CALLING ALL ELECTICAL GENIUSES

Chuck Leeper

Toxic old bastard
Staff member
In late on this...
Does the sensor harness run with any other wires?
Cruise control switch at the column would provide a source, and be out of the engine compartment.
 

Tom Kelly

Active Member
In late on this...
Does the sensor harness run with any other wires?
Cruise control switch at the column would provide a source, and be out of the engine compartment.
Thanks for your input Chuck. I have spent most of the last year trying to find what I thought was electrical interference causing the problem.
Quite by accident and with more time to kill looking I tried moving the harness wires around. Using a suggestion from another member I attached a spare harness and sender to the gauge and hung the sender out the window. I found that the gauge worked fine (in that it initialized correctly). So in increments I moved this sender closer and closer to the one attached to the vacuum hose and each time the gauge worked perfectly until the two senders were side by side. The only difference was one was hooked up to vacuum the other not. I reconnected the gauge to the vacuum one and it failed. I disconnected the vacuum hose and the gauge worked. I repeated several times with the same results. Somehow the vacuum in the line is causing the sender to send an error. Except the first start of the day and when the car has had a few hours to rest. So I figured that somehow residual vacuum which fades over time is causing the problem since at start up there is no residual pressure in the line. This idea had been expressed by a member last year but was debunked by speedhut tech support which said that vacuum is irrelevant to the signal. However, bleeding the hose before attempting to start the car did not help. So there is something about being connected to vacuum hose in a warm engine only. Anyway I have a call in to speedhut to go over the possibilities. I think I am getting close.
 

Tom Kelly

Active Member
Thanks for your input Chuck. I have spent most of the last year trying to find what I thought was electrical interference causing the problem.
Quite by accident and with more time to kill looking I tried moving the harness wires around. Using a suggestion from another member I attached a spare harness and sender to the gauge and hung the sender out the window. I found that the gauge worked fine (in that it initialized correctly). So in increments I moved this sender closer and closer to the one attached to the vacuum hose and each time the gauge worked perfectly until the two senders were side by side. The only difference was one was hooked up to vacuum the other not. I reconnected the gauge to the vacuum one and it failed. I disconnected the vacuum hose and the gauge worked. I repeated several times with the same results. Somehow the vacuum in the line is causing the sender to send an error. Except the first start of the day and when the car has had a few hours to rest. So I figured that somehow residual vacuum which fades over time is causing the problem since at start up there is no residual pressure in the line. This idea had been expressed by a member last year but was debunked by speedhut tech support which said that vacuum is irrelevant to the signal. However, bleeding the hose before attempting to start the car did not help. So there is something about being connected to vacuum hose in a warm engine only. Anyway I have a call in to speedhut to go over the possibilities. I think I am getting close.
Got an email response last night from speedhut tech support. They think the solution is for me to send back the gauge and have them re-program it to skip the startup test sequence. Sounds like a solution but we'll see. Sending it back today. Here's hoping!!
 

Tom Kelly

Active Member
Got an email response last night from speedhut tech support. They think the solution is for me to send back the gauge and have them re-program it to skip the startup test sequence. Sounds like a solution but we'll see. Sending it back today. Here's hoping!!
Well, it would seem I am playing "whack-a-mole" The gauge came back yesterday and I eagerly tested it out. The good news - The gauge set to zero without going through the pre check. Every time. More good news - It accurately displayed boost. BUT - Whenever it displayed boost and reset to zero, thirty seconds later it displayed "767" and stayed there. Restarting the car began the cycle all over again. Question? I have the sender connected to vacuum lines at the vacuum canister. It is on the engine side of the line so that the check valve is between the sender and the canister. For those of you who have a boost gauge, where is your sender plumbed in to the vacuum lines? his is the second time that vacuum (or lack of vacuum) or boost have tripped and error. Maybe if I move the sender???
 

salvageV6

Daily Driver
I would put a real gauge (analog,calibrated, accurate) that can read both boost and vacuum in the line where you have the sender and watch what happens under your testing conditions, check valves can leak.

Or just add a second check valve in the gauge senders line and test it out.

I would also ask the factory what 767 means, assuming it comes up every time as the error.

Another test would be to use a tank of air with the car idling in the driveway and going from say 15 pounds of air into the sender (remove the Buicks air feed line to the sender) and then releasing the air pressure to 0, does the gauge go to zero and show the error or not?

When it starts flashing 666..... sell the car. ;):eek:
 

Tom Kelly

Active Member
I would put a real gauge (analog,calibrated, accurate) that can read both boost and vacuum in the line where you have the sender and watch what happens under your testing conditions, check valves can leak.

Or just add a second check valve in the gauge senders line and test it out.

I would also ask the factory what 767 means, assuming it comes up every time as the error.

Another test would be to use a tank of air with the car idling in the driveway and going from say 15 pounds of air into the sender (remove the Buicks air feed line to the sender) and then releasing the air pressure to 0, does the gauge go to zero and show the error or not?

When it starts flashing 666..... sell the car. ;):eek:
Good idea to replace the check valve. I must admit I am not exactly sure why it is there. Is it to hold vacuum in the system or to keep boost out of the canister?
 

Tom Kelly

Active Member
Good idea to replace the check valve. I must admit I am not exactly sure why it is there. Is it to hold vacuum in the system or to keep boost out of the canister?
[/QUOTE
If the check valve is not working could that screw up the sender after boost is present? Does the check valve allow vacuum to continue to the canister by pulling air from the canister but not allow boost to flow TO the canister?
 

Chuck Leeper

Toxic old bastard
Staff member
s it to hold vacuum in the system or to keep boost out of the canister?
Keep boost out of the can.
The boost gauge on the dash is pretty much useless. Maybe, try to plumb the sensor into the hose that goes from the tube on the intake, to the boost ga MAP sensor.
That's about as clean a vac/boost signal, as you will get, short of drilling into the intake.
 

Tom Kelly

Active Member
Keep boost out of the can.
The boost gauge on the dash is pretty much useless. Maybe, try to plumb the sensor into the hose that goes from the tube on the intake, to the boost ga MAP sensor.
That's about as clean a vac/boost signal, as you will get, short of drilling into the intake.
Thanks to you all we are either finally getting somewhere or we are going down a new rabbit hole. As I said, the sender is plumbed into the vacuum line just before it enters the vacuum canister. There is a check valve in between the sender and the canister (see picture) The white side of the check valve is facing the sender so I assume that is the side that will not let air pass through it to the other side. When I pulled the check valve I found I could blow through it either way with no difficulty so I presume it is faulty. I ordered a new one from NAPA and hopefully I will have it tomorrow. We shall see if that was the problem but in any event it should be replaced. Please correct me if I am wrong about how I tested it and about the white side being the "blocking" side
 

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Tom Kelly

Active Member
I replaced the check valve in the line leading to the canister. It's a dreary day here in Connecticut so I am waiting until tomorrow to see if there is any improvement. If this fails to fix the problem I will take Chuck's advice and move the sender to the vacuum line connected to the map sensor. I downloaded a vacuum line map and it seems to be the second line from the firewall on the vacuum block. It doesn't have or need a check valve so it is indeed the "purest" line. If that fails too I will surrender to the glitch gods and move on.
 

salvageV6

Daily Driver
Your application seems to require a check valve in the line to only allow boost into the sender and block any vacuum from entering that line.

The factory line is without a check valve because the stock MAP boost sensor or idiot lights switch on the digital dash cars doesn't care if it they see vacuum.

You are trying to keep vacuum out of the gauge, the factory check valves are in place to keep boost out of sensitive vacuum controlled circuits such as the tank and also the heater controls/vacuum motors.

If you T into that boost line for that map sensor put a check valve in the sender line that only allows you to blow through the valve, suction is blocked by the valve. o_O
 

Tom Kelly

Active Member
Keep boost out of the can.
The boost gauge on the dash is pretty much useless. Maybe, try to plumb the sensor into the hose that goes from the tube on the intake, to the boost ga MAP sensor.
That's about as clean a vac/boost signal, as you will get, short o
Your application seems to require a check valve in the line to only allow boost into the sender and block any vacuum from entering that line.

The factory line is without a check valve because the stock MAP boost sensor or idiot lights switch on the digital dash cars doesn't care if it they see vacuum.

You are trying to keep vacuum out of the gauge, the factory check valves are in place to keep boost out of sensitive vacuum controlled circuits such as the tank and also the heater controls/vacuum motors.

If you T into that boost line for that map sensor put a check valve in the sender line that only allows you to blow through the valve, suction is blocked by the valve. o_O
I’m a little confused. My scanmaster displays vacuum and boost getting it’s data from the 3 bar MAP sensor connected to the powerlogger so i would think it would need to be able to see both vacuum and boost. Or am I missing something? Plus. Are you saying that since my gauge is boost only (no vacuum reading)!that somehow when boost switches back to vacuum it’s scrambling the gauges brain?
 

dynoman

Well-Known Member
Hmmm. If that’s true I would need a separate line to the gauge with a check valve allowing boat to get to the gauge but not allowing flow the other way. You might be right. But that shouldn’t be.
If you put a check valve in so the gauge only see's boost , it will stay at it's highest boost reading and not go back down cause it has nowhere to bleed off to !!
 

Tom Kelly

Active Member
If you put a check valve in so the gauge only see's boost , it will stay at it's highest boost reading and not go back down cause it has nowhere to bleed off to !!
Yes I can see that. In the current configuration, the gauge sender is between the manifold and the check valve which does not allow air (boost) to flow into the vacuum canister but allows vacuum from the manifold to suck air from the canister. So the sender is seeing actual manifold conditions all the time. Even though it is a "boost only" gauge it should not be deterred from being functional when boost returns to vacuum. I am hoping that somehow (in a way I still don't understand) the defective check valve between the canister and the sender which allowed movement in both directions was screwing up the sender. Today the sun is shining in Connecticut so after breakfast I shall see if replacing the valve has helped. As I said, if it doesn't I think I shall start thinking of getting a new gauge (one which shows vacuum and boost) I do appreciate everyone's willingness to help. If nothing else I have learned even more about my GN during this process. I never even knew there were check valves until now for example,
 

No disintegrations

Well-Known Member
I think it's time to get a refund and find a different product to use. One point Mr spool likes to remind people of. Put the fuel pressure gauge where you can watch it. The boost will raise the fuel pressure 1 to 1. So. 43psi base plus a boost target of 20 equals fuel pressure of 63. You're monitoring both things in real time on one gauge. Easy.
 

Tom Kelly

Active Member
I think it's time to get a refund and find a different product to use. One point Mr spool likes to remind people of. Put the fuel pressure gauge where you can watch it. The boost will raise the fuel pressure 1 to 1. So. 43psi base plus a boost target of 20 equals fuel pressure of 63. You're monitoring both things in real time on one gauge. Easy.
I am fully "gauged". Got my three gauge pod on the A-Pillar with fuel pressure, boost, and wide band A/F mix. Plus a two gauge pod on the console with coolant temp and oil pressure. Not to mention my trusty upgraded (2.2) scanmaster which tells me everything except how the car is felling that day. My opinion is they should have put a GNX instrument panel on all the GN's as well. Of course you will all agree.
 
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