Crossfire 350 won't start, opinions?
06-19-2018, 11:03 PM
#41
Intermediate
Thread Starter
You guys I'm getting SO CLOSE
Turns out, with a bit of digging, the CTS circuit isn't the problem. It's the 5V reference in the gray wire.
I unplugged the MAP sensor and VOILA, the TPS is now reading correctly. I'm getting great spray out of the injectors, but now the motor doesn't want to show any signs of life. I'm cranking like crazy, holding the throttles open, but it won't kick. Is the MAP sensor a "no-go" item? i.e. it's not going to start with it unplugged?
I'm starting the wear the battery down now. :/
Turns out, with a bit of digging, the CTS circuit isn't the problem. It's the 5V reference in the gray wire.
I unplugged the MAP sensor and VOILA, the TPS is now reading correctly. I'm getting great spray out of the injectors, but now the motor doesn't want to show any signs of life. I'm cranking like crazy, holding the throttles open, but it won't kick. Is the MAP sensor a "no-go" item? i.e. it's not going to start with it unplugged?
I'm starting the wear the battery down now. :/
06-20-2018, 12:04 AM
#42
Le Mans Master
If no map is present it won't go iirc. That being said I don't have my fsm in front of me but the map reference links to both the CTS and Tps. That's from memory though. It is something in that path.
Edit: I think the est also runs through the map.
Edit: I think the est also runs through the map.
Last edited by 84 4+3; 06-20-2018 at 12:05 AM.
06-20-2018, 12:08 AM
#43
Intermediate
Thread Starter
I tested the remaining wires (green and purple) for any stray voltage and didn't find any.
MAP has its own ground, so it would be easy to isolate/re-wire if the need arose.
... but something is causing the 5 volt reference signal going to the MAP to become 8 or 9 volts while it's connected.
EDIT: I'm not seeing any direct connection between the MAP and EST, but maybe there's some wizardry inside the ECU that links them together
Last edited by KDMatt; 06-20-2018 at 12:13 AM.
06-20-2018, 12:39 AM
#44
Intermediate
Thread Starter
Okay nevermind. I'm back to losing my damned mind.
I'm getting 5 volts at the TPS again -- it's operating in reverse, AGAIN.
Unplugging the MAP and unplugging the CTS do nothing. I'm getting 5 volts between points B and C on the TPS and it was seriously perfectly like an hour ago.
I was also at one point getting 8 volts at the MAP and now it's back to 5.
I'm about ready to scrap the whole thing and just get a carburetor. This is just nuts.
EDIT:
I tried snipping the blue TPS wire out of desperation, while unplugging the CTS -- which means the only connection going to the TPS is the gray 5v signal, and it's STILL reading 5 volts and operating in reverse... there isn't even a complete circuit??
I've got a serious case of Gremlins. I need to take a break and pour myself a stiff drink...
I'm getting 5 volts at the TPS again -- it's operating in reverse, AGAIN.
Unplugging the MAP and unplugging the CTS do nothing. I'm getting 5 volts between points B and C on the TPS and it was seriously perfectly like an hour ago.
I was also at one point getting 8 volts at the MAP and now it's back to 5.
I'm about ready to scrap the whole thing and just get a carburetor. This is just nuts.
EDIT:
I tried snipping the blue TPS wire out of desperation, while unplugging the CTS -- which means the only connection going to the TPS is the gray 5v signal, and it's STILL reading 5 volts and operating in reverse... there isn't even a complete circuit??
I've got a serious case of Gremlins. I need to take a break and pour myself a stiff drink...
Last edited by KDMatt; 06-20-2018 at 12:58 AM.
06-20-2018, 02:43 AM
#45
Le Mans Master
I need to sleep on this. Problem is I have an 84 fsm which may be different but I think you might have a wiring gremlin.
06-20-2018, 08:30 AM
#46
Burning Brakes
Member Since: Oct 2017
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Okay nevermind. I'm back to losing my damned mind.
I'm getting 5 volts at the TPS again -- it's operating in reverse, AGAIN.
Unplugging the MAP and unplugging the CTS do nothing. I'm getting 5 volts between points B and C on the TPS and it was seriously perfectly like an hour ago.
