Forgive the long title but may make search easier. I consider myself an apprentice at all of this stuff but enjoying it immensely.
I was having an intermittent power issue with our 325 8.3. I had previously damaged the fuel solenoid and decided I would perform Chucks science experiment with an addition or two. Added a vacumn gauge after first filter, replaced lift pump, fuel solenoid, rebuilt KC2600 and replaced overflow valve. Idled beautifully and then went for a test. The issue returned after the first stop. The brake lights remained on at home until I went in and pressed on the brakes.
I had a few issues previously including a treadle not engage, testing confirmed potentiometer was good, stutter start from a stop light in Florida and had Allison read the transmission with no issue. Functioned well until last June. Then as I returned from the Outer Banks every start was a creeping one until it built up steam and top end was 55.
Gave a call to our favorite mobile marine/truck guy. He hooked up an inline gauge, also recommended by Bill Willet, and off we went. Did its trick but fuel pressure was right on the mark. This confirmed that the solenoid was fine etc. vacuum gauge at filter was good. However, during the creeping start the tech noticed the KC2600 would only extend 1/3. Back to the KC manual and bingo. Brake switch. Now I could search the forum for brake switch. Found someone that had the same problem that used the rope drive to get home. The brake switches were replaced and problem solved. I will post part numbers shortly.
The switches are in the wet bay directly under the drivers seat. I replaced both as well as the relay. Parts are about $60 total
So all the fuel stuff you replaced didn't need to be. Well that's the way it goes sometime. I have had a few instances in the past, where I did not have much power. I thought that it was caused by the turbo waste gate getting stuck in the open position, although I was never able to confirm that. The problem would exist for a little bit then suddenly disappear after I had stopped the engine or done something that may not have been related to the real cause. I did clean and reconnect the brake switch wires a few years ago, maybe that has helped, or been the problem. Haven't had a loss of power for over 2 years.
I am sure the starter hangup did kill the fuel solenoid. But the rest of it could have waited until I finished the plumbing work. I was pretty sold on Chucks upgrade work. So I did spend about $250 on replacing working parts and more rebuilding the KC2600. Beginners do tend to throw parts at problems but it does bring a smile when you finally work it through.
Glad to hear you got it figured out. If the "fuel stuff" you replaced was original, then it was 20+ years old. The items you replaced are nice and fresh, and presumably good for another 20 years. You have just shortened your list of "stuff to worry about". Money well spent, in my opinion! ^.^d
Thanks Chuck and thanks again for the "science experiment".
Even better, you posted the final solution on the forum where it will most definitely help someone in the future ^.^d
My history with fuel delivery problems for 8.3 Cummins in 1996 Foretravel.
Owned this motorhome for 17 years. Performed all maintenance and most repairs. No trust of professional shops and unwilling to work to their schedule.
Six years ago, a series of intermittent "partial power" incidents occurred. Caused by the fuel shutoff valve (FSV) binding when opening. This condition restricted fuel for high power. Usually had enough power to roll out; not to accelerate (swiftly). Among these occurrences, I pissed off Dallas drivers while on an elevated single-lane overpass going 10mph. When home, this intermittent-reduced-fuel condition was corrected by removing this electrically-operated (normally ON/OFF; not partially open/OFF) valve. Cleaned the valve and its moving parts. Repaired a keeper ring internal to the valve that caused binding. Re-installed; monitored future operation. (FT forum offered a temporary fix for this condition. Secure this valve open with wire or a wire-tie. Remove restraint for shutdown.)
For two years, I chased a small fuel leak. (Only happened when engine operating.) Leak finally enlarged enough to locate source—a crack in the Lift Pump. $40 Lift/Transfer pump 3917998 replaced in May 2016. (Note: I heard a "clunk" when inserting this new pump, holding this part in-place, as a helper inserted the attaching bolts.) No fuel leakage, or oil from crankcase, detected.
Then fuel delivery problems again. Often, starting led to unexplained shutdown at idle. In cruise, intermittent fuel starvation. (Transmission would downshift from 6 to 5 and then 5 to 4, attempting to maintain set speed. Usually corrected itself before progressing to shutdown. But not always.) Did I install an "under-sized" lift pump? Shutdown became the normal result whenever power loss reared its occasionally unsafe or usually embarrassing head.
Changed Primary and Secondary filters, although Secondary was almost new. This did not help. Generator, driven by a small 3-cylinder diesel engine, ran well as it drew fuel from same tank as big engine. (Generator fuel lines had been replaced several years ago.) So, I dismissed "poor fuel" as cause. However, my 21-year old, 24-foot, fuel line from Tank to Primary Filter could be compromised with air leaks or blockage. As well as the 4-foot line from Primary Filter to Lift Pump. Or objects swirling in the fuel tank, randomly sucked over the tank outlet. Or ....
During a Spring trip, removed FSV and temporarily replaced with wire-tie to hold full open for that day's drive. (Wire-tie removed and fuel lever on HiPressure Pump hand-moved to Off position to shutdown for remainder of 3-week trip visiting ancient Indians in NM-CO-AZ.) Replaced fuel return-check valve in Cortez CO (Cortez Diesel). New one broke while I installed it. Re-installed old one. After "bleeding system" of air, the engine would not continue running using manual pump on Lift Pump to prime for start. (Wife and I became proficient at "bleeding the system" after filter changes and return-check-valve swap.) Repeated (six times) the electric "air purge" using Primary Filter setup. Engine remained operating after start. Electric-Priming became procedure for restart when it quit—to get home.
