No Start After Injectors
10-02-20, 05:38 PM
#16
Instructor
Thread Starter
I just not confident it's a fried ECU though. I would expect way more odd behavior than just EFI.
The gnd wires that attach to the lift hooks were not attached at time of the short incident, so the short current did not enter the wiring harness there, so I suspect that current traveled across the engine to a main GND strap/wire/connections to body/frame. Gnd paths inside the ECU to be least path of resistance seems unlikely, but then again small currents on very small gnd tracks on PCB can make toast.
I believe it has to be something else. I will attempt to get Techstream and do some diagnostics from there.
The gnd wires that attach to the lift hooks were not attached at time of the short incident, so the short current did not enter the wiring harness there, so I suspect that current traveled across the engine to a main GND strap/wire/connections to body/frame. Gnd paths inside the ECU to be least path of resistance seems unlikely, but then again small currents on very small gnd tracks on PCB can make toast.
I believe it has to be something else. I will attempt to get Techstream and do some diagnostics from there.
10-02-20, 06:41 PM
#17
Instructor
Thread Starter
Interesting.
Ohms between driver-side valve cover and batt gnd = 103ohm.
Driver-side head to batt gnd = 0.1 or less. (with the lift-hook gnd wire tied to the head).
So, given my grazed short from batt to valve cover, 12/103 = 116mA. But glad it's mA and not many Amps
Is 116mA enough to throw sparks? Hmmm, makes me wonder where those sparks came from, but I am rather sure it was +V to the valve cover. I guess grazing oxidized AL can make some sparks?
Ohms between driver-side valve cover and batt gnd = 103ohm.
Driver-side head to batt gnd = 0.1 or less. (with the lift-hook gnd wire tied to the head).
So, given my grazed short from batt to valve cover, 12/103 = 116mA. But glad it's mA and not many Amps
Is 116mA enough to throw sparks? Hmmm, makes me wonder where those sparks came from, but I am rather sure it was +V to the valve cover. I guess grazing oxidized AL can make some sparks?
10-03-20, 05:13 AM
#18
Pole Position
The immobilizer is for anti-theft, and I don't know the details of what it does, it wouldn't surprise me to learn it disables spark. But I would also expect it to disable the starter (no-crank), so I don't know how you'd get one but not the other.
Chip H.
Chip H.
10-03-20, 09:06 AM
#19
Instructor
Thread Starter
It's a mystery for sure. Odd that only the C/OPN relay will not be engaged by the ECU (FC pin on ECU). I assume FC for "Fuel Control".
Maybe moving the wiring harness just a smidge behind the intake goofed up some wires? I believe the wire between C/OPN relay and FC on ECU is a homerun wire.
No DTC's either related to failure anywhere. I think the DTC's I saw were just the "pending" type where it needs to do the check after running?
What connectors around the intake could force ECU to not engage the C/OPN relay? I read one post online with same issue but they never resolved it.
I will jump the C/OPN relay to see if the rest of ECU is working (all the EFI stuff, injectors, spark, etc etc).
Maybe moving the wiring harness just a smidge behind the intake goofed up some wires? I believe the wire between C/OPN relay and FC on ECU is a homerun wire.
No DTC's either related to failure anywhere. I think the DTC's I saw were just the "pending" type where it needs to do the check after running?
What connectors around the intake could force ECU to not engage the C/OPN relay? I read one post online with same issue but they never resolved it.
I will jump the C/OPN relay to see if the rest of ECU is working (all the EFI stuff, injectors, spark, etc etc).
10-03-20, 02:54 PM
#20
Instructor
Thread Starter
This one is as close as I can find to my issue. The dealer told him "some connectors". Seems to not be a ECU issue.
Hmmm, what did I miss? Another site mentions the immobilizer, which is security AND accident item (ECU will turn off C/OPN relay if airbag is deployed).
http://forums.pelicanparts.com/off-t...p-problem.html
Hmmm, what did I miss? Another site mentions the immobilizer, which is security AND accident item (ECU will turn off C/OPN relay if airbag is deployed).
http://forums.pelicanparts.com/off-t...p-problem.html
Last edited by Lexus4321; 10-03-20 at 03:11 PM.
10-04-20, 09:33 PM
#21
Instructor
Thread Starter
Hey chiph9,
This info (https://www.clublexus.com/forums/gx-...l#post10907146)
Is the "signal" from crank sensor an actual signal from spinning the crank, or is it just a sensor feedthrough voltage to the ECM?
This info (https://www.clublexus.com/forums/gx-...l#post10907146)
Is the "signal" from crank sensor an actual signal from spinning the crank, or is it just a sensor feedthrough voltage to the ECM?
10-05-20, 10:29 AM
#22
Instructor
Thread Starter
After all this, I don't think the ECU turns fuel on until after the crank sensor send 1st signal while starting. See attached PDF. This is common on almost all Toyota vehicles.
I will test C/OPN with a test setup to see if ECU FC pin is functioning, I might just have fuel starvation issue with air in the fuel rails.
My local dealer service guy also told me that the fuel pump is on when you turn key to run position, but I think he is wrong. I think the ECU only turns on C/OPN when crank sensor sends 1st signal from the tooth plate on crank.
