Skip to main content ↑ ↓
Topic: Engine, Generator and Aquahot Fuel Line Replacement (Read 986 times) previous topic - next topic

Engine, Generator and Aquahot Fuel Line Replacement

Starting on the fuel line replacement project.  Have not had any engine starting issues, but had to run a temp line for the generator this summer.  The ends over the fittings are cracked and at 23 years, it is time.

Been reading about BigDog's challenges and glad he finally got his issues resolved.  I will learn from his experience and appreciate all of the documentation provided by others who have already completed this job.

Fuel line is on order and due in this week, so started by emptying and pulling the fuel tank.

Right off the starting line I had some challenges.  While removing the fuel tank door and trim several of the trim screws twisted off just below the head.  Was using a hand screw driver, and it did not take much effort to twist them off.  The others were not exceptionally tight, so not sure why the heads twisted off so easily.  Did others have this problem?

Also had a challenge pulling the fuel tank out.  It is a very tight fit between the front bulkhead and the bay divider panel.  Tank could not be lifted much due to the aqua-hot supply line but it was enough to clear the low point drain.

Bought a cheap come-along at Harbor Freight thinking it would not take much pull the tank out, but the puller handle folded over.  HF gave me a refund and I purchased a 2 ton model from Home Depot which did the job but it still took a lot of work getting it out.  Pretty sure I will have to use come-along from the opposite side to pull the tank back in.

Added a picture of the engine supply side hose at the tank fitting.  Definably cracking and the same can be seen at primary filter connection.
40ft 1997 U320

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #1 –
Screws can be a pain. Seems brute force snaps them off. I use a cordless impactor and actually prefer a weak battery to tap them out. Kroil helps. Sometimes tapping them tighter a little helps before removing. Striking the head with a hammer wakes them up also. I do own a strike impact and that also is useful. There are several 5/16 bolts on the forward bulkhead that I relieved the sharps on the top of the head. Prevents scraping the tape. Look closely at the routing of the lines on top of the tank. You will have to reproduce that layout to keep from kinking.
Scott
Scott and Kim Davidson
If you're going to be dumb, you got to be tough.
DEGOIWKY
Don't ever get old, it will kill you
June 30, 2020
2001 U320 3610 Barn find
Build 5834

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #2 –
Mine had fiberglass covers over the tank and the truss for the slide prevents removing cover on drivers side. I pushed tank back in. I recall someone saying yours comes out the left side. I went to great lengths to reinstall covers and reseal to control over fueling leaks. Don't forget that the fuel tank drain needs to be removed before sliding tank.
1 engine fuel and return lines
      A pickup to secondary filter/lift pump line
      B secondary filter to primary filter line/pump was a factory-crimped line
      C pump to ECM cooler another factory crimped line
      D ECM cooler to fuel cooler line.
      E cooler to tank return line
2 aqua hot fuel and return lines
      A Pickup line To filter  Note my filter was located behind left headlight
      B filter to Aquahot
      C Inside Aquahot fuel feed line
      D. Inside Aquahot return line
      E. Outside Aquahot return line
3 Generator
        A. Pickup to filter
        B  Filter to back of generator slide box
        C generator slide  box to generator
        D inside generator to fuel pump
        E fuel pump to fuel filter primary
        F injector return line. To box fitting Note mine was 3/16" To box
        G return line to generator slide box 3/8
        H generator slide box tank return line 3/8
Your lines may be a different size , point being there is a lot of lines that should be changed at fuel line change and to complete there is a lot of work involved.  Basically I changed all flex lines one after another till all we're replaced. I did verify that all lines were clear after tank was installed and still dry. I had to re-pull tank to find that my generator line was kinked. I used a piece of 1/4"x2"x4 foot plate With a slight bend about 18" from the end as a shoehorn to insure placement.
Scott
Scott and Kim Davidson
If you're going to be dumb, you got to be tough.
DEGOIWKY
Don't ever get old, it will kill you
June 30, 2020
2001 U320 3610 Barn find
Build 5834

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #3 –
I used a very long straight steel brake line from a auto parts store to feed the generator line from one side to the other. With a side generator, it's easy to see through the bulkhead hole to a light on the tank side. I just pushed the end of the brake line into the hose and wrapped it in tape so it would not catch on anything and then fed it though. When it come time to replace the main fuel lines to the back, I may investigate steel lines as I never though much of rubber hoses to do the job.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #4 –
Quote from: Pierce & Gaylie Stewart –
I used a very long straight steel brake line from a auto parts store to feed the generator line from one side to the other. With a side generator, it's easy to see through the bulkhead hole to a light on the tank side. I just pushed the end of the brake line into the hose and wrapped it in tape so it would not catch on anything and then fed it though. When it come time to replace the main fuel lines to the back, I may investigate steel lines as I never though much of rubber hoses to do the job.

Pierce
Great idea using brake line to stiffen the hose and make it easier to push into place.

Pulling the generator fuel supply and return hose is pretty easy on the 1997 front generator.  The only challenge is the supply connections for both the generator and engine are in the center of the tank and un-accessible without pulling the tank.  The generator supply was pulling in air.  A prior owner has replaced about 4 ft of the hose presumable in an attempt to correct the issue.  I did not want to do the fuel line work in the heat of  the summer, so I ran a new hose into the tank bay and over to the driver's side.  Purchased a replacement tank filler cap, disassembled it to remove the spring, drilled a hole in it and pushed the supply line through.  Put a check valve on the hose and dropped it into the tank.  Worked great, but now I will connect it to the tank generator supply fitting.

