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Topic: Fuel pump  (Read 567 times) previous topic - next topic

Fuel pump

This is my first post so please be gentle if I do this wrong.
I will always try and search for prior posts before asking questions.
We just purchased a 1998 U270 36 ft a couple weeks ago. 8.3 Cummins
Some of you may have seen my fb group post. "We did a thing"
I am pretty mechanical inclined and know my way around most vehicles, construction, plumbing and electrical systems.
This is not my first rv or diesel but is my first pusher, so I have a lot to learn from you folks.
Bus runs great, drove it 400 miles home. Good oil and air pressure, ran cool, didn't use any oil or smoke a drop.
Now my first question,
Is there a fuel pump in the tank. I can hear a ticking that sounds like a pump when the bus is running. It does it all the time and is always in time just like a clock, maybe even 2-3 seconds. I can hear it inside over the tank bay and outside.
Thanks so much

Re: Fuel pump

Reply #1 –
The 8.3 has a mechanical fuel transfer pump on the side of the motor. That is what you are hearing.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Fuel pump

Reply #2 –
This is at the fuel tank! In the first bay.

Re: Fuel pump

Reply #3 –
Greetings and welcome to the Forum!  We are always happy to "see" new faces around here, and will answer your questions to the best of our ability.

The fuel pump (usually called a "lift pump" or "transfer pump") on your C8.3 is located on the side of the engine block, down low on the curb side.  It is as Bruce said a mechanical pump which is powered by a pushrod running on a camshaft lobe.  On a factory stock coach, there is no electric pump in the fuel tank.  The lift pump sucks fuel from the fuel tank, and pushes fuel to the injection pump.  There is a manual (hand operated) priming pump built into the lift pump body.  See the link below for some photos of the lift pump:

new lift pump made a BIG difference

You might find the old discussion thread linked below interesting.  We went into some details on how the C8.3 fuel system operates:

Fuel System Science Project


1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fuel pump

Reply #4 –
Wonderful info and thank you so much. I understood there was a lift pump, and have read about them to a little extent relative to the 6bt and 4bt cummins.
What i didn't expect was to he able to hear it at the tank. Its a very audible chunk, chunk,chunk, chunk! Not so loud that it bothers you or is annoying, but you can here it even inside the coach.
I want to do everything i can to try and bullet proof and maintain the fuel system as best i can.
 I have been driving diesel pickups for 30 years and believe in good clean fuel and good conditioners. Are there any special fuel conditioners that these mechanical pumps and engines really like?

Re: Fuel pump

Reply #5 –
What you may be hearing is the fuel lines above the fuel tank pulsating and making noise,much of the fuel goes to the injection
pump and is returned to the tank,I use Diesel Clean on every tank of fuel,I see your not far from us,we are outside of Millington.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Fuel pump

Reply #6 –
Quote from: Wpduffey –
Its a very audible chunk, chunk, chunk, chunk!
Perfectly normal noise...very familiar to all owners of mechanical C8.3 engine coaches.  No worries.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fuel pump

Reply #7 –
Quote from: Wpduffey –
I want to do everything i can to try and bullet proof and maintain the fuel system as best i can.
The best thing you can do for your fuel system is use quality filters and replace them on a reasonable time/mileage basis.  What is a good quality filter?  What is a reasonable time/mileage basis?  Check your owner's manual for recommendations.  There are alternatives to the factory installed filter system.  Search "fuel filters" on this Forum for varied opinions and suggestions.

If you don't have a engine manual for your coach, there is one available in our excellent Forum library:

https://www.foreforums.com/index.php?action=media;sa=media;in=4294

The Forum Library is a very helpful resource, and provided free-of-charge for all members.  Use it to your advantage!

https://www.foreforums.com/index.php?action=media;sa=album;in=165

The Forum Wiki is also a valuable source of info:

start [ForeForums Foretravel Motorcoach Wiki]



1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fuel pump

Reply #9 –
Quote from: Protech Racing –
A tank lift pump may have been added.
True 'nuff...  I edited my earlier post to now read:  "On a factory stock coach, there is no electric pump in the fuel tank."



1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fuel pump

Reply #10 –
Even if added, still have never seen/heard of in in-tank fuel pump.  FASS and other booster pumps, but not in the tank.

But, I guess never say never.  Are there 12 VDC wires going into the tank?  If electric pump, would have to be.
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: Fuel pump

Reply #11 –
Thanks everyone, this settles my curiosity. It runs fine and we are jot having a fuel problem but i just didnt know what it was. An add one electric pump i assume would just humm.
I am not retired and still have a ways to go, so at this point we will never run enough miles to justify or meet service requirements.
My plan was (correct me if im wrong) we will just service once a year. All filters and fluids except trans, hydraulic and coolant fluids.
Being new to us, im planning to change everything right now. Have everything ordered.

Re: Fuel pump

Reply #12 –
Quote from: Wpduffey –
Being new to us, im planning to change everything right now. Have everything ordered.
Good plan.  Establish a maintenance baseline, where you know everything is fresh, then go from there.

Highly recommended to always carry at least one set (two is better) of spare fuel filters.  Never know when you might get a bad load of fuel.  A plugged up fuel filter will put you on the side of the road - most always happens in a not convenient location.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fuel pump

Reply #13 –
I have a 98 U270 with the mechanical engine. I also hear the ticking noise at the tank. Should have asked your question seven years ago but so confused by my first diesel pusher that it never hit critical mass. Welcome. Suggest you learn about the location of your fuel shut off solenoid and keep a couple of wire ties handy for when it quits working. It can be seen best from the front of engine passenger side, which of course is at the back of the bus near your mechanical fuel pump. I recently posted about my shut off solenoid while at Quartzite in January.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.

Re: Fuel pump

Reply #14 –
Are all the c8.3s 12 valve engines and mechanical bosch injection pumps?
This limits you on monitoring systems with hout the ecm correct?

Re: Fuel pump

Reply #15 –
Yes - 12 valve.
Yes - Bosch P7100
Correct - no engine ECM
Yes - you are limited on monitoring systems

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Fuel pump

Reply #16 –
I've noticed the same ticking noise coming from the fuel tank on our U295.  I thought that maybe it was the ticking time bomb on our original fuel lines :o
Dave and Kelli
1997 U295 40' Build #5188 CSGI
1995 U240 36' Build #4621 SBID-SOLD
2006 Jeep Wrangler Rubicon
 

Re: Fuel pump

Reply #17 –
Thumping sound is normal, the lower the fuel in the tank the louder the thumping..... thump along!  ^.^d
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota