Riello Oil Burner suddenly won't light

belgarboy · 12 Feb 2011

The burner is a Riello 40 G5Q type 443T55, about 15 years old. It suddenly stopped lighting. There is oil entering the fuel pump but when the pump turns no oil exits. After bleeding the pump, still no oil exits. So I removed the pump, checked the flexible coupling which is fine, so am certain that the pump is rotating. With the cover plate removed and manually turning the pump, the residual oil seems to move around. Next I turned my attention to the solenoid valve. The coil has resistance, seems about 100 ohms. I removed the solenoid itself and it was not seized. The next step would probably be to patch in a couiple of wires from the control box to the solenoid and see if the control box is trying to actuate the solenoid. If so I would then be a bit perplexed. Does anybody have experience of the control box itself failing? Do these solenoid valves stick? I could see no obvious debris when I took it apart. The only other clue is that the motor will not stop running. It should timeout after 12 secs and then lockout should occur. But it runs and runs and runs. Any help would be so much appreciated,
Thanks, Peter

Terrywookfit · 12 Feb 2011

You probably have a faulty photo cell.

belgarboy · 12 Feb 2011

Thanks Terry. Just phoned my son and asked him to bring a precision multimeter home from work and then I'll be able to do a light/dark resistance check on the photocell. If the cell is faulty, would the motor just run and run and would the solenoid be prevented from actuating? If so I think you are on to a winner. If I disconnect the photocell and run the burner will that prove anything?
Many thanks
Peter

Terrywookfit · 12 Feb 2011

If you unplug the photo cell the motor will just run as it is now.

A new cell is only a fiver!

Boilerman2 · 12 Feb 2011

If you unplug a faulty Photocell, the sequence will change the burner will purge for 12 sec the fire up for about 5 sec and then lock out if this happens then the PE Cell is faulty as said they are only a fiver!!

belgarboy · 12 Feb 2011

Unplugged the photocell and it changes nothing. The motor still runs on and on. This means the photocell is in fact OK? I wish I could get hold of a proper service manual, any ideas?
Thanks, Peter

Boilerman2 · 12 Feb 2011

The next thing to check is for 50volts AC on the white wire from the motor (you have to disconnect it from the control box and route it out of the wiring base check with a meter on 200vac range red test lead to white wire and black test lead to earth (the motor has to be running for this test you need 50vac =/- 10% if not motor is faulty

other possible cause = Solenoid or faulty control box

belgarboy · 12 Feb 2011

OK Boilerman2 will try, but the motor I'm sure is OK as it runs with the same "noise" as when the system was working properly. By the way, measured the resistance of the photocell, it's about 250 ohms with a light on it, and just about infinity when covered up. Am I right in thinking that the solenoid is driven by wires 1 and 2 from the control box - what voltage should appear across these wires and should the solenoid be powered the monent the motor starts turning? I am assuming yes. If I get no volts across this pair of wires would it be safe to assune that the control unit has packed up?
Thanks, Peter

Terrywookfit · 13 Feb 2011

You need a pressure gauge to find out if the pump is in fact working.

It creates a "wash" pressure of about 50 psi.

slapper · 13 Feb 2011

It will be the solenoid coil,its knackered and creating an open circuit.seemples

belgarboy · 13 Feb 2011

The coil has resistance so I think this is OK. Why do I need a pressure gauge? Won't the oil just spurt out of the outlet - can't see why not. As a diesel fuel injection engineer its how I would do it.

spraggo · 13 Feb 2011

belgarboy said:
The only other clue is that the motor will not stop running. It should timeout after 12 secs and then lockout should occur. But it runs and runs and runs. Any help would be so much appreciated,
Thanks, Peter

Hi Peter
If the motor keeps running and does not go to lock out it indicates that you need a new motor, as the 50v supply on the white wire from the motor is missing.

spraggo

oilhead · 13 Feb 2011

Boilerman2";p="1898675 said:
The next thing to check is for 50volts AC on the white wire from the motor (you have to disconnect it from the control box and route it out of the wiring base

It's possible to check the voltage from underneath the wiring base with a multimeter probe without disconnecting.
Disconnecting will take the voltage off the box and stop it working.
Continuous purge is down to either a p/c fault, but you've eliminated that by removal. A faulty coil. The box checks for continuity. The coil is 2 stage, one at, I think 24 volt 1st stage, then 2.5 volt holding after flame establishment, a faulty motor not producing 50volts, or a faulty control box.

Boilerman2 · 13 Feb 2011

And you do need a Pressure guage to prove the pump!!
Oil Burners differ to Diesel Engines thats why I repair boilers and you repair diesel engines !

belgarboy · 13 Feb 2011

Just probed the control box from underneath and there is 51V between the white motor wire and neutral. From the comments made earlier I assume therefore that the motor is OK. I also probed across the solenoid coil. There are no volts across it, therefore no chance of fuel being pump to the combustion chamber. What could cause this? Obviously a faulty control box is one possibility. Also, is there any other sensor or switch which would prevent the control box from actuating the coil which could be at fault? If not, I think it must be the control box. This would explain why it doesn't time out after 12 secs also - surely if it was working it would detect no fire in the chamber by means of the p/c and lock out. For me, just having the motor permanently energised is either the control box stuck in this position due to a fault with it or, more unlikely, a poor piece of design which allows the motor to run and run if another part of the system is at fault. If you think this is sound, let me know and I'll buy a new box. As for testing the pump to ensure it is capable of reaching the right pressure boilerman2, I totally agree with you. To see if it has any pumping action at all, even though it might be not sufficient, fuel should come out of the outlet with the union cracked open. There isn't a single drop. Once again, thanks to all for your help.

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Riello Oil Burner suddenly won't light

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