wamcneil Posted June 7 Share Posted June 7 (edited) Ok, so I've got a FASS system and I think I have all the fittings that I'll need. Getting ready to do the install. The plan is to mount the system up front by the tank and tee the return in with the passenger-side vent fitting as I've seen others doing. My question is about the original lift pump. I'm thinking I'll do it in two phases: Install everything up front and initially leave everything alone in back. Get the coach running on the FASS pump As a 2nd phase (probably sooner rather than later) go back and dismantle the original filters and CAPS plumbing Cap off the disused ports on the lift pump Remove the original primary filter Relocate the original 2ndary filter Disconnect lift pump and install the fooler relay. So here's the question: is there any good reason to immediately reconfigure the CAPS plumbing when installing the FASS? Assuming the original lift pump gasket is sealed, and I don't start drooling fuel everywhere once the system is pressurized... can I just run the original system under pressure, with the original part-time lift pump active at startup? Thanks! Edited June 7 by wamcneil Link to comment Share on other sites More sharing options...
CMillet86 Posted June 7 Share Posted June 7 Assuming you bought the fass system with the filters. I would remove all the filters in the rear. I had to make some hoses to connect everything. But my system goes from tank to fass with a return in the fill neck, then straight to the caps pump, and a new hose that connects the caps return to the original return hose. I have no filters in the rear, and see no need. I didn’t mess with any wiring on factory on the lift pump nor do I have any fuel, feed or return flowing through it. Link to comment Share on other sites More sharing options...
timaz996 Posted June 7 Share Posted June 7 You will get a lot of different answers. I bypassed the lift pump and I left the secondary filter in for ease of install. Link to comment Share on other sites More sharing options...
wamcneil Posted June 7 Author Share Posted June 7 (edited) Did ya'll read all the way through to the end where I actually ask a question???? 😶 Kinda sounds like y'all stopped reading after "Ok, so I've got a FASS system and I think I have all the fittings that I'll need. Getting ready to do the install..." I actually listed out the plan to make a bunch of changes in the back. The question is specifically- Can I install the pump up-front, run for a period of time before making all the changes in the back? Edited June 7 by wamcneil Link to comment Share on other sites More sharing options...
Rikadoo Posted June 7 Share Posted June 7 So reading your post, if you dont mind i will answer your question with a question… Why would you want to? In that the possability of inducing pressure to in essence a low pressure suction pump, imagine out on vacation an now it decides to 💩the bed🙀 an it leaves you scrambiling to go thru all the effort to bypass it, when originally you just want to enjoy your travel time. Im all for expermenting but for something that im not sure many have done by others before.(i been wrong before an THIS may be one of those times) For me its about if im going thru the effort, do it once cry once. My low pressure pump was over the top of my starter an though i dont believe it would have been a fire issue, it could have caused issues with it. Either way the benifits of the Fass system has been the one most better upgrades i have done for my coach. Link to comment Share on other sites More sharing options...
wamcneil Posted June 7 Author Share Posted June 7 (edited) Well... the work at the front of the coach is 100% separate from the work at the back of the coach. And IMO about 95% of the benefit of the fass system is gained once the front-work is done. I'm not retired. I have a job and two teenagers and a lot of other projects and priorities competing for my time and sometimes breaking up a larger task into chunks is helpful. If the original CAPS system doesn't care about living under pressure or not, and there are no significant downsides to breaking the work into two completely separate phases... then I'll probably do the work in two phases. I "think" my original lift pump is sealed right now. That wasn't always the case... which is what put CAPS failure on my radar. If I start the new pump and find fuel running down the side of the engine, this is a moot point... Edited June 7 by wamcneil Link to comment Share on other sites More sharing options...
tmw188 Posted June 7 Share Posted June 7 Agree with above. Why not install the pump and rough in all the hoses up front how they go without connecting them, that is if you think you may want to use the coach. Do all the FASS pump install wiring and leave the fuses out so the pump won’t run. This may take you some time. Later configure the back. Study the lift pump connections you’re removing, they may not just go end to end to and connect with a coupling. I had to make a bracket and use a U- shaped fitting to connect mine, similar at the filter that gets abandoned. If you haven’t watched the install video of Mike Z I highly recommend watching it a few times. You can find it on YouTube. Link to comment Share on other sites More sharing options...
wamcneil Posted June 7 Author Share Posted June 7 3 minutes ago, tmw188 said: ...If you haven’t watched the install video of Mike Z I highly recommend watching it a few times. You can find it on YouTube. I have watched it a few times! Mike's video and writeup has been very helpful, along with those of several other folks on this forum. Link to comment Share on other sites More sharing options...
