Diesel heater pump help please

[Anderzander]

I ran my tank very low and my heater is not starting now - I’ve put it through a few cycles to prime it, but no joy.

I tried sucking fuel at the heater end - as I’ve done successfully before and only got a really tiny amount and then nothing. 

I’m assuming it’s either some dirt or an air lock?   I wouldn’t have expected dirt as the tank seems pretty clean - but it is a thin line, so I guess it wouldn’t take much.

Would you suggest just blowing the pipework out ? And would you blow it back to the tank or out from the tank?

I’m not sure what the pump is like inside - can you blow through the pump ?

Any suggestions or info very welcome. 

[Maverik]

The pipework is indeed very narrow, it wont take much to block it - i'd pull the pipe section apart and make sure each seciton is clear - also worth checking the pump too, have you tried just pulling of the fuel connection as it goes into the burner and to see if its actually pumping fuel through? - the Webasto/Ebaspacher are pretty intelligent units, and they do lock themselves somtimes, you might have to do a hard reset by pulling one of the power fuses out etc and leaving for a period of time - there's loads of instruction manuals for these units online.

[Anderzander]

Thanks Mav.  I will blow it through and then run it with the pipe off at the heater end. 
 

My pump is like this, with a silencer / filter? crimped on..  I wasn’t sure if I could blow that through without damaging it.

I’ll start with the pipework though. 

[Maverik]

I think that will be a non return valve, I doubt you'll manage to get air through it, as the principle of how the pump works means it wont free flow.

[Anderzander]

I think it’s sorted. 😊

I pulled the pipes and blew through them - pump to tank I blew into it and could here it bubbling the diesel.  

Ran it with the pump to heater pipe off and could see fuel squirting out, then blew through the line to the heater with an airline and then primed with a syringe. 

I could see smoke from the exhaust, so I knew fuel was now getting through, the it started. Got the error soon after, and came right on the next cycle. 

So although I didn’t see anything come out - I’m assuming something either got into the pipework or air locked it somewhere.

I should perhaps pop a filter in it. 

[Maverik]

Well done, I've been running my Webasto without fuel filter for the best part of 8 years I think, the last year it was very unreliable starting. - finally got around to servicing it earlier this year and the burner was full of what looked like petals of carbon/combustion dirt, I can only assume it had burt up additional crud and just kinda blocked the air passages, cleaned - serviced with gaskets and like yours after 1 false start it then started behaving. Been spot on since.

I remeber I did try and fit it with a fuel filter at the very begining, but I could never get it bled properly with the filter and it just kept airlocking in the filter.

[FridgeFreezer]

I've had to sort this multiple times due to air getting in to old pipework - you can pulse power to the pump by running wires to it and tapping one of them to 12v to feed fuel through. It can take a lot of tapping if there's a long pipe run and the whole thing has air in it, you can hear the sound of the pump change as fuel comes through it.

If you're got a long run from pump to heater it can need a lot of priming as the heater will give up trying to start before the pump has been pulsed enough times to purge air - in that case, remove the heater end of the pipe and keep tapping until fuel comes out the end.

The pump moves a very small volume of fuel per pulse, hence why it takes so long - using small bore (4mm OD) nylon hose instead of rubber pipe means a small volume of fuel travels faster through the pipe and will purge faster.

I had issues with the factory setup on mine, in the end I re-jigged it all and spent a few quid on a cheap fuel swirl pot from eBay, that sits in the return line to the main tank. The Webasto draws from the bottom of it, the overspill returns to the tank, so even flat out of fuel in the main tank the Webasto has ~2-3L of fuel it can draw from. It also means it can't draw from the main tank, so if it somehow uses more than 3L of fuel between engine starts, it will run out and stop.

[Anderzander]

That’s a good suggestion. Thanks 😊 

I’ve just ordered this off the back of it :

https://www.ebay.co.uk/itm/165474321860?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=aoJtVHHNTc2&sssrc=2349624&ssuid=8IVqfH45Rgq&var=&widget_ver=artemis&media=COPY

Right near the pump are two spade connectors that feed the back of a 12v socket into the tub.  

