Fuel Pump Issue?

Hi

Car didn't start last week, was low on fuel but still showing 40 km (~25 miles) left to empty. Last year my fuel pump module went bad so I thought this could be the same issue. Car sat overnight at work and the next morning I replaced the module (I wrote another thread about it). Car started right away and revved fine but later that day, when I went to drive home the car stalled when pulling out of the parking lot. Tried re-starting it but it died right away. Added 20 liters (5 gallons) of fuel and tried again numerous times with no luck.
Towed it to a mechanic close to work that I've used before. Car sat overnight.

Next day the mechanic told me he could not get it to start, pushed it into the shop and removed the rear bench. Then they tried and the car started right away, test drove it and at the end, they could not find anything wrong. Picked it up and filled up the tank. Six days later it is still running fine.

There have not been any CEL's or lean codes, only code was for low fuel rail pressure.

Mechanic said these cars had a transfer pump to send fuel from one of the tank to another and a sender pump to send the fuel to the HPFP. Is this correct or does the sender pump pick fuel from both sides?

I've been paying close attention since this happened and I can hear the fuel pump prime every time I unlock the vehicle, so that is working.

I suspect that what could have happened is that whatever picks fuel from the driver's side of the fuel tank failed to do so and the passenger side of the tank ran empty (remember this is a saddle tank divided by the drive shaft). Then it took a while to get the extra 20 liters of fuel I added into the system.

I plan to let it run low again to see if it happens again, this time I'll be carrying extra fuel in the trunk and I won't crank it so the system doesn't go completely dry.
If this happens it will confirm my theory but I still do not know if there is in fact a third (transfer) pump or what takes care of keeping the fuel level equal on both sides of the tank.
Thoughts?

 

Bump*

 

Been reading and lot and this is what I've found so far:

These tanks have two top openings on the top, one on each side. Looking for these pics I just found this diagram that shows a "fuel pump assembly - right" and a "fuel pump assembly - left".





The one on the driver's side is just some kind of fuel level sensor, that's it. I just googled the PN and this came up:




It does have a hose fitting at the bottom, not sure what goes there.

I also just found this interesting article on saddle tank fuel senders http://www.meeknet.co.uk/e38/sender/index.htm, it also talks how fuel is picked from both sides. This one if for a BMW but maybe Ford's is similar.

From all these pics it is evident that there is only one low pressure pump but there are two fuel level sensors. So maybe one of the two is bad in my vehicle and I simply ran out of fuel?

If anyone knows how to check these using Forscan please chime in.
Found the troubleshooting guide in the workshop manual, too complex for me but it says that the fuel level sender should be between 10 and 180 ohms. So I might try measuring that on both if no one replies about Forscan.

 

Update:
I've now confirmed that I am simply running out of fuel, the second module was never the issue.
Yesterday car died on my way home, fuel gauge was showing 1/4. Tried to start it once and it tried to but didn't.
Added 20 liters of fuel and it started right away.

Stopped at the gas station and was able to pump 36 liters (9.5 gallons).
If I add the initial 20 liters (5.3 gallons) that is 56 liters (14.8 gallons). I usually pump 68 liters (18 gallons) when the tank is empty so according to this, there were still 12+ liters (3.2+ gallons) in the tank when the car died.
Now, if the car died and there was fuel in the tank, that would mean the fuel was on the driver's side of the tank where the fuel pump (located on the passenger side) can't pull it.

So, I think the issue could be a loose hose or something related to the part pictured on the previous post. I've been avoiding doing any work on the car as it has been too damn cold these past weeks but I'll have to take that part out and see what I find.

I've learned that the Engineering mode shows left/right fuel levels and this would be very useful for what I am doing. However, the "press RESET while tapping START (without brake)" doesn't work on my vehicle. I know 2010's are different but if anyone know how to access this mode on this model, please chime in.

What still doesn't add up is that if there were 12+ liters on one side of the tank (12/68 = 18%) the fuel gauge reading should have been (18% right+ 0% left)/2 = 9%, which is not 1/4 tank (25%), so maybe one of the two senders needs replacing.
I hate replacing parts just for fun but if I don't see anything weird/obvious or if the resistance is not between 10 and 180 ohms, I'll order the part above, which is not that expensive.

