Air in the fuel and fuel range, Ultimate Solution

retmil46 · **Posted:** Tue Jan 02, 2007 1:38 am

As far as whether or not the gear pump has enough suction to add in a prefilter, I'd have to say the answer is yes. I plumbed in a Permacool 2 micron filter/water separator ahead of the OEM filter about 10K miles ago, and haven't had any problems. As with all the OEM gear, you just have to make sure you don't have any air leaks.

Matter of fact, that Permacool filter has saved my backside a couple of times since they brought out ULSD. About a month ago, I had to stop for fuel on the way to work, at a station I don't normally use. About a week ago, when I was prepping the CRD for a trip to Texas, I drained down the Permacool filter, and couldn't believe the rust, dirt, and water that came draining out of it. It was so bad I junked the filter and put a fresh one on.

I found that I have the same problem on the OEM filter head, the gasket at the joint above the fuel heater leaking. Just repriming the system after draining down the Permacool filter puts enough pressure on it that you can actually watch fuel seeping out past the gasket. I imagine the reverse is happening when running, air getting sucked in.

Reading thru the FSM, you apparently have to replace the entire filter head if this gasket goes bad. That's about $150 if I remember correctly.

Short of that, the one stopgap fix I can think of would be to depressurize and drain down the filter, then put a bead of JB Weld, epoxy putty, or fuel resistant RTV over the joint. Sounds a lot better than $150 plus labor for replacing that POS filter head.

gsbrockman · **Posted:** Tue Jan 02, 2007 1:49 am

MrMopar64 wrote:

My experience with the lift pumps was with the engine on a dyno. I tried using pressures from 1psig up to 7-8psig and all had the same effects. What happens is that the internal gear pump on the CP3 delivers a certain pressure internally to the HP side of the CP3. By using a lift pump, you thus increase this pressure even more. The end result is that by having more pressure on the low-side, you throw off the calibration of the control of the HP metering unit (electric solenoid on the CP3). Additionally, force feeding the gear-driven suction is in no way approved by Bosch as per their documentation on the pumps.

I, too, am puzzled by all of this.

Could the FCA be re-calibrated ? When you say "Additionally, force feeding the gear-driven suction is in no way approved by Bosch as per their documentation on the pumps are you referring to the CP3 utilized only on the CRD's or all CP3's Bosch produces ?

Short of the HPCR Dodge RAM CTD's having a lift pump for easier re-starts after a fuel filter change, why does DC state in their service manuals that there's no specification for pressure---only volume ? The supply lines on the DuraMax are larger than on the CTD's....I'm guessing due to a lack of OEM lift pump and a larger displacement. Although a failed lift pump won't normally take out the CP3 in a Dodge HPCR CTD, it will stop it dead in its tracks within a few miles of failure......just because the CP3 can't "suck" fuel through a dead lift pump.

The aftermarket fuel systems for the HPCR CTD's (primarily FASS and Walbro) can supply upwards of 45---50 psi to the inlet side of the CP3. I've read of no complaints on either....short of some noise issues (loud) of the FASS systems. They also provide much better filtration as well.

Greg

Goglio704 · **Posted:** Tue Jan 02, 2007 2:16 am

It really wouldn't be hard to try this out. Maybe it works on the Cummins and Duramax because nobody told them it wouldn't. :lol:

A lift pump, 5 gal jug of diesel, 5 gallons free space in fuel tank, some 3/8" fuel hose, and you've got yourself a test rig. If stationary testing looks good, build on that. Maybe something was wrong with the pump in Mr. Mopar's test unit? I am not discounting what he said, but maybe there are some other variables. Retmil seems to have found the same section in the FSM that I remember reading and had the same interpretation I did. It would take somebody specialized in the inner workings of the injection pump to explain exactly why this won't work.

RFCRD · **Posted:** Tue Jan 02, 2007 5:37 am

retmil46 wrote:

I found that I have the same problem on the OEM filter head, the gasket at the joint above the fuel heater leaking. Just repriming the system after draining down the Permacool filter puts enough pressure on it that you can actually watch fuel seeping out past the gasket. I imagine the reverse is happening when running, air getting sucked in.

Has anyone disassembled this head/heater to know how this is held together? Intuitave guess that this is the mystery leak afflicting so many CRD's. Simply improving the gasket design could be the cheapest and most effective modification.

