- Thread starter R Kraft
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NO - they are 12V.
Intended to be used on a car battery supply in boats and caravans etc but most people use a 12V 32amp+ psu - cheap enough on Ebay. They use very little current running but draw a good 20 amps + when the glowplug kicks in.
JOEPRO
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I figure lots of people are using them wired to a psu and I am asking if best to wire that to a lead and plug VS a fixed fused spur.
Ahh I see. Mine is just on a 3 pin plug. PSUs are less than 500w so don't need anything fancy. Only use a few amps when running normally so maybe 30 or 40w.
You are better running them flat out for most of the time. Less soot buildup inside.
rcx132
Philip
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BTW I ran
I used a fused spur. Of course that may not meet regs as it's not the only fused spur on my circuit. I used a fused box with a red neon as the PSU has quite a high standby current, so I like to switch it fully off when I'm not planning to start it via remote the next morning.
rcx132
Philip
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I just ran my heaters again. Looks like having the pumps hidden in a box above the heaters isn't working. The pumps draw air out of the diesel due to the strong action of the piston inside of the metering pump. This air builds up and probably causes inconsistent fuel feed. No biggie, I'll move the pumps so each one is right under its heater.
The air isn't an issue, unless the pump is drawing in that much air, the air is making it to the heater.
As long as it's just a consistent bubble at a high point in the pipe, I wouldn't worry, just think of it as damper to smooth out the fuel pulses.
rcx132
Philip
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I bled the hoses but saw that there was still a stream of bubbles coming out of the pump even though the hose into the pump was completely bled. I recently watched John's famous diesel heater videos on YouTube and he said that the air is being extracted from the diesel by the action of the piston. It's too much air... moving the pumps is no big deal and i get something more reliable.
That would be a problem.
The air isn't extracted from the diesel, it's being aeriated into the diesel from a leak.
If the diesel does see enough of a vacuum to cavitate, any air in the diesel just implodes back in and visbily disappears again. If there's any air in the diesel (or any other oil) going into a pump, then that air doesn't magically permanently increase in volume because it's been briefly subjected to a vacuum. As soon as that vacuum is removed, the air goes back to the same volume it was before entering the pump (assuming the outlet pressure is the same as the input pressure).
There will be a leak somewhere, it's just not always practical to cure the leak.
The type of pipe/hose used and the hose clips often don't create a perfect seal. The nipple connections into the pumps are another source, and I'm pretty sure the internals of the pump probably are not the best designed or sealed. They'll be sealed enough to not visibly leak, but the shocking likely allows them to move and let air in.
rcx132
Philip
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I've just finished moving the pumps. I put spring clips on each hose, so they're as air and fluid tight as can be. The spring clips create an even clamp force around the hose, whereas some hose clips pinch the hose and I don't trust those. There is still a steady stream of bubbles being released into the fuel but the air now goes straight up the hose to the heater without building up, so the heater is getting consistent fuel. I did notice that when the pumps were above the heaters, the metering pump frequency would change every so often as though the system was trying to adjust for the inconsistent fuel it was getting due to the air pockets.
Ok, I know nothing about this but keen to follow. There's air in diesel, do we agree on this? I just watched a YouTube video of a guy put diesel into a vacuum chamber and show this. I've also seen pro bicycle riders drawing air out of LHM oil before filling brake systems with the "air free" oil. But are you saying that's not whats causing the bubbles I'm seeing because as soon as the air is drawn out by the metering pump it would soak back in ? I don't get why it would do that? Maybe because the pump piston then re-pressurised the diesel-air to push it out the outlet ?
The ECUs on these are pretty basic, and don't compensate for fuelling issues. They simply spin the fan at X speed, and command the diesel pump at Y frequency.I've just finished moving the pumps. I put spring clips on each hose, so they're as air and fluid tight as can be. The spring clips create an even clamp force around the hose, whereas some hose clips pinch the hose and I don't trust those. There is still a steady stream of bubbles being released into the fuel but the air now goes straight up the hose to the heater without building up, so the heater is getting consistent fuel. I did notice that when the pumps were above the heaters, the metering pump frequency would change every so often as though the system was trying to adjust for the inconsistent fuel it was getting due to the air pockets.
