using washers in oil line coupling

[oilhead]

Is the burner a downfiring unit? If so, then if there is a slight leak in the supply pipework, the pump may be pulling in air and eventually running dry, causing it to seize. A poor oil supply can also affect a forward facing burner, and it can take quite a few minutes for a blockage to manifest itself as a fuel shortage. A new drive dog is supplied with every pump and should be replaced. Misalignment can cause your problems, and overtightening the holding screws in the motor flange can cause this. Very often only two screws are used which can easily misalign the pump. A check for this is to rotate the pump with the fan whilst it is mounted in the burner. At the end of the day, a new burner can be bought for about £300 which should solve your problems if they are totally burner related, but I feel yours are not.

 

[snb]

What age burner is this?
I think the fault may not be with the pump and is with the control cox or the photocell.
If the photocell fails it causes the motor to run continuously and in this causes the oil pump to overheat, the oil pump uses the oil flowing through it to cool it. Problem being when too hot it knackers the bearings. The bearings are sealed and mustn’t get kerosene in contact with them as kerosene has my lubrication.

 

[Tomswan]

For sure, pump failure is greatly hastened by poor fuel or filtering - it uses kero to lube the internals - and excess heat. Kero also disperses the heat.
I've always found the pump filter fine for doing it's job, providing it's clean of course.
I've had couplings fail due to age, contamination or heat but they haven't interfered with the pump at all.
If this was mine, I'd run the burner up on the bench with a separate fuel supply (I use a large Tupperware container with a lid and tap outlet)....crazy I know but I have this because on some installations it's not possible to adjust the pump when the burner is in place.
John

Thanks John. I think I understand something though - I think the couplers are designed to deform so they can absorb excess torque should the pump bind. Bit like the crumple zone in a car. Which would mean they can't really be re-used after the pump binds even once, and it's probably why they say the coupler should always be changed when a new pump is fitted. I just picked up a bag of ten of them (how they are sold) and the new one on has less 'give' than both the older ones, even the one I didn't think had deformed. I am also wondering if once the pump has locked solid once it is more prone to do it again. Gears do wear, don't they? So if the torque hasn't been completely absorbed by the coupler it would transfer into the gear mechanism and may make the assembly sloppier. Since that little blasted but no doubt ingenious crescent shaped component is prone to contribute to binding, even a bit of extra give would make that more likely. However, until I can be reasonably sure it is warranted I am not going to get another new pump. I will once I am sure this is where the fault lies. Good call on the bench. I've been thinking about hooking something up for a while, and will probably do so before long. On the plus side I have a new electric shower downstairs, which I wouldn't have if the boiler had never failed.

 

[Tomswan]

What age burner is this?
I think the fault may not be with the pump and is with the control cox or the photocell.
If the photocell fails it causes the motor to run continuously and in this causes the oil pump to overheat, the oil pump uses the oil flowing through it to cool it. Problem being when too hot it knackers the bearings. The bearings are sealed and mustn’t get kerosene in contact with them as kerosene has my lubrication.

That's interesting, thanks. The burner is about eight or nine years old, so not that old I would have thought. I did check the photocell for crap when it started to cut out originally, but it seemed ok.

Are you saying the motor can run without me knowing? That would mean it running without the burner firing. I know when the burner is firing because I can hear it going. It seems to cycle on and off properly.
The radiators are hot, then cool a little, then the burner kicks in and they get back up to temperature and then the burner switches out again.
I'm not dismissing what you say though, because that hadn't even occurred to me.

Mind you, where are the bearings in a riello pump? The one I took apart had the various chambers, the gears and the drive shaft. The shaft is sealed at the base where it exits the pump to fit the coupler but attached to the drive gear at the top inside the pump. I'm not sure where bearings would be, but if they are a sealed component I wouldn't necessarily be able to find them. Oil is everywhere inside the pump as far as I can tell.