 

Sounds like your crossover hose may have sprung a leak or is disconnected so its not pulling fuel from both sides. The hose connects between the fuel pump basket and the secondary float (blue circle in your pic above).

Here's the procedure to enter "Engineering Mode": https://enginepartsdiagram.com/access-engineering-test-mode-ford-taurus/

 

That is what I think/hope it could be.
The procedure you shared is for the 2013+, not for the 2010, but thanks anyway.

 

Oops!! I wasn't paying attention that you have a 2010. Give it a try anyway and see if it works.

 

Can't give it a try since there is no OK button on the steering wheel, or anywhere else.

 

I'll shut up now.

 

LOL !

 

Scrap and forget EVERYTHING I've written above... the friggin thing died again last night. Got home from work, everything seemed/ran normal. Didn't start at all an hour later, this time the tank is full of gas... all theories went in the garbage. Luckily it died in my driveway and not far away.
So I'm back to square one, either the fuel pump is going bad and has been failing intermittently, there is a bad connection somewhere, the fuel control module I just replaced is bad or there is something else that governs the pump is not working. Only thing I noticed is that didn't hear the pump prime last night when I opened the door.
Going to check the workshop manual to see if there is a way to test the pump.

 

Pull the back cushion and listen to the pump to hear if it's priming when it dies on you. Could be an intermittent pump failure? If you need an OEM one I have 1 used and 1 brand new out of my 13+ if you need one and can make that work. Not sure if there is any difference between 10-12 and 13+ I know they can both be replaced with the same DW300C however.

The crossover pipe that was mentioned when unhooked (I forgot to hook mine up when reinstalling) just makes your range go to shit when the fuel light comes on. Mine dropped from 35miles to empty to like 2 in the matter of 30 seconds and that's when I realized I forgot to put it on. It's my theory that the crossover pump only really turns on when the low fuel light pops on as it goes directly to the bucket of the main pump so I figure it pumps directly to there.

 

Is there an actual pump in the secondary unit or is it just siphoning to the main pump?

 

There is a transfer pump yes. It pumps over the saddle of the tank when fuel is lower.

 

Gotcha.

 

Mine has always been loud enough when it primes that I can hear it standing outside the vehicle, sounded like the washer fluid pump.
As of last night when I last checked, it was not priming when I opened the door.

Thanks for the offer, I did a quick search and so far have not found any info if that is the same part for the 2010, I'll keep looking.

I assume that you have replaced that pump yourself, if so, how hard was it?
I watched this video and that internal hose connector looks tricky and I have no way of emptying the tank, skip to 2:30

 

It's not horrible. You don't have to empty the tank just expect fuel here and there. Just be forewarned that you can't buy solely the pump and only can buy the entire housing which is about $300. Can but a dw300c though I think for about $175 and it'll drop in the 10-12 assembly very easily compared to the 13+

 

I am typing this veeeeeryyyyy sloooowlyy so I don't jinx myself... Read this silently, no popcorn or chips allowed !

Its been 10 days since it last died. That weekend I asked a friend that owns an SEL to let me use his fuel pump module. Swapped them and my car didn't start... this confirmed that the module is not the issue.
Pump was still not priming.

Went to remove the pump, disconnected all 3 plugs and thought "what if one of these is making a bad contact?"... sprayed them all with electronic cleaner and carefully bent (just a bit) each pin to ensure it would make good contact. Then noticed that the connector that goes on some sort of line sensor (???) was not locking (no click). Number 3.


Checked and noticed that the seal that goes way inside the connector was out of place, probably rubber has expanded after so many years. Using a thin nail played with it for a good ten minutes until I was able to put it back in place and get the connector to go all the way in and click (I now love that noise). Car started right away after that and has not failed since.

 

WWOOOOOHOOOOOOO!!! Now when you go to put everything back together make sure your tongue is sticking out and you don't breathe.