CALLING ALL ELECTICAL GENIUSES

Tom Kelly

Active Member
Yes do that first and if that doesn't work separate the boost gauge .
I think 87GNALKY was exactly right when he pointed me to the temperature of the wideband sensor as the "what's different" between the first start of the day and subsequent starts (and key only starts) . I decided to take the GN to Church today and initially planned to disconnect the wideband 12V and see if on the return trip, the boost gauge initialized properly. Previously it took at least 10 hours to "reset". But when I went out into the nippy air of a fall morning I had another thought. Maybe in the cooler temperatures the sensor would cool quicker and just maybe two hours would be enough even with the wideband connected. So always looking to experiment without disconnecting or moving anything I gave it a try. Sure enough, after only two hours, the boost gauge initialized perfectly. This has NEVER happened before all summer. This also squares with the fact that the problem did not originate until the warm weather arrived in May. And so I think the path is clear. The wideband circuit has to be isolated. If only I had the skill to do it. Just like some people are "singing impaired" my weak spot is wiring. I will have to have my shop do it if I want to be sure it's done right.
A man has to know his limitations .
Thanks again to all of you. It took the collective thoughts of so many people to bring me to the solution. Couldn't have done it without you all.
 

87GNALKY

Active Member
I think 87GNALKY was exactly right when he pointed me to the temperature of the wideband sensor as the "what's different" between the first start of the day and subsequent starts (and key only starts) . I decided to take the GN to Church today and initially planned to disconnect the wideband 12V and see if on the return trip, the boost gauge initialized properly. Previously it took at least 10 hours to "reset". But when I went out into the nippy air of a fall morning I had another thought. Maybe in the cooler temperatures the sensor would cool quicker and just maybe two hours would be enough even with the wideband connected. So always looking to experiment without disconnecting or moving anything I gave it a try. Sure enough, after only two hours, the boost gauge initialized perfectly. This has NEVER happened before all summer. This also squares with the fact that the problem did not originate until the warm weather arrived in May. And so I think the path is clear. The wideband circuit has to be isolated. If only I had the skill to do it. Just like some people are "singing impaired" my weak spot is wiring. I will have to have my shop do it if I want to be sure it's done right.
A man has to know his limitations .
Thanks again to all of you. It took the collective thoughts of so many people to bring me to the solution. Couldn't have done it without you all.
Happy to help you brother!
 

Tom Kelly

Active Member
AMEN AMEN.
Well, I have recovered from another hip replacement and the weather has turned nice so I set out to checkout the theory we developed that the wideband sensor and controller "noise" was causing the Speedhut digital boost gauge not to initialize properly once the wideband sensor heated up. So I gave the wideband its own 12V and ground. Tried it out with confidence but alas problem persisted. Then I did what I should have done in the beginning before re-wiring. I disconnected both harnesses from the wideband gauge. This, at least in theory. should have eliminated the possibility of any interference at all from the wideband. Problem still happened. So I am back where I started. The Speedhut digital boost gauge initializes properly when I either 1. Start the engine after it is sitting overnight (or for an extended period) or 2. If I just turn on the key but don't crank the starter. Otherwise it just goes to "Sender error" . The only other change I made before this happened is I switched to an LT-1 MAF with translator. I can't understand what could possibly be different from a cold start and a warmed up car start that would cause the gauge to not initialize. Any ideas?
 

mikestertwo

Well-Known Member
Well, I have recovered from another hip replacement and the weather has turned nice so I set out to checkout the theory we developed that the wideband sensor and controller "noise" was causing the Speedhut digital boost gauge not to initialize properly once the wideband sensor heated up. So I gave the wideband its own 12V and ground. Tried it out with confidence but alas problem persisted. Then I did what I should have done in the beginning before re-wiring. I disconnected both harnesses from the wideband gauge. This, at least in theory. should have eliminated the possibility of any interference at all from the wideband. Problem still happened. So I am back where I started. The Speedhut digital boost gauge initializes properly when I either 1. Start the engine after it is sitting overnight (or for an extended period) or 2. If I just turn on the key but don't crank the starter. Otherwise it just goes to "Sender error" . The only other change I made before this happened is I switched to an LT-1 MAF with translator. I can't understand what could possibly be different from a cold start and a warmed up car start that would cause the gauge to not initialize. Any ideas?
Ok...let's start over. Where are you getting the +12 volts for the gauge and the inverter? Where do you have the grounds for the gauge and inverter tied? Does the gauge initialize properly when the engine is warm, key on/engine off, but then errors when you start the engine?
 

