fuel sensor pull up resistor issue.

kbs200
Posts: 8
Joined: Sun Mar 10, 2019 8:07 pm

fuel sensor pull up resistor issue.

Postby kbs200 » Wed Feb 12, 2020 5:42 pm

i have looked in the forum for an answer but nothing seems like my issue, i am using the ford fuel sender in the stock tank, i have used the 5v reference from the dash 2 and 1k pull up resistor.
i emptied my tank and took a reading of 0.57v, i then started to add fuel 1L at a time and the voltage decreased in increments at a steady rate, i got to 30L and the voltage was 0.19v, i added another 1L and the voltage just dropped out to 164mV.

i was thinking either the pull up resistor was to much of a value to start with or the fuel sender load was a bit too much for the 500ma 5V rating from the dash2 , i was going to empty the tank and use a TO-220 5V regulator and 1K resistor as a stand alone supply but thought i would get some advice here first, i was expecting to see something like 1.5v-2.00v empty to start with but not the low reading i got.
any advice would be appreciated, TIA.

kbs200
Posts: 8
Joined: Sun Mar 10, 2019 8:07 pm

Re: fuel sensor pull up resistor issue.

Postby kbs200 » Thu Feb 13, 2020 9:23 am

ok just took some resistance readings from the sender unit, 10 ohm full and 160 ohm empty, the 1K resistor that is suggested is way off so would a 120 ohm resister be ok?

kbs200
Posts: 8
Joined: Sun Mar 10, 2019 8:07 pm

Re: fuel sensor pull up resistor issue.

Postby kbs200 » Thu Feb 13, 2020 1:02 pm

Anyone!!

racetec
Site Admin
Posts: 295
Joined: Thu Oct 27, 2005 12:02 pm

Re: fuel sensor pull up resistor issue.

Postby racetec » Thu Feb 13, 2020 1:30 pm

Hi

Do you have any other sensors connected to the DASH2 5V ref?

Support (AH)

kbs200
Posts: 8
Joined: Sun Mar 10, 2019 8:07 pm

Re: fuel sensor pull up resistor issue.

Postby kbs200 » Thu Feb 13, 2020 1:35 pm

yes i have a bosch water temp sensor connected that reads the same value as the ecu so thats all working fine.

racetec
Site Admin
Posts: 295
Joined: Thu Oct 27, 2005 12:02 pm

Re: fuel sensor pull up resistor issue.

Postby racetec » Thu Feb 13, 2020 2:20 pm

A 120 Ohm resistor is just about acceptable. Something closer to 150 Ohms would be safer.

In all cases it needs to be 0.25W resistor or larger. A 0.125W resistor may overheat and fail.

kbs200
Posts: 8
Joined: Sun Mar 10, 2019 8:07 pm

Re: fuel sensor pull up resistor issue.

Postby kbs200 » Thu Feb 13, 2020 3:56 pm

A 120 Ohm resistor is just about acceptable. Something closer to 150 Ohms would be safer.

In all cases it needs to be 0.25W resistor or larger. A 0.125W resistor may overheat and fail.
thank you for the reply, so if i got a resistor closer to the full sender swing of 160 ohms like a 180 ohm resistor would that be better, yeah either 1/4 or 1/2 watt.

kbs200
Posts: 8
Joined: Sun Mar 10, 2019 8:07 pm

Re: fuel sensor pull up resistor issue.

Postby kbs200 » Thu Feb 13, 2020 5:32 pm

just threw a couple of resisters in Parallel and got 165.5 ohms, that should do the trick, now shall i use the dash2 5v reference or fit a 5v regulator just for the fuel sender?


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