Low Fuel? Really???

[cbr046]

I hope this is as entertaining as it was painful (for me) . . . .

After being nestled between two idling semis for the night I started driving early this am a when the low fuel light came on.  I had driven 650 miles and figured on another 75 miles before reaching my fuel stop.  OK, maybe I was a little hard on the throttle (using cruise most of the time at 68 mph with a lot of hills).  There was a Love's 24 mile ahead so I should be ok.  So the question became, "How many miles reserve do I have when the fuel light comes on?". . . . . or, "Is this another fun entertainment feature of the Holiday Rambler / Monaco instrument cluster?"

Some internet checking didn't reveal the answer I was looking for, and I didn't want to stop and spend time and fuel driving around a truck stop if it turned out to be a "bad light", so I pulled over on the interstate shoulder and started searching the owners manual.  About the time I gave up on the manual giving me a straight concise answer THE ENGINE QUIT!  Great, that little lean on the shoulder put the fuel on the wrong side of the tank.  I was within sight of the Love's, so started walking with a 5 gal can and a 2 gal can.  The walk back took a LOT longer as 5.4 gal of diesel is HEAVY!  The 2 gal can not so much.  Lots of stopping, breathing, walking, stopping . . . . Dump the fuel in and go through the "prime" routine 4 - 5 times.  Finally it compresses to life!  Waste no time, release the brake, hit D and nurse it on the shoulder.  It pretty much quit right away and wouldn't re-start while rolling so I coasted down the hill and up the other side almost to the ramp.  Now the coach L-R is level but the nose is pointed up sightly.  Sure enough, the sender is on the front-left of the tank. 

The second time to the fuel pump I unloaded my dirt bike and rode it to the station, then backwards on the shoulder back to the coach.  Got another 5.4 gal of diesel, dumped it in, prime routine 4x, cranked up and got down the ramp, past the stop sign, right turn and on my way to the truck entrance IT QUIT FOR THE THIRD TIME!  I rolled to a stop in the middle of the road as there was no shoulder to pull off onto.  Now I'm in the middle, in a sort of turn lane.  I have trucks going by in a single lane on both my left and my right. 

Ok, it's got 12+ gal of new fuel . . . . gotta be the primary filter.  Tested it with the drain valve and it was pretty dark (like dark as coal) with a few flavor specs floating around.  Not good.  This fuel filter had 7,000 miles on it and I didn't figure on it needing replacement with the regular driving I was doing (most weekends).  I don't add any treatment, just keep feeding it diesel.  OTOH, I'm pretty naive with diesel and don't know what a replacement schedule should be.  I (obviously) thought it would be much longer. 

The fun part was closing the side hatch (where AC condenser is) with each semi going by to get access to the filter.  Fortunately it was a slow morning and they weren't going fast.  And it was quiet enough I could hear them pulling out, get out and close the side hatch before they got close (they would have clipped it for sure).  They must have thought I was nuts.  (ok, point taken)

Swap the Donaldson P555001 fuel filter, go through 4 prime cycles (again), crank, crank, crank and fire.  Drive up, get fuel and back on the road.  Only took 3 hours but I got a good workout (and lesson) in the process. 

Now . . . . with all the driving and fuel filling (7.6+5.2+31.7 drive 50 miles +45.6+3.4) I only put 93 gal into a 100 gal tank WITH the 50 miles from the expensive truck stop to cheaper fuel . . . . somewhere around 13 gal remaining when it quit the first time.  I've gone 800+ miles on several occasions, but never with a low fuel light.

The last time this happened, 7,000 miles ago, the ATC light would flicker and transmission downshift while cruise control was engaged. 

WHY WOULD THE LOW FUEL LIGHT COME ON WITH A CLOGGED PRIMARY FUEL FILTER?  I had fuel . . . .

And yes, I'm back home now.

- bob

PS - 48 years ago I had a girlfriend that, after getting stuck on flat ground in an Austin Healy Sprite, said that life with me was never a dull moment.  This one probably tops them all (for me). 

[Jeeper44]

I can't answer about the low fuel light. I can tell you though after 30 years of driving tractor trailers, if I ever ran out of fuel I would get enough to limp to the closest fuel station, then change the fuel filter immediately. Diesel filters tend to clog if you run out of fuel. I don't know if its the crud at the bottom of the tank, or the air hitting the filter element. I just know the couple times I didn't immediately change the filter, I regretted it soon after when the truck would start running rough. This applies even if I had a brand new filter installed when I ran out of fuel.

Edited October 19, 2021 by Jeeper44
typo

[Robert U]

My 2000 Dip's low fuel light comes on when I am down to 15 Gal. I have never trusted the fuel gauge. I go by the odometer. My fuel mileage is 8.1 miles/gal since I bought it new. 100 gal x8 =800 miles. I refuel around 500 miles. 7000 miles on a primary fuel filter is really pushing it.