Tom Kelly

Active Member
Ok...let's start over. Where are you getting the +12 volts for the gauge and the inverter? Where do you have the grounds for the gauge and inverter tied? Does the gauge initialize properly when the engine is warm, key on/engine off, but then errors when you start the engine?
12 V comes from the fuse box. Ground is to body. I don't think it's that because when engine is cold everything works perfectly. If it was a 12V or ground issue it would not be consistently okay when cold and consistently not okay when warm. When warm it will initialize if I go key on/engine off but goes to "sender error" when I crank it and it starts. I am trying to figure this---What is different when engine is cold vs when it has warmed up? I thought it was the wide band sensor which spends a while heating up before it sends a signal but less so when it is already warm. I disconnected the wideband gauge and sender from power and that didn't do it. I thought temperature as the relay for the fan kicks in at 160 degrees but the problem occurs below 160 so I ruled that out. Can't think of anything else
 

mikestertwo

Well-Known Member
---What is different when engine is cold vs when it has warmed up?

The charging system and electrical loads are different depending on temperature. My guess is you have a ground current issue. The fact that the gauge initializes ok until you start the car points towards a grounding issue. Where on the body is the gauge grounded? Do you have a good ground from the negative battery cable to the body? How about the ground from the engine to body? Once the engine is running you have a lot of electrical accessories that come into play. If you have poor grounding, an electrical accessory will use the least path of resistance to go back to the source. If your ground scheme is compromised accessories with use whatever ground is available including the gauge ground. This could cause the ground of the gauge to "Float" offsetting the voltage. I would carefully go back and check the battery to body ground and all other power grounds. You haven't moved any factory grounds have you?
 

dynoman

Well-Known Member
Lets try something different . Remove the Vac/Boost sender from the Vac/boost source but keep it plugged in to the circuit . See if it works on first start up and subsequent warm starts . Don't forget to plug where you remove the sender from .
 

Tom Kelly

Active Member
When you say charging system is varied with temperature do you mean outside temperature or engine temperature? I will re-check all grounds. If it is a grounding issue it would account for being okay when engine is cold and not okay after engine is warmed up?
 

Tom Kelly

Active Member
Lets try something different . Remove the Vac/Boost sender from the Vac/boost source but keep it plugged in to the circuit . See if it works on first start up and subsequent warm starts . Don't forget to plug where you remove the sender from .
Actually I tried that last fall. But speedhut tech support later told me that boost/vacuum in the line makes no difference. The ONLY thing the controller looks for is the 5V from the sender. Absent that it only shows "Sender error"
 

mikestertwo

Well-Known Member
When you say charging system is varied with temperature do you mean outside temperature or engine temperature? I will re-check all grounds. If it is a grounding issue it would account for being okay when engine is cold and not okay after engine is warmed up?
Engine temperature...specifically alternator temperature. Alternators have temperature compensation built into them. That's why your voltage is higher on cold startups then drops as the temperature increases. It could be because the voltage is higher on cold startups, somehow it's compensating for another issue that's affecting your gauge. Check all grounds carefully. You haven't told me specifically where you have the gauge grounded or if you have moved any of the factory grounds.
 

Tom Kelly

Active Member
Engine temperature...specifically alternator temperature. Alternators have temperature compensation built into them. That's why your voltage is higher on cold startups then drops as the temperature increases. It could be because the voltage is higher on cold startups, somehow it's compensating for another issue that's affecting your gauge. Check all grounds carefully. You haven't told me specifically where you have the gauge grounded or if you have moved any of the factory grounds.
thanks for hanging in there with me. I'm pretty sure the boost gauge is grounded to the A Pillar. I have not moved any factory grounds. The boost gauge worked for years grounded as it is until I installed the AEM wideband gauge and sensor and a powerlogger and changed the MAF to an LT-1 with translator. The boost gauge originally was in a 2 hole A pillar pod (with a speedhut digital fuel pressure gauge (which continues to work fine in that it initializes fine every time)). I changed to a three hole pod and installed the wideband gauge in it. Unfortunately I made all three changes at the same time. If one of them is the culprit I won't know which one.

Useful hint?? The boost gauge returns to working normally quicker on cold days than in the summer. In the summer it stays unusable for many hours after the first drive. In the winter it works fine after only an hour. On any day if I make the first start, then turn it off and re-start right away it will work fine. It's only after the engine has run for awhile that it becomes temporarily unusable.
 