Bruce Hull Posted June 8 Share Posted June 8 I installed the fass fuel tank pickup at the bottom of the tank and used the feed as the return, and removed the lift pump and one filter,, the other filter has a hole at the top were I installed a fuel pressure gaauge,,, remove the lift pump it will be a leak now!!!! 2 Link to comment Share on other sites More sharing options...
cbr046 Posted June 10 Share Posted June 10 On my FASS install I left the OEM filters in place. That was 2 years and 25,000 miles ago. The only issue was it identified a leaky lift pump, which I bypassed with some lift pump bypass plumbing. I installed a fuel pressure gauge at the secondary filter, just before the CAPS pump. I'm still running the same psi under load So yes, you can do the front end FASS work now and remove the OEM filters later. - bob 2 Link to comment Share on other sites More sharing options...
wamcneil Posted June 10 Author Share Posted June 10 (edited) Thanks. What I'm thinking is I'll do the front-work and pressurize the system and see if my lift pump, or anything else is leaking. Then if no leaks, I may wait a while to re-plumb the back. At one point, my lift pump absolutely did leak. I bought a replacement gasket, but tightening the fasteners on the pump got the leaking to stop and taught me that I didn't like the contortions involved in working on that blasted lift pump. I haven't caught it leaking again, so I never went back in and replaced the gasket. Edited June 10 by wamcneil Link to comment Share on other sites More sharing options...
wamcneil Posted June 10 Author Share Posted June 10 Ok. How about another question then... Mike Z's post about sharing the vent bung with the FASS and how it didn't work out for him has me concerned. Has anybody else had problems with fuel getting entrained with vent air and blown out the tank vent? I found a no-weld return fitting that would be a pretty simple install. This is a tank return fitting that installs like a big riv-nut. 1 Link to comment Share on other sites More sharing options...
Rikadoo Posted June 10 Share Posted June 10 So as far as combining the return fuel in with the vent bung, i have had no issues in the couple years its been in there, as far as the beauty of the fass system its flawless, plus with the pressure gauge on my last trip from ca to South carolina then back i could actually tell the filters were starting to get restricted. Changed them when i got home an the pressure went right back to were it normally sets. Now that said there has been one issue that has surfaced an that is with my generator. As i drive the coach an with the generator running once i start getting around the 1/2 tank mark the genny starts running strange under load an if im doing mountain driving it has shut off. Yet if im parked with the tank at 1/2 with the main engine off, i can start it an it will run fine all night long. What i suspect is with the return fuel dropping further into the tank from the vent bung i am airaiting the fuel which the genny picks up an since it has no way to seperate the air out it just gets too much air in the line an shuts it down. When the tank has been very low im able to shine a light in both fuel bungs an i can see the two baffels are still in place and both the fuel pickup tubes are in the middle so im just assuming its airated fuel. With how much better the engine runs i can live with it cause for the most part i always stop to fill up when im st 1/2 tank anyway. 2 Link to comment Share on other sites More sharing options...
tmw188 Posted June 11 Share Posted June 11 3 hours ago, wamcneil said: Ok. How about another question then... Mike Z's post about sharing the vent bung with the FASS and how it didn't work out for him has me concerned. Has anybody else had problems with fuel getting entrained with vent air and blown out the tank vent? I found a no-weld return fitting that would be a pretty simple install. This is a tank return fitting that installs like a big riv-nut. Ive never noticed any issues with this arrangement. 1 Link to comment Share on other sites More sharing options...
wamcneil Posted June 11 Author Share Posted June 11 Thanks guys. I've already got the fittings to Tee the vent. So I'll probably go ahead with that. Link to comment Share on other sites More sharing options...
