700 SCI Problems
08-23-2021 | 05:08 PM
#11
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Joined: Feb 2013
Posts: 1,459
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Intake manifold press bouncing= intake/exh valve issue or maybe some oddball blower issue.
I would remove blower belt and see if the press keeps bouncing at idle. If it does, you can rule out the blower.
Compression test would be a good idea too.
I'm assuming the other eng has a steady intake manifold press at idle using mechanical gauge.
I would remove blower belt and see if the press keeps bouncing at idle. If it does, you can rule out the blower.
Compression test would be a good idea too.
I'm assuming the other eng has a steady intake manifold press at idle using mechanical gauge.
08-23-2021 | 05:31 PM
#12
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Joined: Jan 2019
Posts: 16
Likes: 2
From: Seattle Washington
Intake manifold press bouncing= intake/exh valve issue or maybe some oddball blower issue.
I would remove blower belt and see if the press keeps bouncing at idle. If it does, you can rule out the blower.
Compression test would be a good idea too.
I'm assuming the other eng has a steady intake manifold press at idle using mechanical gauge.
I would remove blower belt and see if the press keeps bouncing at idle. If it does, you can rule out the blower.
Compression test would be a good idea too.
I'm assuming the other eng has a steady intake manifold press at idle using mechanical gauge.
06-04-2022 | 04:49 PM
#13
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Joined: Jun 2006
Posts: 764
Likes: 6
From: ILL
Did you ever get this figured out? I have a 700 stg 2 that is running rich at idle and it's a dog when first getting on it from a dig I am sure it's from being so full of fuel. Very short time out back of boat was getting black. Ordered scan tool today.
Thanks
Thanks
06-20-2022 | 12:48 PM
#14
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Joined: Jan 2019
Posts: 16
Likes: 2
From: Seattle Washington
I get a boost valve error on my vessel view also but not all the time. Some times i get it if the motor i just idling and also get it some time up on plane.
Last edited by dirty dogs; 06-20-2022 at 12:50 PM.
06-20-2022 | 02:11 PM
#15
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Joined: May 2012
Posts: 11,428
Likes: 3,955
From: Midwest & T-Rock
picked this from my Whipple install PDF,
Supercharger By-pass system. The supercharger is installed with a by-pass system. This allows the supercharger to operate at higher efficiency under vacuum operation. It is advised to verify the operation of the bypass valve. At idle and low engine loads, the bypass will be open. At higher loads (engine in boost) the bypass will be closed. As the throttle is opened quickly the bypass valve will close momentarily. This verifies the bypass will close and is functioning. Actuator failure could lead to intercooler fires, poor performance and erratic idle. If the actuator fails, it could have an air leak which will result in poor idle qualities. A failed actuator will also allow the bypass to open it’s internal butterfly during boost, which will circulate air and reduce airflow to the engine, consequently lowering the boost level and power
see if you have something that looks like this, these hook to a diaphragm with 2 other hoses that control vacuum while in boost........... I know your blowers are different
Supercharger By-pass system. The supercharger is installed with a by-pass system. This allows the supercharger to operate at higher efficiency under vacuum operation. It is advised to verify the operation of the bypass valve. At idle and low engine loads, the bypass will be open. At higher loads (engine in boost) the bypass will be closed. As the throttle is opened quickly the bypass valve will close momentarily. This verifies the bypass will close and is functioning. Actuator failure could lead to intercooler fires, poor performance and erratic idle. If the actuator fails, it could have an air leak which will result in poor idle qualities. A failed actuator will also allow the bypass to open it’s internal butterfly during boost, which will circulate air and reduce airflow to the engine, consequently lowering the boost level and power
see if you have something that looks like this, these hook to a diaphragm with 2 other hoses that control vacuum while in boost........... I know your blowers are different
06-21-2022 | 07:08 AM
#16
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Joined: Apr 2007
Posts: 595
Likes: 103
From: Ontario
picked this from my Whipple install PDF,
Supercharger By-pass system. The supercharger is installed with a by-pass system. This allows the supercharger to operate at higher efficiency under vacuum operation. It is advised to verify the operation of the bypass valve. At idle and low engine loads, the bypass will be open. At higher loads (engine in boost) the bypass will be closed. As the throttle is opened quickly the bypass valve will close momentarily. This verifies the bypass will close and is functioning. Actuator failure could lead to intercooler fires, poor performance and erratic idle. If the actuator fails, it could have an air leak which will result in poor idle qualities. A failed actuator will also allow the bypass to open it’s internal butterfly during boost, which will circulate air and reduce airflow to the engine, consequently lowering the boost level and power
see if you have something that looks like this, these hook to a diaphragm with 2 other hoses that control vacuum while in boost........... I know your blowers are different
Supercharger By-pass system. The supercharger is installed with a by-pass system. This allows the supercharger to operate at higher efficiency under vacuum operation. It is advised to verify the operation of the bypass valve. At idle and low engine loads, the bypass will be open. At higher loads (engine in boost) the bypass will be closed. As the throttle is opened quickly the bypass valve will close momentarily. This verifies the bypass will close and is functioning. Actuator failure could lead to intercooler fires, poor performance and erratic idle. If the actuator fails, it could have an air leak which will result in poor idle qualities. A failed actuator will also allow the bypass to open it’s internal butterfly during boost, which will circulate air and reduce airflow to the engine, consequently lowering the boost level and power
see if you have something that looks like this, these hook to a diaphragm with 2 other hoses that control vacuum while in boost........... I know your blowers are different
I just went through this late last season with my TCM1200 efi's. Poor idle that had a "blower surge" loading up with any amount of idling, fouling plugs etc. Tested my bypass vlaves and sure enough the diaphragms were blown, easy $300 fix. I was pulling my hair out thinking it was a MAP sensor or IAC which both tested good.
06-21-2022 | 07:33 AM
#17
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Joined: Nov 2004
Posts: 14,097
Likes: 3,687
From: On A Dirt Floor
Sorry to step in, but man…,,that valve sure looks like the GM 3800 motor’s bypass valve found in:
- 97-08 Pontiac Grand Prix
- 96-03 Pontiac Bonneville SSEi
- 96-04 Buick Park Avenue Ultra
- 97-04 Buick Regal GS
- 04-05 Chevrolet Impala & Monte Carlo SS
- 95-99 Buick Riviera
Last edited by SB; 06-21-2022 at 07:37 AM.
06-21-2022 | 08:08 AM
#20
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Joined: Nov 2004
Posts: 14,097
Likes: 3,687
From: On A Dirt Floor
Snd then this. They state they get from same manufacturer that supplies gm snd eaton with them. ??? $80
https://zzperformance.com/collection...0-bypass-valve
https://zzperformance.com/collection...0-bypass-valve
