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Topic: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3 (Read 1777 times) previous topic - next topic

Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Greetings all.

I decided to change my fuel filters yesterday. My plan was to do the one on the suction side of the lift pump first, start the engine, and move on to the one after the pump.

Per the Cummins book that came with the coach I did not fill the filter with fuel.  I did the repeated 30 second cycling of the pump to charge the fuel lines and started the engine.  It started right up and shut down shortly after.  I have not been able to start the engine since.

After repeated attempts I decided to remove the filter to see if it was filled with fuel- empty.  I then tried to fill the filter and give it a go- no start.

I made a call to a reputable service person who said this does happen and I may consider using my compressor to put a little pressure in the tank to move some fuel toward  the filter and get the air out.

Has anyone done this before?  I have seen this suggested on other forums but just wanted to know if anyone here has had success with this and if I need to be mindful of anything before the attempt.

FYI-
1. I do hear the transfer pump coming on when the key is "on".  I can feel it vibrating when "on".  This pump was replaced about 1.5 years ago.  No signs of leaks.
2.  I have looked for leaks and do not see any on the way to the pump.
3.  There has never been any diesel smell in the storage compartments.
4.  After this episode I will be looking seriously at the Fass system.

Any advice or warnings are welcome.  I do have an aqua-hot (I assume a little air pressure in the tank would not impact it)

Thanks in advance.

-FT
2001 U270- 34'
with Aqua-hot
Travel Safely
Have Fun!!

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #1 –
Quote from: FtRoadTrip –
I made a call to a reputable service person who said this does happen and I may consider using my compressor to put a little pressure in the tank to move some fuel toward  the filter and get the air out.

Yes, doesn't take much PSI.  Easier with two people. Small catch basin under primary fuel filter. Loosen the primary fuel filter.  Use your hand and the air hose nozzle at the diesel fill to slightly pressurize the tank. When fuel with no bubbles runs out of the filter, tighten the filter and you are done.

This occurs anytime you remove the fuel filter and the filter head is above the level of the fuel in the tank. The fuel all runs back to the tank, leaving you with 30'+ of air in the fuel line.  If the level of fuel in the tank is higher, fuel will run out the filter housing until levels equalize.

The best solution is to install a diesel-compatible BALL VALVE on the inlet to the primary fuel filter. Close it when changing filters.  BTW, this is also a great anti-theft device.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #2 –
Thanks Brett.  I was hoping you were available today.

I really appreciate the help.

-FT
2001 U270- 34'
with Aqua-hot
Travel Safely
Have Fun!!

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #3 –
As you may have figured out, the ISC lift pump is electronic and only runs for between 30 and 45 seconds or so with each key on event to try and keep the prime for the CAPS injection pump. That means that the CAPS pump must suck the fuel from a long way away in our diesel pushers which adds a lot of potential for vacuum leaks along the way. Unfortunately, it is a lot harder to find vacuum leaks than diesel fuel leaks. In talking about this issue it is good to be clear in the nomenclature. The primary filter is the the one before the lift pump (usually located above the chassis battery on U270s) and the secondary filter is mounted on the block just before the lift pump. The primary filter is not as fine a matrix as the secondary which is a 10 micron filter while the primary will typically be around 30 microns. I assume that the filter you removed and found empty is the primary (suction side)?

How many key on cycles did you do? It can take quite a few cycles to prime the system once it has been open to air. I struggled with Stop Engine lights because of the CAPS system losing prime for a couple of years, keep in mind this after I had Foretravel replace ALL of my fuel lines. Following is an incomplete list of the steps I took before I finally bypassed the Cummins lift pump and installed a FASS full time pump and an  Autometer  electronic fuel pressure gauge with remote display. 
1. Primary filter system (Davco 382)
2. Upgraded the fuel cooler and associated plumbing eliminating several 90 degree elbows in an effort to improve the flow
3. Changed both sets of filters numerous times as the stop engine lights came on.
4. Had the fuel polished by Keith from MOT.
5. Etc. (Other stuff I don't recall at the moment)

All of the issues regarding my fuel system were solved once I installed the FASS lift pump, and the addition of the Autometer gage lets me monitor the situation in realtime. The OEM system constantly has a vacuum all the way from the tank to the  CAPS pump while the engine is operating. With the FASS system supplying the CAPS pump with a low pressure feed of between 13 to 17 PSI depending on the load, there is much less potential for fuel starvation which could result in overheating and damaging the internal seals in the CAPS assembly.

