EGRs

[Chris]

I know there's been tonnes post on this subject, but recently the Old Bus has been running on coal it seems. Even mild acceleration has been quite sooty. Just been for a spin and it was leaving quite a cloud. So I stuck two air rifle pellets in the vacuum pipes and went out again. Well it's not completely cured but then again it's a thumping great big truck engine, but transformed it most certainly is. No soot at all for normal driving. Doesn't feel any different to drive but it was that quick anyway I'm not sure I'd notice.

I shall brim the tank at some point and measure the MPG

 

[Shayne]

Done to death perhaps but it would be interesting to see an mpg comparison of old and clogged V blanked V stripped and cleaned .

 

[frank rabbets]

Black smoke=retarded pump timing amongst other things but if it has not been checked it will defo be retarded as the gears wear.

 

[Chris]

What over the course of a week Frank? It's been fine really. Didn't smoke one bit when I got it from Andy but it's just started. It goes like a bomb. No known history of pump twiddling, but to be this good one has to suspect. But with nearly 30 mpg official up to Scotland it's not been detrimental to the consumption. We may need to explore the 'amongst other things'. Appreciate the pump timing may be out, but to go from no smoke to sink the Bismark virtually over night, I find it difficult to believe. Blocking the pipes has virtually cured it. The little bit that does come out now might be timing.

 

[frank rabbets]

Pump retardation happens slowly Chris.

 

[Chris]

217k on it now Frank so could be some wear. But like I say, I think the EGRs were the culprit here.

 

[Citizen Brown]

Must be common this, i followed a grey 80 up Stannington Road this afternoon in a cloud of smoke. It was a bit like the closing credits to Dad's Army…..Would like to know who it was so i can bill them for the cost of washing the EPO's white volvo!

 

[Chris]

Errm, I was in Stannington this afternoon. Went to Towsure. Wasn't leaving clouds behind me though. Been really clean all day. Sure it can't have been me. Roof tent, rear wheel carrier, High lift etc.

 

[Citizen Brown]

Yup, only joking just a bit of black smoke on gear changes. Thought i recognised the GG from forum and thought i would pull the leg...

 

[Chris]

Oh funny guy, eh?

Yes there is still a bit if I pull away harder but before there really was clouds of it. Must say I don't think it has quite the zip that it had before. It used to just go and go when booted. Mind you, the torque is still staggering. Seems to have sipped fuel today as well.

We decided to have a bit of a day out instead of lying under it today.

 

[Chris]

Oddly, my experience of blanking EGRs is not what I expected. Since blocking off the two pipes to the valves, the engine has felt slightly strangled. Like a blocked air filter almost. No, the air filter isn't blocked. It hasn't smoked at all which is good, but the last half tank of juice since I blocked them off has plummeted. I have unblocked one just to see what difference that makes. All the science says it should be better but it's really lost its get up and go. Are the valves (top hat things) serviceable? Might see if I can clean them out and make sure they work properly. They do lift when I rev the engine. Just not sure why suddenly it got so smokey.

 

[frank rabbets]

Hi Chris

You have an intermittent fault and doubt whether it's anything to do with egr's. I've run mine connected and not connected and it's made no difference to anything. Last year we did nearly 3000 miles in Pyrenees with connected egr's and the truck did 28mpg. Now we've just done 2200 miles same region and she's done 29.6 mpg. No difference in smoke or performance. Mines done 140,000 and the pump has never been adjusted apart from timing.

As you say probably not pump timing and if you've got black smoke it can only come from the pump delivering too much fuel.

I've talked a couple of times to a guy at RVS Swindon just for some general queries. He'll soon point you in the right direction.

 

[Chris]

Difficult to believe that Frank. Drive round the block, black smoke, plug the lines and go round again and the smoke's gone. How can that not be something connected with the valves? See what I mean? This smoke didn't come on gradually over the years. It was utterly clean when I got it. I have done a handful of miles and it suddenly got sooty. Like overnight.

I just feel that it's something to do with the EGRs not working correctly. No? It's not an intermittent fault. Plugging the valves has affected the way it drives which makes me think that maybe they are jammed open or something. Just haven't had time to look.

 

[Jon Wildsmith]

An EGR sticking open might reduce the oxygen content of the intake air enough to cause smoke? They don't look very serviceable, might be time to blank them off properly.

 

[Shayne]

Try it with no air filter , when i got a high flow filter i was astonished at the difference , the paper filters must be very restrictive .

 

[Beau]

My Two pence here... I've seen a 1KZ engine's intake with the EGR blocked off most of it's life and I must say it only had a thin layer of oil/soot (My finger could wipe it off). On the other hand I've seen a 120,000 mile engine with the EGR as usual, the intake was coated in soot, at least4-5mm in thick black carbon that took something sharp to clean out and a lot of patience.

Now I can't really help you here with your problem Chris, but I honestly believe the EGR systems on these old trucks are useless especially in the long run. They send back so much carbon and soot through the intake that over time it really does build up. You may find on lower mileage trucks they're fine but over time they do more bad than good. And for that extra MPG, is it worth it?

 

[Chris]

Jon that's basically what my thoughts were

Beau I agree. I have no corner to fight in relation to keeping them. Just keen not to remove them if it has the effect that blocking them had. If I can get them back to how it was until recently then they can stay. Nearly 30 mpg was fine with me. Valves or no valves.


Running with no air filter? Right that could work

 

[frank rabbets]

I don't think stuck open valves would starve the engine of enough air to cause a problem. I thought the egrs only worked or failed at the margins. But yes try 2 sandwich blanking plates as a quick test as Jon suggests.

If you've used lots of diesel with no black smoke that doesn't sound correct as in the absence of smoke the fuel should have been turned into energy.

Whenever I've run my engine with the valves connected they have left soot around their side vents and on the ally flange they are bolted to. I assume when open they are not completely gastight when open even when new. You might see if you have loads of soot pointing to one or doth being stuck open.

I don't know if the fuel gauge may work differently on the 24 valve cars c/w the 12 valve ones. My gauge drops quickly after it's half way mark.

 

[frank rabbets]

Yes the egrs do cause carbon build up in the inlet manifold but that would not happen suddenly nor be relieved by disabling them.

 

[Chris]

Frank I think the additional consumption has been to so with the loss of power and having to push harder through the gears
Tank profile never linear I know but this dropped like a stone after a very typical first half.
Might get chance for a play tonight if it's fine