w124 Veg oil conversion

[Hibbo]

Hi to everyone, I'm wasting no time and converting my xmas pressie (from myself) to run on veg oil.

It's a '94 E300D estate with the om606 multivalve engine.

I've attached a very badly drawn (I thought computers were meant to make things like that easier!) of my planned conversion. The black bits are what is already on the car, red bits I will be adding.

When the car is started from cold, the selector valve at the mechanical lift pump outlet will be directing the veg oil straight back to the tank. The electric pump will run, supplying derv to the IP, via seperate (additional) filters. The return line selector will direct the fuel back to the derv tank.

When the engine is up to temperature, both selectors will switch over and the electric pump will stop. Thus heated veggie will be supplied to the IP and returned to the main (veggie) tank. The NRV will stop any veg working its way back through the derv pump and lines.

At the end of the journey (if the engine will be left to cool) I will switch back to derv to purge the IP and injector lines/injectors of veg for the next cold start. If I am using two seperate selector valves then I will delay the switching of the return line for however long it takes for the IP to be purged of veg, to avoid veg ending up in the derv tank. However if I end up using a 'six port' valve then this is not possible as both valves are driven by the same motor. I do not think the IP holds that much fuel anyway.

Can anyone see any major flaws in my plan? I have not yet thought about the logistics of where to fit my extra tank yet, but want a general plan in my head before I attack the car.

Does anyone know what pressure the standard lift pump produces? What electirc pump would be suitable for me to use to provide the derv?

One potential issue would be that the (mechanical) lift pump will be trying to suck cold veggie through the standard I/D fuel lines on cold mornings. It will only be pumping it back to the tank so is not an issue in that way, but would it damage the lift pump itself?

Any advice/criticism is more than welcome!

 

[turnipsock]

I'm a bit confussed by the non return valve.

Shouldn't the veg supply have a non return valve as well?


You could put in another valve to stop the supply to the mechanical pump if you are worried about it.

 

[Hibbo]

I'm a bit confussed by the non return valve.

Shouldn't the veg supply have a non return valve as well?


You could put in another valve to stop the supply to the mechanical pump if you are worried about it.

The NRV is there to stop the veg oil working its way back along the derv system, when the electric pump is not running and the veg is being supplied to the IP by the lift pump.

The veg supply doesn't need an NRV as the it will be closed off by the selector valve when running on derv.

I don't want to stop the supply to the lift pump as it can't be good it running dry. I am also keen to have it pumping the veg straight back to the tank as this will start to warm the tank when the heat exchanger warms up.

 

[Flying Scot]

The NRV is there to stop the veg oil working its way back along the derv system, when the electric pump is not running and the veg is being supplied to the IP by the lift pump.

The veg supply doesn't need an NRV as the it will be closed off by the selector valve when running on derv.

I don't want to stop the supply to the lift pump as it can't be good it running dry. I am also keen to have it pumping the veg straight back to the tank as this will start to warm the tank when the heat exchanger warms up.

IF you want to heat the VOT install a heating coil and feed it from the heater circuit - where are you going to put this VOT Hep2O flexi plastic plumbing pipe and fittings are great to work with 8mm to 22mm (from memory)

 

[Hibbo]

David, I am using the normal tank as my Veg Oil Tank, I will not be heating it (aside from the returning fuel), for resons of simplicity (ie laziness) and to leave the car as intact as possible. I will be adding a small extra tank to hold the derv, probably a 5litre jerrican, not sure where yet though.
I am going to use a plate heat exchanger from a combi boiler, plumbed in to the heater circuit (teed into it). One of the reasons I am not using the 'looped return' setup is that the returning fuel will heat the tank (a little bit anyway). The other is that as air ingress seems to be a problem with these engines I wanted to retain the self-bleeding aspect of the fuel system.

From what I have managed to guess and find, the lift pump runs at upto 1bar, so I need an electric pump that'll do the same. The K-jetronic type pump I have runs at up to 8bar, so if i'm to use it some kind of regulator would be in order!

Thanks for all the replies, life is a learning process!

 

[twodogron]

Hi,
Don't know your plans or expected budget for this conversion but thought you might like to look at this web page http://www.diesel-therm.com/veggie-kit.htm
I beleive they do a "kit",
Cheers,
Ron..

 

[Hibbo]

Cheers Ron, But I think their kit may be outside the scope of my budget (about 45quid, maybe 50 )

I have generally found that kits cost a lot more than the sum of their parts, and it's no fun!

