Accurate fuel mileage readings - Page 2

**BroncoHauler** · 08-30-2007, 10:21 PM

Quote:

Originally Posted by Ford_6L_E350

While talking to friends at work, it became clear that not everyone can get accurate fuel fillups, especially with Ford diesels, pickups and vans.

The Ford fuel tank has a vent that gets covered with about 4" of the tank not filled. Maybe the purpose is to allow some room for the fuel to expand, or maybe not. But, after the vent is covered, diesel 'foam' comes up the filler neck and causes the pump to shut off. When that happens depends on the fuel delivery rate and how level the vehicle is and probably other factors, like brand of fuel.

As far as I can tell, there are only two ways to get consistent fillups:

- Fill the tank past the 'foam' point, until fuel is visible in the filler neck.
- Use slow delivery and the automatic shut-off will be pretty consistent.

Filling the tank past the automatic shutoff has frequently caused a Check Engine Light (CEL) on my van. The light would come on about 150 miles after a fillup and stay on for several restarts. I have to admit - it was my wife that actually noticed the connection to the fillups.

Now I run the pump on the slowest setting on the handle and the amount the pump says agrees with my onboard computer (Scangauge) quite well - frequently within 0.1 gallons.

Because there are variations in pump speed and how level the van sits when filling, I don't pay much attention to any single tank. Usually a tank with very high mileage was followed by a tank with very low mileage. That simply means the first tank was underfilled and the next tank took the amount used plus the amount that was underfilled at the previous fillup. I watch mileage over 3-4 tanks to see trends. I record every fillup in a logbook.

I also watch the fuel gauge. With my 46 gallon tank it takes about 150 miles for the gauge to come down to the 'F' mark. Each 1/4 tank after that takes about 100 miles. If the gauge drops faster than that, either we are using more fuel because of conditions (in town, high mountains, 4wd low, pulling a trailer) or I didn't get the tank full (which only affects the 150 miles to 'F').

When I put the Scangauge in my van, the mileage slowly went up as I noticed the conditions that caused high consumption and adjusted my driving habits. Overall I've averaged 16.53mpg over 45K miles. I've never had a tank over 20mpg, but have gotten down below 12mpg with slow off-road driving.

Mike

Hope to be getting a ScanGauge soon. That will give me the good or bad news soon, wrt mileage....

Herb

jage · 08-30-2007, 10:39 PM

I just went rounds with Sportsmobile on this as I only seemed to be getting about 33-35 gallons in after the low fuel light. After a few discussions I came away with the impression that after the fuel light came on I had 16 gallons, not 4ish.

Which caused me to run out of gas (the sputtering that geofff described). The sputtering continued well after getting gas, probably 2-4 miles, which would be most likely air in the fuel line).

These were conversations I had two weeks ago, and I "ran out" of gas nearly in front of the Fresno shop last week Sunday. It wasn't until I showed them a reciept for 38.127 gallons and again complained about the 46 gallon tank... well that led them to look at it. Having looked under the van and determined it was the 46 gallon tank they told me, then and only then, that it was a common problem to foam up and I had to fill slowly after that.

I filled it until I could see fuel in the neck and only got 6 gallons past the first cut off. The second time I tried to fill it slowly fuel poured out somewhere (the vent tube?) and onto the ground behind the side rail. Luckily I didn't get the smell too bad, but I wasn't in the mood to crawl under and see where it had come from.

Since then I haven't bothered to cap it off.

Also, the LOW FUEL warning seems to come on about once a gallon after the first time (or after starting the van if you turn it off during LOW FUEL), and I drove exactly 40.1 miles between the low fuel light and the beginning of the sputtering. I drove normally (thinking I had at least 10 more gallons to go) which is almost always 11.68 mpg.

Buji · 08-31-2007, 08:31 AM

Unfortunate, the scenario was where you got the data from, but useful it will be.

Sorry... I was channeling Yoda there for a minute

**daveb** · 09-03-2007, 03:01 PM

Mike, I seem to have the same problem Jage is having. The diesel is coming from somewhere other than the filler neck futher toward the center of the van. Now I fill slow until it clicks off by itself and add about 3 gallons. At my local station, All the pump handles have the vapor recovery fuction that keeps fuel vapors getting into the air. So the fuel, when delivered real slow, comes out from somewhere else or so it seems. Maybe some kind of a vent hose? All I know it takes about 5 min of high pressure water to get the diesel smell out. I have never let it get down too low because SMB told me that the Espar heater will not operate if the tank is below 1/4 as a safety factor. I plan to run it to the red this week and fill up to see how much it will take...DaveB

jage · 09-03-2007, 03:42 PM

When I was at SMB they said sometimes the something-or-other hose gets knocked loose. I think maybe there is a fill line from you main to the aux tank (the one which is at the same level as the fill tube)... if it's loose or partially out you might be getting spillage out of the middle, or between the two tanks. I haven't crawled under mine to see if what I'm describing is accurate.

My spill came on the fill nozzle and only happened when I was filling really slow, not when I was doing the fill-click, fill-click, fill-click, fill-click, fill-click, fill-click, fill-click, fill-click, fill-click method. Haven't reproduced or tried.

**daveb** · 09-03-2007, 03:58 PM

Jage are you saying that the 46 gal tank is actually 2 separate tanks? Once I get the fuel gage at low I will try to jam in as much as I can and see what happens. I want to know how much this thing holds but I wont go below the empty mark even though I would like to know how far it would run at empty...thanks DaveB

jage · 09-03-2007, 05:39 PM

They were saying something about how the fill tube for the aux tank was level with the fill tube-- I pictured it like this: (the thin blue lines being the tube that backs up with foam that the ford guys talk about cutting off)

But at the time I was convinced I had a 35 or 37 gallon tank and had had multiple conversations with them so I confess I wasn't really listening or asking questions.

kzemach · 09-03-2007, 06:12 PM

Quote:

Originally Posted by jage

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Wouldn't this make it kinda hard for the fuel to get _from_ the aux tank to the main tank? Internal baffles I can understand (all large 18 wheeler tanker trucks have a significant number of internal baffles to reduce sloshing and sudden weight changes), but this doesn't seem to make sense?

jage · 09-04-2007, 03:08 AM

well I've burned all my "what the H*77 is going on with my gas tank?" and probably all my other credit with SMB as well... someone else will have to ask.

alta825 · 09-04-2007, 06:47 AM

how about for those of us who have the chopped 31 gal tank on Quigley conversions instead of the OE 35 gal tank. Does it effect how the fuel guage performs?

I haven't been able to really put any miles on the van since I got it a few weeks ago but it seems like it drops from 'F' pretty dang quick, like alost w/in the first 10 miles or so. I haven't run it below halfway yet, tomorrow will be the inagural road trip as I'm fortunate enough that I have to go to Moab for work for a few days. If anyone w/ a Quigley conversion and the 31 gal tank could chime in that would be great, just looking to see what kind of trends y'all see and also what kind of reserve you get once the needle gets to E

Thanks

d