/-) still on original in-tank transfer pump.

 

[AH64ID]

DTC is diagnostic trouble code, CEL is check engine light. They both appear the same on the dash.

 

[cerberusiam]

If you have a realtively new CP-3 and turbo the mechanical functions are probably not the source of issue. How many miles now?

DTC - diagnostic trouble code

CEL - check engine light, frequently also called a MIL - malfunction indicator light.


Don't knwo what gauges you have but at this point, but Boost, EGT, low side (LP), and high side (Rail) fuel pressure gauges would be extremely helpful in diagnostics.