I was also at one point getting 8 volts at the MAP and now it's back to 5.
I'm about ready to scrap the whole thing and just get a carburetor. This is just nuts.
EDIT:
I tried snipping the blue TPS wire out of desperation, while unplugging the CTS -- which means the only connection going to the TPS is the gray 5v signal, and it's STILL reading 5 volts and operating in reverse... there isn't even a complete circuit??
I've got a serious case of Gremlins. I need to take a break and pour myself a stiff drink...
I'm getting 5 volts at the TPS again -- it's operating in reverse, AGAIN.
Unplugging the MAP and unplugging the CTS do nothing. I'm getting 5 volts between points B and C on the TPS and it was seriously perfectly like an hour ago.
I was also at one point getting 8 volts at the MAP and now it's back to 5.
I'm about ready to scrap the whole thing and just get a carburetor. This is just nuts.
EDIT:
I tried snipping the blue TPS wire out of desperation, while unplugging the CTS -- which means the only connection going to the TPS is the gray 5v signal, and it's STILL reading 5 volts and operating in reverse... there isn't even a complete circuit??
I've got a serious case of Gremlins. I need to take a break and pour myself a stiff drink...
06-20-2018, 11:27 AM
#47
Intermediate
Thread Starter
If I haven't said so already I really appreciate you guys helping me stay sane on this. Thank you.
@64Scout -- B&C are the top two wires on the TPS. So +5v and signal.
I'm just tearing my hair out because, as a test, I snipped the signal wire (blue) which should have effectively killed the circuit, right? ... but I was still getting a 5 volt reading between gray and blue at the TPS.
I brought my FSM with me to work today so I can try to be more intelligible with my responses, but my skills as an electrical engineer are somewhat limited.
@64Scout -- B&C are the top two wires on the TPS. So +5v and signal.
I'm just tearing my hair out because, as a test, I snipped the signal wire (blue) which should have effectively killed the circuit, right? ... but I was still getting a 5 volt reading between gray and blue at the TPS.
I brought my FSM with me to work today so I can try to be more intelligible with my responses, but my skills as an electrical engineer are somewhat limited.
06-20-2018, 11:53 AM
#48
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I've got 12 volts at each injector.
I've checked all of my grounds, and I've got maybe only 1.5 to .9 ohms of resistance to any given point I check, so I don't think it's a grounding issue.
The thing sounds so close to wanting to fire. If I let it sit for a few hours I'll get a fire on the first crank, but it'll die almost immediately after that.
I'm going to keep looking at my circuit diagrams to see if there's anything else that pops out at me.
EDIT:
I've got continuity so far from the EST/Spark circuit to the ECU
I also spent a bunch of time checking the coolant temp sensor circuit, since when I probed the connector it showed no continuity/open. According to my FSM this isn't right... The coolant temp sensor shares a ground with the TPS and MAP. I traced the circuit all the way around. The connector from the Coolant temp sensor to the ECU (yellow) is good. The ground connector from the CTS to the TPS is good, and from the TPS to MAP and ECU is also good.
Given all of that checks out, I then decided to check the TPS itself... This is where it gets a little interesting...
The FSM says to probe ports B & C on the TPS harness, and that the voltage with the key-on in the ignition should read .525 volts, give or take .75.
The voltage I'm getting is well over 4 volts, oscillating a bit as I move the sensor up and down, but still in the neighborhood of 4.3 to 4.6 volts, depending on where I situate the sensor. Would that mean that my TPS failed? Could this be my smoking gun?
I'm not sure how the TPS really works, but I'm wondering if something inside of it has potentially broken the circuit through it to the CTS.
I've checked all of my grounds, and I've got maybe only 1.5 to .9 ohms of resistance to any given point I check, so I don't think it's a grounding issue.
The thing sounds so close to wanting to fire. If I let it sit for a few hours I'll get a fire on the first crank, but it'll die almost immediately after that.
I'm going to keep looking at my circuit diagrams to see if there's anything else that pops out at me.
