Electroair MAP failure

About three weeks ago my left mag failed the pre-flight check. A quick dash back to the hangar and the faulty spark plug was found and replaced with a spare. All systems checked out and I was off to breakfast, albeit, an hour late.

The next weekend while checking the mags, the Electroair EI failed it's quality check during the runup. Usually the EI drops 0-10 RPM during the mag check while the mag drops about 100-125 RPM compaired to the EI. This time the mag dropped 75 and the EI dropped 150. Off to the hangar I went.

I found nothing wrong and since I had the cowl off I decided to do the engine portion of the ACI so I could sign PZ off for another year. The next day a test runup and a functional flight check proved all was well. I did nothing but a lot of TLC. I flew 3 YE later in the day with mag checks at the beginning of each flight and whatever caused the original problem seemed to be fixed. I should know that things never right themselves.

This past weekend prior to the breakfast run all was well in the ignition world. On the flight to breakfast it seemed that I could not lean as much as normal so I did an in-flight mag check. Either system would keep the plane running but at the lean setting it was a little rough which is not normal for the EI. The EI behaved as if it was not getting any additional advance over the nominal 25 degree base setting. It worked only as well as the mag on the other side. I did the check a number of times and sometimes the EI would work properly and sometimes not.

Once back at the airport the plan was to pull the EI and re-install the mag as I have limited time to work on the plane before this Friday's sortie to Dad's house. I could not find the longer studs needed to install the mag (Impulse coupled) so I went to plan "B" which should have been plan "A". Suspecting the electronics I grabbed the brainbox/coil pack from a friends retired system to swap with mine. The MAP sensor is held on by two screws and 3 wires with fast-on tabs so I decided to swap out the sensor first since it seemed not to be getting any advance over the base setting. I cowled it up sure this would fix the problem and headed for the runway.

The runup was normal. A good sign. The flight was normal and in flight mag checks were normal. Problem solved.

So I really don't know if the MAP sensor is bad or if there was a bad connection with the fast-on tabs but I suspect the MAP sensor is to blame. The sensor is listed for $225 on Electroair's site, ouch. I think I'll send in the old one and see if they can test it before buying a spare.

This older Electroair has provisions for a digital display that reports the system advance at a glance. Would have been handy for trouble shooting. A multimeter can also be used for this with .1 volt = to 1 degree of advance.

The map box is pretty simple from an electronics standpoint. I would have to guess the acutal pressure transducer is contaminated with oil and needs to be replaced. If you open it up you may be able to find the map sensor part online for replacement.

My thought too!

rocketbob said:

The map box is pretty simple from an electronics standpoint. I would have to guess the acutal pressure transducer is contaminated with oil and needs to be replaced. If you open it up you may be able to find the map sensor part online for replacement.

Click to expand...

I have the box apart but have not had the time to unsolder the sensor from the board. Unfortunately the numbers were not on the top of the sensor.

MAP plumbing

hey guys, I haven't installed my old 'gold' EI system yet, so really interested when they 'fail'!
is it worth putting a little automotive type inline baffle to stop any oil blown down the tube, from getting at the MAP sensor?
You see them on the vacuum lines here 'n there in the engine compartment.
(Maybe I'm off base here, and they are one-way valves or something.)
Q2, what type of tubing is used for the MP line? The unit had some nice yellow silicone stuff chopped off from a previous install.....but I can't find the same thing anywhere.

thx

They work well.

flyboy1963 said:

hey guys, I haven't installed my old 'gold' EI system yet, so really interested when they 'fail'!
is it worth putting a little automotive type inline baffle to stop any oil blown down the tube, from getting at the MAP sensor?
You see them on the vacuum lines here 'n there in the engine compartment.
Q2, what type of tubing is used for the MP line? The unit had some nice yellow silicone stuff chopped off from a previous install.....but I can't find the same thing anywhere.
thx

Click to expand...

By far the weakest link in the older systems is the Mag Timing Housing that replaces the magneto. Because of it's moving parts, bearings, seals and occasionally the pickup itself need to be replace. I have replace the bearings and seals which is a simple task and the parts are about $5.

The MAP sensor failure I experienced did not inhibit the system from performing its intended task. The system performed as well as any mag without the MAP sensor.

In the spark plug department I run REM37BY's. The guys at P-MAG were kind enough to explain how to install normal aviation type connectors on the plug wires.

I use an inline filter on my mechanical MAP gauge in the cockpit. A simple gas filter that I have changed once in 10 years. The filters you see on the vacuum pump lines are special for that application.

