Crossfire 350 won't start, opinions?
#61
Moderator, Tech Contributor
Member Since: Sep 2013
Location: Cape Coral, Florida
Posts: 9,504
Received 2,116 Likes
on
1,683 Posts
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/
#62
Intermediate
Thread Starter
really don’t understand what you mean when you said that you “grounded the TPS to the negative terminal”...and also that the “current is flowing in reverse”...”conventional current flow” is from positive to negative but electron flow is actually negative to positive...this is a whole other discussion !!!
The potentiometer on the TPS is reading the voltages inverted (i.e. 5 volts closed, nearly 0 volts open), which means, as far as I can tell, that the flow of current is inverted. Which could indicate a positive to ground short to ground somewhere in the car. Feel free to correct me if I'm wrong; my knowledge on electrical stuff is a little rusty. It's been a hot minute since my high-school shop classes.
I intend no offense of course, as your comments and linked videos have been very helpful... but the issue I'm facing is clearly electrical, and it's moved beyond a simple "test this sensor with a DVOM" level, so this is very much "a whole other discussion" already, as we're starting to dive into some electrical-engineering territory with this troubleshooting. I think that's why Hot Rod Roy was scratching his head when you suggested squirting brake cleaner into the PCV as part of a solution when we're more than 3-pages deep into a thread detailing electrical problems.
If you've got some theories on why the current/voltage might be inverted at the TPS... or how/where I might have a positive short to ground ... or how I might prove/rule-out that that's what's happening I'm seriously all ears. Maybe I could do a load test or check for current flow with the car turned off?
#63
Moderator, Tech Contributor
Member Since: Sep 2013
Location: Cape Coral, Florida
Posts: 9,504
Received 2,116 Likes
on
1,683 Posts
64Scout suggested the issue might be with the ground wire on the car itself, which is reasonable. So I cut the ground wire running to the TPS (since it's connected to several other things) ... so I could isolate the circuit and ground it directly to the negative terminal to check for a short to ground elsewhere on the car. This didn't change anything, so I know it's not an issue with specific the ground wire/circuit running to the TPS/CTS. (I suppose I could try isolating the MAP sensor and testing that, since that has its own ground.)
The potentiometer on the TPS is reading the voltages inverted (i.e. 5 volts closed, nearly 0 volts open), which means, as far as I can tell, that the flow of current is inverted. Which could indicate a positive to ground short to ground somewhere in the car. Feel free to correct me if I'm wrong; my knowledge on electrical stuff is a little rusty. It's been a hot minute since my high-school shop classes.
I intend no offense of course, as your comments and linked videos have been very helpful... but the issue I'm facing is clearly electrical, and it's moved beyond a simple "test this sensor with a DVOM" level, so this is very much "a whole other discussion" already, as we're starting to dive into some electrical-engineering territory with this troubleshooting. I think that's why Hot Rod Roy was scratching his head when you suggested squirting brake cleaner into the PCV as part of a solution when we're more than 3-pages deep into a thread detailing electrical problems.
If you've got some theories on why the current/voltage might be inverted at the TPS... or how/where I might have a positive short to ground ... or how I might prove/rule-out that that's what's happening I'm seriously all ears. Maybe I could do a load test or check for current flow with the car turned off?
The potentiometer on the TPS is reading the voltages inverted (i.e. 5 volts closed, nearly 0 volts open), which means, as far as I can tell, that the flow of current is inverted. Which could indicate a positive to ground short to ground somewhere in the car. Feel free to correct me if I'm wrong; my knowledge on electrical stuff is a little rusty. It's been a hot minute since my high-school shop classes.
I intend no offense of course, as your comments and linked videos have been very helpful... but the issue I'm facing is clearly electrical, and it's moved beyond a simple "test this sensor with a DVOM" level, so this is very much "a whole other discussion" already, as we're starting to dive into some electrical-engineering territory with this troubleshooting. I think that's why Hot Rod Roy was scratching his head when you suggested squirting brake cleaner into the PCV as part of a solution when we're more than 3-pages deep into a thread detailing electrical problems.