40ft 1997 U320

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #5 –
Quote from: dsd –
Mine had fiberglass covers over the tank and the truss for the slide prevents removing cover on drivers side. I pushed tank back in. I recall someone saying yours comes out the left side. I went to great lengths to reinstall covers and reseal to control over fueling leaks. Don't forget that the fuel tank drain needs to be removed before sliding tank.
.......

Your lines may be a different size , point being there is a lot of lines that should be changed at fuel line change and to complete there is a lot of work involved.  Basically I changed all flex lines one after another till all we're replaced. I did verify that all lines were clear after tank was installed and still dry. I had to re-pull tank to find that my generator line was kinked. I used a piece of 1/4"x2"x4 foot plate With a slight bend about 18" from the end as a shoehorn to insure placement.
Scott

Scott,  thanks for listing all of the extra hoses.  I will plan to replace all of them but priority at the moment is lines to/from tank so I can get the tank back in place.

I pulled the tank out the passenger side.  It would probably come out the driver side, but all of the return connections are on the passenger side and more importantly, there is a 40ft fifth wheel parked in the space next to me so I do not have room to work on that side.  Fortunately, the vehicle that parks on the passenger side leaves me room and it frequently out of the spot which gives me even more room.

I pulled the tank 3/4 or more of the way out, removed all of the hoses and cleaned it up. I did not remove the drain plug but was able to lift the tank enough to clear it, though the aqua-hot supply hose definitely limits how much the tank can be lifted.

I was able to remove fiberglass cover on the driver's side.  It was caulked heavily and double sided taped to the tank, so it had to come out.  With it removed, it gives access to climb into the bay from that side and push the wires and hoses up out of the way to prevent them from catching on the tank which let me push the tank about half way back in without a lot of effort.  Left it there while waiting on delivery of the replacement hose, but do not think I will be able to manually push it all the way back through without some assistance.....just seems too tight of a fit.
40ft 1997 U320

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #6 –
Tank is out, cleaned up and waiting on new hoses....well not completely out, but enough to access all of the hoses.

The hose connected to connection marked vent in the attached picture is routed and terminates just in front of the front bulk head.  Is it a special vent valve?  Asking because it looks different than the other fittings.
40ft 1997 U320

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #7 –
They changed the configuration between '97 and '99

https://www.foreforums.com/index.php?action=dlattach;topic=26797.0;attach=36832
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #8 –
Quote from: craneman –
They changed the configuration between '97 and '99

https://www.foreforums.com/index.php?action=dlattach;topic=26797.0;attach=36832
Looks like on the 99 they have separate fittings for the aquahot supply and return, which would provide a little more headroom for lifting the tank up some to slide it out.


40ft 1997 U320

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #9 –
My fuel line replacement project is progressing, albeit very slowly. 

Hope to reconnect the aquahot tomorrow.  Will it self prime or do I need to use a vacuum pump to fill the new hose?
40ft 1997 U320

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #10 –
Daydreamer,  The Webasto fuel pump will self prime given enough time.  The blower motor will really rev up on air and you can hear it load up when the fuel finally gets there.

This is not the best use of the fuel pump and any efforts you make to get fuel the the heater will be appreciated by the pump.
Rudy Legett
2003 U320 4010 ISM 450 hp
2001 U320 4220 ISM 450 hp
1995 U320 M11 400 hp
1990 Granvilla 300 hp 3208T
Aqua Hot Service Houston and Southeast Texas

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #11 –
Quote from: DayDreamer –
My fuel line replacement project is progressing, albeit very slowly. 
Sounds like your getting ahead of it 👍👍
Just keep plugging away at it. I always avoid figuring how much is left, it's alway more than I figured, then all of a sudden it's done.
Scott
Scott and Kim Davidson
If you're going to be dumb, you got to be tough.
DEGOIWKY
Don't ever get old, it will kill you
June 30, 2020
2001 U320 3610 Barn find
Build 5834

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #12 –
almost done.  Just need to connect the generator return line and waiting for the hose end fitting to be delivered.  I reused all of the other fittings but this one was not the original and did not have a swivel, so have one on order.  I thought connections at the tank were JIC and ordered the wrong ones,  They are SAE 45deg and the generator supply and return are both dash 6.

Fired up the aqua-hot and all works, no leaks.

Fired up the engine and all working well too.  Although I was taking care to not kink the hose, I did, so had a hard time priming it.  Pressured up the tank with 3 or 4 PSI and was not getting anything out of the line before connecting it to the pre-filter so investigated further and found the kinked line.  After getting that resolved, pressured the tank back up until getting fuel at the pre-filter, then connected the line and used the air purge a couple times.  Engine started, then quit.  Purged a couple more cycles and engine started and ran without issues.  YES!! Success!!

Could have used an extra set of hands putting the bay door back on but got it done.

thanks for all of the help.
40ft 1997 U320

Re: Engine, Generator and Aquahot Fuel Line Replacement

Reply #13 –
Received the generator return line hose end fitting for the tank side and finished up this project.
Used item 10C360 from Grainers which is a brass, straight swivel 3/8" hose barb by 5/8-18 Female SAE.
40ft 1997 U320