Guest Dieselnumpty Posted January 25, 2011 Posted January 25, 2011 I recently bought an old (1992) 1.9 non-turbo diesel Relay Motorhome. It's not a bad motor overall but there is one problem which is wrecking my ability to use it. It runs great around town etc but once I get on the open road and doing 60+ it will suddenly over-rev and pours out dark grey/black smoke from the exhaust. If I take my foot off the pedal and use the weight of the van to hold back the engine it will come back under control but then repeats it all over again next time I build the speeed up. Obviously this is doing the engine no good at all, as well as making the van unusable for it's intended purpose. I've been doing a bit of asking around and getting to know how a diesel works but I can't quite reach a conclusion on what's wrong. I suspect it's either a faulty fuel pump or engine oil is getting into the bores at high revs. Anyone know how to diagnose the problem for sure? Quote
Johndouglas Posted January 25, 2011 Posted January 25, 2011 One reason for the engine running away is when it's consuming its own lubrication oil by having the sump over full. It might be overful because too much oil has been put in, but also excess diesel fuel can be finding its way into the sump and raising the level. Not good because it's also diluting the lubricating oil. Quote
Guest Dieselnumpty Posted January 25, 2011 Posted January 25, 2011 I checked that but the oil level is fine, just below the top mark on the dipstick. Thanks for the suggestion though. The engine is not a heavy smoker under normal running so I suspect the bores are okay, but would worn bores cause the same symptoms? Is there anything else that could cause sump oil to enter the bores? (I hear turbos can leak but mine is a non-turbo). Quote
Guest Dieselnumpty Posted February 7, 2011 Posted February 7, 2011 I called in a diesel mechanic with 20 years experience and he couldn't find a fault, although he did confrm the pump is okay. He also confirmed the engine appeared to be in reasionable condition. He also tried disconnecting the crankcase breather pipe to check if it was breathing okay, which it was, but this gave me an idea and I think I've found a fix, although maybe not the casue. I disconnected the crankcase breather and routed it through an oil catch tank and out to the open air, and blocked off the breather pipe conection on the inlet hose. When I started it there was initally a lot of smoke as if had accumlated oil in the intake hose. I took if for a run - flat out for at least 10 miles with no problems. I was now convinced I had a knackered engine pushing loads of oil through the breather, but when I got back home I checked the tank and nothing - barely even a stain on the filter material! I now guess that when running flat out the engine vacum is drawing oil up from the sump via the breather and straight in to the inlet. I thought this could be caused by a blocked air inlet hose but I've checked it and it's fine. The air filter was also previously replaced so it's not that. So I don't understand the cause but at least I've cleared the symptom that was making it un-drivable at motorway speeds. Anyone got any suggestions to why the engine would draw oil up through the breather? Quote
Johndouglas Posted February 7, 2011 Posted February 7, 2011 Try running it without an air filter - but only for a short time. Quote
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