Bob U

[Flyinhy]

Just from my past experiences of being a mechanic, I never go below 1/4 of a tank. When you go below that the bellows of the tank will allow the water and other contaminates to be easily picked up into the system.Always keep a spare filter and a little extra diesel for such a problem. Not a bad idea to drain your tank every once in a while either.......gallons of hidden surprises in a 20 year old fuel tank. 😀 

[Nevada Rob]

If a fuel tank is listed at 100 gallons that would be the total capacity by cubic volume based on the dimensions of the tank. The critical number is how much you can DRAW from the tank. You will never get 100 gallons from a 100 tank. There needs to be expansion room in the tank to accept the warm/hot diesel being returned from the engine. That is why the fill neck is not on the top of the tank but rather close to the top of the tank. The fuel pick up tube does not sit on the bottom of the tank either.  A good rule of thumb is to figure that one can draw 90% of the total capacity of a fuel tank. My coach has a 150 gallon tank. I figure at 135 gallons used I better be at a fuel pump or risk having a great adventure. I get about 700 - 750 from a tank of fuel. With the Gas Buddy app I usually have no problem finding fuel at a decent price within 100 -150 miles before sucking fumes. 

[jacwjames]

I use a Silverleaf VMSpc monitoring system which does show fuel consumption and miles left to travel on my 128 gallon tank.  I usually never let the tank bet below 1/3 empty, but I know that the VMSpc is providing me with very accurate information (probably within 1% of actual fuel consumption). 

I also know that my generator runs out of fuel at 30 gallons left in the tank (so right at 1/4 tank) and I do not want to be stranded without being able to run the generator. 

That being said I will push it, my last trip I wanted to fuel at the Sam's club ~25 miles from the house.  So when I stopped I ended up pumping 100 gallons into the tank.

I recently installed a FASS transfer pump with the filtering capability, so I am continuously polishing the fuel in the tank.  I installed a fuel pressure gauge on the secondary filter so know how much fuel pressure I have going to the injection pump.  Gives me a warm fuzzy feeling everytime I look at the gauge and know everything is OK.

[Cubflyer]

Your story makes me feel really good about spending about $700.00 and many hours to install a F.A.S.S. filter and pump system to replace my primary filter and bypass the stock lift pump.   I had black diesel fuel when I got my coach last spring, between the filters and the full time running lift pump with a pressure gauge to tell me the pressure between the primary and secondary filter (condition of my primary filter and pump) and biocide, my engine has run flawlessly for 3000+ miles.   

Not sure I could walk with fuel cans like you.....

Ken 

[lake49068]

Don't be fooled by the advertised fuel tank capacity.  My Neptune supposedly has a 75 gallon capacity and I discovered that like a light aircraft, it's the USABLE fuel capacity that matters.  On our first post-purchase trip, I ran out at the Flying J pump thinking I had at least 10-15 gallons remaining based on the trip odometer reading since the previous fill.  I contacted tech service and asked "what's the usable fuel capacity.". Not a clue.  So on the next fill I let the pump auto shut off, used a flashlight to look down the filler neck and continued to add fuel until it rose into the filler neck.  An additional 13 gallons!  So now whenever I refuel I use my flashlight and visually make sure a full tank is actually full.  PITA but now I'm sure that my trip odometer and fuel gage are synched.

Adam

[jacwjames]

14 minutes ago, lake49068 said:

Don't be fooled by the advertised fuel tank capacity.  My Neptune supposedly has a 75 gallon capacity and I discovered that like a light aircraft, it's the USABLE fuel capacity that matters.  On our first post-purchase trip, I ran out at the Flying J pump thinking I had at least 10-15 gallons remaining based on the trip odometer reading since the previous fill.  I contacted tech service and asked "what's the usable fuel capacity.". Not a clue.  So on the next fill I let the pump auto shut off, used a flashlight to look down the filler neck and continued to add fuel until it rose into the filler neck.  An additional 13 gallons!  So now whenever I refuel I use my flashlight and visually make sure a full tank is actually full.  PITA but now I'm sure that my trip odometer and fuel gage are synched.

Adam

I can fill from either side and the fuel tank is angled down into the tank.  When I fill I continue pumping until the fuel starts to burp.

If i tilted the coach (which I've never done) I could probably get 10 more gallons of fuel it it. 

The most I've ever pump was been ~110 gallon after driving ~900 miles (never got out of the drivers seat).  That was pushing it, never done that again. 

Edited October 19, 2021 by jacwjames

[ktloah]

I never let my fuel get below much more than 1/2 before topping off again

[cbr046]

I like to drive, not spend time at the pump.  Apparently I like to walk, too. 😄

Last time the fuel filter clogged I was getting an intermittent ATC light and transmission downshift while in cruise concontrol.  Unless I had low fuel which compounded the trash headed to the filter.  2 issues, not one. 

