190D 2.5 - Veg oil issues

[Adrianh1]

I have a 1993 190D 2.5 with 208k on the clock. 12,000 miles ago it was converted to run on veg oil using a twin-tank Smartveg system, a proprietory veg oil conversion brand (http://www.smartveg.com/how_does_smartveg_work/. The conversion has been a partial success with numerous niggles since it was installed 18 months ago. Most niggles have been ironed out. However the latest issue is proving stubborn to cure. I have uneven running (on veg AND diesel) and engine “missing”, with associated poor pulling performance, also random poor starting (lots of black smoke being kicked out).

To tackle the problem, the car has had a new lift pump, glow plugs, refurbed injectors, all new filters including veg fuel filters (the car was fitted with a Biotuning flat plate heat exchanger plus a Biotuning heated fuel filter). The veg fuel is good quality WVO from a North London gastro pub filtered thoroughly. I have used both my local garage and a diesel injection specialist (Phelps Transport in East London) to try and tackle the problem. My local garage doesn’t have enough knowledge/confidence to deal with veg fuel systems and Phelps hates working on vehicles that run on veg oil (definitely chin scratchers and blame the running woes all on using veg oil). I am planning to test for air leaks this weekend (weather permitting). I am wondering if any others (running on veg oil) have also experienced such problems? I understand O-rings in the fuel lines be worth looking at (I don’t’ know what O-rings are but I’m hoping to find out!). I’m also wondering if fuel pipes themselves may need clearing/replacement?

The car has been serviced meticulously during its life and, when running normally, runs beautifully smoothly and quietly. The pulling problems occur not just when the engine is under load but also when idling, especially when the engine has been working/pulling hard. Very unnerving.

Any thoughts/feedback much appreciated.

Adrian

 

[Number_Cruncher]

I don't run veg (and don't consider it to be a wise thing to do), but, here's what I would do;

1) Check the compressions (wet & dry if you read a low value dry)
2) Install a temporary pressure gauge somewhere where you can see it as you drive on the line between the last filter and the inlet to the injector pump - you want to see at least 10 psi there. If the pressure drops when you have rough running problems, you have a fuel supply problem, if the pressure doesn't drop, the cause is elsewhere.


Don't shy away from checking the compressions - comnpression is vital for a diesel engine.

 

[Bolide]

If it's the same of diesel and veg then it's not likely to be related to the veg conversion unless the IP is now worn. Veg has a lower lubricity than diesel so this will happen over time

Sounds to me like you need to do a compression test & a leakdown test to see what the state of the engine is

Nick Froome
www.w124.co.uk

 

[Adrianh1]

Thanks for the feedback. I will organise a compression test if I cannot isolate any air leaks. In terms of the engine condition, it runs unusually quietly and smoothly, especially given the mileage. Very refined actually. This led me to doubt whether there is any issue over the engine itself and/or compression loss. What is a leakdown test? Also, what (and where) are the O-valves (see my original post!).

Many thanks

 

[roadhog]

O-rings are seals. They can fail and cause leaks after switching to Veg oil.
'Can' but don't have to, mine have been fine so far.

From reading your posts, do I take it that your problem is intermittent?

 

[simon_wall69]

If it's missing it is either lack of fuel or lack of compression. I would use some clear fuel lines to see if there are air bubbles in there; if not then do the compression check.

I have had problems with air in fuel lines in both of my cars and both run on veg oil (although I don't have a separate tank system). In both cases, the problem was cured by replacing fuel lines and the o-rings or jubilee clips.

 

[Adrianh1]

Thanks very much Simon and Roadhog. Will report back in a few days. Adrian

 

[HERBIEMERCMAN]

hi adrianh1, vegi carries more moisture than diesel especially in low temperature, waxing is the term used. in the very cold weather car batteries are put to the test and fuel systems on diesel cars. when diesel is cold and more so vegi, the fuel pump thinks it's pulling porridge so any air leaks on "o" rings, pipes, fibre washers etc. enter the fuel lines as the pump finds it easier to pull air than cold fuel. when fuel gets very cold it cavitates, this means it separates and lets air get in. if you carry out all your testing on diesel then this eliminates any blame for the vegi, however i decided not to use vegi, based on my friend's advice from "merlin diesels" in preston, he said the diesel pumps take on non repairable damage and a recon pump is £1200. this is penny wise and pound foolish, saving 25 pence / litre, plus all the messing about, then finding out you need a new pump. i gave up on the idea. i am also advised that the "o" rings and other seals are solvent in vegi. giving more problems. the "cat" can also suffer unless you raise the temperature of the vegi. enough to release the valency free radicals for complete combustion to occur. in my experience it's more trouble than it is worth if you take a long term view, i saw the attraction initialy but following my research decided not to make the conversion. ask any of the conversion people if they will guarantee your pump etc. for 25 thousand miles ?. herbiemercman.

 

[wireman]

Unless WVO is chemicaly processed the disolved chemical remains of the food stuffs cooked in it are still present in the fuel, this can be acidic and have wear promoting properties, the high pressure parts of the injection system will be the first to degrade as a result of this.
In addition to wear enhancement vegetable oils will exchange with mineral oils which have become absorbed in the surface of flexible/rubber seals and hoses, the exchanged fluids can flush out all sorts of fancy chemicals that are included in the rubber to stabilize and enhance its durability, changing fuel type without changing all the rubber fuel system components is asking for trouble eventualy, in your case about 12000 miles into the trial.

I suspect that you have a damaged injection pump.

 

[Adrianh1]

Thanks for the above replies. The problem has been identified thought not yet sorted 100%. The issue was air leaks - quite substantial, with a lot of air bubbles present in the system, identified through transparent lines. Some of the lines have been tightened; I'm waiting for new hose-rings to tighten up the other leaks. The car is running a lot better in the meantime, though not quite 100%. Big relief. I was concerned about whether the fuel pump was damaged. Will update when all hoses sorted!