I just replaced the fuel pump and sender in my Olds (1992).  The fuel pump
connections on the old pump and the new pump did not appear to be hermetic
in any way.  The fuel tank sender is a wirewound rheostat, open to the
gasoline.  +12V at one end, ground at the other.  I was mystified when I
saw this.  I am used to the marine environment where this is done
magnetically.  However, this rather new car was done the same way my 67
Chevy is done... voltage directly in contact with fuel.

Looks like this is common practice on GM cars and trucks (at least up to
1993... I'd love to hear if GM has changed this).  I haven't looked inside
my truck tank yet, but the schematic in the service manual shows a rheostat
in the gas tank.

This has not made me comfortable, but it has not blown up yet.........

Scott



                    Roman Black
                    <fastvid@EZY.N       To:     PICLIST@MITVMA.MIT.EDU
                    ET.AU>               cc:
                    Sent by: pic         Subject:     Re: [EE]: Conductive Liquid Sensor
                    microcontrolle
                    r discussion
                    list
                    <PICLIST@MITVM
                    A.MIT.EDU>


                    09/22/01 08:41
                    AM
                    Please respond
                    to pic
                    microcontrolle
                    r discussion
                    list






I've been a bit disturbed by the number of people
advocating using electricity in contact with the
fuel...

I have a lot of circuit diagrams for modern vehicles,
and often advise people re installing equpment or
modifying these modern vehicles. It's part of my
job. :o)

I see NO modern vehicles using electricity in direct
contact with the fuel!!!!

The 3 main types of fuel level sensing in modern
vehicles are:

* Simple pressure gauge (senses liquid height above
the pressure sensor)
* Sliding float over sealed tube with reed switch.
* Thermistor sensor (senses difference in heatsinking
between fuel and air)

ALL of these 3 types have one thing in common, there
is NO direct contact between fuel and electricity.

Call me a safety freak if you must, but I would NEVER
consider using live electricals in contact with fuel.
If the fuel container is punctured, and some atmospheric
condition causes the fuel to atomise, you have real
danger situation presented.

Surely if the cost/hassle of contruction is similar,
you MUST prefer a system with no direct electics
in the fuel??

Please argue if you think i'm wrong, or argue with all
the modern vehicle manufacturers if you like...
-Roman

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads