I've gone to test my map sensor and found that the vaccum drops to 0 in less than a minute. It's not the hose or hand pump. Is this bad or is it supposed to do that?

 

I dont really uunderstand what you mean. Your saying that you put the vacuum pump on the hose to the pressure sensor????

it is most likely the pump. try applying vacuum to someting else. the guage will fall slowly. mine does that

 

I have a hand vaccum pump with gauge. When I hook it up to the map sensor and then add vaccum, the gauges slowly falls. When I pull the hose off the sensor and add vaccum, the guage holds steady.

 

Sorry, I wasn't clear enough. Whe I pull off the sensor and cover the open end of the hose with my thumb and then apply vaccum, the guage holds steady

 

Sorry, I wasn't clear enough. Whe I pull off the sensor and cover the open end of the hose with my thumb and then apply vaccum, the guage holds steady

 

hmm
I know that when I do the same to the pressure sensor, the guage will fall slowly...
But then when I would put my thumb over the end of it or something then it will still fall slowly...
sorry I cant help you more. hopefully somebody elso can
However, I don't really think that would mean the sensor is bad.

 

Mine does the same - I don't think its a real problem, I still get the correct voltages out at the corresponding pressure settings. The amount of air that would be sucked into the intake by this leak is so small as to be totally insignificant. The only thing to worry about is that the output voltages are correct ,

 

So, your map sensor gives voltages within the range specified by the shop manual?

Mine reads a little high. <0.5V high. Can't really tell if that's much of a problem. I'm tempted to put a resisitor on it so it reads in range since it's consistent, just high.

 

Sorry. I just put a Mittyvac on my 87 n/a and held 10 in/hg for 3 minutes with zero loss.

 

maybe my Craftsman pump is just a piece of junk...

 

Hmmm.... I have a craftsman pump also. I'll have to double check it and make sure that it does hold vaccum over time.

 

Would you be willing to redo this and tell me what voltages you get at 100, 200 and 300 mm Hg? I've heard that the shop manual might have some specs for Japanese cars and not the imports. I'd like to get a sanity check.