Yet Another Tech Support Tale…
This customer called in for a crank/no start.
Symptoms: Engine cranks, wont start. Has no injector function.
These are the tests that he said he performed...
Test / actual values: Crankshaft sensor fault resets consistently. Verified all engine power supplies. Verified spark. Verified engine speed signal seen in ECU during cranking. Verified power, ground, signal at crank sensor connector. Verified wiring from sensor to ECU is OK. Verified engine compression. Verified cam timing is correct with valve cover off. Verified fuel rail pressure. Found there is no fuel injection into cylinders during cranking. ECU shows 3+ millisecond injector time during cranking. ECU was replaced for this condition. No improvement.
He still has a code for Crankshaft sensor plausibility. So with all this in mind (no injector pulse, showing RPM), I needed to see a scope pattern before moving forward.
He said that he has a Verus but wasn't too familiar with using it. I asked him to get me a signal of the cam and crank sensors while cranking. He said that he would, and would send me the video
This shows me that the sensors are not dead, but I need to see more! I asked him if I could log into his scope to help him capture a good pattern.
After working my black magic, I was logged into his Verus. I messed with his voltages and time base to get a good signal that I could record and zoom in.
As far as I know, there shouldn't be 2 sync notches right next to one another on the sensor ring. Is this a sensor or ring problem? I have my suspicions, but need to confirm. Let's put more time on the screen and check for a repetitive pattern
Well..... That's repetitive.
I now have enough information to have the customer start wrenching. I asked him if he had a borescope. He said yes. I advised him to remove the crank sensor and spin the engine while watching the crank wheel.
Because I'm very demanding, I asked for the pic
We have clearly found the issue. After seeing this, the customer gave some more of the story, This vehicle has been there for a couple weeks, and he was the third in line diagnosing it. This car also came in running, meaning this damage was done in house! Maybe the wheel was damaged while trying to chisel out the original, second, or third (yes, they tried 3) crank sensors. Maybe something else came loose. Either way, the crankshaft has to come out, or engine will have to be replaced.
Before this vehicle, this customer was skeptical about scope usage. This Diagnosis took under 30 min. I think he is no longer skeptical!
Thanks for reading
Great work. It always amazes me the people that spend all of this money and then never end up using the scope function. About a year ago I went to a scope class put on by snap on so I decided I would go. The first 20 minutes of the class were how to find the scope function on the tool and where to plug the leads in at. Chris
Nice write up ... i Always wow them with a scope diagnosis .. and they change their whole perpective about scopes
Very well done! Thank you Chris. I love the "root cause" validation using the bore scope.