Has this ever happened to you

[Marv 920]

30 September 2024

Ford Motor Company

Customer Relationship Center

P.O. Box 6248

Dearborn, MI 48121

 

Subject: Ford Flex fuel starvation follow up

 

“My 2010 Flex 2FMGK5DC4ABA42595 starves for fuel and dies when there is 4 gallons + of fuel in the tank.

When the fuel quantity indicator reaches ¼, it suddenly drops to empty, and the annunciator panel shows 0 miles to empty. Shortly after the engine will die. Refueling shows 4 gallons + left in the tank.

 

What causes this and what is the fix. The local dealer does not have a clue about this issue.

I know other owners have had this problem, so it is not something new.”

 

I originally sent this on 8 August 2024, I have not received any response to my request.

 

Please advise.

Fords Response:  Nov 4th 2024

 

Communication does not always work. Note that I said: The local dealer does not have a clue about this issue.

Ford said: We recommend you contact your local dealer.

So much for that. Now I am asking the experts what you think might be causing this problem. My take on it is that the tank must have two sections and whatever pickup tube there is has broken so the pump does not pick up the fuel when the level drops below the break. Not sure how the quantity indicating system enters the equation.

Marv

[ri702bill 8,301]

As I like to say, "Keeping the Vice in Customer Service"

 

DO ask your local Ford Dealer if there is a TSB (Technical Service Bulletin) on this issue for your car or related model years. You MAY be able to see if there is by your VIN number...

[wh500special 2,167]

Marv,

 

This isn’t first-hand information; just relating to what happened to one of my coworkers.  
 

His Ford truck was suddenly running out of gas with 1/4 tank indicated.  By the gallons added to the tank it seemed like the gauge was approximately accurate.  
 

Tank refilled.  He did a fuel pressure test.  All was fine. Ran the truck down to 1/4 tank and it stalled. 
 

He dropped the tank and removed the fuel pump.   He indicated there is some kind of secondary fuel pickup in the tube a couple of inches up from the bottom pickup location.  Gets covered by a float or

something when the fuel level is low forcing it to take fuel from the bottom of the tank instead.   That float had deteriorated so the hole was just an open hole.  When the tank level dropped to that hole the pump would suck air and the engine would die. 
 

New fuel pump assembly fixed it.  
 

I would guess the upper pickup is meant to keep from taking fuel from the bottom of

the tank most of the time so that it’s cleaner and dry. 
 

I just googled it and found a similar story, so apparently not an off the wall failure. 
 

No idea why the fuel level displayed would also drop to empty in your case.  Wonder if it’s possible the computer won’t let the pump run if it thinks the tank is empty to protect the pump. If a CANbus sensor, this

functionality would be easy to implement.  I just replaced the fuel level sensor in my boat so I guess these things fail regularly. It showed no signs of being bad other than just not working correctly anymore. 

 

I’m interested to find out what you learn as I have a similar platform Ford Edge of the same model year. 
 

Good luck. 
 

Steve

 

[953 nut 55,152]

I had a very similar problem on a Dodge Dakota pick up. The electric fuel pump and level sender unit is inside the tank and moves up and down on a rod as the fuel level changes keeping the pump suction just below the fuel. The rod developed a little burr that would not allow the fuel pump slide past it so it never made it to less than a quarter tank full. The truck would "Run out of gas" at 1/4 tank full. Had to drop the tank and replaced the pump/sender unit.

[Marv 920]

Thanks fellows. Interesting. Falls in line with my thinking. I don' want to take it to the dealer just to have them guess, since they had no clue when I checked with them.

I have been driving it like that for a while. I fill the tank when I approach 300 miles. I am not so agile now to get under the vehicle to work on it anymore. I will have to continue using mileage as my quantity gage.

Marv

[adsm08 2,043]

I'm going to chime in here. Before I start I'm going to drop my credentials. I have been an auto mechanic for 18 years, 2 years in tech school, 5 years working for myself, 13 years as a tech at a Ford dealer, 9 of them holding Senior Master Technician status. My primary specialty is gas engine drive-ability and electrical/electronics diagnosis.

 

The first thing I have to say about your situation is that for any technical matters the absolute best outcome you can hope for from contacting Ford CRC (customer service line) is to waste your time. It would literally be more productive to pick your nose and wipe the results on the windshield.

 

Now, on to technical matters.

 

It looks like your Flex is FWD only, but that doesn't matter much, the Flex only has one style tank. Some other cross-overs like the Edge had a saddle tank for AWD and a more regularly shaped one for FWD.

 

In saddle tanks there is a transfer tube that goes up over the hump in the middle and allows the fuel pump to pull from both sides. Damage to that tube can prevent the pump from pulling from the other side (looks like the pump is on the passenger side of the tank).

 

The fuel level sensing system on these saddle tanks is goofy. There is a traditional level sender/sensor attached to the pump, a simple float and variable resistor card. There is a "fuel level sensor" on the other side. Same basic idea, just no pump attached. These units each report the level on their side of the tank and then the instrument cluster computer averages the two signals and puts that value on the gauge. So for example, if you have 1/4 tank in the side with the fuel pump, and 3/4 on the side with just the level sensor, the gauge is going to show you have 1/2 a tank.

