Fuel Sender 255 Open Reading (Digi Conversion)

[Naylor2006]

I posted recently about a backwards fuel gauge after digi dials conversion, I then got a new sender which is supposed to work the right way round but initially didnt provide any different readings until today.

 

The fuel gauge had been routed to empty with the fuel light on since I brimmed the tank at the weekend which is why I posted originally saying that everything was how it was before but with a new sender, on the way to work today all of a sudden it moved from empty to a quarter from the F, initially I though omg its suddenly started working, id done 100 miles and thats where I would expect the gauge to read, then strangely it started slowly working its way towards the F, bit weird if you ask me, to move to the correct reading and then to slowly move in the wrong direction still....

 

So anyway I remembered that these dials have a self diagnostic capability so I decided to run it and look at what the actual fuel digital reading was showing from the sender. Below is the technical guide for the fuel 'test'.

 

FUEL Displays the code (0-255) for the fuel sender input to the HEC. The fuel gauge will display a filtered fuel level value. This filter will keep the pointer from moving suddenly or erratically.

255 open send +/- 0

232 full stop +/- 0

215 Full mark +/- 10

178 3/4 mark +/- 8

138 1/2 mark +/- 7

93 1/4 mark +/- 5

41 E mark +/- 4

54 Low Fuel (0-59)

0-18 short (0-20 max)

 

So when the tank was roughly a quarter from being full (worked out from how many miles I had done since filling up) I ran test, my fuel reading was around the 'full stop' mark reading 235 ish, I imagine 'full stop' refers to a cut off when the fuel is entering the tank so stop it from filling any further?

 

So i decided to see what happened if I went and brimmed the tank again, so I brimmed the tank and the gauge returned to empty with the fuel light on, I then re-run the above test and it now reports 255 which is the 'open send' reading meaning that no contact is being made on the senders board so it defaults to 255 and this would explain why the gauge had gone back to rock bottom.

 

Does this just suggest that the sender isnt working correctly do you think? Its almost like when the fuel tank is brimmed the that sender reads too high and produces 255 reading and therefore the gauge bottoms out, when you use a quarter tank the senders float drops enough for the gauge to then move back to the correct side of the gauge, all be it a bit higher than it should be, could I have mis installed the fuel pump/sender unit some how?

 

Any thoughts would be great, I will run the car now for much longer and repeat the above test when I have little fuel and see what the readings are.

 

I know its a bit wordy and probably boring to most people but I would like everything to 'work'

 

Thanks for your time.

Edited September 22, 2012 by Naylor2006

[Naylor2006]

UPDATE:

 

Think ive just worked out what might going on here.....

 

My dials are from a mk5 fiesta which is most likely to have a 40l tank, I have a 55l tank, which would explain why after 100 miles or so the gauge sprung into life as the dials or sender is configure for 40l tank?

 

So if I just got the mk5 fuel sender that should work correctly possibly?

[tomsy]

Electrical problems must be the most frustrating things ever to sort out, seems to me you need to double check everything you've already done wiring fitting of dials and sender unit. Then i guess its a case of swapping parts over cant believe that someone cant point you in the right direction, thought this was quite a popular conversion surely someone must have got it working right.

[Naylor2006]

Electrical problems must be the most frustrating things ever to sort out, seems to me you need to double check everything you've already done wiring fitting of dials and sender unit. Then i guess its a case of swapping parts over cant believe that someone cant point you in the right direction, thought this was quite a popular conversion surely someone must have got it working right.

 

JC on here has the same sender as me but with dials from a Puma, his work fine, so I'll try puma dials and see what happens, if no joy ill have to fit a mk5 fiesta sender. As a rule of thumb senders should be matched to their 'other equipment' if you will, I have an escort sender hooked to fiesta dials, the dials all look the same but the more research I do into the eletrics of how the unit works the more I discover the two need to be matched.

[ScORTED]

the fiesta and puma use the same size tank... for just one last time, you need the dials and sender from the same car or to match finis codes.

[Naylor2006]

the fiesta and puma use the same size tank... for just one last time, you need the dials and sender from the same car or to match finis codes.

 

Maybe I was naive to think because all the clocks look and appear to perform identically that they would all be the same.

 

Since white Escort digital dials are so hard to come by I'm on the hunt for a mk5 fiesta sender to match my clocks.

