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300 Tdi Running problem. Any ideas ?


smallfry

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A friend has two Disco 1 facelift 300Tdi Autos. Both are semi derelict and are not run often, but now one has a running problem.

Now, I am unfamiliar with Discos, so I dont know where everything is, and how it works, so bear with me.

Its been twenty odd years since I have touched a 300 Tdi, and they were in Defenders, so they had a cable operated throttle direct to the fuel pump, but both these Discos appear to have no physical connection to the pump at all (that I can see)so I assume they are completely fly by wire.  Is this correct ?

When the ignition is turned on, there is a "coarse" buzzing noise from the pump area on both of them. Is this normal ?

One of them starts and runs normally, and sounds just as I remember, but the other does not. The diesel clack clack clack sounds subdued. Less sharp than normal. It seems to idle just fine, but smokes a bit, which it never did before (it has not been started for about two years) However, when the throttle pedal is pressed, it seems to semi misfire and smokes A LOT, and will only get up to just over 2000 RPM before the check engine light comes on. The smokes looks blueish which suggests oil burning, yet it smells distinctly of unburnt diesel and stings your eyes.

Have checked the air filter for mouse nests etc,  disconnected the flap type AFM electrically, and then removed the air hose between it and the turbo inlet, which made no difference at all.

Then disconnected the intercooler to inlet manifold hose which had a fair bit of oil in it, but again, this made no difference to the running OR the smoke.

ISTR the 300 had a problem with lift pumps, but I can see this might cause lack of revs, but surely not cause the smoke. Or could it ? Could the timing belt have slipped ? Is it likely ? 

The smoke is similar to a common rail electronic injector failure, but can a 300 Tdi injector fail like this ?

I cannot offhand think of anything else it can be. One thing though, it was run on chip fat/vegetable oil for a time, so I wondered if it was possible that some of this has seperated and congealed inside the pump ?

Other that these things, anyone got any ideas ?

Do they have a diagnostic socket ? If so, where is it ?

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Contrary to popular myth, the Tdis don’t run well on plain vegoil unless the fuel is heated and the injection slightly advanced.  But the vegoil needs to be purged with clean diesel for the last part of the run.  Apart from sludge and deposits, running with vegoil without modifying the oil or the vehicle will also cause the moisture in the oil to corrode parts of the pump and injectors, a lacquer to be deposited, gumming them up, and it also condenses on the bores and badly gums and comes the rings.  Without more frequent oil changes, the vegoil that makes it past the rings polymerises the oil in the sump and starves the lubrication system and bearings.  Just a one off trial of a 25% mix of new rape seed oil in an up modified 300Tdi damaged my injection pump, causing minor surging at mid revs, and the specialist who repaired it said that was typical.  I think a lot of people just don’t pay enough attention to their vehicles to spot the smaller symptoms.  So, I’d say that was a likely candidate for the trouble.  Regardless, it sounds like a fuel injection issue, perhaps with an addition oil burn issue (likely the rings and scrubbed bores).

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4 hours ago, Snagger said:

Contrary to popular myth, the Tdis don’t run well on plain vegoil unless the fuel is heated and the injection slightly advanced.  But the vegoil needs to be purged with clean diesel for the last part of the run.  Apart from sludge and deposits, running with vegoil without modifying the oil or the vehicle will also cause the moisture in the oil to corrode parts of the pump and injectors, a lacquer to be deposited, gumming them up, and it also condenses on the bores and badly gums and comes the rings.  Without more frequent oil changes, the vegoil that makes it past the rings polymerises the oil in the sump and starves the lubrication system and bearings.  Just a one off trial of a 25% mix of new rape seed oil in an up modified 300Tdi damaged my injection pump, causing minor surging at mid revs, and the specialist who repaired it said that was typical.  I think a lot of people just don’t pay enough attention to their vehicles to spot the smaller symptoms.  So, I’d say that was a likely candidate for the trouble.  Regardless, it sounds like a fuel injection issue, perhaps with an addition oil burn issue (likely the rings and scrubbed bores).