EDIT:
I've got continuity so far from the EST/Spark circuit to the ECU
I also spent a bunch of time checking the coolant temp sensor circuit, since when I probed the connector it showed no continuity/open. According to my FSM this isn't right... The coolant temp sensor shares a ground with the TPS and MAP. I traced the circuit all the way around. The connector from the Coolant temp sensor to the ECU (yellow) is good. The ground connector from the CTS to the TPS is good, and from the TPS to MAP and ECU is also good.
Given all of that checks out, I then decided to check the TPS itself... This is where it gets a little interesting...
The FSM says to probe ports B & C on the TPS harness, and that the voltage with the key-on in the ignition should read .525 volts, give or take .75.
The voltage I'm getting is well over 4 volts, oscillating a bit as I move the sensor up and down, but still in the neighborhood of 4.3 to 4.6 volts, depending on where I situate the sensor. Would that mean that my TPS failed? Could this be my smoking gun?
I'm not sure how the TPS really works, but I'm wondering if something inside of it has potentially broken the circuit through it to the CTS.
Dude, You said you don't really know how your TPS works...well, you can watch this 2 part video...knowing how the system works is ESSENTIAL to accurate diagnostics...and remember if any of these sensors /potentiometers that have a 5 volt ref. and this 5 volt ref. is shorted you'll have a no start !! !!
Last edited by C5 Diag; 06-20-2018 at 12:33 PM.
06-20-2018, 12:49 PM
#50
Intermediate
Thread Starter
@rwobs Thank you for the video series! I already knew about 75% of what he's going into, but that last 25% is pretty critical stuff! It will definitely inform where I go with my TPS diagnosis.
@64Scout
I'm having the same thought. I was under the assumption, I think, based on what 84 was saying, that the TPS is grounded *through* the CTS, and that disconnecting the CTS would remove the ground signal, but looking at the schematics it looks more like a parallel circuit - that they share grounds.
When I get some time tonight I'm going to see if there's still some rogue voltage in that ground connection. I'm concerned about some of the other places that circuit goes, that being the case.
My schematics show that it goes to a 15-pin connector, and then gets passed on to both "39 CKT" and, also it looks like, a grounded 10 amp fuse.
Needless to say, I'm going to have to check that fuse regardless of what I find.
@64Scout
I'm having the same thought. I was under the assumption, I think, based on what 84 was saying, that the TPS is grounded *through* the CTS, and that disconnecting the CTS would remove the ground signal, but looking at the schematics it looks more like a parallel circuit - that they share grounds.
When I get some time tonight I'm going to see if there's still some rogue voltage in that ground connection. I'm concerned about some of the other places that circuit goes, that being the case.
My schematics show that it goes to a 15-pin connector, and then gets passed on to both "39 CKT" and, also it looks like, a grounded 10 amp fuse.
Needless to say, I'm going to have to check that fuse regardless of what I find.
06-20-2018, 01:17 PM
#51
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@rwobs Thank you for the video series! I already knew about 75% of what he's going into, but that last 25% is pretty critical stuff! It will definitely inform where I go with my TPS diagnosis.
@64Scout
I'm having the same thought. I was under the assumption, I think, based on what 84 was saying, that the TPS is grounded *through* the CTS, and that disconnecting the CTS would remove the ground signal, but looking at the schematics it looks more like a parallel circuit - that they share grounds.
When I get some time tonight I'm going to see if there's still some rogue voltage in that ground connection. I'm concerned about some of the other places that circuit goes, that being the case.
My schematics show that it goes to a 15-pin connector, and then gets passed on to both "39 CKT" and, also it looks like, a grounded 10 amp fuse.
Needless to say, I'm going to have to check that fuse regardless of what I find.
@64Scout
I'm having the same thought. I was under the assumption, I think, based on what 84 was saying, that the TPS is grounded *through* the CTS, and that disconnecting the CTS would remove the ground signal, but looking at the schematics it looks more like a parallel circuit - that they share grounds.
When I get some time tonight I'm going to see if there's still some rogue voltage in that ground connection. I'm concerned about some of the other places that circuit goes, that being the case.
My schematics show that it goes to a 15-pin connector, and then gets passed on to both "39 CKT" and, also it looks like, a grounded 10 amp fuse.
Needless to say, I'm going to have to check that fuse regardless of what I find.
