Saab Tech Talk (STT)

Workshop for classic Saab models => Classic Saab 9-5 (MY 1998-2010) => Topic started by: sgould on 08 May 2019, 07:52:52 PM

Title: Fuel level issues.
Post by: sgould on 08 May 2019, 07:52:52 PM
Tonight I set off for a meeting 20 miles up the motorway with DTE showing 29 to empty. I planned to fill up before returning home. Iíve only been driving around town lately and the fuel consumption was showing 19.3 mpg.

As I drove along slowly in fairly heavy traffic the DTE went up to 32 mpg as it would normally do. The fuel gauge was in the middle of the red section. We proceeded in this way for a few miles. However, the next time I looked at the DTE it was showing 61 miles to empty and the fuel gauge had jump to around a quarter full st the top of the red section. The fuel consumption was showing the same reading as before, but that may not be significant as it will have been a while since it was reset.

I donít plan to believe this. So Iím wondering what caused it. I remember something like this happening on my old Aero saloon on  a long trip when I was starting to look for a fuel stop. DTE jumped from about 40 to around 120 then.

Any thoughts?
Title: Re: Fuel level issues.
Post by: carrera on 08 May 2019, 11:00:29 PM
It's a sticky float.

That's my assumption anyway as the same thing happens from time to time on my blue Aero.
Title: Re: Fuel level issues.
Post by: sgould on 08 May 2019, 11:25:05 PM
When I got back in the car to come home the DTE had dropped to 24.  I drove off and went uphill and the DTE dropped a bit.  Back on the motorway and it rose to 29.  Then I looked and it was 68!!  It dropped down and I tiptoed back to Tesco.  I stopped at the pumps in the queue with DTE at 39.  Turned the ignition off.  Started the car a minute or two later to move to the pumps and was on "Refill fuel now" which only comes on at 20 miles to empty.  Filled up and it took 71 litres.

Looks like it's time to take the pump out and look.  Not sure when I'll have the time though.  Next job is to get the Carlsson serviced and through the MOT ready for Sweden at the end of the month.
Title: Re: Fuel level issues.
Post by: carrera on 08 May 2019, 11:29:56 PM
A decent drive and a few roundabouts will likely sort it out without needing to lay any tools on the car  ;)

In the meantime, don't run on fumes, it can give the pump and filter a harder life.

(One day I might even take note of my own advice) ;)
Title: Re: Fuel level issues.
Post by: sgould on 08 May 2019, 11:35:38 PM
Yes, I know.  I ALWAYS keep my tank at least half full!! ::)  ::)

On the older cars which had a DTE that went down to 0, I drove two miles with it on 0 and then a few weeks later we ran out of fuel in Luxembourg with DTE on 15...

I might have a look because it might explain a rattle.  I wonder if the baffles in the tank have come loose.  They used to on some older cars and it was supposed to have been fixed, but I keep remembering that the DE models were "value engineered" by GM.
Title: Re: Fuel level issues.
Post by: TomPaine on 09 May 2019, 05:16:57 PM
I could have sworn I remember reading on here years ago that under 50 DTE the measure was very unreliable; for that reason and being risk-averse I don't let it go that low. (If I learned that from anyone it was probably you Will!)
Title: Re: Fuel level issues.
Post by: sgould on 09 May 2019, 10:36:49 PM
Yes, I know.  It is unreliable. I do a lot of short journeys these days, it can take a week to get fromm 100 down to 50.  So I often forget (old age?).  But I always console myself that it's downhill all the way from here to the Tesco filling station. :D