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tawnypipit
tawnypipit

Posted: Thu Jan 10, 2013 11:07am

Post Subject: diesel in the oil sump

Hi I have an Isuzu 38hp and the sump oil has diesel in it.How? and is it a big job to fix. Many thanks. Paul Bartlett

Tony-B
Tony-B

Posted: Thu Jan 10, 2013 6:49pm

Post Subject: diesel in the oil sump

I have been unable to find a sufficiently detailed picture of your engine on the web and I understand some have an electric lift pump and some a mechanical one. This is important because if it is a mechanical one then a leaking pump diaphragm may well put diesel into the sump. If it is electric it can not. A very badly dribbling injector can cause this but as you are not complaining about smoke, vibration and a lack of power I think that we can discount the injectors. That just leaves the injector pumps and I think you have 4 of them spread out down the crankcase. I suspect one or more of them is leaking from their plunger into the sump, but make sure that you have an electric pump before you do anything else. I expect those injector pumps would have to be adjusted and in any case you can not cure such a leak so I fear it is time to find a good engineer. Sorry, Tony Brooks

ray840
ray840

Posted: Sat Jan 19, 2013 4:58pm

Post Subject: diesel in the oil sump

Hi, I have a BMC1.5L engine and have had this problem twice. The first time it was a faulty fuel lift pump,(mechanical), and although I am not mechanically minded I had no problems fitting a new one, following Tony's instructions. The second time it was the seal on the fuel injector pump shaft that was at fault so I paid for a mechanic to remove the pump which I then had serviced and then the mechanic refitted it for me. I was advised by a couple of people not to let the oil get too contaminated with the diesel because the engine can feed of the diluted oil mixture and you can't switch the engine off. Can't say if this true or not. Regards, Ray Moore.

Tony-B
Tony-B

Posted: Mon Jan 21, 2013 3:38pm

Post Subject: diesel in the oil sump

There is a possibility that the engine can feed on oil mist & fumes form the sump but to a degree that depends upon the crankcase breather system. The fuller the sump gets the more mist the crankshaft is likley to whip up and the more diesel in the oil the more it may vaporise on the underside of the pistons. You are lucky in that you only have one injector pump that is dead easy to change and re-time. Paul has, I am sure, 4 individual pumps. If an engine just refuses to stop you have lots of time to think about it but if it runs away (keeps accelerating until there is a very loud bang), which it can do with lost of diluted oil in the sump, it is far more serious. Tony Brooks

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