87 GN boost builds up and then goes to 0

AJ_08

New Member
Joined
Oct 12, 2021
Stock 87 GN builds up boost and then dumps it all (goes to 0, does not maintain pressure). Is this a sign of a failed wastegate actuator?
 

Jerryl

Tall Chinese Guy
Joined
Dec 14, 2004
Stock 87 GN builds up boost and then dumps it all (goes to 0, does not maintain pressure). Is this a sign of a failed wastegate actuator?
Possibly but not likely.
More likely a leaking a leaking silicone coupler, if everything else is in good order (not cutting out, etc)
 

AJ_08

New Member
Joined
Oct 12, 2021
Possibly but not likely.
More likely a leaking a leaking silicone coupler, if everything else is in good order (not cutting out, etc)
Verified that the vacuum lines are in good condition. I'm thinking it could be a worn out ignition module or coil pack. As more power is applied there is some pooping and backfiring. Runs great at idle and under low load conditions. Replaced the MAF to LT1 and got the translator. CAM is set and installed a new crank position sensor.
Ignition module is not oozing or melting but I'm leaning towards that or the coil pack (both still original). I don't have the Casper tool to test.
This or its not getting enough fuel pressure under greater loads (stock pump).
 

SCOOBY DOO

I'M NOT A MONSTER, I'M JUST AHEAD OF THE CURVE!!!
Joined
Feb 18, 2007
How old is the pump? Can you verify fuel pressure is rising 1 to 1 with boost?
 

AJ_08

New Member
Joined
Oct 12, 2021
How old is the pump? Can you verify fuel pressure is rising 1 to 1 with boost?
Stock fuel pump, so 34 years old. I will verify this weekend when I see the car. I'm curious, any recommendations for an aftermarket pump on a stock engine?
 

AJ_08

New Member
Joined
Oct 12, 2021
I would invest in a electric FP gauge, they are pricey at $200+ but that's much cheaper that a rebuild...
Ok thanks for the advice. I will look into one. Any suggestions?

Also, I am going to install a scanmaster g this weekend. Are there any notable clues or metrics I should be looking for that can help diagnose the problem?
 

TTA308

Active Member
Joined
Feb 27, 2012
I use Autometer # 5763 , another good investment is a Powerlogger, which i have so i can log FP, with a PL you can buy just the transducer for around $100 and log with it, then the question of FP is forever put to bed, it will also tell you when the pump is getting weak , that has saved my ass more than once since my set-up is far from stock and the margin for error is very small.
 

AJ_08

New Member
Joined
Oct 12, 2021
Pump is 34 years old...surprised it even runs. Grab a 255 for it.
Yeah still kicking, it's about time for an upgrade regardless if it's the issue. Thanks for the advice. Will update the thread Sunday when I do the fuel pressure test.
 

AJ_08

New Member
Joined
Oct 12, 2021
I use Autometer # 5763 , another good investment is a Powerlogger, which i have so i can log FP, with a PL you can buy just the transducer for around $100 and log with it, then the question of FP is forever put to bed, it will also tell you when the pump is getting weak , that has saved my ass more than once since my set-up is far from stock and the margin for error is very small.

I use Autometer # 5763 , another good investment is a Powerlogger, which i have so i can log FP, with a PL you can buy just the transducer for around $100 and log with it, then the question of FP is forever put to bed, it will also tell you when the pump is getting weak , that has saved my ass more than once since my set-up is far from stock and the margin for error is very small.
Thanks for the great advice. Will definitely look into the powerlogger and electric fp gauge. So the scanmaster and powerlogger are extremely important, perhaps essential, for this car and understanding what's going on. I'll update the thread on Sunday about the fp test I do. Appreciate the help.
 

SCOOBY DOO

I'M NOT A MONSTER, I'M JUST AHEAD OF THE CURVE!!!
Joined
Feb 18, 2007
So 255 lph, any suggested or recommended brands I should consider?
Im up here in Canada so I bought from Racetronix in Toronto which is only 1.5 hours away. Many of the Buick vendors sell them. There's a list of vendors on here towards the bottom.

 

AJ_08

New Member
Joined
Oct 12, 2021
Im up here in Canada so I bought from Racetronix in Toronto which is only 1.5 hours away. Many of the Buick vendors sell them. There's a list of vendors on here towards the bottom.
I'm in Canada too, 30 min from downtown Toronto. Great thank you. Appreciate the help. I've been ordering everything from the states, like Kirban, full throttle, highway stars at one point... I'll look into racetronix 255 fuel pump. Appreciate the help.
 

SCOOBY DOO

I'M NOT A MONSTER, I'M JUST AHEAD OF THE CURVE!!!
Joined
Feb 18, 2007
If all you're doing is crusi
I'm in Canada too, 30 min from downtown Toronto. Great thank you. Appreciate the help. I've been ordering everything from the states, like Kirban, full throttle, highway stars at one point... I'll look into racetronix 255 fuel pump. Appreciate the help.
I have free Canada wide calling. If you need help, PM me and I'll call.
 

TTA308

Active Member
Joined
Feb 27, 2012
Stock 87 GN builds up boost and then dumps it all (goes to 0, does not maintain pressure). Is this a sign of a failed wastegate actuator?
Are you saying it nose's over ? And what are you using for a boost gauge ? Btw if i had a stock GN and could only do one mod above stock it would be a FP gauge, then fuel pump, why would i do that before a new fuel pump ? Because new don't mean shit anymore and hasn't for a long time... like i said ..put it to bed.
 

AJ_08

New Member
Joined
Oct 12, 2021
Are you saying it nose's over ? And what are you using for a boost gauge ? Btw if i had a stock GN and could only do one mod above stock it would be a FP gauge, then fuel pump, why would i do that before a new fuel pump ? Because new don't mean shit anymore and hasn't for a long time... like i said ..put it to bed.
Not sure what you mean by nose's over, like the power nose dives to 0/no boost/does not maintain the boost it built with throttle open? If this is correct, then yes. Stock turbo boost gauge. Yes I will look into the autometer gauge you recommended, i have the z-series electric for water and oil going to be installed soon, along with a scanmaster g. Looking into a new fuel pump now, recommended by Scooby, but still going to test the fuel pressure put out by the pump under load. Inherited the car in an unfortunate circumstance and learning more about it. I truly appreciate the help.
 

TTA308

Active Member
Joined
Feb 27, 2012
Not sure what you mean by nose's over, like the power nose dives to 0/no boost/does not maintain the boost it built with throttle open? If this is correct, then yes. Stock turbo boost gauge. Yes I will look into the autometer gauge you recommended, i have the z-series electric for water and oil going to be installed soon, along with a scanmaster g. Looking into a new fuel pump now, recommended by Scooby, but still going to test the fuel pressure put out by the pump under load. Inherited the car in an unfortunate circumstance and learning more about it. I truly appreciate the help.
Ok just stay out of boost for now until you find the problem, but it sounds ign related, also even if your pump test good replace it anyhow after you know what its doing, BTW you are doing better than most new guys here who hammer the hell out of it first then come here and want to know WTF happened... :oops:
 
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