My experience is quite different Snagger. My 200tdi runs on 100% SVO for the warmer months of the year (generally April through to at least October) and runs as well, if not better than on diesel. I have done this for nearly 100,000 miles. I am however careful not to use it in cold weather and I dont do stop start journeys on 100% SVO. I have all the gear (heat exchanger and heated fuel filter bit have never had the need to fit it). My FIP was reconditioned a few years ago for preventative measures and there was no laquering (timing was advanced at this point but it hadnt been a problem before). I did a head gasket about two years ago and the bores on the engine were as new, no signs of gumming.

I always try to put some diesel in if the vehicle is going to be left as well so its diesel not SVO sat in the pump but in the summer this doesnt seem to hurt at all if I forget. 
 

Its hard to understand how 25% rapeseed did damage to your engine. The only time I have experienced surging is when I had neglected to clean the prefilter on my facet lift pump. 
 

I never touch used veg oil, so this could be the problem here if it hasn't been processed properly. I would at least change the filters at this point. I also don't think the lift pump diaphragms like veg oil hence I switched to an electric lift pump as I had too many failures of lift pumps. 

Edited by reb78
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My lift pump was OK - that was the first thing I replaced with no effect.  But having the injection pump rebuilt sorted it.  He was quite explicit about the need for some heavier duty parts being needed for the Bosch pump if running on SVO, and about the small timing advance.  Oddly enough, using multiple fuel tanks and a fuel heat exchanger, the 12J in my 109 ran very well on rapeseed, and nearly as well on sunflower oil.  My 200 Tdi seemed to run well on heated rapeseed, but was well down on power on sunflower oil.

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On 12/31/2020 at 1:47 PM, Yostumpy said:

if They are both semi-derilict , why bother at all?    

Basically the cars are scrap. Would need way too much welding, plus the rooves ? have rotted. It is to ascertain if the engines are worth keeping for further use.

Had another look at this yesterday. Took out the tank sender and found both the feed and return blocked solid with what looks like lard, but a lot harder. Also in the tank itself is what looks like sold lard/congealed chip fat, so I assume thats what the PO used ?

The metal parts on the tank sender are also rusty, even where it has been submerged in the gloop, so this is not a good sign. The stuff in the pipes took some shifting too. Almost like rock. Gloop also in the lift pump, so changed that for a used one that works. Blew through the feed and return with petrol and got them clear.

We then stuck a big yoghurt pot in the tank sender hole, filled with fresh BP ultimate diesel and put the feed and return lines into it and started the engine. It runs slightly better but still smokes as much. I guess FIP is either semi blocked, or is rusty inside, and most likely not done the injectors any good either.

Hopefully leaving the fresh diesel in it will dissolve some of the gloop, but what it really needs is a replacement FIP that is not electronic, and probably injectors too.

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I'd have said that the engines are definitely worth saving - the 300 is such a simple engine in the grand scheme of things that it doesn't take much to strip down, clean them and rebuild them into a reliable working engine.

I had similar behaviour (albiet on a Nissan LD28 engine) where it had been sat for a while (although not on veg oil). The diesel itself had congealed as well as as started getting fungal growth in it. I'd drain the tank if it's easy, change out fuel filters and perhaps bung a tub of diesel cleaner in the tank as well.

If there's lots of diesel coming out the exhaust then I wonder whether the injector tips have got bunged up and are "hosing" rather than spraying a mist and thus giving the effects of a mis-fire. If you've got someone nearby with an injector tester (I can send you the details of someon in Guildford who'd do it for some biscuits) then it'd be worth chucking them on that because they can deliver far more fuel through the injectors than a normal injector pump and can often clear blockages. I was amazed at the difference in some good injectors after running them through my mates tester - you could see the jets spraying better and better each "flush" (test).

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