wamcneil Posted June 28 Author Share Posted June 28 2 hours ago, Rgoodman said: ... I did ALOT of reading and read that you DO NOT want to put pressure to the lift pump. I can’t confirm for sure the reason so I won’t say why you should not leave it... If there are good reasons, I'd sure like to understand them. The lift pump appears to be a vane pump, and I can't imagine why that pump would care about having a relatively small (<20psi) pressure applied to its inlet fitting. So far, the only reason I can come up with is a high probability of the lift pump gasket leaking, which is the whole reason I was motivated to install a fass in the first place. So while I do plan to bypass the lift pump and one filter in the near future, I'm not concerned about harm that might result from running like this indefinitely. If the lift pump is leaking, then obviously it needs to be bypassed. But as far as I can tell, the lift pump and CAPS system shouldn't object to being fed fuel at 15psi rather than pulling against some small negative pressure. If one were to install a fuel pump up by the tank, and make NO other changes to the system, what harm would that do? Assuming I'm not leaving a trail of diesel... 1 Link to comment Share on other sites More sharing options...
jacwjames Posted June 28 Share Posted June 28 (edited) When I installed my FASS system I got advice from VanWill and he told me when he installed his he contacted Cummins and their only recommendation was not to use the original return line from the engine if the FASS pump was mounted at the rear of the coach. My guess is they were concerned with the additional flow/pressure and that it might cause a problem with the sensors in the CAPS pump. I have had an occasional CEL the first time it threw a 94-10 code which had to do with erratic fuel pressure, at the time I was fueling up and left the engine running, I'm guessing I might have put air into the system. The second time I got a 94-2 code which was fuel pressure sensor. I believe it might have been caused by a bad connection at the harness. Edited June 28 by jacwjames 1 Link to comment Share on other sites More sharing options...
wamcneil Posted June 29 Author Share Posted June 29 On 6/27/2024 at 5:40 PM, tmw188 said: Yeah report back on that please. On the subject of possible degradation in the hoses…. After pulling out the hose from the primary filter to the original lift pump, I’m seeing a black coating inside the fitting on both ends. Same from lift pump to secondary filter. Final hose from secondary filter to CAPS is much cleaner looking. At this point I don’t have any direct evidence that the hose is degraded, but the logistics of dragging a rag and solvent through the hose to try and make it squeaky-clean, plus it’s stiffness and the 90deg fitting on the caps end makes me feel like it’s best to replace. So I’ve ordered 10’ of 1/2” fuel hose and 5/8JIC fittings to just replace it. I don’t think there’s any good reason to go back with 5/8” hose. 1 Link to comment Share on other sites More sharing options...
tmw188 Posted June 29 Share Posted June 29 52 minutes ago, wamcneil said: So I’ve ordered 10’ of 1/2” fuel hose and 5/8JIC fittings to just replace it. I don’t think there’s any good reason to go back with 5/8” hose. Thanks for the report back, however to me the good reason would be that’s what it was originally? Link to comment Share on other sites More sharing options...
wamcneil Posted June 29 Author Share Posted June 29 Well… in the original configuration, 5/8 was probably justified … Originally, the CAPS pump was sucking fuel through two filters, a lift pump and 40 feet of hose. Now it’s being force-fed fuel at 15psi by a pump that can push at least three times the necessary volume. I’m pretty confident that the last 9’ of 1/2” hose won’t create a measurable pressure drop. 1 Link to comment Share on other sites More sharing options...
wamcneil Posted June 29 Author Share Posted June 29 How are you guys connecting the relay to the lift pump wires to fool the ECM? Just cutting off the plug and crimping to the wires? Or does someone know what kind of plug for the original connector? Link to comment Share on other sites More sharing options...
Rgoodman Posted June 29 Share Posted June 29 8 minutes ago, wamcneil said: How are you guys connecting the relay to the lift pump wires to fool the ECM? Just cutting off the plug and crimping to the wires? Or does someone know what kind of plug for the original connector? I just cut the original connector off and used a crimp connector and used this relay https://a.co/d/05Gg78fo Hooked the 2 wires from lift pump to 85&86 and zip tied it up right by lift pump 1 Link to comment Share on other sites More sharing options...
tmw188 Posted June 29 Share Posted June 29 (edited) To be honest I forgot how I did mine exactly, but I believe I did something with the connector to where I could reverse it if I needed to while out on the rd. I left the primary filter in place. After a few yrs though I think the lift pump probably wouldn’t be reusable anymore? Edited June 29 by tmw188 2 Link to comment Share on other sites More sharing options...
tmw188 Posted June 30 Share Posted June 30 (edited) 13 hours ago, tmw188 said: To be honest I forgot how I did mine exactly, but I believe I did something with the connector to where I could reverse it if I needed to while out on the rd Here’s what I did. I used the connector at the lift pump to wire the new pigtail up to the relay. I left the wires coming from the lift pump long enough and taped them up so that if I had to reverse it later I could, then I put caps on the pump. Edited June 30 by tmw188 2 Link to comment Share on other sites More sharing options...
dl_racing427 Posted June 30 Share Posted June 30 Unless there's a pushrod or some other reason to leave the lift pump, I'd make a block-off plate and just remove the pump completely. Be aware, if there is a pushrod, it may also have an oil feed hole, and removing the pushrod would bleed off oil pressure. Link to comment Share on other sites More sharing options...
wamcneil Posted June 30 Author Share Posted June 30 (edited) 44 minutes ago, dl_racing427 said: Unless there's a pushrod or some other reason to leave the lift pump, I'd make a block-off plate and just remove the pump completely. Be aware, if there is a pushrod, it may also have an oil feed hole, and removing the pushrod would bleed off oil pressure. Well… CAPS lift pump is a part-time electric pump that runs for about 2-min after ignition on. Definitely not pushrods or oiling involved. The lift pump housing is also a manifold where the fuel return line attaches. I’m not sure how the return fuel gets there, but I think it might be a port in the engine. Making and installing a block off plate would be a major PITA. Lift pump is staying right where it’s at! 😬 Edited June 30 by wamcneil 1 Link to comment Share on other sites More sharing options...
