jrbe
Newbie level 5
I am trying to repair an old standalone ECU. I had 2 bad ignition transistors out of 4. I google searched the # on the transistor but came up with nothing. I dont have the old ones in front of me but can add their part # in later.
A 0-3.3v signal was going in but nothing was coming out of the 2 dead transistors. all 4 transistors had the same signal in but only 2 were working. Their grounds and pull up voltage and traces all checked out ok. I contacted the company to see what they replace the transistors with because the old ones were discontinued. They recommended IRFIZ48V (pdf datasheet link in 3rd post below, sorry, posting rules...) which are way overkill but its "what they use because we have them in stock" I bought some and installed them by their directions but now the new mosfets are all not fully pulling to ground on all of the channels now.
A simplified diagram of how i have the mosfet wired in the ecu and important stuff to the waveform is (in my 3rd post below)
There is a 0-3.3v signal that makes a nice square wave that turns the mosfet on while the ecu wants to fire the coils (image in 3rd post) which is the same on all 4 channels
the ignition output (out of the mosfet) holds at ~5v until the ecu sees all the crank and cam signals then starts firing the coils. Thats what the long pull to ground is, but then only pulls from the 8v to about 7v which isnt enough to fire the coils. (image in 3rd post) Its strange it will pull to ground before the ecu wants to fire the coils but then only pull to 7v when it wants to. The 8v is steady and constant the whole time. It runs a hall sender that is used as a sync (cam/reset) signal that is working
Anyone have an idea whats wrong?
---------- Post added at 08:42 ---------- Previous post was at 08:41 ----------
2nd post so i can post oscilloscope traces to help the above wording
---------- Post added at 08:52 ---------- Previous post was at 08:42 ----------
Or not. if someone could reply to this i can post links to the scope waveforms to help see whats going on.
A 0-3.3v signal was going in but nothing was coming out of the 2 dead transistors. all 4 transistors had the same signal in but only 2 were working. Their grounds and pull up voltage and traces all checked out ok. I contacted the company to see what they replace the transistors with because the old ones were discontinued. They recommended IRFIZ48V (pdf datasheet link in 3rd post below, sorry, posting rules...) which are way overkill but its "what they use because we have them in stock" I bought some and installed them by their directions but now the new mosfets are all not fully pulling to ground on all of the channels now.
A simplified diagram of how i have the mosfet wired in the ecu and important stuff to the waveform is (in my 3rd post below)
There is a 0-3.3v signal that makes a nice square wave that turns the mosfet on while the ecu wants to fire the coils (image in 3rd post) which is the same on all 4 channels
the ignition output (out of the mosfet) holds at ~5v until the ecu sees all the crank and cam signals then starts firing the coils. Thats what the long pull to ground is, but then only pulls from the 8v to about 7v which isnt enough to fire the coils. (image in 3rd post) Its strange it will pull to ground before the ecu wants to fire the coils but then only pull to 7v when it wants to. The 8v is steady and constant the whole time. It runs a hall sender that is used as a sync (cam/reset) signal that is working
Anyone have an idea whats wrong?
---------- Post added at 08:42 ---------- Previous post was at 08:41 ----------
2nd post so i can post oscilloscope traces to help the above wording
---------- Post added at 08:52 ---------- Previous post was at 08:42 ----------
Or not. if someone could reply to this i can post links to the scope waveforms to help see whats going on.