Running out of gas

I’ve decided to test my fuel tank warning light, as I’ve never let my tank get down below 1/4. Just would like to know my distance I can safely go on a fill up. And where I am on the tank when at E.

My 88 XJS Coupe says it’s capacity is 25 U.S. gallons. I assume that’s 24 tank, and 1 gallon surge tank.

So I am going with a 24 gallon capacity. I’ve been reliably getting 12 mpg, so that means about 288 miles to empty. Right now, I’m sitting a hair above E, and the odometer reads 244 miles. The light has not come on yet. FYI, about 1 1/2 years ago I put in new tank and new fuel level sender. I also do not have the trip computer anymore.

Most of my other cars, the light comes on when there are 2 gallons left.

I’m starting to think of the Seinfeld episode…and see how far I get? I may purchase a gallon of gasoline and keep it in the car with me!

Any details of your own experiences would be welcome.

…ehm. How to say that in polite way… What makes tou think yoir XJS has reserve light…?

It can be a dangerous game, the only real way to know for sure is to run it dry. So defintely keep a spare can in the boot. I would be cautious of doing it, so as not to drag the dregs of the tank through the system, but you have a new tank so that shouldn’t be a big worry.

On my old Alfa I built an electronic anti-slosh module to stop the massive needle swings, and also incorporated an adjustable low level warning light. That worked well as the low level system was a separate sensor, and I could drive it from the main level sensor with a differential offset. I don’t think the Jag system is the same, you have to live with whatever low level warning has been programmed in to the system.

er, because i have one on the instrument cluster, and tested the circuit when I had it out last year.

yeah, when I put in my new tank, i cleaned out the surge, cleaned the sock filter, new pump and new filter. So fingers crossed no junk to suck out.

As i’m only 44 miles from where I ‘think’ empty is, next trip I’m buying a gallon of gas to keep in the trunk.

Got 89 version, haven’t seen reserve light even with plumber out and waved… Maybe the US version is slightly different or the control light was required to get certification ;D

ehm…There is a yellow Low Fuel Level warning light on the instrument panel of my wife’s 1990 XJ-S convertible that is described on page 45 of the XJ-S Drivers Handbook for the car. Does your 1989 not have that light? What does your Drivers Handbook say?


There is a low fuel indicator light (and it works) on my ‘88; mine is on when gauge indicates a half needle above “E”. The most I have put in with the warning light on is about 21 gallons, which puts the gauge at 7/8. I have never had it read full, but seems accurate otherwise.
You must drive more aggressively than I, as I average about 14-15 mpg summer, and 12 in winter. Although no city driving in that.

Im at 250 miles now, no warning. Have a gallon of gas along for the ride.

I get 12 mpg, that’s mostly city driving.

Great, give us a shout when the reserve light kicks in - we can finally confirm first example with working low fuel warning :slight_smile: :wink:

We purchased our 1990 XJ-S convertible in 2005 and have put just over 70K miles on it since then. We keep a book in each of our Jaguars to record servicing, repairs and how much fuel we add. I occasionally calculate MPG the old fashioned way and record it in the book. Looking over the numbers, the normal range (90% of the entries?) show 12-15 MPG. There are occasionally entries above and below that. We live in a rural area but travel regularly on local freeways but rarely spend any time in traffic.


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well, at 260 miles, i’m sitting a sliver above empty with no fuel warning light on. Car still runs, but I noticed a stutter as I made a right turn from a stop. Surge tank low?

I grounded the sender wire for low fuel light, and it turned on in dash, so that part works.

So either my newish sender isn’t working, or i need go drive a bit more?

Greg, trust me - no need to do this. Forget about tell-tales and page 45 of XJS manual made by cheaters for rich parasites…

With ancient fuel system like one in our XJSs - you don’t want to go that low on petrol. You don’t wanna go below a quarter really… :wink:

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you’re probably right. But since I have the tank so low, i’m going to take out the sender and test it in hand.

Still good exercise :slight_smile:
Done the same with factory sender, probably you’ll get the same conclusion. Good advice, remove the sender - after switching ignition on…

Had a similar issue on my pre-HE so it really goes through gas quick-

After a while I found that my fuel tank (purchased from SNG barratt) and my fuel sender (also from SNG) had an interference issue and the sender was physically hanging up on the cutouts inside the tank. For a while, it wouldn’t read below half, then after tinkering, I found it wouldn’t read more than half or so.

I ended up pulling the sender out after verifying the tank was mostly empty (with a wooden dowel as a dipstick) and measuring clearances using the sender as a reference point. Then I just kept adjusting the sender arms to make it work. The geometry is certainly different but it seems to work better now, (and I set it up to read as almost empty with a little more fuel left in the tank so I have a larger reserve)

Note: It seems the float was also on the wrong way when i looked into the tank with a flashlight, So I ended up flipping it.

OK, I have some good research. :slight_smile:

I pulled the sender, and determined the low fuel light circuit indeed works. It was just a hair from turning on low fuel light. I bent the wire that the float is on, so it comes on a little sooner. I filled up, took 22 gallons. So based on my 24 gallon tank (plus 1 extra gallon in surge), i was at 2 gallons left in the tank. I put in one gallon at a time - with the bend in the float, the low fuel light now triggers at 4 gallons left in the tank. BUT, when filled up, the gauge reads just below Full, which I don’t like. So I siphoned 16 gallons from tank so I could pull sender again and bend it back.

Based on my experience of the engine stuttering going around a turn with 2 gallons left in tank, obviously with those 2 gallons sloshing around it is unable to keep the surge tank full enough. I do not want my fuel pump to ever pull air again.

So moral of the story, I will probably never see that low fuel light again. Only time I could see it useful, is if you’re driving on the highway in the middle of nowhere, going nice and straight so the surge tank stays full, and when it comes on you know you have about 2 gallons left to get to the next gas station.

I wish there was a way to adjust it so it came on earlier and didn’t interfere with gas gauge, but the way the sender is made, there is no way.

Real moral is you should never, unless an emergency, run below half a tank.

Better for the system (less chance of condensation) and always a good idea.

Paul, I don’t have my copy of Driver’s handbook. It was quite smelly, like manure or something… I’ve exchanged it for some knowledge of English workmanship and the book full of servicing/refuelling records, like your one. :wink: