EnglishFirebird

I almost ran out of fuel in central London today!
A few times over the past few years I have had to resort to a spare can to get me to a filling station because I got too low, but it would have been pretty unacceptable to be filling from the spare can in the middle of a traffic jam in London.
The problem is that every other car I have owned has a fuel warning light that comes on when you are in the red zone. Not only does my Firebird not have that, but also the fuel gauge is pretty much covered by my right hand in normal driving. Great job on the design!

I want to add a warning light. Has anybody done this before?

I expect I will need to break into the fuel level sender line and monitor the voltage and use this to trigger a light and/or beeper/other alerts. I am deciding whether to do this with a simple analogue circuit, or use a micro-controller (Arduino etc) and start to monitor more of the levels and even log the data.

Can anyone tell me anything useful about the electrical signals that come from the fuel sender in normal operation? I want to avoid interfering with the stock operation at all.
Is it normal that right when I fill my tank, the needle is way off above the top line of the gauge? It seems to go down fairly consistently and the car runs out a little off the bottom of the red section.

l_dis_travlr

Fuel sender signal is 0 - 90 ohms.
Can't remember how the range correlates to Full/Empty.
And unfortunately, calibration of the dash gauge is ... haphazard.

As part of my restoration, I put exactly 5 gallons in the totally empty tank,
disconnected the fuel line at the TBI, powered the fuel pump
till it ran dry, and measured the output. (Turns out there's
about 1 gal. in the tank is not accessible.)
Turn on the ign. & note what the gas gauge indicates.
That will be the "running on fumes" level -- which these vehicle don't.

Good luck, and share with us any circuitry you fab that does warning light.

EnglishFirebird

That's the truth! I have had Volvos which after the red light comes on will pretty consistently drive another 40-50 miles, and then the engine starts 'coughing' at which point there is probably up to a mile to limp to a petrol station... BMWs similar. The Firebird... just metres!

84 1LE

iTrader: (9)

How about motorcycle set-ups? I read somewhere a resistor in the tank is submerged in fuel, when the level falls below said resistor. With no fuel to keep it cool causes the LED to illuminate, due to resistance falling and voltage rising.Might be missing some details by now, its been a while.

Or an aftermarket gauge w/ a built in light, speedhut comes to mind.

RBob

iTrader: (1)

A bunch of late '80s GM cars were available with a low fuel warning indicator. Here is a picture of one.



The fuel level sensor is a variable resistor, 90 ohms full, 0 ohms when empty. Just need a circuit to sense when the level sensor voltage goes low enough. Then turn on a light.

RBob.

Drew

iTrader: (58)

Once you run a tank empty and have to wait three hours in bumfudge for a tow, or have to pour gas from a small can when it's -15*, or have to sit on the side of the interstate in December waiting for someone to bring you gas, you just sort of learn to refill often and not let that happen again.

Watch the needle. Oh look, it's down to 1/2 tank, better start looking for a gas station. It works.

WildCard600

^^^ That. I ran out of gas in a vehicle once. This was in the era before cell phones, it sucked. After that I compulsively check the fuel level when getting in the car, getting out of the car and while driving. At half a tank, I start thinking about where to get fuel.

EnglishFirebird

OK I appreciate those might seem like obvious and helpful suggestions to work around the problem 'like a normal person' but they are off topic for this thread.

I definitely need to add a more prominent warning for three reasons:
1) The Firebird lacks the main visual warning (getting low light) that ALL other cars I've owned had - as far as I'm personally concerned this is a glaring defect.
2) to make this worse the fuel gauge is fully covered by my right hand in normal driving position - again unlike any other car I've owned
3) I have adult ADHD and as a result, the fewer things I have to actively check for on a routine basis, the better.

It's not as though I regularly run out of petrol, and I keep a spare 5 litre can in the boot, but this recent time it was in central London, I did not have the spare can full (just a couple of litres), and although I had been aware I was running low for some time, filling stations were rare, traffic very bad (and aggressive) and it would have been an absolute nightmare if I had run out and stopped and had to fill up - I was in a 'red route' area which means you can get a ticket just for stopping, as it would have blocked a lane of an already jammed road. The moment I realised I was in the red I had programmed my sat nav to find a filling station - but I just barely made it and it was very uncomfortable. I am willing to invest some effort now to prevent that happening again, and reduce reliance on my own attention in future.


And I WANT to add one because I am not interested in keeping the car 'authentic' and restoring a classic, and would like to modernise the car any way I can.

Rather than just a sudden warning, I would ideally like to have an amber then red warning, starting with amber when there is about 1/2 tank remaining - to promote the good behaviour you suggest - and then going red (with a beep!) when there is about 50 miles to go - just like the BMWs and Volvos I've owned.

EnglishFirebird

So for the HOW...

Thanks for both the comments confirming the fuel sender is a 0-90 Ohm variable resistor. That should be fairly straightforward to work with.

I have already got several Arduino MEGA2560 boards - [[url]https://store.arduino.cc/mega-2560-r3] and MCP2515 based CAN Controller/Transceiver cards.

So the plan is to begin to build a new 'body control module' for the car from scratch. The fuel sender and readout can just be its first pair of inputs and outputs.

I am deciding right now whether to leave the gauge connected to the fuel meter and connect the Arduino in parallel with it - in which case I will need to be careful to ensure the Arduino input is high impedance to avoid affecting the reading - or, as it's pretty poorly calibrated, cut the link altogether and use an analogue output from the Arduino to drive the original fuel gauge, as well as a digital pin to drive a 'neopixel' for the warning light, and a beeper.

Also looking at the service manual and wiring loom before taking apart the dashboard - I'd like to make the changes as reversible as possible.

OrangeBird

iTrader: (1)

Well , what I'm about to say may also be off topic for the thread , but too bad so sad , I speak my mind and really couldn't give a whit less who gets their panties in a bunch over it or not ;

Your taking quite the risk there , regularly driving around with about a US gallon of gas in your trunk ! One good rear end hit and it could be English Dude Flambe . The first lesson in "How not to become a crispy car critter 101" is "Thou shalt not regularly carry gas in the passenger compartment of the car" . And before you say it , yes indeed the trunk most certainly IS part of the passenger compartment of our cars , there is no sheet metal between you and the spray of gasoline that could ensue if you get hit from behind hard enough .

Look up "Ford Pinto" for a sad lesson in what happens if fuel ends up inside the car during a rear end collision , not pretty .........

EnglishFirebird

Haha no, my knickers remain untwisted as I completely agree it's a safety risk.

The only reason I have it there is because of the very problem that it has proven much to easy for ME to get close to running out of fuel in THIS car - hence looking for a better solution which first gently taps me on the shoulder and then slaps my face to re-fuel the car. There is a reason BMW and Volvo implement the warning light...

Also the other comments are perfectly valid - I'm just focusing on doing this upgrade and interested in any tips/ideas/pitfalls people know of towards that end.

OrangeBird

iTrader: (1)

Cool , I'm glad you didn't take offence . I've spent a few weeks in London's "Hyde Park" area and oh hell yea I wouldn't want to run out of gas there ! If this were my project , I'd take RBob's idea and adapt a unit like the one he shows in his post out of a late 80s "upscale" GM model (Cadillac , Buick , the luxury cars all had low fuel lights) . Why invent (or reinvent) the wheel when GM has already done the heavy lifting ?

EnglishFirebird

Nice - it seems that 0-90 Ohm is a standard resistance across all 3rd Gen era GM cars.

https://www.summitracing.com/int/par...1005/overview/

EnglishFirebird

Definitely an option and I'm glad to see it's been done - thanks RBob

At minimum I want to try to find and compare a schematic for our instrument clusters and one of the 'upscale' GM models with this feature, and see how they wired it in. If I can just splice in a module and get the job done, great.