Jeger · **Posted:** Tue Jan 02, 2007 9:23 am

Ranger1 wrote:

I'm interested in your check valve idea, especially if one that fits inline with the rubber inlet hose is available. If anyone has a link to an inline check valve suitable for our CRD diesel fuel, I'd be interested.

www.microchek.com

I was going to use one of their valves for a releif valve on a homemade CCV filter but have never gotten around to it. I think they should have a check valve suitable for our application.

I would think a check valve followed by a prefilter then the stock filter then an air eliminator might fix a lot of problems. I am not sure if something like the gold top air vent found here would work or not.

www.murrayequipment.com also has some check valves and air eliminators listed if you search their site. No pictures of the air eliminators though.

I just dont think there is an air eliminator designed to work with a negative pressure system though. Anyone know of such a thing?

retmil46 · **Posted:** Tue Jan 02, 2007 12:03 pm

All you need to create an "air eliminator" in a closed fluid system is a low flow area to allow the entrained air to separate from the fluid stream, and a high point with enough volume to allow the air to rise up out of the fluid stream and remain trapped in the separator. Doesn't matter if the system is at negative or positive pressure, as long as pressure is equal across the separator.

Basically, you could take any type of filter housing (air, fuel, etc) that has a bowl type arrangement on the bottom of the housing (such as an oil or moisture filter for an air system), remove the filter, and then invert the housing such that the bowl is the high point. The bowl will provide the low flow area and high point out of the fluid stream for accumulation of the removed air.

On board submarines, there were such air traps designed into many of the fluid systems throughout the boat.

That's why the OEM filter accumulates air until it builds up to the point it starts getting sucked into the fuel pump - as designed, it's the high point in the system and the area of lowest flow. DC inadvertently designed a pretty good air trap. :roll:

Best place to put this type of separator would be between the outlet of the OEM filter and the fuel pump, and use a see-thru bowl so you could know when you were starting to accumulate air. You'd know that it was time to vent and reprime the OEM filter and possibly start searching for an air leak depending on how fast the air was accumulating.

Putting the separator between the OEM filter and fuel pump would also allow you to use the priming pump and check valve in the OEM filter to pressurize the separator and vent off any air, without having to add an extra check valve or having everything drain back to the tank.

Jeger · **Posted:** Tue Jan 02, 2007 12:24 pm

retmil46 wrote:

All you need to create an "air eliminator" in a closed fluid system is a low flow area to allow the entrained air to separate from the fluid stream, and a high point with enough volume to allow the air to rise up out of the fluid stream and remain trapped in the separator. Doesn't matter if the system is at negative or positive pressure, as long as pressure is equal across the separator.

Basically, you could take any type of filter housing (air, fuel, etc) that has a bowl type arrangement on the bottom of the housing (such as an oil or moisture filter for an air system), remove the filter, and then invert the housing such that the bowl is the high point. The bowl will provide the low flow area and high point out of the fluid stream for accumulation of the removed air.

On board submarines, there were such air traps designed into many of the fluid systems throughout the boat.

That's why the OEM filter accumulates air until it builds up to the point it starts getting sucked into the fuel pump - as designed, it's the high point in the system and the area of lowest flow. DC inadvertently designed a pretty good air trap. :roll:

Best place to put this type of separator would be between the outlet of the OEM filter and the fuel pump, and use a see-thru bowl so you could know when you were starting to accumulate air. You'd know that it was time to vent and reprime the OEM filter and possibly start searching for an air leak depending on how fast the air was accumulating.

Putting the separator between the OEM filter and fuel pump would also allow you to use the priming pump and check valve in the OEM filter to pressurize the separator and vent off any air, without having to add an extra check valve or having everything drain back to the tank.

I thought about my post for awhile and thought of using a settling bowl like you see on tractors and just flip it upside down like you said. Wouldnt be an automatic thing but with the clear bowl you could monitor it easily enough. Again like you said. :lol:

Soooo I guess the only question I have is how big would it need to be?

DarbyWalters · **Posted:** Tue Jan 02, 2007 12:26 pm

Sounds like a carb fuel bowl to me...glass window and all...lol

retmil46 · **Posted:** Tue Jan 02, 2007 12:39 pm

Jeger wrote:

Soooo I guess the only question I have is how big would it need to be?

Simple for me - whatever Northern Tool, Advance Auto, or Home Depot has on sale! :lol:

Goglio704 · **Posted:** Tue Jan 02, 2007 3:02 pm

A compressed air filter with a polycarbonate bowl and the filter element removed should work. What would normally be the drain, would become the vent.