06-20-2018, 01:28 PM
#52
Intermediate
Thread Starter
'82 Crossfire Schematic from the Firebird Service Manual
06-20-2018, 03:19 PM
#53
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Not to clear...maybe someone can post something that's from a CD...I finally sprung for a factory service manual for my car...3 volumes and each volume is about 4 inches thick...if you've checked enough of these sensors you really don't need a wiring diagram for different cars...they all operate the same way...I usually print out the page I need and color code all the powers and grounds from the sensor back to the PCM !!...if you REALLY want to learn this stuff go to Scanner Danner.com and subscribe to his Premium site...it's $11.00 a month and go basically go into the classroom where he teaches at a tech college in Pittsburgh...I've been watching him for almost 2 years and am a member of that premium site and my diagnostic abilities have improved 1,000 percent...even watching his Youtube videos you can learn a lot...he is the Jedi Master of auto diagnostics !!
06-20-2018, 04:56 PM
#54
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If I haven't said so already I really appreciate you guys helping me stay sane on this. Thank you.
@64Scout -- B&C are the top two wires on the TPS. So +5v and signal.
I'm just tearing my hair out because, as a test, I snipped the signal wire (blue) which should have effectively killed the circuit, right? ... but I was still getting a 5 volt reading between gray and blue at the TPS.
I brought my FSM with me to work today so I can try to be more intelligible with my responses, but my skills as an electrical engineer are somewhat limited.
@64Scout -- B&C are the top two wires on the TPS. So +5v and signal.
I'm just tearing my hair out because, as a test, I snipped the signal wire (blue) which should have effectively killed the circuit, right? ... but I was still getting a 5 volt reading between gray and blue at the TPS.
I brought my FSM with me to work today so I can try to be more intelligible with my responses, but my skills as an electrical engineer are somewhat limited.
Last edited by C5 Diag; 06-20-2018 at 04:58 PM.
06-20-2018, 06:07 PM
#55
Intermediate
Thread Starter
This might help !!...I don't know how you are electrically checking this circuit with your DVOM ??...some circuits you have to backprobe and some you disconnect the connector !!
https://www.youtube.com/watch?v=h17kYyFrExE
https://www.youtube.com/watch?v=h17kYyFrExE
"Signal Integrity Check" that's great. Totally going to use that. I'll have to do it with a multi-meter though.
06-20-2018, 06:19 PM
#56
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Member Since: Sep 2013
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ps- did you ever spray some brake clean or propane into the intake to see if it tried to start ????...that is always my next thing after spark when I troubleshoot...that helps me in the direction I’ll be going !!
Last edited by C5 Diag; 06-20-2018 at 08:10 PM.
06-20-2018, 08:08 PM
#58
Le Mans Master
This is the diagram I have been looking at.
Last edited by 84 4+3; 06-20-2018 at 08:08 PM.
06-20-2018, 10:30 PM
#59
Intermediate
Thread Starter
I'm working on the car right now.
I tried grounding the TPS directly to the negative terminal, and the current is still flowing in reverse.
EDIT:
I'm going to test to see if perhaps the 5v source itself has grounded out.
https://www.motor.com/magazine-summa...nder-may-2016/
I tried grounding the TPS directly to the negative terminal, and the current is still flowing in reverse.
EDIT:
I'm going to test to see if perhaps the 5v source itself has grounded out.
https://www.motor.com/magazine-summa...nder-may-2016/
Last edited by KDMatt; 06-20-2018 at 10:38 PM.
06-20-2018, 11:26 PM
#60
Intermediate
Thread Starter
Well lads, new problem.
When I was testing the ECM grounds, the lead for my multimeter slipped out of the terminal, shorted something... big poof of smoke from the battery, and now the check engine light won't come on, and the fuel pump won't come on.
EDIT: Quickly diagnosed it as a blown fusible link. So there's THAT at least.
When I was testing the ECM grounds, the lead for my multimeter slipped out of the terminal, shorted something... big poof of smoke from the battery, and now the check engine light won't come on, and the fuel pump won't come on.
EDIT: Quickly diagnosed it as a blown fusible link. So there's THAT at least.
Last edited by KDMatt; 06-20-2018 at 11:38 PM.