 

From the Ford Shop Manual:

Quote

The fuel tank is a saddle tank design with variable resistance senders, driven by floats, that provide resistances related to the fuel level in each side to the Instrument Cluster (IC) . The fuel level is determined using variable resistance fuel sender units, with an approximate resistance range between 180 ohms ± 4 ohms at empty (E) and 10 ohms ± 2 ohms at full (F). The IC sends a reference voltage to the fuel pump module (RH side) and the fuel level sensor (LH side). As the fuel level changes, a float actuates a variable resistor on the fuel pump module and fuel level sensor, raising or lowering the fuel level signal voltage depending on the resistance of the fuel level sender (float and card). The IC monitors the changes in voltage from both senders and commands the fuel gauge with a corresponding movement of the pointer. If the IC detects the fuel level sensor circuitry is open, the fuel gauge defaults to the fuel pump module value only and the fuel gauge indicates E to one-half tank. If the IC detects fuel pump module circuitry is open, the fuel gauge defaults to the empty position.

 

Since high resistance is low fuel, and the system defaults to an empty indication when the pump side of the circuit goes open, that, along with the stalling, tells me the pump side is running out of fuel, while the other side probably isn't.

 

You say the gauge suddenly drops from 1/4 to 0 but refueling says you have about 4 gallons left. The Flex has an 18.6 gallon tank, so you are taking on about 14.5 gallons at fueling. That's roughly consistent with a 1/4 tank reading. All that is consistent with a damaged transfer tube. The tube is only serviced as part of the tank assembly, and I don't know of any way to test it, aside from removing the tank and inspecting the portions of it that are visible with the pump and level sensor removed. I'd suspect that you find a crack on the level sensor side, probably 1/4 to 1/2 way up the depth of the tank.

 

Last thing: DO NOT rely on the DTE (distance to empty) display in the cluster as a reliable measure of how far you can actually go before needing fuel. Ever. It is not an accurate or reliable indication by any stretch. It is the computer's best guess based on a rolling average of calculated fuel use over the last 500 miles and CURRENT driving conditions. This means that (and I have seen this happen) if you are near the end of the tank and you have been on the highway for a few hundred miles, then suddenly move into a stop and go or city-type driving situation it is possible for the number to go negative. If you reverse that scenario it is also possible to run out of fuel while it still shows 75 to 100 miles left to E.

 

 

 

 

[wh500special 2,167]

3 hours ago, adsm08 said:

I'm going to chime in here

 

 

 

 

I clicked on the excellent horse head in response to your post but I’m not sure that’s adequate to acknowledge what a great post you made.  This is fantastic!  Hopefully that takes care of Marv’s problem!   Seems unlikely very many would diagnose such a scenario.  
 

Excellent. 
 

Steve

Edited yesterday at 04:41 AM by wh500special

[Marv 920]

On 11/19/2024 at 8:23 PM, adsm08 said:

I'm going to chime in here. Before I start I'm going to drop my credentials. I have been an auto mechanic for 18 years, 2 years in tech school, 5 years working for myself, 13 years as a tech at a Ford dealer, 9 of them holding Senior Master Technician status. My primary specialty is gas engine drive-ability and electrical/electronics diagnosis.

 

The first thing I have to say about your situation is that for any technical matters the absolute best outcome you can hope for from contacting Ford CRC (customer service line) is to waste your time. It would literally be more productive to pick your nose and wipe the results on the windshield.

 

Now, on to technical matters.

 

It looks like your Flex is FWD only, but that doesn't matter much, the Flex only has one style tank. Some other cross-overs like the Edge had a saddle tank for AWD and a more regularly shaped one for FWD.

 

In saddle tanks there is a transfer tube that goes up over the hump in the middle and allows the fuel pump to pull from both sides. Damage to that tube can prevent the pump from pulling from the other side (looks like the pump is on the passenger side of the tank).

 

The fuel level sensing system on these saddle tanks is goofy. There is a traditional level sender/sensor attached to the pump, a simple float and variable resistor card. There is a "fuel level sensor" on the other side. Same basic idea, just no pump attached. These units each report the level on their side of the tank and then the instrument cluster computer averages the two signals and puts that value on the gauge. So for example, if you have 1/4 tank in the side with the fuel pump, and 3/4 on the side with just the level sensor, the gauge is going to show you have 1/2 a tank.

 

From the Ford Shop Manual:

 

Since high resistance is low fuel, and the system defaults to an empty indication when the pump side of the circuit goes open, that, along with the stalling, tells me the pump side is running out of fuel, while the other side probably isn't.

 

You say the gauge suddenly drops from 1/4 to 0 but refueling says you have about 4 gallons left. The Flex has an 18.6 gallon tank, so you are taking on about 14.5 gallons at fueling. That's roughly consistent with a 1/4 tank reading. All that is consistent with a damaged transfer tube. The tube is only serviced as part of the tank assembly, and I don't know of any way to test it, aside from removing the tank and inspecting the portions of it that are visible with the pump and level sensor removed. I'd suspect that you find a crack on the level sensor side, probably 1/4 to 1/2 way up the depth of the tank.

 

Last thing: DO NOT rely on the DTE (distance to empty) display in the cluster as a reliable measure of how far you can actually go before needing fuel. Ever. It is not an accurate or reliable indication by any stretch. It is the computer's best guess based on a rolling average of calculated fuel use over the last 500 miles and CURRENT driving conditions. This means that (and I have seen this happen) if you are near the end of the tank and you have been on the highway for a few hundred miles, then suddenly move into a stop and go or city-type driving situation it is possible for the number to go negative. If you reverse that scenario it is also possible to run out of fuel while it still shows 75 to 100 miles left to E.

 

 

 

 

You have confirmed my suspicion. Thank you very much. Perfect response. I do not rely on distance to go indication. I go by mileage driven and I keep track of MPG on each fill up.

Marv