Service Manuals & Fuel Capacity

Erics40 · Post by **Erics40** » 14 Oct 2008, 20:33

I had yesterday off and just couldn't leave well enough alone. I pulled the fuel pump and sender assembly and bent the arm. At the mount end, I bent the wire straighter making the float rise and extend. It probably moved out a half inch and up a half inch.

Then I bent the lower kink to make the float droop. I put the pump/sender on a flat table and the float was about 1 inch above the surface. I bent the lower kink to drop the float to about a half inch below the table. At this point I twisted the arm at the float so the wire going into the float was the low point and the float points up at 10-15 degrees. With me?

I put it back in and hoped. I drove to work today (40 miles) and here's where the numbers lie: I have 280 miles on the odometer, the Miles to Empty reads 160 and the guage is at 1/3 full. It looks about right!! I am looking forward to the light and empty to see where the bottom is, but it's close enough now I will be able to live with it.

The best part, it can be done.

Regards, Eric.

Post by **billofdurham** » 15 Oct 2008, 11:45

Thank you for the update.

Other S/V40 owners will be awaiting the final outcome.

Bill.

Erics40 · Post by **Erics40** » 04 Nov 2008, 08:31

Here's the final result. I have adjusted the resistance to read 104 ohms when the pump/sender unit and the float are both on the table. This pops the fuel light on at 14.5 gallons, leaving the reserve amount to 1.5 gallons.

The float arm has to be bent 'shorter' (closer to the sender body) so the float at the top uses as much of the resistor as possible. On mine, the float at the bottom of the rubber sleeve (top of the tank) measures about 5 ohms.

This may be too much for casual fiddlers and parts changers but I'm posting just to show that it can be done. As a side 'benefit' I can pull the pump, adjust the float and reinstall everything in about 10 minutes. It's that easy. Be brave.

Eric.

Post by **billofdurham** » 04 Nov 2008, 11:19

Eric,

You have succeeded where others have failed, or even failed to go.

My friendly Volvo tech has been given a copy of your modifications. He told me that no-one where he works had come up with a solution for this common S/V40 problem. They would only advise trying a new sender unit which invariably read the same as the old one.

I am putting this in the Repair Database for future reference.

Bill.

deej · Post by **deej** » 22 Feb 2009, 06:58

hi, what a interesting read this has been

i have just taken delivery of a new S40 Rdesign sport and its a lovely car apart from its fuel tank range. i am currently managing to get 42litres into the tank from empty and managing to get 240miles out of a tank. As its a new car ive taken it into my local volvo dealer to inspect,last week I ran it nearly dry and it went into the dealer with the orange fuel light on,the needle deep in the red and yet when the technician removed the tank there was over 1/3 of a tank of fuel left. when i left the dealership and refuelled i managed to squeeze 43litres into the tank.
This week its going back in for a new sender unit as thats the only fault they can think it will be,after reading this im not sure if it will make much difference. I will repost once ive had the new unit fitted and any difference noticed, I hope it works as im getting fed up of filling the tank up twice a day.

Post by **billofdurham** » 23 Feb 2009, 11:43

deej, welcome to Matthew's Volvo Site.

Having read, on this and other forums, the numerous complaints about this problem it appears that most dealers are not aware of it and certainly don't know what to do to correct it. A new sender unit has not been successful in the cases I have read.

The only successful solution to this has been that of Erics40. See what the dealer has to say to that one.

Bill.

Erics40 · Post by **Erics40** » 06 Mar 2009, 06:52

Just a brief update on the fuel tank issue for those still in doubt. I performed the above sender modification some months ago and have used countless tanks since. When the light comes on, I have about two gallons remaining in the tank. When the "Range to Zero" indicator reads "0" (no miles left) there is less than a gallon, time for a fill. It takes 15.2 gallons at that point and I've gone 440 miles on the tank.

I am well pleased with the range because I get about a week between fillups.

Regards, Eric.

Post by **billofdurham** » 06 Mar 2009, 12:47

Eric,

Have you tried to sell this modification to Volvo? I think you should be able to earn a few $$$ as Volvo still don't accept there is a problem.

Bill.

RDEJR · Post by **RDEJR** » 15 Mar 2012, 15:52

Sorry for reviving an old thread, but here is my reasoning for the fuel gauge reading lower than it should.

Electric In-Tank fuel pumps use the fuel to cool the pump motor. If you have less an 1/4 tank in there, there is not enough fuel to reach up and tough the motor to keep it cool. By setting the sender so it makes the gauge read low, you will likely fill the tank while there is still some amount of fuel in the tank to keep the pump cool.

Pumps that fail early in my experience have always been with people who constantly run their vehicles low on fuel.

My .02