If you've got some theories on why the current/voltage might be inverted at the TPS... or how/where I might have a positive short to ground ... or how I might prove/rule-out that that's what's happening I'm seriously all ears. Maybe I could do a load test or check for current flow with the car turned off?
#64
Le Mans Master
Well he has fuel pressre and some injector pulses. Hopefully it isn't something like the distributor stabbed in 180 off or something. That being said, 5 volts on the tps cuts ignition and fuel delivery to clear a flood so in this case going to electrical first would be correct. Not saying you're wrong but on these I go electrical first because they are old enough they just crap out. You're good though.
#65
Intermediate
Thread Starter
Well, it takes Fuel, Air, and Spark for an engine to run...This gentleman that scratched his head wondering why I would spray brake clean into the intake, or as I do into the PCV is to perform BASIC engine diagnostics...I don't jump into the electrical system diagnose .I would check for spark and if ignition and if good I'll check fuel...you spray brake clean or propane into the intake and the engine starts or tries to start you have a FUEL DELIVERY issue...I can't make it any simpler than that...if I check fuel pump pressure and that is good I move on to something a little more involved !!
I already know it's a fuel delivery issue. I said as much in the opening post of the thread. I used a noid light, and later on checked fuel pressure to confirm that it was electrical and not mechanical. There's no need to redundantly check for fuel delivery problems when it's already very clear that this is the problem.
Nobody is "jumping in" to an electrical system diagnostic - it's just very clear from the tests and symptoms that the problem isn't mechanical. You aren't wrong in suggesting that a spray of brake clean into the PCV would be a valid test, it's just an unnecessary one that doesn't reveal anything that I don't already know - hence the head scratching. I mean I'll do it if it'll make you happy.
Here's the rundown:
- I know I've got air, and spark because the engine will run for a few seconds if I dump some gas down into the intake. It just tends to buck and backfire if left to its own devices.
- I know I've mechanically got fuel, because the fuel pressure indicated between the two TBI's (which is the place you're supposed to take the reading) is within spec, which on a crossfire system is 9 to 13 PSI.
- That leaves the electronic delivery of the fuel, which I can also confirm visually since the injectors on the crossfire system are easily accessible and visible with the air-cleaner assembly removed... and I can see them as they spray.
- The basic sensors that deliver information to the ECU are giving me strange readings (i.e. the voltage on the TPS is backwards)
If I have to eat some humble pie I will, (and I have - your videos about the TPS were genuinely insightful) but at this point I'm not sure you can convince me it's anything other than an electrical problem.
As always, the replies are appreciated and I thank you, even if they're bugging me a little.
Last edited by KDMatt; 06-21-2018 at 03:22 PM.
#66
Safety Car
With everything hooked up "correctly", key on, and your DVM common (should be black) on your battery neg (-) terminal:
1. What is the voltage on your TPS pin A (blk)?
2. What is the voltage on your TPS pin C (gry)?
3. With the throttle in the idle position, what is the voltage on your TPS pin B (blu)?
4. With the throttle at 50% position, what is the voltage on your TPS pin B?
5. With the throttle at full open position, what is the voltage on your TPS pin B?
#67
Intermediate
Thread Starter
I'm a little "bugged" by this situation, too. Your backwards voltages don't make sense. Let's take this one step at a time.
With everything hooked up "correctly", key on, and your DVM common (should be black) on your battery neg (-) terminal:
1. What is the voltage on your TPS pin A (blk)?
2. What is the voltage on your TPS pin C (gry)?
3. With the throttle in the idle position, what is the voltage on your TPS pin B (blu)?
4. With the throttle at 50% position, what is the voltage on your TPS pin B?
5. With the throttle at full open position, what is the voltage on your TPS pin B?
With everything hooked up "correctly", key on, and your DVM common (should be black) on your battery neg (-) terminal:
1. What is the voltage on your TPS pin A (blk)?
2. What is the voltage on your TPS pin C (gry)?
3. With the throttle in the idle position, what is the voltage on your TPS pin B (blu)?
4. With the throttle at 50% position, what is the voltage on your TPS pin B?
5. With the throttle at full open position, what is the voltage on your TPS pin B?
I've been testing from the ground wire on the manifold, but perhaps I should be testing straight from the negative terminal on the battery. If there were a small positive short to ground via a chassis ground, I wouldn't detect it if I were using anything other than the proper negative on the battery would I?
