FASS pump--bypassing the lift pump

[Vanwill]

Originally Posted by MountainMike

Vanwill what's going on with your rig?

Mike, my coach is at MTR Fleet Services in Cumming, GA. It was towed the 90 miles by a great tow service.

MTR has the Cummins INSITE software and is scheduled to begin working on it Monday.

Ever since I installed the VMSpc over five years ago, it has reported a "251 Power Supply Voltage--Data Invalid" code. I could never find anything that caused it and the coach always performed perfectly. So, I just ignored the code for years. I am HOPING that a young tech's diagnosis is correct--that there is a bad connection somewhere in the power coming to the ECM. If that is NOT the problem, then it is likely the ECM itself.

I'm just waiting...

[imnprsd]

It might be worth mentioning this for anyone experiencing engine poor start and/or stop problems.

It was a very cold morning (sub-36F)... and on the fourth attempt to start and keep my engine running, I was able to drive my coach to a nearby fueling station, where I filled the tank from 1/4 to full (without turning off the engine), and then I found a local mechanic to check my fault code history.

The stored Fault Codes in the ECM history were 434 and 456. These fault codes point to "low un-swiched voltage to the ECM" and "low fuel pressure", but when you can't start your motor... and are just about ready to call a tow truck... all sorts of things go through your mind.

It turns out I did not find the final solution to my engine start and then stop problem until 8 month later. And luckily, all I had to do was tighten those 3 loose Lift Pump bolts.

Prior to fixing my fuel delivery problem (air in the fuel line), I learned the ECM needs to receive a "clean" +12V from the ignition key switch. I also read how these things can fail. So for lest than $30 I decided to replace it as a PM service and discovered something interesting. You can read more about it here:

Why Did My Cummins ISC-350HP Motor Run Better After Changing The Key Ignition Switch?

https://www.irv2.com/forums/f123/why...ch-421913.html

[rikadoo]

Good morning VANWILL, so im VERY interested in what you discovered with your problem, a couple days ago I just ordered my FASS pump and after this coming Holiday will be installing it. I had decided to just remove my primary filter and replace it with the FASS system like you did. Having read several posts from others on this website it sounds like it should be no problem. Im taking this approach first cause the limited room in which to work around the engine, (standing on my head for hours on end makes the world look funny when I stand back up) When you said it would run ok then bellow black smoke it sounds like you may have had a sticking open injector or some type of fuel pressure regulator issue. either way im really interested in what you found.

[Vanwill]

Originally Posted by rikadoo

Good morning VANWILL, so im VERY interested in what you discovered with your problem, a couple days ago I just ordered my FASS pump and after this coming Holiday will be installing it. I had decided to just remove my primary filter and replace it with the FASS system like you did. Having read several posts from others on this website it sounds like it should be no problem. Im taking this approach first cause the limited room in which to work around the engine, (standing on my head for hours on end makes the world look funny when I stand back up) When you said it would run ok then bellow black smoke it sounds like you may have had a sticking open injector or some type of fuel pressure regulator issue. either way im really interested in what you found.

My problem had nothing to do with the FASS system, and would likely have occurred with or without me having installed the FASS system. My problem was an ECM failure, which occurred AFTER installing the FASS system.

I believe the FASS (or competitive system) is a good upgrade for CAPS pump-type systems. I have never been comfortable with not "pre-filling" fuel filters until I installed the system. I also installed a fuel pressure gage at the same time, so when I install a filter without "pre-filling" I get to see on the pressure gage whether it primed correctly.

Yes, I know the "lift pump" is supposed to fill a dry filter. But as I always say, the reason to pre-fill filters is that if your lift pump is working correctly, your engine will PROBABLY start with a dry filter. If you pre-fill the filter, it WILL start, regardless the condition of the lift pump.

Yes, I installed my FASS system in place of the primary fuel filter. So I now have a 25 micron primary and 10 micron secondary on the FASS unit itself, before it pushes fuel through a 2 micron final filter. When I see fuel pressure drop (at the inlet of the CAPS pump) under WOT conditions, I know it is time to change filters. It is usually the very first filter (25 micron) that is contaminated.

[BigLar368]

Van....In know I am a little late to the party but I went through the extra effort to bypass the stock lift pump when installing my FASS pump. All fuels lines that see FASS pump pressure were replaced including the suction and pump to tank return fuel line. From the pump I went straight into the secondary filter housing and from there straight to the pump. I used SS braided PTFE fuel line so it should last a lifetime. Glad ya got it fixed and up and running.

[Cheeko]

Did the shop figure anything out for you?

[blckhnd]

Can you email me the 250 page Cummins 350ISC troubleshooting manual? I am having trouble with my CAPS injector pump and I need the parts breakdown. Your help is greatly appreciated. blckhnd@yahoo.com

[mackwrench]

Originally Posted by blckhnd

Can you email me the 250 page Cummins 350ISC troubleshooting manual? I am having trouble with my CAPS injector pump and I need the parts breakdown. Your help is greatly appreciated. blckhnd@yahoo.com

Best way is use your engine S/N and make a free account at Cummins Quickserve, you'll have access to complete service, electrical diagnostic and parts manuals for your specific engine.