 

[Flying Scot]

i would have thought an 'old' SU electric fuel pump as used on BMC cars of the past would work fine look in some classic car mags - there is even a dual version used on Rolls Royce and Bentleys if you need more flow and a higher pressure. I am sure some of the serious car tuners will be able to recommend a good HP pump but at some cost to your budget so a scrap yard and an old mini or morris minor looks like the best place to start. I would have though some pre heating of the SVO would be worthwhile before it gets to the injector pump and should be easy to fabricate or cobble together maybe even some copper micro bore pipe wound around the filter bowl and fed with hot water and of course you can get electrical heating tape not sure if you can get a 12V form though

 

[turnipsock]

I seem to remember having a problem with an SU pump years ago, the contacts wore out or something. Though the contacts were replacable I eventually replaced it with a Bendix pump (I think that was what it was called).

 

[Hibbo]

Thanks for the replies chaps,

David, I am heating the veg, the coolant heated heat exchanger will heat it before it hits the prefilter (then lift pump, then main filter, then (when engine is hot and switchover has happened) the IP).

David & Turnip, Cheers for the pump pointers, I will do some googling and get down the breakers.

Does anyone know much about pressure regulators? Can a gas regulator be used to regulate liquid? I ask as I have a couple of gas regulators as used on beer pumps.

Cheers again!

 

[turnipsock]

I wouldn't think a gas regulator would work with liquid.

You can certainly get fuel pressure regulators. Carbs with needle valves can suffer from the fuel pressure being to high and forcing fuel past the needle valve so the solution is to fit a fuel regulator.

 

[Flying Scot]

I seem to remember having a problem with an SU pump years ago, the contacts wore out or something. Though the contacts were replacable I eventually replaced it with a Bendix pump (I think that was what it was called).

just clean the points and adjust them SU pumps are easy peasy to maintain and very reliable (just keep the points dry) as in DONT mount the pump underneath the car as in the BMC Mini beside the ever rusting rear subframe:sad:

 

[Flying Scot]

Hi to everyone, I'm wasting no time and converting my xmas pressie (from myself) to run on veg oil.

It's a '94 E300D estate with the om606 multivalve engine.

I've attached a very badly drawn (I thought computers were meant to make things like that easier!) of my planned conversion. The black bits are what is already on the car, red bits I will be adding.

When the car is started from cold, the selector valve at the mechanical lift pump outlet will be directing the veg oil straight back to the tank. The electric pump will run, supplying derv to the IP, via seperate (additional) filters. The return line selector will direct the fuel back to the derv tank.

When the engine is up to temperature, both selectors will switch over and the electric pump will stop. Thus heated veggie will be supplied to the IP and returned to the main (veggie) tank. The NRV will stop any veg working its way back through the derv pump and lines.

At the end of the journey (if the engine will be left to cool) I will switch back to derv to purge the IP and injector lines/injectors of veg for the next cold start. If I am using two seperate selector valves then I will delay the switching of the return line for however long it takes for the IP to be purged of veg, to avoid veg ending up in the derv tank. However if I end up using a 'six port' valve then this is not possible as both valves are driven by the same motor. I do not think the IP holds that much fuel anyway.

Can anyone see any major flaws in my plan? I have not yet thought about the logistics of where to fit my extra tank yet, but want a general plan in my head before I attack the car.

Does anyone know what pressure the standard lift pump produces? What electirc pump would be suitable for me to use to provide the derv?

One potential issue would be that the (mechanical) lift pump will be trying to suck cold veggie through the standard I/D fuel lines on cold mornings. It will only be pumping it back to the tank so is not an issue in that way, but would it damage the lift pump itself?

Any advice/criticism is more than welcome!

some books here but you will need to invest some $'s

http://www.mercedessource.com/taxonomy/term/62

http://www.mercedessource.com/node/2161

http://www.mercedessource.com/node/333

STEAL some ideas here

http://www.mercedessource.com/node/2482


regards

 

[pcman_jh]

E300 Veg oil converson

My 99 E300 (which I assume is very similar to your engine/IP) was converted using the ATG system. This means it has two 3-way valves, which changes the fuel lines to a closed loop system once fitted, except when purging for 40seconds (it has a timer relay) of the last few minutes of a day before switch off for the night.The closed loop is designed this way to reduce the constant 'suction' load of the thicker veg oil from the main tank thus meaning it only sucks in what it's using. Apparently the 'slight' heating of the main tank if using the full flow/return original method is not worth it. The ATG kit has a heat exchanger that's plumbed into the car's heating plumbing, and a thermostatically controlled glow plug built into the 2way valve that switchs back to the tank or keeps it closed loop.