I will check again once I get the fusible link situation taken care of.
But so far my readings have been:
- Voltage from TPS Pin A (black/ground) to manifold ground is 0 volts.
- Voltage on TPS Pin C (gray) is a little over 5 volts
The crux of what I'm facing right now is that the reading I'm getting between ports B and C (blue and gray) is about 5 volts at idle, and 0 volts at WOT... which is the reverse of how it should operate.
#69
Moderator, Tech Contributor
Member Since: Sep 2013
Location: Cape Coral, Florida
Posts: 9,504
Received 2,116 Likes
on
1,683 Posts
Well he has fuel pressre and some injector pulses. Hopefully it isn't something like the distributor stabbed in 180 off or something. That being said, 5 volts on the tps cuts ignition and fuel delivery to clear a flood so in this case going to electrical first would be correct. Not saying you're wrong but on these I go electrical first because they are old enough they just crap out. You're good though.
Well first off thanks for the complement. I guess after reading all that was checked with this car and trying to decipher what was done electrically my brain was just going into overload...LOL !!! ...yes, you are correct Sir...TPS at idle is around 1 volt and WOT around 5...and WOT puts the engine in clear flood mode. I see you are in Jersey...I'm in Monmouth county so if you're in my area or need to borrow some diagnostic equipment drop by !!
#70
Intermediate
Thread Starter
Yep. See. It's one of those things that makes sense in your head while you're in the process of doing it, but as soon as you say it out loud or type it you realize there may have been a better way to do it.
#71
Moderator, Tech Contributor
Member Since: Sep 2013
Location: Cape Coral, Florida
Posts: 9,504
Received 2,116 Likes
on
1,683 Posts
I've been testing from the ground wire on the manifold, but perhaps I should be testing straight from the negative terminal on the battery. If there were a small positive short to ground via a chassis ground, I wouldn't detect it if I were using anything other than the proper negative on the battery would I?
I will check again once I get the fusible link situation taken care of.
But so far my readings have been:
The crux of what I'm facing right now is that the reading I'm getting between ports B and C (blue and gray) is about 5 volts at idle, and 0 volts at WOT... which is the reverse of how it should operate.
I will check again once I get the fusible link situation taken care of.
But so far my readings have been:
- Voltage from TPS Pin A (black/ground) to manifold ground is 0 volts.
- Voltage on TPS Pin C (gray) is a little over 5 volts
The crux of what I'm facing right now is that the reading I'm getting between ports B and C (blue and gray) is about 5 volts at idle, and 0 volts at WOT... which is the reverse of how it should operate.
Last edited by C5 Diag; 06-21-2018 at 04:45 PM.
#72
Le Mans Master
Hello my friend,
Well first off thanks for the complement. I guess after reading all that was checked with this car and trying to decipher what was done electrically my brain was just going into overload...LOL !!! ...yes, you are correct Sir...TPS at idle is around 1 volt and WOT around 5...and WOT puts the engine in clear flood mode. I see you are in Jersey...I'm in Monmouth county so if you're in my area or need to borrow some diagnostic equipment drop by !!
Well first off thanks for the complement. I guess after reading all that was checked with this car and trying to decipher what was done electrically my brain was just going into overload...LOL !!! ...yes, you are correct Sir...TPS at idle is around 1 volt and WOT around 5...and WOT puts the engine in clear flood mode. I see you are in Jersey...I'm in Monmouth county so if you're in my area or need to borrow some diagnostic equipment drop by !!
And I agree, accurate ground to double check the stray current. If you want you can disconnect the battery and use the ohm setting to check wires for continuity to ground. Just a tip.
