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FCV failure related to fuel filter head failure?
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Author:  paulslund [ Fri Jun 17, 2011 12:15 pm ]
Post subject:  FCV failure related to fuel filter head failure?
Recently my CRD died on me. It turns out it was the old style fuel filter head that caused the malfunction (the same thing other people have posted where the connection appears to have burnt/melted, etc). But the CRD was also throwing a CEL light about a week before it happened. Now, I was scheduled to go in to have the new head installed and fuel filter replaced anyways, it just happened to die on me the day before I was supposed to go in.

However, one of the CEL codes is the FCV failure. I told him I didn't want it replaced until I did more research ($788 for the part alone, I believe). So of course I've found postings indicating that until my emissions test (not until next year thankfully) I can actually unplug the MAF and leave it be, and as a precaution unplug the FCV (precaution or necessity?).

The dealer called me back because he had gone a on course this past Monday and a part of the course was specific to the Liberty CRD (he had only really worked on the Grand Cherokee CRD). He said he would ask the instructor about what happened to me. He had a concern that the faulty FCV was the cause of the fuel filter head overheating and failing. He called to confirm that if I don't change the FCV, I run the risk it could cause the fuel filter head to fail again. (he keeps calling it the EGR throttle valve, but I know he is talking about the FCV as he printed out the diagnostic paper work for me).

I haven't read anything on here that would indicate the two items are related, but could this be true? Could it be that if I don't unplug the FCV and the MAF that the faulty FCV could cause another failure? Have I been risking anything not unplugging it since the replacement head was installed last week? (I plan to do it, just haven't gotten around to it yet).

I'm planning on having a GDE tune done which would disable the FCV and EGR and get rid of the CEL before my next emissions test anyways as it's cheaper than replacing the valve but I have to finish paying off the previous repair bill...not to mention that both my rear window control motors broke on me at the same time...so 600$ in window repairs (unfortunately it was not the item covered by the extended warranty, either).

Any thoughts?
Thanks in advance,
Paul
Author:  papaindigo [ Fri Jun 17, 2011 2:02 pm ]
Post subject:  Re: FCV failure related to fuel filter head failure?
EGR air flow control valve? If so it sound bogus to me. The heater puck in the 1st gen fuel head fails primarily because it's undersized for the power pushed thru it to heat the fuel hence it overheats and "burns" the sealant which causes a fuel out/air in leak and secondarily because it overheats worse if there is enough air in the fuel head so as to place the heater in air above the fuel. This can be made worse by an air leak at any one or more of the fuel line quick disconnect fittings between the fuel filter head and the tank (the fix for the latter is 1) lift pump; 2) in tank pump; or 3) just cut the stupid fittings out and replace with hose and hose clamps. I'm somewhat of a heretic with the 3rd suggestion as lots of folks are not fond of "sucker" fuel pumps and prefer "pusher" fuel pumps back by the tank. While I don't disagree with the preference I'm, I hate to say it, old enough to remember when virtually every vehicle in production had a cam driven fuel pump on the engine block that worked just fine, until the diaphragm died, with solid lines back to the fuel tank. IMHO the engineers have once again "improved" a functional design so it no longer works dependably (the benefit of a difficult to operate "quick" disconnect over a simple worm clamp totally escapes me but maybe that's why I'm not an automotive engineer).

The 2n gen head fixes 1 and 2 but won't help with 3. As far as I know none of that has anything to do with the above referenced FCV assuming that's what is being talked about.
Author:  onthehunt [ Fri Jun 17, 2011 2:26 pm ]
Post subject:  Re: FCV failure related to fuel filter head failure?
Quote:
secondarily because it overheats worse if there is enough air in the fuel head so as to place the heater in air above the fuel.


How does the heater get exposed to air when the fuel must go through it first on the way to the fuel filter? If the engine wasn't running I could see that happening but with it running I don't think so. I believe the underspec terminals were the cause of all the failures. That was the only thing they changed.
Author:  warp2diesel [ Fri Jun 17, 2011 2:37 pm ]
Post subject:  Re: FCV failure related to fuel filter head failure?
papaindigo wrote:
I hate to say it, old enough to remember when virtually every vehicle in production had a cam driven fuel pump on the engine block that worked just fine, until the diaphragm died, with solid lines back to the fuel tank.

Like some, I am old enough to have worked with the Cam Driven sucker fuel pumps.
Cam driven fuel pumps work great as long as you are dumping the fuel into a Carburetor bowl where all the bubbles that come in can float to the top and get sucked into the intake. With any diesel made after Robert Bosch invented and started producing the injection pump (Rudolph Diesel's engine had a carb and a small injection cylinder that injected a very rich fuel air mix), air bubbles are a big PIA.
The newer the generation of the diesel (very few exceptions), the bigger of a PIA the bubbles are.
Author:  papaindigo [ Fri Jun 17, 2011 2:48 pm ]
Post subject:  Re: FCV failure related to fuel filter head failure?
You have to consider the internal geometry of the filter head. Viewed from the front fuel comes in from the hose that enters on the passenger side lowish (hose comes up along the firewall) and then fuel goes thru the filter. The fuel pickup hose and fitting "appears" to be on the top of the filter head and the hose runs off toward the engine. This appearance is deceptive as the actual internal pickup is the "tube" that the filter screws onto which extends down inside the filter (e.g. below where the filter rim/gasket engages the bottom of the fuel head) hence the fuel pickup point is actually down inside the filter. In contrast the heater element is up inside the filter head well above the top of the filter. If air gets into the head it "pools" at the top of the assembly until the bottom of the air pool is sufficiently far down into the filter (well below the heater) to where the pickup tube starts to suck air; hence the engine stall symptom. When you bleed the head what you are doing is venting the air in the top of the head out thru the bleeder screw which is also located pretty much at the high point inside the filter head.

Incoming fuel doesn't so much go "through" the heater element so much as it goes past it when the heater element is immersed in the fuel at the top of the filter head if everything is working right.

I concur with warp2diesel's comments on bubbles. My only old history point was elimination of the source of the bubbles by cutting out the quick disconnect fittings is an approach. In fact as far as I know those that install intank pumps do cut out the inline quick disconnect fittings for just that reason. Alternatively to any pump suggestion you can use BlackLibertyCRD's interesting automatic bleeder rig that simply dumps any air back into the fuel return line.
Author:  onthehunt [ Fri Jun 17, 2011 3:37 pm ]
Post subject:  Re: FCV failure related to fuel filter head failure?
The fuel passes through(or whatever you would like to call it) the fuel heater before entering the filter. How does the heater overheat due to being exposed to air? If you had that much air the vehicle wouldn't run. You can't have that much air trapped to expose the heater and have a running CRD.
Author:  Joe Romas [ Fri Jun 17, 2011 4:05 pm ]
Post subject:  Re: FCV failure related to fuel filter head failure?
The fuel filter is the hightest part in the fuel system.
Air being lighter then fuel is trapped in the hightest part of the system, the fuel head :jester:
Fuel heater overheats and melts connecter :frankie:

I have my original 5 year old fuel head and have no leaks but I've had a lift pump from early on.
When they started melting way back when a member looked up the properties of the plastic used and it should be good beyond any normal temperatures. Normal would be a fuel head full of fuel and not air :ROTFL:

Papa.

Most of us who have put on intank lift pumps did NOT cut out the original plastic o ring couplers. They work fine under pressure just tend to leak when under a vacuum
And the fact our fuel system is under a vacuum until it reaches the CP3 pump is at the root of the problem.
Author:  dgeist [ Fri Jun 17, 2011 4:48 pm ]
Post subject:  Re: FCV failure related to fuel filter head failure?
paulslund wrote:

I'm planning on having a GDE tune done which would disable the FCV and EGR and get rid of the CEL before my next emissions test anyways as it's cheaper than replacing the valve but I have to finish paying off the previous repair bill...not to mention that both my rear window control motors broke on me at the same time...so 600$ in window repairs (unfortunately it was not the item covered by the extended warranty, either).

