Flex-Fuel Sensor Technical Info
5th Wheeling
Joined: Aug 2008
Posts: 43
Likes: 2
Hey guys.
Built the emulator, get a pretty decent output on the oscilloscope.
The truck doesn't recognize it... it shows zero hz with or without the emulator, and 170 hz with the crappy broken sensor plugged in.
Is the signal line supposed to be pulling through a 10k ohm resistor? or is that internal to the computer?
The truck doesn't recognize it... it shows zero hz with or without the emulator, and 170 hz with the crappy broken sensor plugged in.
Is the signal line supposed to be pulling through a 10k ohm resistor? or is that internal to the computer?
Elder User
Joined: Aug 2006
Posts: 761
Likes: 0
From: Southeast MI
I'm watching too.
Never know & I'm a mild geek too, so never know when somebody might need something like that. I'm not as clever as all this, but I followed easily the diagrams. I'm impressed so far. Keep it coming!
Last edited by matt's2.9STX; Aug 29, 2008 at 09:07 PM. Reason: misspelled - sticky key
5th Wheeling
Joined: Aug 2008
Posts: 43
Likes: 2
Ok!
I'll draw up a hand sketch tomorrow and scan it in.
The problem with the original circuit is that the frewuency is right, but the sensor also changes pulsewidth depending on the fuel temperature. It was giving a pulsewidth of 8 milliseconds, which is telling the computer that the fuel is boiling, and is way outside normal range of 1-5, so the computer just doesn't recognize the signal.
I'll draw up a hand sketch tomorrow and scan it in.
The problem with the original circuit is that the frewuency is right, but the sensor also changes pulsewidth depending on the fuel temperature. It was giving a pulsewidth of 8 milliseconds, which is telling the computer that the fuel is boiling, and is way outside normal range of 1-5, so the computer just doesn't recognize the signal.
5th Wheeling
Joined: Aug 2008
Posts: 43
Likes: 2
I'd also like to do some testing to make sure it's working 100%. I'll hook up the computer and see what frequency the ECM is seeing, and make sure it is in the proper range for 87 octane gas.
Who knows, I can even make an e-85 version, or a manually switchable version!
Who knows, I can even make an e-85 version, or a manually switchable version!
5th Wheeling
Joined: Aug 2008
Posts: 43
Likes: 2
OK,
Hooked up the scanner and voila, the ecm is seeing the frequency. It is reading out as 67 Hz, a little higher then the design frequency of 60 Hz, but math only takes you so far with electronics.
So, all systems seem to be go. 67 Hz is about perfect for 10 percent ethanol, which is the norm in most of the country anyway.
The pulsewidth is about 3 ms, indicating a fuel temp of about 90 F, which is right in the middle of the range. I can't see this causing a problem either way.
If anybody wants these who doesnt feel up to messing with electronics, i've been seriously considering making a bunch of them to sell.
I'll get the schematics posted soon.
Hooked up the scanner and voila, the ecm is seeing the frequency. It is reading out as 67 Hz, a little higher then the design frequency of 60 Hz, but math only takes you so far with electronics.
So, all systems seem to be go. 67 Hz is about perfect for 10 percent ethanol, which is the norm in most of the country anyway.
The pulsewidth is about 3 ms, indicating a fuel temp of about 90 F, which is right in the middle of the range. I can't see this causing a problem either way.
If anybody wants these who doesnt feel up to messing with electronics, i've been seriously considering making a bunch of them to sell.
I'll get the schematics posted soon.
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5th Wheeling
Joined: Aug 2008
Posts: 43
Likes: 2
Another update:
Finished the emulator. I put it in a small box and completely filled it with epoxy so that it will be watertight. I spliced it into the harness and strapped it to the side of the framerail. It actually looks very professional and i'm very happy with the result.
I took the truck for the maiden voyage. Drove it about half an hour with no check engine light.
Looks like it worked. I'll keep testing to ensure longevity, but I don't see any reason for it to not last for many many years, especially with it being encapsulated in epoxy
Finished the emulator. I put it in a small box and completely filled it with epoxy so that it will be watertight. I spliced it into the harness and strapped it to the side of the framerail. It actually looks very professional and i'm very happy with the result.
I took the truck for the maiden voyage. Drove it about half an hour with no check engine light.
Looks like it worked. I'll keep testing to ensure longevity, but I don't see any reason for it to not last for many many years, especially with it being encapsulated in epoxy
Tuned
Joined: Oct 2002
Posts: 370
Likes: 0
From: Southern Connecticut
Toehead, or anyone else, I just found this post and would be interested in any diagrams or pictures you may have. I have a 2000 Ranger with a bad Flex Fuel sensor, and would love to be able to bypass this sensor on my own.
Any help would be appreciated
Thanks
Mark
Any help would be appreciated
Thanks
Mark