From the pump wiring it looks just like a live and an earth…. So If I terminate that connector with a couple of male spade terminals, perhaps also with an inline switch, I’ll be able to have a plug in bypass to control the pump for this kind of thing.
 

 

 

[FridgeFreezer]

That's exactly what I did, it's the same connector as Rover V8 fuel injectors & sensors so I had a few knocking round

And yes, 12v a ground on the wires, it doesn't seem to matter about polarity from the official wiring diags.

[Anderzander]

Bugger has stopped working again ! 

[simonr]

The pumps do stop working - generally due to dirt getting in the non return valves built into the pump.  It only needs the most microscopic bit of dirt!  It's damn near impossible to dismantle & not servicable once you do.  However, you can buy cheapo Chinese pumps for next to nothing & they seem to work just as well as the Webasto ones!

Working intermittently and / or needing frequent priming are a sign of this.

Fridge's suggestion for priming is good - it takes forever to prime otherwise.

Si

 

[Anderzander]

Thanks Simon.

Ebay seems awash with pumps for about £10 .. is there anything to separate them? Or are they all much of a muchness ?

[toenden]

On 5/31/2022 at 11:47 AM, FridgeFreezer said:

I've had to sort this multiple times due to air getting in to old pipework - you can pulse power to the pump by running wires to it and tapping one of them to 12v to feed fuel through. It can take a lot of tapping if there's a long pipe run and the whole thing has air in it, you can hear the sound of the pump change as fuel comes through it.

If you're got a long run from pump to heater it can need a lot of priming as the heater will give up trying to start before the pump has been pulsed enough times to purge air - in that case, remove the heater end of the pipe and keep tapping until fuel comes out the end.

The pump moves a very small volume of fuel per pulse, hence why it takes so long - using small bore (4mm OD) nylon hose instead of rubber pipe means a small volume of fuel travels faster through the pipe and will purge faster.

I had issues with the factory setup on mine, in the end I re-jigged it all and spent a few quid on a cheap fuel swirl pot from eBay, that sits in the return line to the main tank. The Webasto draws from the bottom of it, the overspill returns to the tank, so even flat out of fuel in the main tank the Webasto has ~2-3L of fuel it can draw from. It also means it can't draw from the main tank, so if it somehow uses more than 3L of fuel between engine starts, it will run out and stop.

This got me thinking... could a wire from the trailersocket flasher output  to the pump do the trick? Then it is just a matter of how long you need to flash 😏/take a brew🍺/do other small checks🤒 in the meantime. 

/mads

[simonr]

5 hours ago, Anderzander said:

Thanks Simon.

Ebay seems awash with pumps for about £10 .. is there anything to separate them? Or are they all much of a muchness ?

I just bought the cheapest one!

2 hours ago, toenden said:

This got me thinking... could a wire from the trailersocket flasher output  to the pump do the trick? Then it is just a matter of how long you need to flash 😏/take a brew🍺/do other small checks🤒 in the meantime.

That's a nice simple solution.  I left mine pulsing at about twice indicator speed for maybe 30 mins with 3m of tube between the tank & pump.  It probably didn't need that long but it only wasted a trivial amount of fuel & I wanted to be sure!

[Anderzander]

I’m still picking away at this…  I’m just going to type the sequence out to help me think it through.

So Airtop stopped igniting and I’d get the no start / no flame fault. 

I used a syringe to inject diesel into the line and it fired but wouldn’t keep going. So I thought pump.

Fitted a new pump - same problem.

Read a bit and it seemed that the burn chamber getting blocked can stop it firing - so bought a service kit and fitted it. Came with a new glowplug, which snapped on installation - but the old one was working - so that went back in.

Still the same problem.

I noticed the fuel line joiners were a bit perished - so I thought it might be letting air in. 

So bought and fitted all new fuel lines - hard nylon clear ones, so I could hopefully see the bubbles.

Still wouldn’t flame.