If your engine/fuel layout is the same as mine, you'll benefit from the closed loop design reducing any air ingress issues as the 2 valve seal-off/reduce the fuel lines flow from the tanks when switched off. I can now change my main fuel filter without having to do the 2 minute cranking to bleed the system!

One issue I did have was gelling of the fuel filter especially noticeable on first run of the day. Even after only 150 miles of use with a new filter on Veg oil, I'd get noticeable fuel starvation within the first 5 miles of each new day due to gelling in the filter even although I was starting on 100% diesel. Obviously any residue SVO was retained in the fine filter structure of the fuel filter. The cure is to either modify your morning route to not include *any* hills/moderate acceleration for the first 5/10 miles, or, buy the ATG fuel filter silicon based heater jacket (£80 for basic components). This has a 12volt heater and thermostats to keep the temperature within a range of about 80 - 120 'C. This appears to work for me - I say this as I've only had it on the car for 2 weeks now and the weather has been unseasonably mild.

The ATG kit cost me £490 (the wife thinks it only cost £200), with about another £20 for additional fuel pipes as the supplied lengths are not long enought for this car. It took me about 3 whole days to fully fit everything and test it. The heater jacket only took about 2 hours to fit.

Hope this helps.

 

[Hibbo]

Cheers for the info pcman,

1) Does your system use the same (main) fuel filter for the derv and SVO? My plan is to use completely seperate ones so as to avoid the plugged filter problems on cold starts. I am not planning on heating the SVO filter (the standard one already on the engine) as it will be have heated veg going through it as soon as the engine heats up (even before switch over).

1.5) Also by using seperate filters I will not have to wait for the veg to be purged out of the filter when shutting down (a good 1/3 of a litre I'd guess), and I can also get the switchover valve right against the IP inlet, again reducing the amount of precious (ie expensive!) derv needed to purge the system.

2) Is 40secs long enough to purge the system? The injector lines are quite long on the 606 and fuel flow through them is EXTREMELY slow, you really don't want cold veg sat in cold injectors in a cold cylinder head on a cold morning for a cold start!

3) I did consider using a 'looped return' when on veg, and a standard return setup when starting on derv. I may still do this, but I am too concerned with the lack of self-bleeding when using this setp. Could you send me a flow diagram of your system please?

Cheers mate!

 

[pcman_jh]

Converting to SVO

1) Does your system use the same (main) fuel filter for the derv and SVO? My plan is to use completely seperate ones so as to avoid the plugged filter problems on cold starts. I am not planning on heating the SVO filter (the standard one already on the engine) as it will be have heated veg going through it as soon as the engine heats up (even before switch over).

REPLY - Uses the same filter. There are too many pipes (6 in total !! some obvious, some not!!) to plumb in a second filter on my model.

1.5) Also by using seperate filters I will not have to wait for the veg to be purged out of the filter when shutting down (a good 1/3 of a litre I'd guess), and I can also get the switchover valve right against the IP inlet, again reducing the amount of precious (ie expensive!) derv needed to purge the system.

REPLY - Fair point but there's also the fuel still in the pump, high pressure lines, injectors and bleed off. Would have to balance the extra plumbing components and their lifetime maintenance against worth of just letting it run for a few more minutes.

2) Is 40secs long enough to purge the system? The injector lines are quite long on the 606 and fuel flow through them is EXTREMELY slow, you really don't want cold veg sat in cold injectors in a cold cylinder head on a cold morning for a cold start!

REPLY - The 40 secs is just for the return valve switching, then it closes (automatically) leaving the fuel system in closed loop mode which means I need to drive long enouhg for any SVO to be used/burnt out before stopping for the night. I've found through trial and error that I need to continue driving for around 4 minutes (incl the initial 40 second purge) which I now have mental markers for on the road I use, and by smelling the exhaust when I get home.

3) I did consider using a 'looped return' when on veg, and a standard return setup when starting on derv. I may still do this, but I am too concerned with the lack of self-bleeding when using this setp. Could you send me a flow diagram of your system please?

REPLY - The diagram is copywrited by ATG Diesel Veg so I can't post it here publically. I've also read that you've got to be careful that any 2 tank open loop system should never return SVO to the diesel tank as it can go lumpy when hitting cold diesel (don't know the accuracy of this as I would have thought it's no different when manually mixing SVO into your main tank on an unconverted car.) I've also read that closed loop systems can cause the fuel in the closed loop to get too hot thus reducing lubricity. On some AMerican systems they don't do closed loop systems as full open systems also allow the fuel to loose it's heat in the engine plumbing. I don't have an opinion on either of these statements other than to say my conversoin has now done about 5000 miles with no obvious detriment - too early to give anything conclusive.