 

7,000 miles / 5 months on this filter.

 

Without dropping the tank, is there a way to clean the fuel and minimize tank trash?  A particularly good additive?

 

- bob

Edited October 19, 2021 by cbr046

[Chuck B 2004 Windsor]

Many decent size yacht clubs has the equipment to clean the fuel tanks and polish the fuel in them.  Chuck B 2004 Windsor

[seadoo200hp]

Seems to me when I fill from the drivers side I can get more fuel in the tank every time versus the passenger side.  My fuel gauge needle goes way past the full mark which I love.  Just got back from a 2300 mile trip on mostly flat land pulling a toad and mileage was very good with cruise control at 60.  Noticed just a 3 to 5 mph higher speed and mileage goes way down.

[cbr046]

51 minutes ago, seadoo200hp said:

Noticed just a 3 to 5 mph higher speed and mileage goes way down.

I think that was part of my problem, plus the previous 2 fillups calculated out to 11.0 and 10.0 mpg meaning I didn't have near a full tank when starting that long leg (or a full deck for that matter).  *AND* I was maintaining ~68 mph with cruise control vs 64 ish and a manual foot. 

Still, the tank gauge read 1/8 tank when low fuel light came on. 

Never drive faster than your guardian angel can fly.

- bob

[Chuck B 2004 Windsor]

I like to know where my fuel level is in my tank.  So I calibrated my gauge to be just on full to get a more accurate reading with the gauge.  Chuck B 2004 Windsor

Running out of fuel putting me on the side of the road was a two timer for me.  The first and last time I did that.  I tried not to let the fuel level in the tank go below 1/2 a tank.  Chuck B 2004 Windsor

[96 EVO]

When I hit 1/3 tank, I'm fueling up at the next truck stop (unless I'm nearly out of California 😉)!

BTW.... I'm not convinced you pick up a bunch of nasty crap off the bottom of your tank when you get very low.

Your fuel pickup is always getting the fuel from close to the bottom of the tank, no matter how full the tank is!

Edited October 20, 2021 by 96 EVO

[Chuck B 2004 Windsor]

Yes but when the coach is moving the contents of the tank get mixed up with anything else that is in the tank.  When the level in the tank gets lower,  any foreign matter in the tank becomes more prevalent.   Chuck B 2004 Windsor

[ktloah]

I never let my fuel get below much more than 1/2 before topping off again. You will get water and crap when you let it run low...remember,  these are diesels, not gas which can operated on a very low tank...

Right on Chuck,  we'll said 

[Ivylog]

Many years ago at a rally the best explanation of our dash gauges was it’s an entertainment center… the reason I put in a Silverleaf system. Our fuel gauges seem to get less accurate with time. I reset my odometers and mpg at each fillip.

The bottom of the short nipples on my 150 gallon tank are below the top of the tank by 1” or more. The vent must be on the driver’s side as I can lean away and put 15 more gallons in without it putting fuel… unlike the passenger side. The fuel pickup is on the passenger side and having run out within sight of the station, I leaned the rig to the right and primed 4 times (2 minutes) so it cranked up and got me to the pump…put 160 gallons in my 150 tank.  I do not lean and fill if I’m headed to a CG as there’s very little air in the tank and the ground is usually colder than the air…fuel could warm and expand onto the ground.

Like 96 EVO ^^^, I don’t buy into you’ll get more crap if you run the tank down to near empty. The pickup is very close to the bottom of the tank and it’s cut at a 45 degree angle. It’s always getting the fuel from the bottom 1” of the tank. Only time I don’t put in 130+ gallons is when I top off near home when it will sit for several months. I usually get 30,000 miles out of the primary fuel filter and 40,000 on the secondary… no I’m not into annual much of anything. Your mileage may be different.

Edited October 20, 2021 by Ivylog

[dandick66]

I have a 2012 Diplomat with a 100 gallon tank.  Three years ago when returning from a trip the low fuel light came on.  I told myself I had plenty of fuel to make it home.  Well, about 1/2 mile from home I got a check engine light.   I continued and made it home.  The next day I went to move the coach and it stalled in the driveway.  The code was for low fuel pressure.  I added 5 gallons of fuel and primed the pump and all was well.  I drove to the fuel station and it took 98 gallons.   I will never push the limits again.

One lesson I learned is that now I level the coach when I’m refueling.  This makes a big difference in the amount of fuel you get in the tank.  I figure it was about 10-15 gallons. 
 

Dan D

[jacwjames]

I tried to rely on my fuel gauge when I first bought our coach, I even recalibrated it, which helped.  The only two readings that were correct is when it was full or empty, it was a guessing game anywhere in between.  The gauge would barely move for ~300 miles and then it would drop quickly.  I kept a written record of odometer and gallons to fill between fill ups and knew how many miles I could safely travel. 

