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Incorrect fuel temp reading

Posted: Tue Nov 11, 2008 8:34 am
by edsz31
I found my fuel temp reading wrong, it should ambient when its cold. it reads apx 260deg cold. I checked the ECU wire connection good. My fuel temp reads apx 80 deg after the car is fully warmed up. So then I get a hot restart because my fuel pressure regulator contol valve will not increase fuel pressure for better hot starting untill fuel temp is above 170 deg.

Posted: Fri Nov 21, 2008 12:07 pm
by Matt
let me know if its any better now in the latest beta release. i've put in a different offset for the reading but dont have a fuel temp sensor here to check it out on

Posted: Thu Nov 27, 2008 10:33 am
by magic formula
fuel temp readings are now in the negative, on my car anyway. They were similar to the above in version 9271. Cold start has the temps at about -60 if i remember correctly. at operating temp they settled to about -30. This is just a display problem correct? Will it actually affect how the ecu/car operates?

Brian

Posted: Fri Nov 28, 2008 12:53 am
by Matt
its only a display problem. wont affect car are all

are we talking degrees or Fahrenheit here in that last post?

if you can let me know the required display offset in degrees required I can adjust that so its correct. Farenheit just confuses me :cry: since all the ECU reported stuff is in degrees and 0C = freezing point / 100C = boiling point

nissan ECUs normally work -30 .. 120 degrees C

thanks!

Posted: Tue Dec 02, 2008 5:05 pm
by magic formula
Matt,

I suppose that we are talking in degrees C (the values i gave in my last post are what nistune was displaying). I would be glad to help if i knew how to figure out this required display offset. Should i record the ambient temp and then record the fuel temp that nistune displays?

Thanks,
Brian

Posted: Wed Dec 17, 2008 11:11 am
by Turbozkid
i have an aftermarket afpr and i dont have the fuel temp wire hooked up does this matter?

Posted: Wed Dec 17, 2008 12:13 pm
by Matt
ambient temp vs reported temp is probably a good start. i'll trace through the code also and see if I can work out how the ECU determines this

have you got any info from the FSM how the fuel temp converts temperatrue to resistance (like with coolant temp sensor which I've seen for other vehicles)

if you dont have a fuel temp sensor, I'm not sure how this affects things. The ECU would probably use it for some injection coefficient when the temp is higher than a certain value

Posted: Sat Dec 20, 2008 6:48 am
by magic formula
Image

Posted: Wed Feb 04, 2009 11:44 am
by magic formula
i've been away for a while, been real busy and haven't worked on the car in a while. Recorded the displayed temp vs. ambient fuel temp today. The ambient temperature i recorded was 3 C, coolant temp as reported by nistune was 2 C, and fuel temp reading right at cold start was -76 C. Not sure if this info is relavent or not at this point but here it is.

Thanks,
Brian

Posted: Wed Feb 04, 2009 10:06 pm
by Matt
thanks for the info guys.... i've put the link to this one in my bug list to look at again