Availability of OEM parts might be an advantage or a disadvantage depending on where you live. I live in the UK so not a lot of Buicks in junkyards near here! But it would make the project easier for some people to replicate. Most people on the forum seem to be on first name terms with their local breakers' yards! I had that with my old BMW E30 when I was a student in the late 90's, I could go once a month and expect to find a fresh carcass to pick over!

A good reason to start from scratch is I can source new components, and if anyone else wants one, manufacture them to order without having to source old parts. Whatever works! Will definitely look for Cadillac/Buick etc parts now.

It amuses me the difference in 'basic spec' between US and European cars of this era. Mine is a base model Firebird but has A/C, cruise control and motorised seats which would have been expensive options on a European car in 1991, but it doesn't have things like heated seats and the fuel light which have been standard on every Volvo I can remember. Things have happily levelled up for the most part! Better this way round though, it will be a lot easier for me to add a fuel light than cruise control

EnglishFirebird

From the Cadillac forums:
OK I had previously heard it was a bad idea to run a car low on fuel because of the crud that builds up at the bottom of a tank - but this is also worth knowing. I assume it's true of our cars too?

I wonder how to work out at what level the pump is uncovered...?

Aside: Seinfeld covered 'running on empty'...

EnglishFirebird

https://www.corvettecentral.com/c3-6...-module-393019



Aftermarket Corvette fuel warning module. Looks really simple.

DynoDave43

iTrader: (11)

Nice find EnglishFirebird.

I wonder how is wires in? I see no tabs, terminals, wires...?

Drew

iTrader: (58)

Pretty sure the Corvette and G-bodies have a socket already in the dash and traces on the circuit board for a low fuel light circuit, the little board in the pic just pops in like any other cluster bulb and that makes the contact.

On our cars you'd have to find a place to mount it and run a jumper from the light/board to the gas gauge.

I've only ever had one vehicle with a low gas light. I've run thirdgens out of gas at least three times, because I'm dumber than most. I've also killed the fuel pump in an S10 by running the tank dry at the tail end of a 6hr trip less than 5 miles from home, because I was an idiot. In South Dakota, North Dakota, Iowa, Nebraska, and countless other sparsely populated states out here, you can get out on the interstate at 2am and drive for hours without finding an open gas station. You can also die from exposure during the winter. If you need a warning light to remind you to get gas, how do you drive without a warning light to remind you to check your mirrors and blind spots before changing lanes, or hey, don't forget to put on pants this morning... Just make it part of your routine. Get in, buckle up, check your mirrors, adjust your seat, look at the gas gauge, drive to Starbucks...

DynoDave43

iTrader: (11)

Got it. There's something similar on my '77 Chrysler. It's a small pcb that slides over the two threaded contact studs on the gas gauge itself, while a small red LED on the pcb aligns with a small hole in the face of the gauge.

EnglishFirebird

I've found two more very similar boards for Corvette - with different markings on the PCB but such similar looking layouts I think they're all clones of the same original.

https://www.ebay.co.uk/p/1977-1982-C...1199761&chn=ps

https://www.zip-corvette.com/77-82-l...ng-module.html

Hoping to reverse engineer a circuit from these.

Anyone got a Corvette technical manual with a wiring diagram featuring this?

EnglishFirebird

Here's the original Corvette light it appears Willcox and others have already re-created:
http://repairs.willcoxcorvette.com/w...amp-module.jpg

Galaxie500XL

iTrader: (1)

As far as where to put the bulb...I know that my ‘88 IROC has that useless upshift light in the dash..does the Firebird have one as well? If so, perhaps repurpose this for a low fuel light?

Drew

iTrader: (58)

There's a thread elsewhere on the forum recently about a well used race car for sale... Noticed the label printed and applied to the center of the steering wheel... Said "HOOD PINS". As in, Hey Dummy, did you remember to put the hood pins back in? Something similar that says "GAS?" might help.

scooter

iTrader: (11)

THe three tabs around the perimeter of the bulb. I am assuming that when you twist the socket into the back of the cluster it just lands on traces on the printed circuit board.

