CALLING ALL ELECTICAL GENIUSES

No disintegrations

Well-Known Member
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.
Right, but not too easy to watch three gauges and drive the car.
Focusing on fuel pressure gauge tells you the boost and fuel pressure simultaneously.
 

Tom Kelly

Active Member
Right, but not too easy to watch three gauges and drive the car.
Focusing on fuel pressure gauge tells you the boost and fuel pressure simultaneously.
You are right about watching two thing at once. My fuel pressure at idle is 40 (vacuum connected) Would you say that the increase of 1 for 1 with boost is EXACT? In other words can I rely on, say if fuel pressure is 62, then I am at exactly 22 psi of boost? Of course I can check it out next time I am at 22 psi (my personal limit to protect my rebuilt engine) which will come the next time I am tuning. Interesting thought. If the relationship is exact then you are right; who needs a boost gauge?
 

Tom Kelly

Active Member
Well, took it out for a spin and unfortunately there is no change. It sets to "0" correctly upon each start. It correctly reads boost and correctly returns to "0" each time. However each time after going back to "0" it changes to "767" after 30 seconds and stays that way. I fooled around with the wires and found that it will start over again if I either restart the car or pull the gauge and disconnect it from it's 12V and re-connect. Speedhut has already made it clear that since I am not the original owner, the "lifetime warranty" does not apply. So my choices are to either 1. Live with it as is, 2. Put a switch somewhere to disconnect the 12V to the gauge as needed, 3. Keep banging my head against the wall, or 4. Buy a new gauge and go through the expense of buying it and the annoyance of having to run the wiring again. So many choices.
 

1986 Buick GX1

GX1 #001 [The One and Only]
You are right about watching two thing at once. My fuel pressure at idle is 40 (vacuum connected) Would you say that the increase of 1 for 1 with boost is EXACT? In other words can I rely on, say if fuel pressure is 62, then I am at exactly 22 psi of boost? Of course I can check it out next time I am at 22 psi (my personal limit to protect my rebuilt engine) which will come the next time I am tuning. Interesting thought. If the relationship is exact then you are right; who needs a boost gauge?

You’re on the right track, however to reiterate, the boost starts at 0 psi. The fuel pressure should start at 0 pressure as well (line off), which for most is 43 psi.
When both start at 0 you end up with 43 psi fuel pressure + 20 pounds of boost = 63.
It NEEDS to be 1:1 otherwise, if it’s less you are running lean and bad things will happen.

Keep up the diligence and thank you for updating us with your progress.
 

Tom Kelly

Active Member
Well gentlemen, (and ladies), I think we are at the end of our saga. Today I installed a momentary "off" button right next to the gauge. Since the gauge works fine every time it was reset after a boost reading I can now "reset" it by pushing the button for a second and letting go. Voila! Here is a picture. It actually doesn't look half bad does it? Thanks to all of you who chimed in. This was a group effort an one of the many reasons I always get a Buick.
 

Attachments

  • Momentary off.JPG
    Momentary off.JPG
    803.2 KB · Views: 109

Mr.Spool

Well-Known Member
I am reaching out to all you electrical gurus for help. I can’t think of anything else to try.

I have a Speedhut digital boost (only) gauge in my 86. It came with the car when I bought it. It worked fine for years. This Spring I made some changes including the installation of an AEM A/F gauge, changed to an LT-1 MAF with translator and added a powerlogger which also upgraded my scanmaster to 2.2.

At about that time, or soon after, my boost gauge started acting up. It went through some weird phases but here is what it does now.

First start of the morning: Works fine. Initializes properly and settles on “0”. In operation it reports boost numbers consistent with the scanmaster (v 2.2 reports boost and vacuum)

Subsequent starts: Gauge immediately goes to “Sender error” and stays that way. No function at all.

All starts: If you just turn the key on but don’t start the car it initializes normally and settles on “0”. If this is a “subsequent” start as soon as I start the car it shifts to “Sender error”

I have replaced the sender and sender harness. Speedhut has replaced the circuit board twice. None of these have changed anything.

I have tried resetting everything after that initial start by disconnecting the battery for an hour. No change,

I have tried disconnecting the gauge after it has gone to sender error and then reconnecting it. It just goes right back to sender error.

Speedhut has advised me that the gauge ignores vacuum/boost conditions when initializing. They say all it looks at is the 5 volt signal.

Maddeningly it works the first start of the day all the time.

What am I missing?
Ohm the wires,and check volts
 
Top