Ok, I know nothing about this but keen to follow. There's air in diesel, do we agree on this? I just watched a YouTube video of a guy put diesel into a vacuum chamber and show this. I've also seen pro bicycle riders drawing air out of LHM oil before filling brake systems with the "air free" oil. But are you saying that's not whats causing the bubbles I'm seeing because as soon as the air is drawn out by the metering pump it would soak back in ? I don't get why it would do that? Maybe because the pump piston then re-pressurised the diesel-air to push it out the outlet ?
Any change of tone is likely to be some air going through it (or the pump failing).
Basically if you have any fluid with gas in it, and you place that fluid in a vacuum (to be technically correct, decrease the pressure being applied to it), that gas will expand (Boyle's Law). If you then remove that vacuum and let the fluid return to it's original pressure, that gas will contract back to it's original volume.
The example of bike brakes you use, is using that principle to expand the gas so it forms larger bubbles and 'floats' out the fluid. It's the same reason why people use vacuum chambers for some castings/mouldings, the vacuum expands any air out the material so it's more likely to float out, then when the vacuum is removed, any air bubbles that are left, get compressed in size. Although if you manage to pull a perfect vacuum, there should be no air left.
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Philip
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The pumps generate bubbles, see attached pic, or this video:
The whole video is largely about air issues.
Classic youtuber who doesn't understand why something is happening.
I got as far as him starting to waffle about the bigger tube absorbing the pulses, and how that's supposedly bad.
The way these heaters work, that makes no difference. The fuel passes into the gauze that surrounds the glow plug, where an air bleed then pushes the fuel through the gauze where it vaporises the fuel creating the flame. The gauze also smooths out those pulses from the pump, otherwise the flame would be very inconsistent.
If anything, a smoother delivery of fuel makes that vaporisation more consistent.
rcx132
Philip
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He's still worth watching as he's understood many parts of the heater even if he has made mistakes. As for the pulsing, maybe only the OEMs know if that's a desirable feature.
To be honest @m_c I'm not following your explanation as to why the bubbles can't be from air that was dissolved in the diesel. The pump's piston extracts the air, something I have seen just by putting oil in a syringe. Dissolving the air back into fluid is a slower process, so this air now appears as bubbles exiting the pump. It sounds consistent to me, maybe others can comment ?
Last night I also worried that my pumps and heaters are now below the fuel tank. Can fuel seep through the pump by gravity while switched off? IIRC on my Vevor heater the pump was at the side of the tank, suggesting that it won't let fuel past.
Misterg
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In this context, IME, bubbles = air leak (or there is still air inside the pump that is slowly coming out).
He's calling it cavitation which is when you get vapour bubbles (not air) forming due to a drop in pressure. In that case, the bubbles disappear immediately the pressure recovers, so you wouldn't see anything in the hose coming out of the pump (there is nothing to "dissolve").
If you put anything under a vacuum, you will get the ingredients with higher vapour pressure boiling off (i.e. forming bubbles). It doesn't mean there is "air in it". The outlet hose from the heater pump is just at atmospheric pressure (not under vacuum).
Pulsing is irrelevant - all the pump is doing is delivering a known amount of fuel to a metal mesh wick were it burns off. If you've ever heard these heaters running, you can hear the flame flare up after each pump pulse (some are more noticeable than others). The heater also burns for a few seconds after the pump stops.
If there are bubbles in the fuel, the small bore hose clears them more quickly. The bigger bore hose lets bubbles build up so that if/when they do get through they can interrupt the fuel supply long enough for the heater to go out.
Eberspacher and Planar supply short lengths of rubber hose for joining the fuel line (hard plastic, small bore). This is an extremely tight fit on the fuel pump spigots and the fuel line before hose clamps, etc. are involved - No bubbles. The hose in the video above looks to be just about hanging onto the spigot on the pump.
