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rfmaster · 10-06-2014, 02:24 AM

Yes, MAP sensor functionality can be checked with hand held vacuum pump (MitiVac). With WinALDL running, Ignition ON you should see MAP sensor voltage.

At idle Vacuum = 18 to 16 in-Hg (30 to 40 kPa) MAP voltage 1.3 to 1.8 V range.
WOT 0 in-Hg (100kPa)MAP voltage around 4.5 to 4.7 Vdc.

Below - two typical GM 1-bar MAP sensors characterized over the expected vacuum range.

TPS can be checked with DVM - it is a variable resistor. A to C ~ 5kOhm and A to B 1 to 6kOhm varying with shaft position.

CTS is thermistor - resistor that varies vs. temperature. -40C ~103kOhm; 25C ~2.8kOhm; 85C ~338Ohm.

Assuming there are no fuel delivery issues it feel as if you are loosing power to distributor - I would put a DVM on the pink wire just to make sure that dizzy is not loosing power.

//RF

10-06-2014, 02:24 AM	#25
rfmaster Registered User Join Date: Oct 2003 Location: OC CA Posts: 1,374	Re: TBI Fuel Pressure Yes, MAP sensor functionality can be checked with hand held vacuum pump (MitiVac). With WinALDL running, Ignition ON you should see MAP sensor voltage. At idle Vacuum = 18 to 16 in-Hg (30 to 40 kPa) MAP voltage 1.3 to 1.8 V range. WOT 0 in-Hg (100kPa)MAP voltage around 4.5 to 4.7 Vdc. Below - two typical GM 1-bar MAP sensors characterized over the expected vacuum range. TPS can be checked with DVM - it is a variable resistor. A to C ~ 5kOhm and A to B 1 to 6kOhm varying with shaft position. CTS is thermistor - resistor that varies vs. temperature. -40C ~103kOhm; 25C ~2.8kOhm; 85C ~338Ohm. Assuming there are no fuel delivery issues it feel as if you are loosing power to distributor - I would put a DVM on the pink wire just to make sure that dizzy is not loosing power. //RF __________________ "The Beast" 1975 Chevrolet C20 longbed 350/700R4! with 3inch body lift Dual Flowmasters Super 40's! TBI retrofit completed (2007-07-29) New 383CID (+030) 08-304-8 9.5:1CR x36,005 (2012-12-17)