My oil pressure gauge maxes off the dial when I start the engine or it revs past idle. After a good run it reads around 2.5-3 bar when idling but as soon as i accelerate it jumps off the dial 5 bar + Do you think is something electronic like faulty earth or could the engine need some breathing Engine is 1776 deep sump twin 40 dels mildish cam stock heads electric fuel pump The mechanical fuel pump cover has a breather port in it should I run a tube from that to the top of an air filter or a breather box. There is no breathers in the rocker covers. The oil pressure sender is a twin pin Any thoughts welcome
That’s an unbelievably high hot pressure at idle, I’d expect that pressure at high revs. Has this suddenly occurred, or has the engine always been like it? Oil pressure has nothing to do with breathing but tell us about the engine spec - oil pump size, so called HD relief valve springs, oil cooler, oil filter and of course oil grade.
Gauge/sender mismatch? When I've done 'em the wrong way round the gauge reads full until I start it, then reads zero. The oil light stays lit.
That’s a good question I think it’s a sender Dan Simpson put it in when he built the engine And yes previously it ran at around 2-3 bar The engine is full flow, standard oil cooler very rarely gets above 100c usually 95 on a long motorway run at 65-70 mph Seems to be running fine, I usually put in 20/50 mineral oil with the zinc additive as recommended by Dan I couldn’t tell you the oil pump size or relief valve springs Perhaps the senders gone faulty? if I vent the case through the fuel pump block off it’s not going to make any difference?
No the light goes off when the engine starts, occasionally after a long hot run the gauge will read about 1.8 bar at idle which I think is about right Also I don’t seem to be getting through more oil than normal so I don’t think the pressure relief valve is needing to be used
You need some venting/positive ventilation to get rid of hot crankcase fumes, otherwise the case may slowly pump itself up. The stock venting is fine. Venting things like rocker covers is just absurd. Folk just slap this stuff on because their mate told them to.
Also people with stroker counterbalanced cranks sometimes find the breathing can't keep up with the windage the occurs to to the rear pistons moving in opposite directions to the front ones, but adding more vent via the fuel pump pedestal doesn't help that, you need another vent at the gearbox end.
The crankcase must be vented and the standard vent is fine, but venting has nothing to do with oil pressure. Oil is pumped from the sump to the bearings and drains back to the sump. If you don’t vent the crankcase there will be oil leaks but not because of oil pressure.
If your engine has developed a sticky pressure relief plunger from the plunger vibrating a step in the side of its bore, extremely high cold start pressures may appear.. I actually saw 7 bar on my old engine on cold days or over 105psi... On that one the plunger was a git to get out as it had developed a lean and wedged so you had to straighten it up to get it out. At -5C it spat a hose off the oil cooler . Running.. way down to 0.3 bar hot idle .. old AS21 case, too loose bearings, needed align boring. New engine 34k miles from new is 4 bar cold start, 1 bar hot idle. Same 26mm pump moved over to new Autolinea aluminium case. However from the way all your gauge readings moved up together I would try another sender or use another simultaneous method of checking the oil pressure to compare it against. Or if the gauge has a voltage regulator inside that has popped so the meter is being fed from 12 volts instead of maybe 5 or 6 volts.. would double all the readings. Bike pump and creativity with some T pieces and an eBay 5 bar pressure gauge ? Or what does it read when the warning light comes on compared with the ??0.6bar warning light of a 2 pole sender.