Don
Quote from: FtRoadTrip –
Greetings all.

I decided to change my fuel filters yesterday. My plan was to do the one on the suction side of the lift pump first, start the engine, and move on to the one after the pump.

Per the Cummins book that came with the coach I did not fill the filter with fuel.  I did the repeated 30 second cycling of the pump to charge the fuel lines and started the engine.  It started right up and shut down shortly after.  I have not been able to start the engine since.

After repeated attempts I decided to remove the filter to see if it was filled with fuel- empty.  I then tried to fill the filter and give it a go- no start.

I made a call to a reputable service person who said this does happen and I may consider using my compressor to put a little pressure in the tank to move some fuel toward  the filter and get the air out.

Has anyone done this before?  I have seen this suggested on other forums but just wanted to know if anyone here has had success with this and if I need to be mindful of anything before the attempt.

FYI-
1. I do hear the transfer pump coming on when the key is "on".  I can feel it vibrating when "on".  This pump was replaced about 1.5 years ago.  No signs of leaks.
2.  I have looked for leaks and do not see any on the way to the pump.
3.  There has never been any diesel smell in the storage compartments.
4.  After this episode I will be looking seriously at the Fass system.

Any advice or warnings are welcome.  I do have an aqua-hot (I assume a little air pressure in the tank would not impact it)

Thanks in advance.

-FT
The selected media item is not currently available.
Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #4 –
Thank you very much Don.

I am super busy and not able to digest all of your information at this moment.

I did see on a different forum they talked about cycling at least nine times or more before trying a start.  I did that three or four times and I stopped as I started to worry about my starter, lift pump, start batteries, and everything else that could possibly go wrong.

I will be looking up your information in regard to the Fass system.  We are on the road for an extended time and after I educate myself there will be the never ending "ok, where am I going to be able to do this" issue.

Thanks again.  I always look for your past input when I research the modifications.

-FT
2001 U270- 34'
with Aqua-hot
Travel Safely
Have Fun!!

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #5 –
The cycling that Don was talking about is with the ignition key. Don't try and start the engine
until you have turned on and off the ignition key with empty filters at least 5 times and leaving
the key on for at least 30 seconds maybe  time would be better. I also installed the Fass System.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #6 –
Correct.  Just turn ignition from off to first position.  Do not turn more to start position.

You (or someone near the rear of the coach) can hear the pump start and run for 30 seconds or so.  To prime, repeat ignition off/on until you hear the pump RPM drop (going from pumping air to liquid).
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #7 –
Thanks Oldguy.

I was doing just as you outlined.

I will be trying to get it started on Monday. 

I will post my results.

Have a great weekend.

-FT
2001 U270- 34'
with Aqua-hot
Travel Safely
Have Fun!!

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #8 –
My pump had a prime button at the rear of the coach so it was easy to prime. Also I have my
old  pump, spare filter and a spare plastic refilter and all the wiring in a box if anyone wants it
PM me. It was working fine when I removed it to put on the Fass System.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #9 –
Oldguy,

I'd like the parts.  PM previously sent.

Thanks,

Rich
Rich and Peggy Bowman
2002 U270 3610 WTFS, build #5939--"Freedom"
2022 Jeep Grand Cherokee Summit 4xe
SMI AirForceOne brake system
PakCanoe 15

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #10 –
After seeing the engine pump sucking fuel from the tank under a vacuum it became clear to me that this would hide any leaks and decrease the pressures that the fuel injection system operate lowering the performance. The FASS system makes sense to me and with the added fuel polishing and increased bypass fuel that can be used on the ISM ECM cooling plate. I will eventually convert as others have already done. Not to mention closing the door on no start issues that so many have spent so many hours and dollars trying to resolve. Simply change the filters out dry, turn the ignition on for a couple minutes and then start like you did yesterday. All the air is separated from the fuel and returned to the tank. This causes the pump to work smoother, injectors to close correctly. Should have been original equipment IMO. The single only downside I can see is the added power load electrically and one more thing to wear out.