#73
Moderator, Tech Contributor
Member Since: Sep 2013
Location: Cape Coral, Florida
Posts: 9,504
Received 2,116 Likes
on
1,683 Posts
I'm actually in jackson. If you have gone to the chick-fila shows in howell we may have crossed paths before lol.
And I agree, accurate ground to double check the stray current. If you want you can disconnect the battery and use the ohm setting to check wires for continuity to ground. Just a tip.
And I agree, accurate ground to double check the stray current. If you want you can disconnect the battery and use the ohm setting to check wires for continuity to ground. Just a tip.
#74
Le Mans Master
Cool !!...no, never been to those shows...with all this TPS sensor stuff here I just finished checking mine with my labscope I purchased last month...my 01 has 2 separate TPS signal wires... one a pull up and the other a pull down circuit...1 volt at idle to 4.5 at WOT and the other 4.5 at idle to 1 volt at WOT...those GM Engineers were pretty sharp !!
#75
Safety Car
with all this TPS sensor stuff here I just finished checking mine with my labscope I purchased last month...my 01 has 2 separate TPS signal wires... one a pull up and the other a pull down circuit...1 volt at idle to 4.5 at WOT and the other 4.5 at idle to 1 volt at WOT.
#76
Intermediate
Thread Starter
Alright well, I fixed the fusible link -- I replaced it with a standard inline fuse designed for a battery. Both the CEL and Fuel pump are coming on again when I switch the key to on.
I did notice that some of the insulation on the positive power feed for the ECU had rubbed away, and thought perhaps that was the source of my problem, but sadly, the symptoms have not changed, except...
Unlike last night, I am now no longer getting any 5volt reference signal at all. I even probed the gray 5v signal wire right at the ECU and checked it against the ground at the battery.
However, when I checked against the positive terminal, I got a full 12 volt reading, which would mean that the 5 volt wire is grounded. The same goes for the blue reference wire on the TPS, and (of course) the black ground wire for the TPS.
I might snip the gray wire near the ECU as a test to see if I can get 5 volts without any of the rest of the circuit in play... if I can't, then what... my ECU is hosed?
I did notice that some of the insulation on the positive power feed for the ECU had rubbed away, and thought perhaps that was the source of my problem, but sadly, the symptoms have not changed, except...
Unlike last night, I am now no longer getting any 5volt reference signal at all. I even probed the gray 5v signal wire right at the ECU and checked it against the ground at the battery.
However, when I checked against the positive terminal, I got a full 12 volt reading, which would mean that the 5 volt wire is grounded. The same goes for the blue reference wire on the TPS, and (of course) the black ground wire for the TPS.
I might snip the gray wire near the ECU as a test to see if I can get 5 volts without any of the rest of the circuit in play... if I can't, then what... my ECU is hosed?
#77
Safety Car
#78
Intermediate
Thread Starter
Snipped the wire... no change.
I'm not getting a 5 volt signal out of the ECU. The 5v reference wire is no longer reading as grounded though.
My ECU wasn't connected when I zapped my fusible link so I really have no idea what's going on here.
Last edited by KDMatt; 06-22-2018 at 02:22 AM.
#80
Intermediate
Thread Starter
The zap that killed the fusible link is the only thing I know of that changed. I also replaced the battery cables and the primary chassis ground near the battery all for good measure since everything was looking a bit ratty.
The white power connector (the one that carries/completes the 5v signal) was definitely disconnected when the "zap" happened though. This is why I'm scratching my head even harder now.
EDIT:
I've confirmed that the ECU ground has continuity to chassis ground. I guess the next thing to do would be to make sure it's getting power? After that... take it out and crack it open and look for popped capacitors or any blown components? Starting to get out of my depth here.
The white power connector (the one that carries/completes the 5v signal) was definitely disconnected when the "zap" happened though. This is why I'm scratching my head even harder now.
EDIT:
I've confirmed that the ECU ground has continuity to chassis ground. I guess the next thing to do would be to make sure it's getting power? After that... take it out and crack it open and look for popped capacitors or any blown components? Starting to get out of my depth here.
Last edited by KDMatt; 06-22-2018 at 03:33 AM.