Any thoughts?
Thanks in advance,
Paul


I think your dealer doesn't understand basic mechanics and fluid dynamics. How in the world could a faulty flapper valve on the intake manifold cause a fuel filter head to develop a leak? The FCV can be disabled if it dies by simply unplugging the connector on it (assuming it died...open). The gears in mine stripped themselves about a year ago and I disconnected it to prevent further damage...and promptly forgot about it. No CEL, no perceivable difference driving, etc. Try unplugging it and clearing the codes and see if the code comes back :)

With respect to the GDE tune, it doesn't disable the EGR and FCV, it just reduces their use a LOT. In fact, GDE will tell you that in certain circumstances, it's marginally helpful for the seals in the engine if the FCV actuates a little. That said, I also have the GDE tune and having no FCV hasn't effected it either.

Dan
Author:  papaindigo [ Fri Jun 17, 2011 4:50 pm ]
Post subject:  Re: FCV failure related to fuel filter head failure?
Joe - thanks for the clarity on fittings and intank pumps although I think if I did an intank pump (no air problems right now and I have lift pump on hand if I need one) I'd personally replace those fittings. Just personal bias as I had a very difficult time with similar fittings failing on a gasoline system that was under mild pressure; no fire but lots of dripped gasoline until extra "O" rings sealed the fitting. As I noted earlier I'm not fond of the design which IMHO is an overly complex solution to a non-problem.
Author:  geordi [ Fri Jun 17, 2011 5:01 pm ]
Post subject:  Re: FCV failure related to fuel filter head failure?
Simple and clear answers for you:

There is ZERO CONNECTION between the failure of the FCV and the fuel head. NONE.

The fuel head fails because despite what onthehunt thinks, a suction system cannot EVER completely fill all the voids in a system where the highest point (the heater head) is ABOVE the fuel injection pump. Air will collect there, and because that is a suction side, the incoming fuel will only fill in enough to balance against the already existing air pressure. The air will not be extracted. The heater overheats due to the air, and melts the plastic. You are lucky that it only leaked, and not caused another fire. (There have been several)

The FCV will ALWAYS fail OPEN, it has a giant spring that forces the valve open. The motor (when it works) can only shut the valve. The sound you hear after you key off is the spring fighting the motor to re-open the valve, the motor is powered off.

Your dealer mechanic is a moron. He is only following the "never let the customer leave with a full wallet" clause in their directions.
Author:  paulslund [ Sat Jun 18, 2011 12:03 am ]
Post subject:  Re: FCV failure related to fuel filter head failure?
geordi wrote:
Simple and clear answers for you:

There is ZERO CONNECTION between the failure of the FCV and the fuel head. NONE.

The fuel head fails because despite what onthehunt thinks, a suction system cannot EVER completely fill all the voids in a system where the highest point (the heater head) is ABOVE the fuel injection pump. Air will collect there, and because that is a suction side, the incoming fuel will only fill in enough to balance against the already existing air pressure. The air will not be extracted. The heater overheats due to the air, and melts the plastic. You are lucky that it only leaked, and not caused another fire. (There have been several)

The FCV will ALWAYS fail OPEN, it has a giant spring that forces the valve open. The motor (when it works) can only shut the valve. The sound you hear after you key off is the spring fighting the motor to re-open the valve, the motor is powered off.

Your dealer mechanic is a moron. He is only following the "never let the customer leave with a full wallet" clause in their directions.


Thanks...I hate that directive of mechanics. I did find it a bit odd that they would say it could have been the cause...I think their theory was that if the valve wasn't working properly it might draw more fuel than normal and strain the filter head??? I don't know, but I did know that it sounded a little odd.

