"Blow in the Tube" safe for MP Sensor?

Will blowing in the tube for Emag/Pmag timing damage the manifold pressure sensor? Do I need a way to disconnect the sensor when timing?

Thanks,

Tony,

I'm not sure whether blowing will damage the sensor, but using a hair dryer (low or no heat) is a good way to simulate air flow into a pitot or other tube without getting too much pressure.

greg

No damage on my Dynon supplied MAP sender setting up my PMAG

Really Suction

Wouldn't you have to suck on the sensor? I believe that manifold pressure is less than ambient pressure.

Just my $.02

Tom
RV-7A Flying

Good Advice

Greg Arehart said:

Tony,

I'm not sure whether blowing will damage the sensor, but using a hair dryer (low or no heat) is a good way to simulate air flow into a pitot or other tube without getting too much pressure.

greg

Click to expand...

Tony,
Greg makes a great suggestion. Don't use your mouth. My fear would be that moisture from your mouth might get into the electrical circuits and cause a failure at some time in the future.
One thing to consider is that unless you are using a (turbo)supercharged engine, the sensor measures "absolute pressure". You actually need to apply a partial (or full) vacuum to the sensor to see it it's working properly. You can purchase a nice hand vacuum pump from your local Sears store, in the tool department. Stay away from the all plastic Mityvac brand of hand vacuum pumps. I've owned a number of these. The plastic pumps are flimsy pieces of $hit. Stick with a tool made of brass and steel. See

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=57626

http://www.bizrate.com/automotiverepairtools/oid524677048.html

http://www.sears.com/shc/s/p_10153_12605_00996250000P?keyword=hand+vacuum+pump

My Craftsman pump looks like the models shown in the top two photos. 30 years experience has shown me that is the most durable style. I paid $36 for my pump, about 10 years ago.

Charlie Kuss

PS Maybe you have a mechanic friend you can borrow one of these from?

I should have been clearer with my post. I was in a hurry.

I am not trying to test my MP sensor. The quick and easy way to time the Emag/Pmag's is to blow into the MP tube. This puts the mags into a "setup" mode. My concern is that blowing into the tube might "over pressure" the manifold pressure sensor and damage it. I asked Brad at EmagAir about this and he said he couldn't comment on whether it would damage MP sensors or not.

I'd like to have a blow tube branch in the MP line that I normally have plugged. I am trying to figure out if Ialso need some easy way to disconnect the line to the MP sensor.

Just did mine yesterday

apatti said:

......
I am not trying to test my MP sensor. The quick and easy way to time the Emag/Pmag's is to blow into the MP tube. This puts the mags into a "setup" mode. My concern is that blowing into the tube might "over pressure" the manifold pressure sensor and damage it. I asked Brad at EmagAir about this and he said he couldn't comment on whether it would damage MP sensors or not.
.......

Click to expand...

I actually didn't think of this potential problem before doing it.

However, 1/2 PSI is only one inch of MP pressure. That hardly seems enough to damage anything. I guess I could have blown much harder than 1/2 psi.

One way of being careful is just blowing hard enough to see the result, which should be 1/2 PSI or less.

Not to worry

If you are using the GM automotive style MAP sensor, Black rectangular, with the 3 wire connector, it is built to withstand engine backfire and turbocharger induced positive manifold pressures without using a restrictor in the feed line. This is a very durable and reliable sensor that will not be damaged with a blow in the tube. Likewise, small amounts of moisture doesn't seem to bother them, as they are exposed to plenty in the engine bay. Mounting them higher than the engine fitting is advised, as we had trouble years ago with accumulated moisture freezing in the line, hence, no MP until the thaw. GM tech for 38 years, and have seen many replaced, but only a handful of really failed sensors.

Light shedding I hope....
Chris

Senior moment

When I thought about it carefully I remembered that my MP pressure gauge was disconnected. The place where I opened the system left the two mags only on the side I was blowing into.