Any tubing should work to plumb the map sensor. The sensor itself has 1/8" barb fittings on it. You could also contact Electroair and they may be able to supply you with a piece.

Electroair.

The basic electroair module and coil pack are manufactured by a company called Electromotive.
The map sensor is part # 71120 from Electromotive. It is a 2 bar map sensor.
The GM part # is... 12247571. I think it is ultimately manufactured by AC Delco. (I forget the part number.)

You can buy it on ebay for $49.95 with free ship from 'crespocams' Search 'Electromotive map sensor.' Comes with connector. (Why pay $225?)

http://www.distributorless.com/products/index.php Web site for Electromotive.

The Electroair runs just fine without the map sensor if it's giving you trouble. Just disconnect it.

Sensor.

After re-reading your problem... I was wondering if you had the 'Old' Jeff Rose ignition instead of the newer XDI (Electroair) unit. The info I gave is for the new unit.
The voltage going to the unit for the map advance on the old unit is negative voltage instead of positive for the newer units. I gave you the NEW part number for the electromotive/electroair.

I had to do the research on my old Jeff Rose unit. Of course Electroair sells the old sensor. ($225? Owtch!) I never could figure out which sensor was for the old unit. This was even after I called the tech department over at Electromotive. (Did I mention that the old Jeff Rose is an HPV-1 from Electromotive?) They had no idea what the old map sensor even was since they gave up support for that unit many moons ago. They haven't manufactured the HPV-1 for years. This is also why the unit from Jeff Rose/Electroair changed.

Testing yoiur map...

If you look at the Map sensor you can do a simple test on it.
Apply 5v to the red wire. (You can plug the sensor into your ignition with it powered up.) Ground the black wire. Whatever wire is left (White I think.) you can check with a voltmeter on the lowest setting. Take a (Clean!) tube and attach it to the suction input. Then with the meter across the ground and white wire, you can suck on it with your mouth or maybe an engine vacuum tester. The voltage you see should be in the millivolt range and give you your actual advance setting. .25 volts = 25 degrees of timing advance. This is why you see errors with a map sensor since the voltages are so minute.

You can actually read the amount of advance on the unit while it is powered up at the ADV tab where you plug in the connectors.

http://www.electromotive-inc.com/manuals.html
Even the HPV-1 manual tells you not to confuse the old vacuum sensor with the new Map sensor on page 20. If you have the old Jeff Rose unit you have an HPV-1.

Hope this helps!

Old one here

Schmeddz said:

If you look at the Map sensor you can do a simple test on it.
Apply 5v to the red wire. (You can plug the sensor into your ignition with it powered up.) Ground the black wire. Whatever wire is left (White I think.) you can check with a voltmeter on the lowest setting. Take a (Clean!) tube and attach it to the suction input. Then with the meter across the ground and white wire, you can suck on it with your mouth or maybe an engine vacuum tester. The voltage you see should be in the millivolt range and give you your actual advance setting. .25 volts = 25 degrees of timing advance. This is why you see errors with a map sensor since the voltages are so minute.

You can actually read the amount of advance on the unit while it is powered up at the ADV tab where you plug in the connectors.

http://www.electromotive-inc.com/manuals.html
Even the HPV-1 manual tells you not to confuse the old vacuum sensor with the new Map sensor on page 20. If you have the old Jeff Rose unit you have an HPV-1.

Hope this helps!

Click to expand...

Thanks for all the research. I have done nothing yet with the old HPV-1 sensor except take it apart and look at it. It's on the list of things to do. Again Many thanks.

zilik said:

Thanks for all the research. I have done nothing yet with the old HPV-1 sensor except take it apart and look at it. It's on the list of things to do. Again Many thanks.

Click to expand...

I've actually had all the research done for alternative ignitions. It helps to know the product! I actually spoke to to a gentleman in Oklahoma city who was designing a modern ignition back in the seventies. He did an article about it way back then. It was a cut down magneto that used the shaft and bearing as a trigger wheel for a GM ignition module. He flew a custom job called a "Skeeter" with parts designed by Steve Whittman. It was a low wing tailwind. I think it was on an early seventies sport aviation cover. I don't remember his name.

That was definitely old school!

Oklahoma city Gentleman.

The man's name was Leonard Eaves. He had an aircraft called a Skeeter. He came up with an accesory case triggered electronic ignition. This was back in the seventies! All stuff was available at the auto parts store. I think there was an article for an alternative for aircraft electronic ignition in 'Contact' magazine about him.