Incorrect fuel temp reading

edsz31 · Post by **edsz31** » Tue Nov 11, 2008 8:34 am

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.

Matt · Post by **Matt** » Fri Nov 21, 2008 12:07 pm

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

magic formula · Post by **magic formula** » Thu Nov 27, 2008 10:33 am

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

Matt · Post by **Matt** » Fri Nov 28, 2008 12:53 am

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

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!

magic formula · Post by **magic formula** » Tue Dec 02, 2008 5:05 pm

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

Turbozkid · Post by **Turbozkid** » Wed Dec 17, 2008 11:11 am

i have an aftermarket afpr and i dont have the fuel temp wire hooked up does this matter?

Matt · Post by **Matt** » Wed Dec 17, 2008 12:13 pm

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

magic formula · Post by **magic formula** » Sat Dec 20, 2008 6:48 am

magic formula · Post by **magic formula** » Wed Feb 04, 2009 11:44 am

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

Matt · Post by **Matt** » Wed Feb 04, 2009 10:06 pm

thanks for the info guys.... i've put the link to this one in my bug list to look at again