Edit:

Was speed reading earlier, didn't realize a compressed air filter had been mentioned already. :oops:

kb61751 · **Posted:** Tue Jan 02, 2007 3:31 pm

Wouldn't you have to start with a bowl filled with fuel first, and then see if you have air in it. If you have air in it and open the vent (drain) while the engine is running, it would suck air in to the system, if you did this with the engine off, where would the extra fuel come from, while bleeding off the air? Maybe pumping the prime pump?

Goglio704 · **Posted:** Tue Jan 02, 2007 3:43 pm

You've answered your own questions. Yes, you would start with the bowl full of fuel. No, don't open it while running, and yes you would need to use the primer pump to displace the air.

Ripple · **Posted:** Tue Jan 02, 2007 8:17 pm

I found these nice filters from racor. it looks like this unit would be good to have right close to the tank, as a first line of defence.

http://www.go2marine.com/product.do?no= ... .mc_id=gb1

they have a sight bowl, check valve, 200watt electric heater and a screw on 2-micron filter. plus look like replacement filters could be scored at any marine shop.

Joe Romas · **Posted:** Tue Jan 02, 2007 8:58 pm

The filter does look nice but could it worsen our sucking air problem by increasing the vacume necessary to pump the fuel :?:

Goglio704 · **Posted:** Tue Jan 02, 2007 9:02 pm

Yes, if you have an air leak, an additional filter could make it worse.

RFCRD · **Posted:** Tue Jan 02, 2007 9:16 pm

Joe Romas wrote:

The filter does look nice but could it worsen our sucking air problem by increasing the vacume necessary to pump the fuel :?:

Very much so, especially if the two filter are separated (one by the engine and the other by the tank). Usually get the best results when the filters are directly in series. In cold climates, you are asking for trouble if you hang a filter in the wind near the tank.

Kniggit · **Posted:** Tue Jan 02, 2007 10:37 pm

New owner, Just reading up, but I know this wouldn't work because those automatic air vents are designed to work under pressure and most often relive vacuum. I know, I am a Hydronic heating Service person. There were some Steam vents that were designed to operate at a small amount of vacuum, but eventually relive the vacuum before the system turned on. Good idea though. I think the Fuel Bowl/Air filter idea is the best so far.

K

Jeger · **Posted:** Wed Jan 03, 2007 9:30 am

Kniggit wrote:

New owner, Just reading up, but I know this wouldn't work because those automatic air vents are designed to work under pressure and most often relive vacuum. I know, I am a Hydronic heating Service person. There were some Steam vents that were designed to operate at a small amount of vacuum, but eventually relive the vacuum before the system turned on. Good idea though. I think the Fuel Bowl/Air filter idea is the best so far.

K

Welcome, Kniggit!
I need to talk to you about some radiant floor heating :lol:

You should introduce yourself in the New member introductions section and let us know where you are from what you drive etc etc.

retmil46 · **Posted:** Wed Jan 03, 2007 12:02 pm

Did a quick google search last night for compressed air filters, came acros the website for MSC Industrial Supply Co. Looked thru the Pneumatic filter section to see what was available.

Looks like you could get a filter housing that would work for as low as $18. I'd say go with 1/4" NPT ports, 1/4 pipe pretty well matches our 3/8" ID fuel hose, also what is on the Permacool filter I already have installed and works fine with no restriction.

They had close to 15 pages of different filters listed just under this one section. The 1/4" NPT port models are the smallest and cheapest. Height seems to range from 4 1/2" and up, diameter from 1 3/4 to 3 inches. Pressure ratings ran up to 200 psi. Plenty of them have clear polycarbonate bowls with drain fittings.

First one listed, made by Ingersoll Rand, listed for 18 and change. 1/4" NPT ports, 200 psi rating, clear polycarbonate bowl with drain fitting, 4 1/2" height, 2" diameter.

For the price, sounds like this might be a good place to start.

retmil46 · **Posted:** Wed Jan 03, 2007 12:23 pm

Using an upside-down filter housing as an air trap/separator isn't going to cure your air leaks. Main idea is to keep air from getting sucked into the fuel pump and high pressure rail. To be effective, it needs to be as close to the pump as possible, downstream of all the potential leaks, so that it can catch all the air getting into the system.

It's also going to serve as an indicator as to whether or not you do have an air leak, and need to do some troubleshooting. It will also give you an idea of just how good a job the fuel filter is doing catching all the crud/water in the system.

At best, as RFCRD said, this is a band-aid fix until you could replace the fuel lines with some quality components.

Air in the fuel and fuel range, Ultimate Solution

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