10 June 2016: Replaced Fuel Return Check Valve 3924726 (Arkvalleydiesel, $21).
16 June: As advertised, ordered a $403 new FSV 4089574 from Arkvalleydiesel. (This was the original Cummins part.) They sent a Synchro Start 3935649 instead! (Previous online purchase $65, China-made, 3935649 did not hold open—after "starter circuit" of solenoid released when ignition key position changed. Only the "ignition circuit" solenoid portion was powered. Ignition switch? Failing relay in hold-circuit? Perhaps wiring was different on this revised model of FSV?) Barry's photo on Foretravel website has this numbered part as a replacement for original FSV. Cummins Technical Service Bulletin contains testing and installation details for this Synchro Start FSV: minimum pull-in voltage 8.3, min hold-in voltage 4.4, energized rod length 2.93 inches. Returned over-priced Arkvalley unit for credit. Much "fiddling" (I appreciate that this might be a professional term.) with my previously purchased 3935649 FSV unit to discover correct adjustment for open and closed conditions.
22 June: a (now) bookmarked forum thread includes other additions, considerations, and changes to the fuel delivery system. Some useful, such as: installing a fuel pressure gauge at HP, and the adjustable Tork Return Valve on the HP.
29 June: slowly died on way back from a Taos fueling run. Twice! Of course, once while at center of Taos with no way to get off the road. Installed Tork-Tec Adjustable Return Valve. Set for normal pressure. No leaks.
02 July: Vowed to re-tighten ALL connections removing possible AIR leaks in fuel system. New washers at banjo connections. Tightened filters; line junctions. Re-cleaned Primary pre-filter and replaced O-rings.
Next step should be a fuel pressure reading. Local diesel shop said, "Have no fittings." And shrugged with a smile. While visiting brother in Kansas, an Olathe truck repair shop technician said he had a gauge and fittings when I phoned. But, did not after I backed in to his slot. Before departing my brother's place, all fuel components had been changed, including the fuel lines. Still had starting problems, and power loss episodes, on way home to NM.
In December 2017, used CorrosionX on all "drive-by-wire" throttle connections. Sensor at pedal, and all electrical junctions on the engine firewall. This improved throttle response. Test run was okay with wind from behind on level 13-mile jaunt to weigh scales. (... new carpet installed.) On return, into the wind: slow acceleration, with coolant temperature of 170F. (180 was normal before fuel woes.) Reduced coolant temp, even when climbing hills, indicated to me that excess fuel never gets to the cylinders. I still had a fuel-delivery problem.
Finally, in January 2018, I installed an electronic fuel pressure gage in the dash, $130. (Wires had been laid under new carpet. From snubber+sensor installed on engine, to the former electric clock hole in dash.) Inserted gauge, connected ignition circuits, and 12vdc instead of headlight-switch-ON. This provided continuous dimmed presentation of green lit dial and red needle plus the digital PSI number. Operation now showed that priming, before start, produced 17psi, which reduced to 0 (@30 seconds later) as fuel pressure was spent during start and idle. No one ever said my engine would ran at 0 psi! Nevertheless, this suggested the lift pump was not functional. Removed AC compressor+mounting bracket to expose Tork-Tec adjustable HP return valve. Increased priming pump pressure to 20 psi. (With no lift pump working, I reasoned.) Installed two new air brake valves that switched the cruise control off. These air-electric valves had been reported by Foretravel Forum as being a possible problem for cruise operation.
20 January, I ordered a new lift pump, $93. And a stud bolt kit, $22, for relaxed, single-worker installation of lift pump. A week later, I installed the new pump without a clunk. Operation now has continuous idle pressure of 20psi. Parked, no load, mid-range throttle has 23psi. Have I solved my fuel delivery trouble? (A snow packed, descending, twisty road from my house prevents a highway test—for now.) May need to adjust fuel-return-valve pressure for proper Cruise and Climb performance (temp and up-shifting). So, strap AC compressor out of way; leave wrenches for Tork-Tec adjustment on floor near Pax seat.
REVIEW/LEARNED:
1. During installation of second lift pump, piston shaft to engine cam broken-off on previously installed lift pump. (Arm strength created a problem. Mis-directed thinking pushed this to a pointless parts pursuit....)
2. Now, my motorhome has a renewed fuel delivery system from tank to HP. These new components irregularly kept my engine going without an operating lift pump. However, this type of operation did not supply excess fuel to the HP—to help cool the HP as excess fuel went through the HP to be returned to the tank. I hope two years of operation with this lack of excess fuel will not shorten the life of the HP.
3. In-dash fuel pressure gauge allows constant monitoring of fuel delivery. From now on, diminished running fuel pressure should indicate fuel filter changes needed.
4. If priming, or air removal is required, this should be accomplished using the tiny electric pump on the Primary Filter System. Ignition ON and activated with "Purge" button on control panel by poking a slim rod through louvers of engine door. And not the raised bed, heart-attack-inducing-bending-over-extended-left-arm action of repetitively pressing the lift pump plunger.
Hello Lewis, thank you for useful post. Have you had any issue with cracked fuel lines?
I was told improper adjustment of fuel shutoff valve can not only create non start or running issues, but that it can also cause premature failure if set wrong.