Tom Kelly

Active Member
thanks for hanging in there with me. I'm pretty sure the boost gauge is grounded to the A Pillar. I have not moved any factory grounds. The boost gauge worked for years grounded as it is until I installed the AEM wideband gauge and sensor and a powerlogger and changed the MAF to an LT-1 with translator. The boost gauge originally was in a 2 hole A pillar pod (with a speedhut digital fuel pressure gauge (which continues to work fine in that it initializes fine every time)). I changed to a three hole pod and installed the wideband gauge in it. Unfortunately I made all three changes at the same time. If one of them is the culprit I won't know which one.

Useful hint?? The boost gauge returns to working normally quicker on cold days than in the summer. In the summer it stays unusable for many hours after the first drive. In the winter it works fine after only an hour. On any day if I make the first start, then turn it off and re-start right away it will work fine. It's only after the engine has run for awhile that it becomes temporarily unusable.
One more thing that might be helpful. Since the gauge ALWAYS works if I just key on, I thought it might have something to do with the cranking process after warmup so I tried this. When the gauge was acting up (after warmup) I disconnected it from the harnesses. Then I started the car and then reconnected the harnesses to the gauge. Same problem. This led me to believe it wasn't noise or voltage issues during cranking.
 

mikestertwo

Well-Known Member
Another question..... How is the sender for the gauge plumbed in? Is it grounded or isolated from ground? Is the ground for the gauge on it's own ground screw or is it shared with something else? Do you have pictures of your setup...Where the sender is mounted?
 

Tom Kelly

Active Member
Another question..... How is the sender for the gauge plumbed in? Is it grounded or isolated from ground? Is the ground for the gauge on it's own ground screw or is it shared with something else? Do you have pictures of your setup...Where the sender is mounted?
The ground screw (and the 12V) is shared with only the fuel pressure gauge which is lso a speedhut digital and which always initializes perfectly.
The sender is plumbed into a vacuum line leading to the canister. The other side of the sender is plugged into the harness to the gauge. That's where it gets its power and also how it transmits to the gauge. The techies at speedhut said the ONLY thing the gauge looks for to initialize is a clean 5V from the sender. It gets that clean 5V in the morning every time. It's the rest of the day that's hit and miss. Like I said it resets itself quicker in the winter.
 

mikestertwo

Well-Known Member
Another dumb question. Both your fuel pressure gauge and the boost gauge use an inverter to run the display...correct? Do they use the same inverter or two separate inverters?
 

Tom Kelly

Active Member
Another dumb question. Both your fuel pressure gauge and the boost gauge use an inverter to run the display...correct? Do they use the same inverter or two separate inverters?
The gauges just have harnesses which fan out to 12v, ground and sending units. I’m not sure what u mean by inverter in this scenario. Must be being dense.
 

No disintegrations

Active Member
Sounds like a bad ground. I haven't read every last word though. I skimmed through. Here's an example. Following a car at night. Tail lights are on. They hit the brakes. Tail lights turn off and one brake light struggles to turn on. They let off the brakes and the tail lights ooze their way back on. This is the classic illustration of not enough current flow for the jobs at hand.
Food for thought.
Many electrical circuits with poor connection will work better when cool vs when hot. Just throwing it out there. Try adding grounds to the body from bat neg. Even just temporarily to test a theory. The area you grounded to might not be too sturdy.
 

Tom Kelly

Active Member
Sounds like a bad ground. I haven't read every last word though. I skimmed through. Here's an example. Following a car at night. Tail lights are on. They hit the brakes. Tail lights turn off and one brake light struggles to turn on. They let off the brakes and the tail lights ooze their way back on. This is the classic illustration of not enough current flow for the jobs at hand.
Food for thought.
Many electrical circuits with poor connection will work better when cool vs when hot. Just throwing it out there. Try adding grounds to the body from bat neg. Even just temporarily to test a theory. The area you grounded to might not be too sturdy.
Thanks for your input. Many responses have focused on grounding so I will focus on that next. I had ruled that out due to the fact that it works consistently on first start and when key on without starting but now I am hearing from multiple members that cold/hot can affect electrical flow. I will try to find a more secure ground and also to help the battery ground to the body better and try again. Thanks to everyone who has tried to help. I have always found that Buick guys are the best. That's why I stick to them.
 
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