Mick Adair Posted June 11 Share Posted June 11 I've done my return just like the above post. If you think about it the vent will be sucking air into the tank as fuel goes out to the engine. just make sure the vent hose still has a rise to it and the end of the hose isn't trailing back creating a vacuum. Don't know what could have happened with Mike Z's installation. 1 Link to comment Share on other sites More sharing options...
cbr046 Posted June 11 Share Posted June 11 (edited) 2 hours ago, wamcneil said: Thanks guys. I've already got the fittings to Tee the vent. So I'll probably go ahead with that. Keep an eye on your overflow after Billups. Mine was spritzing fuel out, small amounts but seen on side of coach. I ended up tee-ing with the engine return line. - bob Edited June 11 by cbr046 2 Link to comment Share on other sites More sharing options...
wamcneil Posted June 11 Author Share Posted June 11 1 hour ago, Mick Adair said: I've done my return just like the above post. If you think about it the vent will be sucking air into the tank as fuel goes out to the engine. just make sure the vent hose still has a rise to it and the end of the hose isn't trailing back creating a vacuum. Don't know what could have happened with Mike Z's installation. Yeah, under normal circumstances there shouldn't be air moving OUT the vent. I'm thinking maybe Mike's issue was a combination of the tank oil-canning and the smaller 1/2" tee that he used. He said it happened when the tank was unusually low and a rough road. Maybe the reduced weight of fuel allowed some part of the tank to start popping in and out, and then the smaller tee fitting would be more prone to getting fuel entrained with the airflow. I'm currently working on a plan to extend the fuel return with a short piece of 3/8 copper tubing down through the tee and down into the tank. That would keep the fuel and air absolutely separated. I'll post some pictures if the plan works out. 1 Link to comment Share on other sites More sharing options...
dl_racing427 Posted June 11 Share Posted June 11 It's definitely best to have the return go to the bottom of the tank. Diesel fuel likes to foam, and entrained air isn't good for your fuel system, or for performance. I like the idea of that Riv-not style fitting. Is it threaded for a dip tube on the inside end? Link to comment Share on other sites More sharing options...
wamcneil Posted June 11 Author Share Posted June 11 3 hours ago, dl_racing427 said: It's definitely best to have the return go to the bottom of the tank. Diesel fuel likes to foam, and entrained air isn't good for your fuel system, or for performance. I like the idea of that Riv-nut style fitting. Is it threaded for a dip tube on the inside end? It's internally threaded, but not meant to attach a tube. Holly sells one that is a lot more expensive, but does have a dip tube: Earl's 166025ERL Earl's Weld-less Fuel Return Fitting (holley.com) 1 Link to comment Share on other sites More sharing options...
wamcneil Posted June 12 Author Share Posted June 12 (edited) Ok. Here's what I came up with. I had planned to hold the tube in there with a 3/8 NPT > 3/8 Compression fitting, but the hardware store had that bin chock full of the wrong fitting... So I drilled out a 3/8 Flare plug, drove the copper pipe through it and then flared the end of the pipe. Edited June 12 by wamcneil 1 Link to comment Share on other sites More sharing options...
Mick Adair Posted June 12 Share Posted June 12 What is holding the copper fitting in the 90 degree fitting? Did you tap it? Link to comment Share on other sites More sharing options...
wamcneil Posted June 12 Author Share Posted June 12 Yes. Tapped straight threads in the 90deg fitting. I’ll use some thread sealer for final assembly Link to comment Share on other sites More sharing options...
Mick Adair Posted June 12 Share Posted June 12 I really like that! I may retrofit mine later. 2 Link to comment Share on other sites More sharing options...
jacwjames Posted June 13 Share Posted June 13 5 hours ago, wamcneil said: Ok. Here's what I came up with. I had planned to hold the tube in there with a 3/8 NPT > 3/8 Compression fitting, but the hardware store had that bin chock full of the wrong fitting... So I drilled out a 3/8 Flare plug, drove the copper pipe through it and then flared the end of the pipe. What size copper tubing did you use?? Any concern about adding back pressure due to the restriction? 1 Link to comment Share on other sites More sharing options...
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