bad MAP sensor voltage
 

Man I'm getting tired of trying to get this thing to run right. I checked the voltage of my MAP sensor and it was way off the specs. At under 1000' sea level with the key on but not running it was supposed to read 3.5 - 5.0 volts between B and C terminals...it was less than .5 volts. Manual was pretty clear that it was faulty and to replace it. I did...ran it for awhile and didn't notice much improvement..checked the new one in the same way and it read 1.3 volts when it should have been 3.5 - 5.0. Am i doing something wrong in the checking of it..followed the manual to the letter but it doesn't say if anything else could be effecting the MAP voltage. If the brand new MAP sensor is reading below specs, any idea what else could be causing this? It's a pro-built 2.8 with less than 5000 miles on it with new ESC module, knock sensor, coil, cap, rotor, EGR is fine, no vacuum leaks, TPS voltage is bang on with no dead spots, thanks in advance for any help.

RE: bad MAP sensor voltage
 

Have you checked the input voltage to the MAP sensor?

RE: bad MAP sensor voltage
 

Nope...not yet..should it be 12 volts?

RE: bad MAP sensor voltage
 

more likely 5 volts and will be supplied by the PCM, but I do not have my references here with me at work. What year are you working on again? With that, I can check my references when I get home tonight.

RE: bad MAP sensor voltage
 

It's a '86 Blazer 4x4..2.8 TBI...I've got the factory repair manual..there should be a reference for it somewhere in it, haven't come across it yet but then I wasn't looking for it either. Thanks for the tip and I'll keep you posted if I find it or not.

RE: bad MAP sensor voltage
 

Kyle...you were right, it is 5 volts, while I was checking the wiring to the MAP I found a bad connection...now it reads what it should. Thanks for the help.

RE: bad MAP sensor voltage
 

Great!! [sm=groupwave.gif]

Glad I could help and congrats on getting it repaired!!

Does the truck run better now?

RE: bad MAP sensor voltage
 

Hi Kyle...no it isn't...still got a problem with the fuel delivery i think. Can't get it to go over 2500 ish rpm, both injectors got a bit of a drip at idle and when revved up there's a nice conical pattern but the drip in the center almost turns into a stream. If I pinch off the return line and jumper the pump there is no leakage anywhere around or from the injectors. Thought it was a timing issue but it's bang on 10 deg. BTDC and recently I've replaced the knock sensor, coil, cap + rotor, wires, spark control module, MAP sensor, fuel pump, pick-up screen, fuel pressure reg. diaphram, new gaskets, O rings and inj. screens. Dead head fuel press. is 18 psi and flow amount seems to be good (line unhooked from carb andpumping into a container) The only fuel test I haven't done is check the pressure while running. It throws no codes and idles fine but a road test has no power over about 1/4 throttle. I'm starting to think it's an injector problem but sure would like to confirm it before I shell out $200 for new ones. Any thoughts you got on where I should focus on would be greatly appreciated. Thanks again for your help. Tom