Those of you that have a Fass pump do you loose prime if the truck sits for a week or more? Do you have to loosen the last filter to get it to prime again? After trying to figure out why I loose prime, Fass told me that since the pumps don't hold pressure and if the truck sits too long that I would have to go trough the priming procedure every time. If that it true, then I have a Fass for sale.
sounds like a bunch of bunk... total bunk.
have a look at:
Carter P4601HP
4770 Filter Head
Don't trust a 'cheap' pump? Buy 4 and still be cheaper than FASS.
These trucks don't hold pressure. But it sounds like you have an air leak somewhere in your fuel system. The banjo bolt for the return line on the back of the head is a common one :thumbsup:
First thing I checked was the banjo bolt on back of the head. It was tight. Second, I installed a 1 psi check valve on the out put side of the pump to make sure no air could enter the system. Pump still bled down. The real problem is, that the pump will not prime if there is a little bit of air in the pump. If I disconnect the pressure line then it will prime. According to Fass anytime the truck sits for any long period it will have to manually bled.
Fair enough after it sits for a week maybe try bumping the key let it run that 25 second cycle will it start after that? I can see how this would piss you off, I had a similar issue I turned out the 3/4 pipe thread to 3/4 jic fitting coming out of the pump had a defect in the threads and was allowing it to leak air into the system
I fail to believe they would by design have people that leave their truck set for a week to loosen the filter just to start the truck, weather it looses prime or not... what was their idea of "too long"?
According to the person I spoke with, about a week. Today I took the pump back off, disassembled it, replaced all the o rings, reinstalled it and it primed itself. Will wait a week and see if it still looses prime.
I agree with previous posts- these pumps don't loose prime just based off sitting for a length of time. Personally I've had two different pumps on different trucks I've let sit for multiple 4-7 month periods of time and they fired up without issue.
Well my saga continues, it looses prime intermittently, goes for weeks then looses prime again. The line from the VP to the pump is full, the last filter is usually low, if I loosen the filter run the pump tighten the filter I'm good to go. If I turn the key on I usually get 5psi, start the truck and within 2 seconds I will have 16psi on the gauge, truck runs fine. On my last trip home from CO it was pretty hot, upper 90's to 117 in Vegas. Fuel pressure went from +15 to 11psi. Of course FASS tells me everything is normal because the bucket test shows its pumping.
Just another horror story. I guess you could put another one to prime the one that don't prime, or put on a mechanical pump & call it a day. my mechanical pump sits lower than the bottom of the tank. If it ever quits I'll post it up. Stay tuned. Grow old slowly&wisely.
I just dealt with a similar problem with my fass 150. I pulled the spring and ball on the return side and found that the ball had indentations from what looked like the spring. I replaced the ball and the problem hasn't shown up since. Just something that's easy to check but could be your problem.
Pickup one (or two for redundancy if wanted) P4601HP pumps ($85), two NAPA Gold 4770 / WIX 24770 Filter Mounting Base ($20)
Sell the FASS to some other sucker.
... or be lucky like myself and have a 10 year old AirDog 150 that is still running and over 200k miles on it and still going. I'll most likely rebuild my AirDog when the time comes.
Yes you got a good one Mike I don't think I would personally trust AD these days, heard too many bad things. I really don't understand guys who bad mouth FASS though. Back when I had one of their pumps and had some issues, they were very helpful and great to work with, and that was on a ten year old pump and I wasn't even the original purchaser! Only reason I don't have one of their pumps now is because I found the Fuel Boss Only way I can see someone having a bad experience with a FASS would be if you buy from a less than reputable dealer who doesn't want to help you with warranty issues....so just do your homework and buy from a trusted source....
That's the problem there is just a handful of solutions out there that meet the requirements of this engine. AirDog shot them selves in the foot, FASS is big size wise and expensive. Fuel Boss or belt driven solutions are expensive as well and have limitations of their own. All them are expensive. Each one has it limitations and down falls. So where is a Cummins owner to go? Just depends on how deep your pockets are and how much money your are willing to toss at the problem.
I'll have to say stock pump are highly under rated for even stock applications and do not meet any of the requirements at all. Either the Carter pump on the block or the intank pump. Both are weak in flow volume and pressure under full load. I remember the days of playing with big line kits, relocation kits, holly blues and blacks, etc. Still in all the full FASS or AirDog today is one of the best solutions... IMHO...
My problem is that the pump is not operating properly, went back to FASS once, came back as been checked out and working properly. They claimed it puts out 20psi, max that I saw was 16. Plus this does not explain the heat related pressure loss and the inability to overcome a partially empty filter. Anybody know what the side clearance for the rotor should be?
Have you tightened up all JIC fittings? Sometimes even an 1/8th of a turn is the difference between tight and not tight.
Make sure however you have your fuel pressure gauge plumbed that it's tight
What kind of sealant did you use on the non JIC fittings?
Was the new spring about 1in to 1 & 1/8in long? New ball completely smooth and no indentations?
Is the O-ring on the water separator side seated correctly?
Generally speaking if there's no visible leaks then it typically points to a leak in the return line somewhere. Only other thing I could think to replace would be the overflow check valve on the VP.
After speaking with FASS I did reseal all the fittings with teflon tape. Relocated the fuel pressure sender to the pump port as per their recommendation, installed a new ball and spring which they sent me. As a test I installed a 1psi check valve on the outlet side of the pump to see if there is an air leak upstream. The line to VP stayed full, the pump still would not reach full pressure unless I started the engine. What concerns me now is the pressure loss when it gets hot outside.
Well the pump shouldn't give full pressure unless the truck is started, otherwise you'll have troubles starting, but that's a different subject.
Honestly I'd remove the check valve just to eliminate that as a possible fault. If it wasn't there to begin with and the truck worked fine at one point then it's not needed now, only band aiding the situation.
How do you have your fuel lines from the FASS routed to the tank/fuel module? You running a drawstraw? Sump?
Have you checked for clogged filters or screens?
Loosing pressure 'while hot' seems like a leak to me, just a matter of finding where it's coming from.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Cummins Diesel Forum
8.8M posts
379.2K members
Since 2005
A forum community dedicated to all things Cummins Diesel! Originally founded for owners and enthusiasts of Cummins powered Dodge pickups, the Cummins Forum has expanded to include ALL Cummins Engine applications! Come join the discussion about reviews, drivetrain swaps, turbos, modifications, classifieds, builds, troubleshooting, maintenance, and more!