I will test C/OPN with a test setup to see if ECU FC pin is functioning, I might just have fuel starvation issue with air in the fuel rails.
My local dealer service guy also told me that the fuel pump is on when you turn key to run position, but I think he is wrong. I think the ECU only turns on C/OPN when crank sensor sends 1st signal from the tooth plate on crank.
10-05-20, 10:50 AM
#23
Lexus Fanatic
The fuel pump never runs unless the engine is being cranked or is actually running this is a safety measure. For example in a crash (especially roll over) you don't want the pump potentially dumping fuel everywhere due to damaged lines, tank etc.
10-05-20, 11:10 AM
#24
Instructor
Thread Starter
I asked the Q early on in this thread, the key 'run' position was said to turn on the pump before starting, and dealer guy said the same thing. No foul, but I think they are wrong. C/OPN should only energize when starting and stay on when engine is actually running.
10-05-20, 01:32 PM
#25
Instructor
Thread Starter
Ran through some electrical tests with the relays. And confirmed, C/OPN will not energize unless the vehicle is cranking, or when the engine runs after start.
The fuel side of ECM seems normal to me.
I did also confirm fuel pumping by taking off fuel line in engine bay and manually running the pump. What I don't know is, is if the fuel pressure correct.
I only have 1/4 tank of gas. Would that matter?
It tries to start, but sounds like an old GM distributor on cam gear that is off by one tooth and you got the cap twist all the way over, it kind of starts to putt putt putt, but then nothing.
More sleuthing around to do.
The fuel side of ECM seems normal to me.
I did also confirm fuel pumping by taking off fuel line in engine bay and manually running the pump. What I don't know is, is if the fuel pressure correct.
I only have 1/4 tank of gas. Would that matter?
It tries to start, but sounds like an old GM distributor on cam gear that is off by one tooth and you got the cap twist all the way over, it kind of starts to putt putt putt, but then nothing.
More sleuthing around to do.
10-05-20, 03:17 PM
#26
Lexus Fanatic
1/4 tank is fine that won't matter. Can you post a video?
10-05-20, 03:38 PM
#27
Instructor
Thread Starter
Fuel pump. The pump simply does not sound right at all. It should be a quiet humm/purrrrr, but sounds more like grrrrrrrrrrrrrrr, and sometime will go very quiet.
I suspect the impeller on the pump is NG, or the motor shaft bearings are NG. Probably got the final nail-in-coffin hen it spun freely when I had air in the fuel rails.
I did remove one of the fuel lines in engine bay wrapped in paper towel while I jumped the pump via FP relay, some fuel came out but it did not appear to be 40-50psi.
I also did a 3nd check on the snap-in fuel line near back of intake, and my memory was right, I never did here that fitting click-in, took a little more effort getting that one back on right. My 1st and 2nd attempt at that line there was no click but the cover locked in place and it appeared to be locked. Glad I went there for a 3rd time.
All other tests seem ok, and ECM is not throwing codes. Although low fuel pressure should throw a P0087 DTC ?
Let me see if I can get a vid of it.
I suspect the impeller on the pump is NG, or the motor shaft bearings are NG. Probably got the final nail-in-coffin hen it spun freely when I had air in the fuel rails.
I did remove one of the fuel lines in engine bay wrapped in paper towel while I jumped the pump via FP relay, some fuel came out but it did not appear to be 40-50psi.
I also did a 3nd check on the snap-in fuel line near back of intake, and my memory was right, I never did here that fitting click-in, took a little more effort getting that one back on right. My 1st and 2nd attempt at that line there was no click but the cover locked in place and it appeared to be locked. Glad I went there for a 3rd time.
All other tests seem ok, and ECM is not throwing codes. Although low fuel pressure should throw a P0087 DTC ?
Let me see if I can get a vid of it.
10-05-20, 05:17 PM
#29
Pole Position
The NE signal reports the crank position to the ECM.
Did you know that you can just turn & release the key to the start position, and the ECM will continue to crank the engine for you? This is how it knows that the RPMs have come up to idle and it can release the starter relay. It's a nice feature.
Chip H.
Did you know that you can just turn & release the key to the start position, and the ECM will continue to crank the engine for you? This is how it knows that the RPMs have come up to idle and it can release the starter relay. It's a nice feature.
Chip H.
10-05-20, 05:55 PM
#30
Instructor
Thread Starter
The NE signal reports the crank position to the ECM.
Did you know that you can just turn & release the key to the start position, and the ECM will continue to crank the engine for you? This is how it knows that the RPMs have come up to idle and it can release the starter relay. It's a nice feature.
Chip H.
Did you know that you can just turn & release the key to the start position, and the ECM will continue to crank the engine for you? This is how it knows that the RPMs have come up to idle and it can release the starter relay. It's a nice feature.
Chip H.
Yes, it's a turn to START & release back to RUN. The turn-release key was a step shy of push-button start. Not sure why Toyota just didn't go push-button back then, or just a key to get to ON/RUN with a small button next to it named "start". The ECM has a no-start timer on starter.