Engine
Posted: 26 Jan 2005, 09:49
Sorry for replying in English. I read German very well. My writing is like many Fulvia's, a bit rusty.
Bad starting is often caused by bad and/or badly adjusted contact points assuming that coil, wiring, condenser etc are in order.
About the oil pressure.
First you have to make sure that the oil pressure sender is of the same make as the instrument. A Jaeger instrument with Veglia sender gives a reading which is much too low. Vice versa, a Veglia instrument with a Jaeger sender reads much too high.
Then make sure the water temperature is correct. The water temperature influences the viscosity of the oil and thus the pressure. The needle should just be above 70 degrees C.
Note that the oil reaches its normal temperature a few minutes later than the water.
The oil should be 15W40, mineral. I find Shell Helix to be very good. The oil filter should be MANN W940/1 or equivalent.
There is an overpressure valve which determines the maximum pressure. Whatever the rpm, this max pressure is never exceeded. It is at about 80-90 % of full scale. With a cold engine this maximum pressure is easily reached at medium rpm's. If not, you have a serious problem. If the needle goes to full scale, there is also something not in order.
The pressure depends on the rpm's as the oil pump is a Hobourn Eaton rotor pump driven by the crankshaft.
With the engine at normal operating temperature, a rule of thumb is that the pressure is about equal to the rpm's. This means if the rpm's is 3.000 (30 on the rpm counter) than the oil pressure should indicate 30psi.
Or 20 psi at 2.000 rpm.
If the oil pressure is much less, you should check if the waterpump is new. If it is new, the O ring on the shaft may be damaged or gone. The original waterpumps did not have O rings but a thicker shaft. Nevertheless a good idea to machine a groove and install an O ring.
If the oil pressure is still too low. You probably have excess wear on bearings. Most likely crankshaft main and / or big end bearings, but also bearings of camshafts, rocker shafts, waterpump drive wheel, fuel pump drive gear and auxiliary shaft should be checked. Also the chain oiler may have broken off.
It is possible to change the crankshaft bearings from the bottom after removing the sump. However, if the engine has run on oil of the 70's, you will have to clean the channels in the crankshaft. In those days the oil was very very very bad. Someone trying to sell that oil today will probably be put in jail. The channels in the crankshaft will be full of dirt. It is always a good idea to clean the crankshaft. The holes for the big ends are on the side and not where centrifugal force is highest. The crankshaft thus functions as a centrifugal filter and collects a lot of dirt.
Just changing the oil pump will hardly have an effect. If it is worn the rest of the engine will have much more wear.
Bad starting is often caused by bad and/or badly adjusted contact points assuming that coil, wiring, condenser etc are in order.
About the oil pressure.
First you have to make sure that the oil pressure sender is of the same make as the instrument. A Jaeger instrument with Veglia sender gives a reading which is much too low. Vice versa, a Veglia instrument with a Jaeger sender reads much too high.
Then make sure the water temperature is correct. The water temperature influences the viscosity of the oil and thus the pressure. The needle should just be above 70 degrees C.
Note that the oil reaches its normal temperature a few minutes later than the water.
The oil should be 15W40, mineral. I find Shell Helix to be very good. The oil filter should be MANN W940/1 or equivalent.
There is an overpressure valve which determines the maximum pressure. Whatever the rpm, this max pressure is never exceeded. It is at about 80-90 % of full scale. With a cold engine this maximum pressure is easily reached at medium rpm's. If not, you have a serious problem. If the needle goes to full scale, there is also something not in order.
The pressure depends on the rpm's as the oil pump is a Hobourn Eaton rotor pump driven by the crankshaft.
With the engine at normal operating temperature, a rule of thumb is that the pressure is about equal to the rpm's. This means if the rpm's is 3.000 (30 on the rpm counter) than the oil pressure should indicate 30psi.
Or 20 psi at 2.000 rpm.
If the oil pressure is much less, you should check if the waterpump is new. If it is new, the O ring on the shaft may be damaged or gone. The original waterpumps did not have O rings but a thicker shaft. Nevertheless a good idea to machine a groove and install an O ring.
If the oil pressure is still too low. You probably have excess wear on bearings. Most likely crankshaft main and / or big end bearings, but also bearings of camshafts, rocker shafts, waterpump drive wheel, fuel pump drive gear and auxiliary shaft should be checked. Also the chain oiler may have broken off.
It is possible to change the crankshaft bearings from the bottom after removing the sump. However, if the engine has run on oil of the 70's, you will have to clean the channels in the crankshaft. In those days the oil was very very very bad. Someone trying to sell that oil today will probably be put in jail. The channels in the crankshaft will be full of dirt. It is always a good idea to clean the crankshaft. The holes for the big ends are on the side and not where centrifugal force is highest. The crankshaft thus functions as a centrifugal filter and collects a lot of dirt.
Just changing the oil pump will hardly have an effect. If it is worn the rest of the engine will have much more wear.