I took the mystery out it by adding the Silverleaf VMSpc.  Besides being able to track the vitals on the engine and transmission I find that the trip meter with fuel usage to be extremely accurate.   I use this in conjunction with Gasbuddy to plan my fuel stops and try and save money. 

[tomevansfl]

On 10/18/2021 at 8:40 PM, Jeeper44 said:

I can't answer about the low fuel light. I can tell you though after 30 years of driving tractor trailers, if I ever ran out of fuel I would get enough to limp to the closest fuel station, then change the fuel filter immediately. Diesel filters tend to clog if you run out of fuel. I don't know if its the crud at the bottom of the tank, or the air hitting the filter element. I just know the couple times I didn't immediately change the filter, I regretted it soon after when the truck would start running rough. This applies even if I had a brand new filter installed when I ran out of fuel.

We bought our Diplomat last summer. I have always bought fuel when I got down to about 1/4 tank. On trip before last, I got to the campground and the gauge said just under 1/4 tank. The campground was about 1-1/2 miles from the interstate and there was a station with diesel at the interstate.
 

When I left the campground I headed straight for the station. I got into the left turn lane waiting for a gap in traffic and the engine quit and wouldn't restart. After 15 minutes of calling and using Yelp I found a mobile diesel mechanic and called. He towed the RV into the station to get it out of the turn lane and to safely work on it. I knew he would have to re-prime the fuel pump. He showed me a sample of the fuel and said there was trash/debris in the fuel.  To be honest, it looked clear and I saw no debris but I did have my sunglasses on, though.

 

Thirty minutes and $730 later, I pulled up to the pump and put 50 gallons in to get me back home. On the way home the engine skipped a few times but at that point I was almost back to the storage lot so I pressed on. On the last trip (40 miles each way) the engine skipped when going up hills on he way home. 
 

Would this just be air or debris in the fuel line? My wife is worried about engine trouble until I can get it serviced. I live in Orlando and none of the RV dealers in town will work on a Monaco.  I have an appointment in May at the Cummins Coach Care. They didn’t want to work on a Monaco either until I insisted that I just wanted the engine checked, nothing to do with the chassis.  Then the scheduler was willing to include servicing generator. 

Anyway, should I get a new fuel filter?  It was replaced in July by the dealer before I picked the RV up.

[cbr046]

Probably sucked up the trash from the bottom of the tank and clogged the primary filter.  *IF* the mechanic replaced the primary filter I'll bet he missed the secondary filter, which shouldn't need changing but it will clog much faster if debris got past the primary.  If you can change filters try that, then take it for a test drive.  Remember to prime the primary filter with fuel.  The secondary filter doesn't need to be primed (I would fill it 1/2 anyway).  After filters are changed turn the key to 'on' for 30 seconds.  Turn it off and back 'on' 5 times, waiting 30 seconds in the 'on' position each time.  On the 6th time start the engine. 

If you don't take a lot of trips start using Biobor JF or some other fuel biocide. 

Oh, and my fuel gauge has been known to lie to me.  Ran out showing 1/4 tank.  Other times I could run it right down to 'E'. 

- bob

[jacwjames]

When we first bought out 2002 Windsor we relied solely on the fuel gauge, just dumb luck we never ran out of fuel for the generator and maybe even the engine.  One time I drove +800 miles before a fillup. 

I always park my rig with a full tank of fuel, this will limit the amount of condensation.  Initially I didn't use any additives and then when I was doing a service I changed fuel filters>>>the primary filter was almost completely clogged with a black slime (algae).  I knew of the additives from work and I started to use Biobor and after some more research and found another product called Startron which is an enzyme which is suppose to breakdown the dead algae.  Since doing this I have never had another problem, and this was after parking the rig with limited use as we built our new house. 

I use a Silverleaf VMSpc to monitor my engine but it also has a fuel consumed funtions which is VERY accurate.  Once you set it up with the size of your fuel tank it will show how much fuel is left and how many miles you can drive based on the mpg consumption.  Usually when I fill up I'm within 1% of what the Silverleaf says. 

I also know that my generator pickup tube will let me use 100 gallons of my 128 gallon tank, I was using the generator and it died, figured it was low fuel so went and filled up the rig.  So in most circumstances I'll try and get fuel before  I need more then 80 gallons, this will allow me ~20 gallon buffer for the generator just in case I get stranded on the side of the road.  It does happen, had road debris take out my radiator and it took 2 days to get a tow on a memorial day weekend. 

[Ivylog]

Having to change the fuel filters after running a tank dry or close to empty is BS. I run to near empty all the time… having put 160 gallons in a 150 gallon tank. The pickup tube is at the bottom of the tank… takes fuel off the bottom all of the time. I usually get 25-30K miles out of my fuel filters which I only change when the engine will not make 100% power.