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #11 –
Just thought that I would put this out there. I know FASS has many after market lift pump assemblys with filters and that these, according to the instructions and most on the internet, requires a separate return line. This is good if you can add a return line and and get it back into your tank (say you were replacing fuel lines anyway), but in my experience not necessary for the ISC because the OEM system uses a manifold built into the OEM lift pump assembly to return the unused fuel so I simply bypassed the OEM  pump on the supply side and used the now vestigial OEM pump's builtin manifold for the return line, so only the supply plumbing after the primary filter needs to be altered. Thus far I haven't seen a downside to this approach, but I consider a fuel pressure gage essential for confidence. The lowest I have seen the pressure go while under 100% load is a hair under 13psi and that was a very long pull up a steep grade. I set the pressure at idle to 17psi and have room to take it higher as the UP95 has adjustable fuel pressure. By the way the FASS UP95 I installed conveniently has a port for a pressure gage. Since I had previously installed the Davco 382 which makes changing the filter a clean and easy job and you can also see when it is time to change the element.
I bought a kit that included the FASS UP95 lift pump, some fittings, some fuel hose, and a relay that puts enough of a load to signal the Engine Computer that the factory lift pump is still there during the start up sequence, otherwise it won't let the engine start. Installing the Fass pump without the fuel filter assembly and the extra return line is much easier in my opinion. Most I have read about that were experiencing stop engine lights caused by what amounts to fuel starvation have ended up replacing the CAPS pump, the Caps accumulator, or the the whole assembly which can be north of 5 coachbucks. At the very least, I have punted my CAPS problem down the road, and in my opinion, probably rendered it a non issue. The coach runs better than it ever did before the changeout.
Don
The selected media item is not currently available.
Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #12 –
Quote from: oldguy –
The cycling that Don was talking about is with the ignition key. Don't try and start the engine
until you have turned on and off the ignition key with empty filters at least 5 times and leaving
the key on for at least 30 seconds maybe  time would be better. I also installed the Fass System.
Another advantage of the FASS system is that since the FASS pump is operating all the time when you turn the key on, air is easily purged after filter change and adding a manual WOG ball valve before the primary will practically eliminate air getting in the system.
Don
The selected media item is not currently available.
Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson
 

Re: Lost Prime After Pri. Fuel Filter Change-2001 ISC 8.3

Reply #13 –
Quote from: Don & Tys –
As you may have figured out, the ISC lift pump is electronic and only runs for between 30 and 45 seconds or so with each key on event to try and keep the prime for the CAPS injection pump. That means that the CAPS pump must suck the fuel from a long way away in our diesel pushers which adds a lot of potential for vacuum leaks along the way. Unfortunately, it is a lot harder to find vacuum leaks than diesel fuel leaks. In talking about this issue it is good to be clear in the nomenclature. The primary filter is the the one before the lift pump (usually located above the chassis battery on U270s) and the secondary filter is mounted on the block just before the lift pump. The primary filter is not as fine a matrix as the secondary which is a 10 micron filter while the primary will typically be around 30 microns. I assume that the filter you removed and found empty is the primary (suction side)?

How many key on cycles did you do? It can take quite a few cycles to prime the system once it has been open to air. I struggled with Stop Engine lights because of the CAPS system losing prime for a couple of years, keep in mind this after I had Foretravel replace ALL of my fuel lines. Following is an incomplete list of the steps I took before I finally bypassed the Cummins lift pump and installed a FASS full time pump and an  Autometer  electronic fuel pressure gauge with remote display. 
1. Primary filter system (Davco 382)
2. Upgraded the fuel cooler and associated plumbing eliminating several 90 degree elbows in an effort to improve the flow
3. Changed both sets of filters numerous times as the stop engine lights came on.
4. Had the fuel polished by Keith from MOT.
5. Etc. (Other stuff I don't recall at the moment)

All of the issues regarding my fuel system were solved once I installed the FASS lift pump, and the addition of the Autometer gage lets me monitor the situation in realtime. The OEM system constantly has a vacuum all the way from the tank to the  CAPS pump while the engine is operating. With the FASS system supplying the CAPS pump with a low pressure feed of between 13 to 17 PSI depending on the load, there is much less potential for fuel starvation which could result in overheating and damaging the internal seals in the CAPS assembly.

Don
Hi Don, do you have pictures of the upgraded fuel cooler installed?  Thanks!
1999 U320 40 WTFE build #5462