Is there any risk that the FCV valve can fail closed? It doesn't sound like it, but should I somehow check anyways? Of am I safe just unplugging it and the MAF and be done with it. Actually, if I only unplug the FCV, does that disable the EGR, or should I also unplug the MAF? I don't have a code scanner so I can't clear the codes without going to a dealer, unfortunately...unless there is a trick to it.

Thanks for the input everyone
Paul.
Author:  papaindigo [ Sat Jun 18, 2011 8:02 am ]
Post subject:  Re: FCV failure related to fuel filter head failure?
I'll let geordi or someone else more familiar with that system reply but with respect to code clearing you are not necessarily limited to the dealer. Places like Autozone often but not always have code readers that can communicate with our KJs and clear codes which they generally will do for free.
Author:  geordi [ Sat Jun 18, 2011 11:16 am ]
Post subject:  Re: FCV failure related to fuel filter head failure?
Here's a sad thing - Diagnosing our CRDs and dealing with their problems is EASIER than trying to hack a previously un-hacked iphone when Lord Steve Jobs has decreed that you shall not fork with his devices. Oy... Going on 12 hours now fighting with this thing.

As to the codes - You can clear the idiot light with just about any code reader. A few members here have one of the cheap ones from Actron (I think thats the name) from AutoZone or Advance Auto. Its like $40 or so for the scanner, and its an ugly orange little thing.

Now, the bad news: You WILL get that idiot light back every single time you start your engine, if you have the EGR, FCV, or MAF unplugged. (Or all three)
The FCV is ONLY used as part of the EGR system, to force even more abrasive soot back into your engine than would normally flow. It does NOT assist in a "soft shut down" at all. Like I said before, when you turn the key off, the power to that thing is cut instantly. What you hear grinding is that big spring forcing the FCV back open against the unpowered motor gears. This is why the gears strip, IMHO. They are plastic, and that spring is STRONG. The default position is open, there is no way that I can think of for the FCV to ever fail closed. So good news there.

Back to the fuel manager for a second - The ONLY way to completely prevent a fuel heater failure (When it is plugged in, of course) is to put the fuel system under positive pressure - A lift pump by the tank is the easiest way. There are lots of threads about this, search on "Mr Gasket Pump" and you should find the info.

Now... Fixing the codes once and for all. You can always just clear the idiot light every time you start, leave the MAF disconnected, and just live with it. This is the cheapest option, but messy.

A more elegant solution comes from one of the members here, TurboTim. He developed a small circuit that you can build yourself (or have built) which will satisfy the computer's nanny checks about the EGR... And electrically UNPLUG it so it cannot EVER activate. No idiot light. The device is called the SEGR device, there are threads about it all over the board. I have one of these, and it is a wonderful device.
This will require careful cutting into the wiring harness of the computer to install, which I know can be a scary proposition. Cost is about $100.

Least invasive, but may not *completely* remove the EGR due to legal restrictions (that I understand and will NOT discuss in open forum, to avoid risk to them) is a complete engine tune from Green Diesel Engineering. The EGR function is greatly reduced to a minuscule amount. The FCV is not used at all AFAIK, and the MAF sensor and "Mercedes Logo Sensor" (Another MAP sensor used by the nanny-system) are basically deleted from the computer.
You don't even need to open the hood with this one if you don't want to - The Flash Tool is a scan tool AND a tuning device that will reprogram the engine computer directly. Or you can pull the computer and send it to GDE, who will program and overnight it back to you. 3 days downtime, but WELL worth the $500 cost. As a side benefit of the tune, you get greatly increased economy, power, and a return to the way this engine is SUPPOSED to perform, all VERY well tested to remain within the manufacturers tolerances.

With the GDE, I don't know if you could completely unplug the FCV or EGR without getting a code. I have BOTH the SEGR device and the GDE eco-tune, so I know that even if the computer tries to use the EGR or FCV... Neither will work. This is probably overkill, but it keeps the computer happy. The MAF code might re-appear once every 6 months or so, but I believe that is only b/c I still have it connected, and need to get an updated program from GDE (who provides AWESOME levels of support to the CRD crowd). I can deal with that.
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