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you dropped down the combustion air through pilot assembly, i have also put a #10 screw into rubber pilot hose to cure this.

Good ol ENG A. A fella and I had cleaned up the burner and accessories on a direct fired mua. It was doing the same thing. Turns out he had hit one of the differential air pressure tubes. It would attempt ignition, the pilot solenoid would open but no cigar. Makes troubleshooting a little difficult at times.

It turns out that on some of these units the rigid pilot air tube was too close to the center of the burner motor housing so too much air was being forced into the tube when the blower wheel is centered in the housing. just moving the wheel a hair to compensate would eliminate this problem. Replaced many of these motors and wheels before and have never had this.....many hours burt on this one but at least it working.

well then... gonna have to have another crown and coke waiting this one out.....

Originally Posted by Elfshadow

well, only thing I can think of is if you moved it closer to the inlet, it was sucking air in from the cabinet creating turbulence that was keeping the pilot from lighting.

Good thinking but nope....you would have to see the housing. It would be next to impossable to draw air from the burner cabinet..unless the motor was going backwards

well, only thing I can think of is if you moved it closer to the inlet, it was sucking air in from the cabinet creating turbulence that was keeping the pilot from lighting.

Originally Posted by nismo1

I hate suspense

The issue was not in any service or installation manual......

I hate suspense

Originally Posted by Elfshadow

Wild shot in the dark, based on having looked at that manual that was linked earlier in the thread, speed sensor was not correctly sensing speed thus was spinning to fast??

Nope.... will let a few more chime in

Nope..

Originally Posted by b5srt

FIXED UP AND RUNNING...........We went back today with one of my guys and went over every inch of the burner, settings, pressures, etc......Called Eng Air and discused the situation at great lenght over multiple calls and they agreed that everything appears to be right but found it "very strange" why the pilot wont light. After multiple call back and forth Eng air decided that they are going to have to come and take a look....Just as I am packing up (not very happy as this is a prime client) I get a call again from Eng Air telling me to slighly offset the burner motor blower wheel 1/16-1/8" to the air inlet side of the housing and BOOOYAAA she fires right up runs like a charm with the air dampers in there original set-up. Take a ***** guess what the issue was......

Wild shot in the dark, based on having looked at that manual that was linked earlier in the thread, speed sensor was not correctly sensing speed thus was spinning to fast??

FIXED UP AND RUNNING...........We went back today with one of my guys and went over every inch of the burner, settings, pressures, etc......Called Eng Air and discused the situation at great lenght over multiple calls and they agreed that everything appears to be right but found it "very strange" why the pilot wont light. After multiple call back and forth Eng air decided that they are going to have to come and take a look....Just as I am packing up (not very happy as this is a prime client) I get a call again from Eng Air telling me to slighly offset the burner motor blower wheel 1/16-1/8" to the air inlet side of the housing and BOOOYAAA she fires right up runs like a charm with the air dampers in there original set-up. Take a ***** guess what the issue was......

Originally Posted by slctech

Wonder if the DMJ board is not operating properly, I know the light off speed is factory set, but this may be the issue. Have you tried Taking a DMJ off of another operating unit and try it on this unit?
Another thing I was thinking of is that the burner may not be centered properly and setting too ow in the chamber causing excess air over the top. Make sure the burner is centered.
This is a public document...sure you have it, but here is the link. If all else fails after checking all they have here, I would be contacting a factory tech and pick their brain.
http://www.engineeredair.com/manuals/Manual1.pdf

Thanks for the input, I am bringing one of my of my tech's down with me tomorrow for a 2nd pair of eyes...I have been a service tech for 25 years and every so often there is a machine that throw's you for a loop....I am hoping to solve this mystery tomorrow, will let you know. Thanks

Wonder if the DMJ board is not operating properly, I know the light off speed is factory set, but this may be the issue. Have you tried Taking a DMJ off of another operating unit and try it on this unit?
Another thing I was thinking of is that the burner may not be centered properly and setting too ow in the chamber causing excess air over the top. Make sure the burner is centered.
This is a public document...sure you have it, but here is the link. If all else fails after checking all they have here, I would be contacting a factory tech and pick their brain.
http://www.engineeredair.com/manuals/Manual1.pdf

Originally Posted by slctech

Does this unit just have the basic combustion air, or does it utilize any of the G or X Trac controllers. I would assume that your getting too much air from the combustion motor and it is blowing the pilot gas being released off of and away from the spark electrode. Need to get in and double check that your combustion air % is correct, once operating check your flue outlet pressure, and get your CO and O2 readings and start making the necessary tweeks to the system and possibly gas pressure.
I work on plenty of these too, but not one comes from the factory exactly the same. So hard to say which gas valve set-up (modulating) you have, dampers (angle or flat), type of ignition controller, etc...but I am probably preaching to the choir, my friend.

Honeywell ignition module S8610
Maxitrol modulating main valve ( blue valve with dc voltage control) operating at 3.5" when on high fire
24v Pilot valve operating at 3.5" when open.
combustion air motor is controled by the DJM 2.3 board which ramps the motor speeds up and down according to demand.

I do agee with you that the pilot is being blown out or there is to much air to establish pilot. I have to close the air damper almost fully to get the unit to fire up, when on high fire the O2 is less than 1% which is far too low. Once running if I adjust to the min of 3.2-3.5% O2 and restart the machine it will not establish pilot. A few thing that dont make any sense.....

1) Combustion analisys was done less than 30 days ago and all was near perfect....the air damper was set roughly is the same position as all the other machines on the roof.
2) Machine was working with no issues until the combustion air motor failed. (all replacement parts are Eng Air OEM), not my first time replacing these motors....done probably 10-15 without issues.

Originally Posted by jsin

What is your combustion readings with the air damper in that position....Is it within Eng. Air's specs?

no, it's less than 1% O2 when it should be between 3.5-4.5%.

Does this unit just have the basic combustion air, or does it utilize any of the G or X Trac controllers. I would assume that your getting too much air from the combustion motor and it is blowing the pilot gas being released off of and away from the spark electrode. Need to get in and double check that your combustion air % is correct, once operating check your flue outlet pressure, and get your CO and O2 readings and start making the necessary tweeks to the system and possibly gas pressure.
I work on plenty of these too, but not one comes from the factory exactly the same. So hard to say which gas valve set-up (modulating) you have, dampers (angle or flat), type of ignition controller, etc...but I am probably preaching to the choir, my friend.

What is your combustion readings with the air damper in that position....Is it within Eng. Air's specs?

yes, the pilot will not light. The only way I can get the pilot to light is to almost close the air damper fully. Then the pilot will light and the unit will go to main burner no problem.

The PILOT itself is not lighting?