trickymicky Posted August 15, 2018 Share Posted August 15, 2018 I posted this on another site but doesn't seem to be a very busy site. Can anyone shine a light on this problem? 92 200tdi, fuel tank under the seat. Engine running sweet as a nut. The problem is it sounds like I've got a one cylinder diesel in my fuel tank! The knock increases speed with the engine. I don't know if the tank is acting like a sounding board but i can feel it through the tank pick up pipe. The knocking starts when I push the throttle hard then continues until I restart the engine then its back to normal. The problem could be the lift pump transferring the knock down the pipe to the tank, but the pump seems ok, no noises. Any ideas? Quote Link to comment Share on other sites More sharing options...
Yostumpy Posted August 16, 2018 Share Posted August 16, 2018 (edited) Have you changed the fuel filter, sometimes pumps get noisy when filter needs changing. Mine did. (300tdi) also I had similar noise , another 2 times. First was brake servo pump on way out, second time bolt was missing from air filter box diagonal support bracket ( taken off to change servo pump 2 years earlier) but 300 may be different. I'd change filter and clean out lift pump if it has a screw in the top , first. Edited August 16, 2018 by Yostumpy Quote Link to comment Share on other sites More sharing options...
miketomcat Posted August 16, 2018 Share Posted August 16, 2018 Is the tank vacuuming while it's knocking try removing the filler cap. If you get a sharp intake or can't get the cap off the breather is blocked and the pump is trying to turn the tank inside out. Mike Quote Link to comment Share on other sites More sharing options...
trickymicky Posted August 16, 2018 Author Share Posted August 16, 2018 The filter is new, only been run two or three hours but i haven't looked at the pump filter. It never entered my head, so thanks Yostumpy for that, I'll check it out. The vacuum in the tank also makes sense. I'll try that first because its the easiest. Quote Link to comment Share on other sites More sharing options...
trickymicky Posted August 16, 2018 Author Share Posted August 16, 2018 The pump hasn't got a filter on it so that's a bust. Took the fuel cap off, just made the knocking louder. I think the next thing to do is change the pump. I'm a bit weary about that because a lot of people seem to have problems with new pumps i.e. they don't last long. I've only seen the pattern ones on ebay. I don't know the make of the original pumps. I guess that would be the one to go for. Quote Link to comment Share on other sites More sharing options...
ianmayco68 Posted August 16, 2018 Share Posted August 16, 2018 Is it a 110 ? If it is have you checked the fuel return , it goes into the top of the tank on the 110 and it’s metal , could that be loose or corroded? Long shot but a possibility. Ian sorry just saw tank under the seat Quote Link to comment Share on other sites More sharing options...
trickymicky Posted August 16, 2018 Author Share Posted August 16, 2018 It only happens when I rev the engine hard and continues to knock at tick-over, so i'm thinking it has to be mechanical. Maybe the diagram has become stiff with age or a build up of sediment. It is the original pump, twenty six years old. But it has only done 100,000 miles. I've ordered a pump so should know by next week. Quote Link to comment Share on other sites More sharing options...
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