Hainsworth Posted June 20, 2019 Share Posted June 20, 2019 Hi, Can anyone help with an oil pressure issue I have on my Stag ?. I have petrol going in my oil, which I believe is the reason the oil pressure is low (more so on idle) as my oil is now extremely thin and smells really strong of petrol. Is this a likely reason for low oil pressure ?. I guess I can switch my oil to see if that returns the pressure to normal, but I need to stop fuel getting into my oil sump or I will be back to this thinned down oil in some weeks. Can this be something like a sticking float valve in the carb(s) that is dumping too much fuel through ?, or something like this ? Many thanks Ian. Quote Link to comment Share on other sites More sharing options...
glang Posted June 20, 2019 Share Posted June 20, 2019 I know not a lot about Stags but on most engines the mechanical fuel pump is a possible way of getting fuel into the oil when it's diaphragm is damaged and leaks. This of course will affect the pump performance but the engine can still run while fuel is effectively being pumped into the engine internals... Quote Link to comment Share on other sites More sharing options...
nang Posted June 21, 2019 Share Posted June 21, 2019 Whatever you do don't leave it too long or you will stuff your bearings and generally cause wear to your motor. I second Glang, fuel pump is a good place to start looking.😲 Tony. Quote Link to comment Share on other sites More sharing options...
RobPearce Posted June 21, 2019 Share Posted June 21, 2019 Quoted from nang- I second Glang, fuel pump is a good place to start looking. ... except that Stags have electric fuel pumps. It takes quite a severely over-rich mixture to get fuel in the oil, and if you do then it's via bore washing, so your rings and bores are going to suffer even before the bearings. I can't immediately think of another easy route in, though. Quote Link to comment Share on other sites More sharing options...
glang Posted June 21, 2019 Share Posted June 21, 2019 ah yes an electric pump wont do that. As Ian said as the Stag Strombergs point upwards where does the fuel go if the float chambers overflow? Quote Link to comment Share on other sites More sharing options...
Hainsworth Posted June 21, 2019 Author Share Posted June 21, 2019 Thanks for the help. Correct. It is an electric fuel pump, so I can only think its the carbs. I have had issues starting it in recent weeks and a bad smell of fuel, leaving it for some hrs can sort it out and then she fires up. The bore washing theory could therefore be the source. I have just heard the fuel pump ticking over slowly with just the ignition on, meaning it is pushing fuel through when it isn't running, so I am more going in the direction that it is a float valve that is stuck. Quote Link to comment Share on other sites More sharing options...
glang Posted June 21, 2019 Share Posted June 21, 2019 The usual Stromberg design is for the float chamber overflow to exit on the inlet face into the airfilter housing so perhaps you could remove this to check while the pump is operating.... Quote Link to comment Share on other sites More sharing options...
RobPearce Posted June 21, 2019 Share Posted June 21, 2019 With the orientation of the Stag carbs I think the float chamber overflow ends up higher than the venturi, so it probably overflows into the manifold. Quote Link to comment Share on other sites More sharing options...
glang Posted June 21, 2019 Share Posted June 21, 2019 sounds like a strange design because if the overflow outlet is higher than the jet and the needle valve doesn't close fully fuel is going to pour out of the jet into the intake.... Quote Link to comment Share on other sites More sharing options...
nang Posted June 21, 2019 Share Posted June 21, 2019 Sorry for the misinformation. Being a 2500 person didn't realise about the SU''s. Tony. Quote Link to comment Share on other sites More sharing options...
mole42 Posted June 23, 2019 Share Posted June 23, 2019 If a Stag carburetter overflows (needle valve stuck, usually) the excess is routed through a pipe onto the nearside chasdsis rail, or the nearside exhaust pipe, which ever is nearer. This will cause the strong smell of petrol that you notice, and really needs fixing before the car sets on fire. Quote Link to comment Share on other sites More sharing options...
Hainsworth Posted June 24, 2019 Author Share Posted June 24, 2019 Thanks again for all the advice. I stripped the carbs at the weekend and did find the issue. With the air filter and intake elbows off. I turned the ignition on to pressure the fuel pump and I could see fuel being forced through the jets and into the manifold as described earlier in this thread. Stripping the carbs down to see what was going on I found that a former owner must of put the needle valves back in without a spacing washer for getting correct float height. Therefore, the float was extremely high and allowing fuel through the jet. I purchased new needle valves and set the float height per instructions using the spacers, re-tested it, and no fuel coming through any longer with just the ignition switched on. It runs an absolute treat now, and no wonder I was permanently running rich on idle .......... Quote Link to comment Share on other sites More sharing options...
glang Posted June 24, 2019 Share Posted June 24, 2019 result and brilliant we were on the right track! Quote Link to comment Share on other sites More sharing options...
RobPearce Posted June 24, 2019 Share Posted June 24, 2019 Excellent news! Really glad we were able to help. Quote Link to comment Share on other sites More sharing options...
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