Changing resistance of fuel level sender
Changing resistance of fuel level sender
(OP)
Hi,
I need to increase the resistance of the signal coming from the fuel level sender in a Miata going into the ECU of an LS2 engine. The Miata ranges from ~5 ohms (full) to ~115 ohms (empty). The LS ECU expects a range from 40 ohms (full) to 250 ohms (empty). Reading the full point is most critical because the fuel level sender is used by the ECU to trigger the evap solenoid. When the tank is full, it absolutely should not run. So if I have to pick one accurate point, it would need to be full. Of course it would be nice if both full and empty points are accurate. So, can a simple mix of resistors accomplish this change in range? If not, perhaps just target the full point; go from 5 to 40 ohms?
Thank you in advance,
Jon
I need to increase the resistance of the signal coming from the fuel level sender in a Miata going into the ECU of an LS2 engine. The Miata ranges from ~5 ohms (full) to ~115 ohms (empty). The LS ECU expects a range from 40 ohms (full) to 250 ohms (empty). Reading the full point is most critical because the fuel level sender is used by the ECU to trigger the evap solenoid. When the tank is full, it absolutely should not run. So if I have to pick one accurate point, it would need to be full. Of course it would be nice if both full and empty points are accurate. So, can a simple mix of resistors accomplish this change in range? If not, perhaps just target the full point; go from 5 to 40 ohms?
Thank you in advance,
Jon





RE: Changing resistance of fuel level sender
http://www.yogisinc.com/index.cfm/page/ptype=resul...
RE: Changing resistance of fuel level sender
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Changing resistance of fuel level sender
Jon
RE: Changing resistance of fuel level sender
RE: Changing resistance of fuel level sender
RE: Changing resistance of fuel level sender
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: Changing resistance of fuel level sender
feeding into something from here: https://www.maximintegrated.com/en/pl_list.cfm/fil...
That's getting a little beyond my skillset, but I can give it a try.
Constraints: it's an auto application, so 12 volts, roughly. It's going from a sender with a 5-115 Ohm range to an ecu looking for 40-250 Ohms. I'm not sure what else to look for.
RE: Changing resistance of fuel level sender
where mx = 1.9 and offset = 30.5
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: Changing resistance of fuel level sender
The expert video is hilarious!
RE: Changing resistance of fuel level sender
Thanks,
Jon
RE: Changing resistance of fuel level sender
The processor is possibly something like: http://ww1.microchip.com/downloads/en/DeviceDoc/30...
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm
RE: Changing resistance of fuel level sender
That is available voltages. Your auto voltage may vary from less than 12 Volts, when cranking to 14 V, 15 V, or 16 Volts when charging.
Then there are load dump transients that may hit 100 Volts.
A proven commercial unit will have these issues considered and protected.
A roll-your-own unit may let the smoke out the first time you turn off the headlights with the engine running fast.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Changing resistance of fuel level sender
Yes, time is money. Combined with the additional benefits of an OTS item as mentioned above, the cost is well worth it. plus it supports an industry expert.
RE: Changing resistance of fuel level sender
Jay Maechtlen
http://www.laserpubs.com/techcomm
RE: Changing resistance of fuel level sender
We ended up using a modified version of the converter unit I mentioned above called MeterMatch from TechnoVersions. Brian from TechnoVersions worked with us to remove one of its resistors. He was a big help. We then ran the engine and adjusted the output of the MM by reading the percent fuel tank level on a OBD reader with the tank full. Knowing the tank was full, we adjusted the MM until the OBD read nearly 100%. That meant that the MM was sending the correct signal strength to the PCM. When the tank is empty we will set the other extreme. Quarter and three-quarter tank levels can also be set. Uneven tank shapes can be accounted for with that. Pics to follow. Feel free to ask me if you want more details.