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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.
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???
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?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.
Keep boost out of the can.
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
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?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.
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 !!
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,
Excellent point. It would be like inflating a tire.
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.
