VinceB Posted November 7, 2023 Share Posted November 7, 2023 I noticed a fuel leak but only when the engine was running. Bottom line is that the electric lift pump (transfer pump on the bill) had developed a leak. My mechanic says these fail all the time and last only about 60,000 miles. Doesn't sound right to me. Thoughts? 330 ISC manufactured in September of 2000. Link to comment Share on other sites More sharing options...
jacwjames Posted November 7, 2023 Share Posted November 7, 2023 How was it fixed? Did you replace it?? A leaking lift pump is pretty common, happened to me at ~107K miles. I was aware of the problem and kept an eye on mine. Fine one day, leaked the next. The lift pump only leaks when the lift pump runs, ~30-60 seconds, and then it shuts off and the CAPS pump takes over. The real problem is that if it leaked while it ran, it probably was sucking air when the engine was running. The air in the CAPS injector pump causes lots of problems and ultimately the CAPS pump will probably fail. Do a search for FASS and/or Air Dog transfer pumps, a number of Monaco owners have installed one of these. I installed a FASS pump. 1 Link to comment Share on other sites More sharing options...
timaz996 Posted November 7, 2023 Share Posted November 7, 2023 There are a lot of threads about lift pumps on here and irv2 forum. After I lost my injection pump ($6500) I bypassed my lift pump with the FASS pump/filter setup. If your lift pump is leaking your injection pump is sucking air. (very bad) Look up FASS on the forums or youtube. My lift pump never leaked but when you pull fuel through 35' of line you are inducing air in the fuel. I had plans of doing the FASS before I lost my injection pump but waited too long. Link to comment Share on other sites More sharing options...
VinceB Posted November 7, 2023 Author Share Posted November 7, 2023 30 minutes ago, jacwjames said: How was it fixed? Did you replace it?? A leaking lift pump is pretty common, happened to me at ~107K miles. I was aware of the problem and kept an eye on mine. Fine one day, leaked the next. The lift pump only leaks when the lift pump runs, ~30-60 seconds, and then it shuts off and the CAPS pump takes over. The real problem is that if it leaked while it ran, it probably was sucking air when the engine was running. The air in the CAPS injector pump causes lots of problems and ultimately the CAPS pump will probably fail. Do a search for FASS and/or Air Dog transfer pumps, a number of Monaco owners have installed one of these. I installed a FASS pump. Yes, replaced it. I think I caught it right away as there was no fuel in the RV bay and only on restart in front of my house. I drove it directly to the shop - maybe 5 miles. Maybe I lucked out. Link to comment Share on other sites More sharing options...
jacwjames Posted November 7, 2023 Share Posted November 7, 2023 14 minutes ago, VinceB said: Yes, replaced it. I think I caught it right away as there was no fuel in the RV bay and only on restart in front of my house. I drove it directly to the shop - maybe 5 miles. Maybe I lucked out. My leak was hitting the exhaust, never made it to the ground for quite a while. Found it cause I crawled under the coach to do some maintenance on the jacks and heard the fuel hitting the exhaust and evaporating. Hope you caught it in time but its a gamble. Link to comment Share on other sites More sharing options...
m.demeere Posted November 8, 2023 Share Posted November 8, 2023 I had a leak in the lift pump and I tightened the 3 bolts on the top of the pump the gasket will shrink with the low sulfur diesel it’s been 3 years ago and no problem since. Link to comment Share on other sites More sharing options...
bobdinsmore Posted November 8, 2023 Share Posted November 8, 2023 I've had the same good luck as m.deere that tightening the three bolts on the top of the pump fixed the problem for at least five years so far. Link to comment Share on other sites More sharing options...
scottjo02 Posted November 8, 2023 Share Posted November 8, 2023 Over the 140,000 miles in my 02 Knight, 300 hp ISB, I have replaced the lift pump three times. When I learned that low pressure from the lift pump can damage the injection pump ($$$$$$$), I installed a 5 psi warning light on the lift pump output. It tells me when the lift pump is getting weak. I carry a spare lift pump and can change it out on the road. The pump is much less expensive when you can buy it at your leisure at home, rather than getting it from Cummins on the road. Scott 02 Knight Link to comment Share on other sites More sharing options...
Rocketman3 Posted November 8, 2023 Share Posted November 8, 2023 Just after I bought my rig -83kmiles the mechanic noticed the lift pump was leaking- had him replace it. At about 100k I installed the FASS lift pump. I also installed two fuel pressure gauges on the fuel lines after all the fuel filters. A mechanical one to read in the engine bay, and one to display at the driver seat. I really like the gauges… it lets me know what fuel pressures are being fed to the engine and if/when I need to replace the fuel filters. Good Luck Link to comment Share on other sites More sharing options...
dennis.mcdonaugh Posted November 8, 2023 Share Posted November 8, 2023 3 hours ago, bobdinsmore said: I've had the same good luck as m.deere that tightening the three bolts on the top of the pump fixed the problem for at least five years so far. I bought a new gasket from a company in Alabama. Link to comment Share on other sites More sharing options...
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