QM & others, I'm pulling these comments from the Parallel Pump thread as I don't want to detract from that discussion for this one, which I think needs more discussion.

Mine makes about 3 psi at idle and abruptly drops to zero without heavy acceleration. I've tried numerous things to isolate the problem, but can't seem to do so. I've tried new Delphi pumps, checked voltage, wired the pump direct with a switch (bypassing the OPS) and other things I can't even remember.

Bill Heath has been walking through this with me from the beginning and he and I are both stumped. He did suggest that he had a customer a while back that had a similar problem and the guy plumbed in two lift pumps to cure his problem. I've been reluctant to do so because I didn't want to cut the factory lines. I just can't help but believe there has to be another solution, but don't have any idea what it is.

Keep in mind that this truck makes power. I do not notice a power loss at 0 psi. fuel pressure. It should buck and kick like a wild horse, but does not. At any rate, please post or PM me with pictures and a parts list of your dual pump set-up.

Thanks!
SnowDriftHave you tried clearing your lines with compressed, "dried" air?

Have you tried to blow down the lines with compressed air? I find that the fuel filter housing is prone to clogging internally and blowing air back down the fuel line into the IP and out the drain T will backflush the bowl and remove crap that otherwise woldn't be accessable. t

QM is this a byproduct of your grease added to fuel, I've never heard of #2 only"sludge/blockage" you are referencing occurring, except on a very-very cold morning with gelling of fuel heater is inoperative and no anti gel additive in use.

t

I'm meeting many 6.5L owners in my area. I put cards on thier trucks when I spot them around town. I do this to every truck I evalueate and so far everyone has blown big chunks of ??? particles out. If I'm the only guy doing this, fine but it's still profound that I'm running ~30% grease in my tank and a backflush on the filter every two weeks or so is all I've had to do. It seems to me that if thats where it clogs then that's where it clogs. t

If this is truly the case all the more evidence then for frame mounted filters, I just can't fathom solids collecting there, but if only filtration is the on engine 5 micron one; stuff larger than 5 micron has got to deposit somewhere I guess.



Maybe you have hit on something, next time you blow one try to capture what comes out, I assume you are disconnecting at outlet of lift pump so you aren't just blowing crud back into the pump or tank.



It would be interesting to know if it's dirt/gelled fuel, tank rust, or lift pump guts of one fixing to fail that is plugging the system.
t

I went back and reread this, where do you backflush to; flushing every 2 weeks seems to me to be very high frequency rate, are you flushing and catching flushed crud, or just blowing it back to the tank, and if blowing it out the filter bowl drain, do you have a valve on the filter bowl inlet to close off so the crud can't go 2 directions, the drain and to the tank.t

jmkglloyd,



Yes, vented cap. OEM part and double checked the part numbers. The cap I have is used on Diesels and maybe one other engine, I think.



QM,



No, I have not blown air back through my lines. I have the ability, but have not heard of doing so, except to attempt to blow the "sock" off the inlet line inside the tank. My sock, however, is new. Can you give me directions on how to do this properly?



Thanks,

SnowDriftt

No, I just blow the bowl from the IP inline and out the drain T. You can't push fuel back up the line very well with the LP installed, without opening the drain T. I'll take a picture of some of my samples, they're pretty nasty looking.
t

QM,

You might want to re-examine your process, yes the LP will sort of act like a check valve, but blowing from the IP feed line back and only opening the drain of the filter bowl you still have possibility of blowing stuff into the LP . Maybe open both the drain and disconnect the outlet of the LP.

My biggest concern though regardless of your method, is that you have said that you are having to do this more or less every 2 weeks ??? Decrudding the filter this way is only a band-aid IMO, you got some serious contamination issues going on, I suspect biological growth. That grease you add to your fuel may be that growing medium/food for bacteria just needs to thrive.

In the Navy we had this same problem running JP-5 in our ships small boats (boat refuel station was plumbed to JP-5 system be design), we would put in clean fuel and in short order fuel filters would clog up, we switched to running Marine Diesel and biocide treatment and that vitrually eliminated our growth problems in fuel.

Tim, I only have to do it that often due to glycerine buildup from yellow grease. I started doing this when I opened the drain T to purge the bowl and nothing would flow even under pressure. I blew back into the bowl and all the bottom crud can freely.

The next time a guy said his truck was hesitating I blew his down and the bottom crud was not to different from what I see on mine.

QM,
I'm not trying to debate you only trying to better understand.

If this sludging you suspect to be a problem is as prevalent as you suspect, why then do we not read from the 6.5 community reports of sludge in the bottom of the bowl or covering the filter when removed.

Do you do this 1st for all wayward folks your card introduces you to, how long does this fix keep them up and running? I suspect a fiter change would do the same thing; it does not take much blockage to reduce performance. I had my own truck lie down on me with a "fresh filter" only 5K on it since last change, all fuel bought from reputable sources. When towing I ran like a dog, I changed the fitler viola restored power.

How much air pressure you use to backblow the filter, any risk of "holing" the filter element filters have a design psi limit, even excess air could damage it. My concern there is that you fix it by blowing a hole and free flowing unfiltered fuel to the IP.

I'm using 90 psi but it would blow the fuel line to give it that much pressure. I gently let a pulse or two off and watch what comes out. Total fuel displaced from the bowl is about 12 ounces total and you must bleed all the air out or it will stall if you don't.

90 psi Yikes, I don't know what the paper in the element is rated to but considering it operates at 10 psi or less I'd maybe do some experiments to see how much it can take, or call Stanadyne to see what the element can stand, it's only 5 micron rated paper, a hole from a burst of 90 psi air might be hard to see with naked eye.

A small poly pre-screen is in the bottom of the filter cannister, meant to block the large particles, where they will settle and can be flushed out at the water-drain petcock.

Often, this pre-filter has been pitched out with the fuel filter, having been stuck inside it.

The cannister should never be 'back-flushed', even off-vehicle.

When chainging the fuel filter, 'sop' the fuel remaining in the cannister with an old washcloth, or sock, or anything cotton.

The pre-filter will be on the bottom of the vertical fuel tube.

If the bottom of the cannister is not clean, remove it from the engine, and clean it.

This procedure will be required at intervals dependent on where you shop for fuel, incl whether you shop for food or\and fuel at mcdonald's equiv.

Mine required cleaning once, five years ago, shortly after installing the engine - I then replaced the cannister because the fuel tube was heavily rusted.

gmctd,

any photos or part numbers? Maybe this is my problem causing my low pressure.

SnowDrift