That's what I am thinking

I was in the same mind set as you a while ago. I went and bought one of those less expensive, reproduction, versions for my car. But since there is no place for it in our dash, I was just going to try and solder wire to the terminals and wire it in parallel to the fuel level gauge and see what happens. I THINK I found the schematic, or it came with. I will look for it. I was thinking I would put a hole with a 3mm LED through the cluster face for indication. I am not sure whether it is going to work or not. For the $40, or whatever I paid, I was willing to give it a shot and see if it worked.
This was all before I wound up switching my fuel module for my 4th gen tank though, and the Grand Prix sender didn't fit in the new bucket, so my fuel gauge hasn't worked in over a year. I was looking at getting this to recalibrate the gauge to work with the 4th gen sender. It has a warning output
https://www.summitracing.com/parts/cin-sn34

I really do value your advice on almost everything, but I have to disagree with your sentiment towards the OP here. I am right there with this guy on wanting a warning. 5 years ago I would have probably said the same thing as you to him, but now that I am a little older my CRS is getting really bad, especially since I don't have to drive any of my personal vehicles to work anymore. I jump in the car and start driving since I don't get fuel anymore for weeks or months on end. I have a company vehicle and I often forget that my car may be low and don't anticipate that I need fuel before or after I am running out the grocery store at 9-10pm.

IROCU2

Go to You/tube. There is a video of a guys putting a light in a thirdgen Camaro there.

Drew

iTrader: (58)

Don't get me wrong, my mind is always cluttered like someone is channel surfing my thoughts... My poking and prodding is intended as good natured ribbing, not as trolling. And I'm absolutely serious when I mentioned the hood pin note. Anyone that has ever forgotten to replace the hood pins, or plug the brake booster vacuum hose back into the plenum, or reconnect the battery cable spur to the alternator power stud, can understand and feel the pain, I just wouldn't go so far as to call it a defect.

There's a thread or two around here somewhere showing how a forum member added a low fuel light, and cruise control status light, and maybe some other features to a 90-92 Camaro cluster. But a person would have to find the thread...

As for open spots to add a light, there are usually a couple open unused spots. Early cars often has a spot for a choke or shift light that some cars never use, some have spots that never had anything. Later cars specifically Firebirds can be a bit harder, because for example the "SHIFT" light in 89 turned into an "INFL REST" light in 90. So just one example of how a socket can change purposes from year to year. Beyond that, an existing socket probably won't have the correct traces to line up to the socket. You might find one with a ground you can repurpose, maybe a 12v switched, but I'd expect with these other GM modules you need a 12v switched, a ground, and then create a new 'trace' by running a jumper from the gas gauge post to the third pin on the gas light module. That's assuming I remember correctly.

A person could use the logic circuit from one of those modules, and wire it to a warning LED, and somehow add it to the gauge face of the gas gauge. Hardwire it, and the LED should last forever, tuck the other components of the circuit into an open spot of the cluster somewhere they'll be out of the way... An LED would take up less space than a 192 or 168 bulb. Another option might be the micro bulb like the HVAC lights of the later Firebirds, they're set up with a two wire socket. Just thinking out loud...

Figures I'd have the harness handy but all the bulbs are in a bulb box 20ft away...

scooter

iTrader: (11)

Got ya, sometimes it's hard to gauge when someone is being facetious on a message board.

I wouldn't call it a defect either, it's a pony car, not a sports car or luxury car so GM either didn't care to add, or left it off because it cost a few more doll hairs.

Drew

iTrader: (58)

Doesn't help that I dally with sarcasm, facetiousness, and borderline trolling for the humor, and entertainment value. If just one person gets a kick out of one of my stupid comments, it's worth it. No one should take anything I say too seriously. I'm not infallible or brimming for a fight, so I hope it wouldn't come across that way.