[Stu]

If the float in your tank goes higher up than in a Fiesta tank then that could explain the reading. Unlikely, but possible. More than likely a faulty sender.

[SteveB]

Rather than a fault, I would suggest that it's either the calibration in the Fiesta digidials different to those used in the Escort, or the signal range from the Escort level sensor is greater.

[Naylor2006]

Rather than a fault, I would suggest that it's either the calibration in the Fiesta digidials different to those used in the Escort, or the signal range from the Escort level sensor is greater.

 

Yes, thats what I have discovered, im going to get the matching sender from a mk5 fiesta, escort white digi dials almost dont exist which would be the easiest thing for me to do.

 

Cant find a mk5 fiesta sender about so ive found a brand new unit from ALS Parts for £150 so ill fit that next month, nothing wrong with a brand new fuel pump

[Naylor2006]

UPFATE: If anyones bothered.

 

So ive run the car down to empty and as before the fuel gauge went from '255 open' to the 'F' after 130 odd miles and then proceeded to work in the right direction down to around half full when in actual fact the tank was nearly empty.

 

Found some dials with the same part number as JC so I will be running the same setup as him, if still no luck then its new fuel pump/sender time.

[lee grout]

UPFATE: If anyones bothered.

 

So ive run the car down to empty and as before the fuel gauge went from '255 open' to the 'F' after 130 odd miles and then proceeded to work in the right direction down to around half full when in actual fact the tank was nearly empty.

 

Found some dials with the same part number as JC so I will be running the same setup as him, if still no luck then its new fuel pump/sender time.

You've got some serious patience! I think I would have binned it by now and gone back to stock LOL. The amount of time and cash you've put intothat car....it owes you big time!

[Naylor2006]

UPFATE: If anyones bothered.

 

So ive run the car down to empty and as before the fuel gauge went from '255 open' to the 'F' after 130 odd miles and then proceeded to work in the right direction down to around half full when in actual fact the tank was nearly empty.

 

Found some dials with the same part number as JC so I will be running the same setup as him, if still no luck then its new fuel pump/sender time.

You've got some serious patience! I think I would have binned it by now and gone back to stock LOL. The amount of time and cash you've put intothat car....it owes you big time!

 

Everything has to be right, the older style dials are simply dreadful by comparison, I never used them before as I had an X reg, I dont think its one of the mods I would have done if I didnt know what they were like but to go from digi to the old style was a big shock in quality. Ill get there in the end, as I have done with everything else.

 

Way I see it, either there dials from a fiesta and escort have different ranges configured which will be sorted once I get JC's OR I have a faulty sender, if the puma dials dont work ill just get a new fuel pump and sender which isnt a bad idea on a 14 year+ old car.

 

Hopefully puma dials will work and ill just swap all my blue stuff over and plug them in, the hard bits done which is the 32pin digi plug loom work.

[tomsy]

Everything has to be right exactly my philosophy why bother to do something if your not prepared to get it right its a pity more people dont have this mentality.In my experience to many people do a second rate job for top rates of pay. GOOD ON YOU FOR STICKING AT IT YOUR PATIENCE IS A CREDIT TO YOU.

[Naylor2006]

Everything has to be right exactly my philosophy why bother to do something if your not prepared to get it right its a pity more people dont have this mentality.In my experience to many people do a second rate job for top rates of pay. GOOD ON YOU FOR STICKING AT IT YOUR PATIENCE IS A CREDIT TO YOU.

 

The car right now is running like a dream and its taxed and MOT'd for another year so it does give me time to focus on the smaller things.

[Naylor2006]

the fiesta and puma use the same size tank... for just one last time, you need the dials and sender from the same car or to match finis codes.

 

This is a very old topic but just like my year long battle with idle I want to post that I fixed it for anyone else.

 

If i'd listened to the above first of all it would have been fixed the first time I dropped my tank.

 

Ive fitted a MK5 Fuel Pump/Sender along with my MK5 Fiesta Gauges and this is finally fixed, 3 times the tanks been off.

 

Using the later Escort fuel pump sender DID NOT WORK as ScORTED says, you need the dials and sender from the same car or to match finis codes.

 

I tried some Puma gauges as a test for the record and they had the same part number as the MK5 Fiesta ones, Im guessing the Escort gauges have a different part number but ive never found a set of white digital dials thats were stock in an Escort.