I have a 2nd heater - bought to go in the 90. So I thought I’d piggy back that off of the Airtop, check it worked and perhaps end up fitting it. (it did need a different pump fitting - but other than that it piggy backed all the fuel lines)

So I set it up and lo and behold - it wouldn’t fire 🔥 😳 same no ignition issue.

Now, I’d blown through the pick up pipe when I changed the fuel lines and it seemed clear - but to rule it out I tied a weight to another bit of fuel line and dropped it directly into the tank to bypass the pick up pipe. 

Lo and behold - the new heater now worked.

So this made me think - is all this because the pick up line was blocked or partially blocked?  

So I tried the original heater with the bypassed pick up … and ….it almost works. 

The exhaust does get warm and it starts to heat the air, but it doesn’t seem to fully ignite- and I it shuts down with the same error.

Thats confusing … I assume this means there is / was more than one thing stopping it working. The pick up and something else … maybe the glow plug isn’t getting hot enough ? 

I’m waiting for inspiration now.

I guess I could try the syringe trick from right at the beginning - and if with that it does fire then it must still be something to do with fuel delivery. 

 

 

[hurbie]

i would give it a try with a alternative fuel source , small container with fuel rigged up to the heater , and see if that works 

 

[smallfry]

What I have learned.

I have had five vehicles fitted with Webasto Thermo Top water heaters. Two were factory fit Freelander 1s, and the other three I have installed used units myself.

The main fuel line needs to be 1.5mm ID. I have tried the easily available and cheaper larger bore pipe, but it does not seem to work well, mainly causing the heater to cut out, or making it more difficult to get the fuel through.

The pick up dip tube should be minimum 40mm from the bottom of the tank, in order not to pick up sediment or water. Also to prevent inadvertently running out of fuel.

I have not had good results teeing into the main vehicle fuel pipe.

Replacement non genuine diesel pumps can be a bit hit and miss. I have found, after having problems with the heater starting OK but fuming at lot then cutting out. I have tried them on another heater and it works fine, as did the smoky one when subsequently  fitted with another one. I believe that the heaters can be adjusted to suit with the correct equipment.

Non genuine glowplugs do not seem to work properly of for long. They also act as a thermocouple, and this can cause the heater to shut down if not working correctly.

As to your problem, I dont think a syringe will work, as too much fuel will not burn. As Hurbie has suggested, try drawing fuel from a can or whatever, then try a another replacement pump as it may have some carp stuck it it, then if no joy, try another genuine glowplug. I am not familiar with the Airtop, but I cannot think what else it could be, apart from a very unlikely blocked exhaust.

[FridgeFreezer]

My experiences of various diesel heaters have been that fuel pickup/plumbing is critical - as others have said, air locks, position, angle, gravity feed, etc. etc. etc. can all cause issues.

With genuine heaters (webasto / eberspacher) they can be fussy about  battery voltage at the heater as they draw a lot of amps when starting, so any voltage drop on the supply wires can easily take them below their happy threshold and they cut out / lock out.

The chinese ones may or may not be fussy, I'm guessing they will err on the side of not caring so much.

Due to the slightly fangled way the V8 one was plumbed I ended up buying a cheapy ebay 3L fuel swirl pot / tank and putting that in the fuel return line with the eberspacher picking up from the bottom:

Fuel return fills the tank, overflow spills from the top back to the main tank, heater picks up from the bottom so it's always got 3L of fuel to draw from with a very short fuel line run (4mm shiny black nylon pipe in pic) which means any air bubbles etc. have far less distance to travel to be purged through. Also means the heater can't use more than 3L of fuel before stopping, which is about 6-8 hours running absolutely flat out, and it can't suck up air even if the main tank is low.

[ped]

i've used a Chinese one for a couple of years in the shed with no real issues  and my dad has one fitted on his camper
for my work truck rebuild we have a 2kw that was sent to my dad to test by one of the suppliers in China(he admins on a diesel heater group))
not sure where it'll be fitted but my dad always recommends a seperate fuel supply as close as possible to the heater ,i do like the swirlpot in the return line idea