Rgoodman Posted June 30 Share Posted June 30 1 hour ago, dl_racing427 said: Unless there's a pushrod or some other reason to leave the lift pump, I'd make a block-off plate and just remove the pump completely. Be aware, if there is a pushrod, it may also have an oil feed hole, and removing the pushrod would bleed off oil pressure. You need to leave the old lift pump for the fuel return to the tank or bypass it for the return also. I see no need to go through that trouble. 1 Link to comment Share on other sites More sharing options...
Mick Adair Posted June 30 Share Posted June 30 The return fuel from the caps goes to the lift pump at the banjo fittings and then goes back to the tank through the return line. 1 Link to comment Share on other sites More sharing options...
dl_racing427 Posted June 30 Share Posted June 30 Sorry guys, I was thinking of my C-8.3 mechanical engine. It has a lift pump on the side of the engine, I think powered by the camshaft. 1 Link to comment Share on other sites More sharing options...
wamcneil Posted July 5 Author Share Posted July 5 (edited) Check out this tidy fitting I found for the top of the fuel filter housing! It’s a 1/8-NPT extended street tee with an additional 45 deg port. Oil pressure sensor adapter from GlowShift gauges. Edited July 5 by wamcneil 3 Link to comment Share on other sites More sharing options...
tmw188 Posted July 5 Share Posted July 5 (edited) Looks like it should work, be careful working around it if it’s sitting up a little tall. I think I used a T and a close nipple. Edited July 5 by tmw188 1 Link to comment Share on other sites More sharing options...
dl_racing427 Posted July 6 Share Posted July 6 22 hours ago, wamcneil said: Check out this tidy fitting I found for the top of the fuel filter housing! It’s a 1/8-NPT extended street tee with an additional 45 deg port. Oil pressure sensor adapter from GlowShift gauges. Do you have a link to a source, and/or a part number? Link to comment Share on other sites More sharing options...
wamcneil Posted July 6 Author Share Posted July 6 Here you go! About the same price on Amazon. https://www.glowshiftdirect.com/oil-pressure-sensor-thread-adapter-for-chevrolet-small-block-305-350 1 Link to comment Share on other sites More sharing options...
wamcneil Posted July 10 Author Share Posted July 10 (edited) On 6/29/2024 at 6:36 PM, wamcneil said: How are you guys connecting the relay to the lift pump wires to fool the ECM? Just cutting off the plug and crimping to the wires? Or does someone know what kind of plug for the original connector? Well... I cut the plug off of the lift pump plug and just crimped spade connectors onto the wires and connected a relay right there by the original lift pump. On my rig, it's very tight down by the lift pump and a horrible location to work. Filthy from leaking valve cover gasket. Figuring out what kind of plug it is would have been aggravating down in that cramped dirty location, but I wish that I had made up a harness to connect to the original plug instead of cutting it off. I don't think I'll ever be motivated to reconnect the original lift pump, but both of the wires are black, so I don't know how I will figure out how to pin it the right way if that day ever comes. For anybody else in this situation... the original lift pump plug is a Deutsch DT06-2s. And if you're not geared up to buy terminals and shells and just want a simple pre-made solution, here's a pre-made 3m extension harness that you could just plug in at the pump and run back to the run bay where others have installed their relays. DT 2-Pin Extension Wire, 3m (diodedynamics.com) And, if you're relocating the original secondary filter, the Water In Fuel sensor plug is Metri-Pack 150.2 Edited July 10 by wamcneil Link to comment Share on other sites More sharing options...
cbr046 Posted July 10 Share Posted July 10 I just stuck a 210 ohm 2W resistor from the junk box from 1975 into the plug. Literally stuck it in there, taped and tie-wrapped in place. That was 1.5 years ago. neverthrowanythingaway - bob 2 Link to comment Share on other sites More sharing options...
wamcneil Posted July 10 Author Share Posted July 10 (edited) I thought a resistor might make a more elegant solution than the relay! But that's what everybody seems to have been doing. And I happened to have several relays in the junk box from 2022. 🙄 Edited July 10 by wamcneil 1 Link to comment Share on other sites More sharing options...
tmw188 Posted July 11 Share Posted July 11 I put the relay in the rear electric bay 2 Link to comment Share on other sites More sharing options...
wamcneil Posted July 11 Author Share Posted July 11 On 6/14/2024 at 12:07 PM, dl_racing427 said: I like your configuration, but copper or galvanized fittings should never be used in a diesel fuel system. Copper is a catalyst for diesel to break down and gel, and zinc leaches into the fuel, clogging injection pumps and injectors. Ok. I made another one with 1/2” aluminum tube from my old tank level sensor. I hope y’all are happy now. 😳 1 Link to comment Share on other sites More sharing options...
dl_racing427 Posted July 12 Share Posted July 12 3 hours ago, wamcneil said: Ok. I made another one with 1/2” aluminum tube from my old tank level sensor. I hope y’all are happy now. 😳 Thanks. That looks great, and I can sleep well tonight. 😃🤣 1 Link to comment Share on other sites More sharing options...
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