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Tech Area => General Buick Tech => Topic started by: Shimy87 on July 14 2018, 11:30:15 AM

Title: MAP sensor
Post by: Shimy87 on July 14 2018, 11:30:15 AM
My alky won't activate under boost but test button works fine. Have 5.06 volts on grey wire at MAP....green wire has .09 volts. Question is when I blow hard in tube going to map voltage on green wire dosent change....it should unless a person can't blow hard enough to make it change??
Title: Re: MAP sensor
Post by: earlbrown on July 14 2018, 11:41:33 AM
If you can blow hard enough to make it change, I have a new and exciting field of work for you!
Title: Re: MAP sensor
Post by: Steve Wood on July 14 2018, 11:48:58 AM
LOL  yeah, you need a bit more air pressure
Title: Re: MAP sensor
Post by: Shimy87 on July 14 2018, 11:50:44 AM
Ha ha. Ok thanks...i didn't know.
Title: Re: MAP sensor
Post by: aminga on July 14 2018, 07:43:46 PM
It should have some voltage at atmospheric
Title: Re: MAP sensor
Post by: daveismissing on July 14 2018, 08:05:57 PM
Assuming stock 2Bar MAP

 
Manifold Pressure2 Bar
(relative sea level / absolute)
MAP Output
14.31psi / 29.01psi4.90V
14.00psi / 28.70psi4.84V
13.00psi / 27.70psi4.67V
12.00psi / 26.70psi4.50V
11.00psi / 25.70psi4.33V
10.00psi / 24.70psi4.16V
9.00psi / 23.70psi3.99V
8.00psi / 22.70psi3.82V
6.00psi / 20.70psi3.47V
4.00psi / 18.70psi3.13V
2.00psi / 16.70psi2.79V
0.00psi / 14.70psi2.45V
5.00inHg / 12.24psi2.03V
10.00inHg / 9.78psi1.61V
15.00inHg / 7.33psi1.19V
20.00inHg / 4.87psi0.77V
25.00inHg / 2.41psi0.35V
29.10inHg / 0.40psi0.02V
Title: Re: MAP sensor
Post by: Steve Wood on July 14 2018, 08:16:28 PM
he has a 3 bar sensor so give him the table for that
Title: Re: MAP sensor
Post by: Shimy87 on July 14 2018, 08:29:25 PM
Worked fine....stoppe d for a beer and quit.....every thing seems in order so I'm stumped...will be calling julio....any ideas??
Title: Re: MAP sensor
Post by: Steve Wood on July 14 2018, 08:38:09 PM
I think you were on the right track to check the map output.  You did check the line from the sensor (vacuum) to make sure it is not cracked or broken?

Here's a link that shows voltages for a 3 bar  http://injector-rehab.com/shop/mapsensor.html (http://injector-rehab.com/shop/mapsensor.html)
Title: Re: MAP sensor
Post by: daveismissing on July 14 2018, 09:30:04 PM
A 2 Bar should be around 5volts at 30 lbs, a 3bar 5v at 45lbs. Got a compressor with a regulator that turns way down?
jury rig connection to tire pressure?
EDIT ;absolute numbers so subtract 14.7
Title: Re: MAP sensor
Post by: good2win22 on July 15 2018, 09:13:35 AM
I used my oxy-acetelyne rig to calibrate the MAP table.  Gauge is a little easier to read at those low pressures
Title: Re: MAP sensor
Post by: Shimy87 on July 15 2018, 11:24:39 AM
Thanks guys...yes line is good so I gotta figure out a way to put regulated air to it to test. My compressor regulator is shot so it's to much. Gives me a reason to replace it now I guess :icon_eyes:
Title: Re: MAP sensor
Post by: earlbrown on July 15 2018, 01:32:22 PM
Unplug the compressor and blow it down to 30psi.  Then hook it to the MAP.
Title: Re: MAP sensor
Post by: Scoobum on July 15 2018, 01:50:20 PM
Quote from: earlbrown on July 15 2018, 01:32:22 PM
Unplug the compressor and blow it down to 30psi.  Then hook it to the MAP.

Earl...didn't Bison do a test on those with different brands?
Title: Re: MAP sensor
Post by: Shimy87 on July 15 2018, 02:26:12 PM
The gm one is $100....dont want to get a cheap one and have another issue. Will be testing it tomorrow
Title: Re: MAP sensor
Post by: aminga on July 15 2018, 03:56:14 PM
Quote from: Steve Wood on July 14 2018, 08:38:09 PM
I think you were on the right track to check the map output.  You did check the line from the sensor (vacuum) to make sure it is not cracked or broken?

Here's a link that shows voltages for a 3 bar  http://injector-rehab.com/shop/mapsensor.html (http://injector-rehab.com/shop/mapsensor.html)
it's about 4.9/3 at atmospheric pressure or 1.6V
Title: Re: MAP sensor
Post by: daveismissing on July 15 2018, 05:10:48 PM
Quote from: Scoobum on July 15 2018, 01:50:20 PM
Quote from: earlbrown on July 15 2018, 01:32:22 PM
Unplug the compressor and blow it down to 30psi.  Then hook it to the MAP.

Earl...didn't Bison do a test on those with different brands?
https://turbobuick.com/threads/failed-3-bar-map-sensor-my-upgrade.451242/#post-3758619
Title: Re: MAP sensor
Post by: Shimy87 on July 16 2018, 03:59:56 PM
Well with 0 pressure to it green wire read .25 volts. With 30 and then 40 lbs put to it no change...const ant .25....im thinking I need a new map
Title: Re: MAP sensor
Post by: Steve Wood on July 16 2018, 04:47:43 PM
sure sounds like it.  The GM sensor, if real, is the only factory style that I would buy and I suspect if they are coming from China, they are not worth it.  You could try one from Julio as he claims his are the real deal.

I guess the SSI technologies P51 pressure sensor is supposed to be the creme de la creme.  I think Bison is selling a 3.5bar version that he uses. Bout $150 each but is probably worth it if it saves you an engine
Title: Re: MAP sensor
Post by: Steve Wood on July 16 2018, 04:53:08 PM
also, Eric has one from AEM  https://www.turbotweakstore.com/ProductDetails.asp?ProductCode=1024 (https://www.turbotweakstore.com/ProductDetails.asp?ProductCode=1024)
Title: Re: MAP sensor
Post by: Shimy87 on July 16 2018, 05:25:10 PM
Called Julio to order one...we talked about it and he had me test it a different way...its good....he walked me through more tests and it turned out to be the factory boost gauge shorting it....eliminat ed that connection as I don't need it anyway and bingo!!  Just wanted to update if anyone searches for this problem they could check that.  Thanks guys!!
Title: Re: MAP sensor
Post by: Steve Wood on July 16 2018, 07:02:21 PM
good news
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