2G Hard starting and CAS over voltage

[TC1995]

Summary
1995 GSX manual abandoned 18yrs.
Have gotten it intermittently to start and idle even briefly move into the driveway under it's own power

Full background and build thread if desired (https://www.dsmtuners.com/threads/9...-recommendations.549900/page-3#post-153969965)

I'm having difficulty easily getting it started and maintaining idle, once it does I'm starting to suspect that something is telling the car not to send fuel spark etc. Might be unrelated, but when the car does idle, pushing throttle down is very sluggish and basically gave very little response.

I'm going to change out fuel filter to ensure no restrictions under higher load but with the fuel that dumps out when I tested my new fuel pump at the rail I highly doubt I have fuel issues at idle and on startup. I did just get in a fuel pressure gauge test kit to confirm either way eventually.

Starter is cranking motor just fine at good speed

Battery always charged when I test as I keep a low amp tender on between working on it.
I narrowed down my thoughts to the Camshaft sensor up top near the intake.

Thought process was if it's getting dirty or bad signal about camshaft etc car goes into limp mode and makes starting very difficult and very resistant to reving once it does.

To test the sensor, not only did I have to remove the headlight, motor mount and timing cover but apparently only Jesus is getting to that camshaft sensor behind the intake cam gear cause no way I'm getting that . So switching gears to testing electrically through the connectors.

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Oddly enough when probing my multimeter into the harness for the signal wire and the incoming 12v power with the key turned on I'm getting ~7.4v which is odd. If anything, I think the pull down resistance voltage should be 5v and go to zero when sensing the cam. So I then connected the sensor back up and left probes in and instead when operating/cranking motor I'm getting between ~6v-8.5v. I know signal wire is square waveform so not best to use multimeter for checking signal pulse (I don't have a noid light) but either way it's not at all the voltages I expected.

Ironically enough I think it might point to wiring short or break instead of bad sensor which would be easier to fix, I think, but still quite confusing. Thinking about wiring up a speaker with resistor to listen to pitch of the signal and do quick check if it's at least increasing when engine cranks and rpm goes up. (Or if I can get it started and rev it listen to signal). But open to ideas as to what might be the issue.

My next steps are to confirm good continuity and clean ground at the harness side plug, might also check timing on the off chance somewhere along the line skipped a tooth or something dumb. (doubt this though since when it idled sounded good smooth and all four cylinders were firing I have some videos in the thread of it running)

 

[steve]

If in fact you're seeing 7.4v on the cam sensor signal line, I'd check some of the other signals that have 5v pullups from the ECU.
While cranking battery voltage usually drops quite a bit from the current the starter draws but you should still only see ~5v on the signal pullups since they are from the ECU's +5v voltage regulator.

 

[TC1995]

If in fact you're seeing 7.4v on the cam sensor signal line, I'd check some of the other signals that have 5v pullups from the ECU.
While cranking battery voltage usually drops quite a bit from the current the starter draws but you should still only see ~5v on the signal pullups since they are from the ECU's +5v voltage regulator.

I'm assuming other easy systems to check that refernce voltage would be the Crankshaft Position Sensor (CKP) — same Hall-effect style as CAS right in same spot I already have pulled apart, same 5V pullup circuit. Hopefully to help tell me if I might be dealing with bad ground, short etc somewhere?

 

[TC1995]

""""If in fact you're seeing 7.4v""""

"IF" was the key word here, thank you !!

I went back to test this today with fresh brain rather than the potato brain of last night.

Oddly enough when probing my multimeter into the harness for the signal wire and the incoming 12v power with the key turned on I'm getting ~7.4v which is odd.

I was checking reference for my voltage, against incoming 12v, instead of ground. So yeah 12v - 5v = 7v.
Checked a few other sensors like crankshaft as well to confirm but exactly ~5v on the signal wire when key is on, so at least we know incoming conditions are normal.

I will reconnect sensor to harness and try to crank again with crude multimeter test (properly probed this time) to see what type of action we're getting roughly, but I'm thinking the sensor is likely ok? Going to see if I can track down proper tools so I don't have to try and remove the sensor cause seems not worth the effort with it behind that intake cam gear.

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I started to look at some other potential causes and relays, took center console apart and found my main starter relay behind the dash is just jumped right now (so assuming the relay present is toast) I have another ordered that I will throw in once I test it.

And realized as well that the clutch pedal switch is either broken or intentionally jumped (I would assume they did it for crankwalk reasons?)