Okay - this is driving me nuts.
The boiler (Oil Combi from 1997) stopped working and went to lockout. Quick inspection revealed that the expansion vessel had failed. I replaced this and the boiler now holds pressure. Briefly fired and then stopped. The motor was HOT. I took the motor and pump apart and found that the coupler was mangled and the pump was stiff. New pump and coupler installed, pump bled and boiler fires up. Great until this morning, 12 hours later. Now, there's no oil coming from the pump. There's oil to the pump, but not coming from the nozzle to the burner. Could it be the solenoid/electronics? How would I test this? What am I missing?
We had our boiler oil pump out and refurbished a few weeks back, it started ok then stopped a few hours later and we thought it had finally died (we had water in the oil which could kill a pump) turns out to have been an airlock which the plumber bled out.
A few things to look at:
Have you tried bleeding it?
Is there a filter in the fuel line that needs cleaning?
Solenoids do fail - the one on mine would work for 10-15 seconds but then shut off. I do my own servicing and it was cheap and easy to swap (if a Riello burner).
So, I've now tested the voltages and there's 240v to the main board and 20v to the solenoid, but it doesn't actuate when the boiler starts. I've also tried another solenoid and another valve and again nothing moves. There's oil to the pump, the pump ran for over an hour last night, but as soon as it stopped, it seems to have FULLY stopped, like something is stuck. There's definitely no shortage of oil to the pump (and it is oil - it stinks) but still no oil past past the solenoid valve.
20v to the pump sounds correct (it is on my Riello 40) - for the sake of £20 I'd fit a new one.
What burner is it? Is the fan running as the solenoid doesn't open until the fan is running (but if you're getting a 20v output to the solenoid then it probs must be OK).
Yes, the blower motor/fan is running, but there's no movement of the valve. I have two different solenoid valves and coils - surely they can't both be faulty? I'm not sure that there's any cross connection on mine between the blower and the coil. They both go into the control electronics, but I'm fairly certain it's just power...maybe the control box monitors power draw, but I have no real idea. Like I mention, it's really odd that it worked perfectly and then just stopped, like the valve or coil died.
Does it try to ignite, you say the fan starts up, and then there shoudl be some clicking when the ignitor sparks. The solenoid starts/stops the fuel delivery. The photocell checks the flame is working, If it is not igniting at all, but is trying, then it’s most likely the solenoid. If it does light, but goes out quickly, it will probably be the photocell. Both symptoms could point to a failed control board. Both components can be checked with an ohmmeter, iirc, a good solenoid is around 100 ohms across the terminals. The photocell is variable, put the probes on, then cover it up, and the resistance should change. More modern digital photocells are far harder to test, but if yours is from 97, it’ll be analog.
You should really test the fuel pressure and CO2 readings whenever the burner or pump is adjusted/removed/replaced. Also, if trying to start but failing, a knackered nozzle can cause the same symptoms, though that is usually accompanied with an excess of oil dribbling into the ehat exchanger.
The boiler starts, motors come on, there’s a click, then nothing for a few seconds and then it stops. The solenoid measures 2.14 at 20k ohms.l and the power cable measures 20v at the solenoid. Photocell is an interesting thought - I’ll have to check that
is the sequence definitely 1.) start motors, 2.) try to ignite, 3.) activate solenoid?
That might explain why both solenoids don’t work.
Ill have a look.
is the sequence definitely 1.) start motors, 2.) try to ignite, 3.) activate solenoid?
Well on mine it's: blower starts, then the fuel solenoid a couple of seconds later and then ignition.
I wonder why you've got two solenoids?
Old pump and new pump. So I have two
solenoids valves and two coils.
You’ve got two pumps, or you mean you have a solenoid from the old pump as a spare? If it is reading 2.14k ohms(or is that 21.4k ohms?), its had it, and you need a new one. The reading, rather than the 100 ohms I said above, should be around 1300 ohms. 20k is well out of range, so check it again. They are cheap, HWOS do a next day service, and are reasonably priced. Also, check the connections at the control board, it is common for them to come loose, or not be seated correctly.
So was it starting and then stopping rather than just not firing at all?
On mine the photocell will only shut off the fuel if it doesn't see a flame.... And for that to happen it needs to complete the firing sequence.
Anyway, good result.... But you may be burning a bit rich if the photocell is sooting up.
Well, it would start the sequence to fire up, the motor would spin, it would try to spark, but then would trip out. It obviously couldn't detect the spark/flame and do never activated the solenoid coil to activate the oil flow valve, just like alanl said above.
It obviously couldn't detect the spark/flame and do never activated the solenoid coil to activate the oil flow valve, just like alanl said above.
That's the wrong way round - you can't have a flame [for the photoelectric cell to detect - they don't detect sparks] without the fuel first!
So what was happening was:
Fan starts > fuel solenoid opens and fuel pump starts > igniter runs and boiler starts > Photoelectric cell didn't see the flame (because it was dirty) and shuts everything down straight away.
If simply cleaning the photoelectric cell has fixed it then the boiler was always starting - it was just being shut down quite quickly.
Hmm - anecdotally, when the solenoid started to work after cleaning the photocell, i could feel it and hear it activate. I even had another solenoid valve which was removed from a pump and i could watch it activate. it only does this once, so there may be something where there's some form of immediate short in the circuitry in the photocell based on resistance. when it's dirty, the resistance is high and thus it knows that even if the boiler started, it couldn't see the flame anyway.
Well all I know is that a photoelectric cells sole job in life is to detect a flame, and you can't have a flame without the fuel supply being turned on first.
Actually if you think about it if it was dirty enough it couldn't see anything.... Which would be the same a not having a flame!
But if that were the case it would never fire!
Chicken meet egg.
My feeling it has to fire and see the flame/light within a few milliseconds.