Oil Pumps
Pumps that do not use front pickup tubes
Pumps that use front pickup tubes
Your Starion/Conquest service manuals never had the correct printed pages for the oil pump pickup tube except for the 83 Starion.
Here's the page you need to replace in all the 84-89 manuals:
BSEK
Different brands, different materials and shapes
You can cut out the openings yourself to expose all of the two cavities
Oil must pass under the gasket to flow in the relief on the pump backing plate. Any type of RTV/silicone or other sealant applied that could block either of these passages could lead to engine damage
The "L" shape cavity feeds oil to the cylinder head (through the block) and the chain tensioner (tiny hole) but it doesn't enter this cavity lined up with either exit opening, all the oil must flow in this cavity to the opposite end(s)
The "I" shape cavity feeds oil to the two oil pumps gears and continues on through one of those gears to the rear balance shaft bearing
This is what happens over time. The gasket falls into the oil path and the oil is divided and has to flow on each side of the gasket making increased resistance to the oil flow resulting in decreased volume to the pump gears but more importantly the rear balance shaft bearing.
This is the path all the oil to the head passes over.
This portion doesn't raise up but over time it does swell the gasket.
Mitsubishi knew about this problem and corrected the early gasket to include only a hole over the tensioner opening.
These are picture representations of that TSB:
http://www.b2600turbo.com/TSBs/26 pump chain1.jpg
http://www.b2600turbo.com/TSBs/26 pump chain2.jpg
http://www.b2600turbo.com/TSBs/26 pump chain5.jpg
Here's your lubrication path as shown in the B2600 service manual, the only difference is the pickup tube location
The relief valve opening pressure is 78psi@3000rpms. 78psi is all your pump has pressure regulated to and excessive rpms may result in excessive oil pressure.
Pressure relief valve passage
Relief valve has two exit holes
The "high" volume oil pump
This picture below is from the 1983 Tech. highlights manual. T/C is the turbocharged engine, N/A is normally aspirated. The 1983 trucks had thinner gears and a thinner front cover to house those gears but the total height including the chain gear shaft was the same. There were not different parts for the silent shaft drive guides for these two different pumps. In 1984 what could have been called a "low" volume pump was discontinued. Don't fall for the term "high" volume pump and pay more for it thinking you are getting something special. The output in volume and pressure from all the 1983 T/C pump and all pumps 1984 and up is the same. What did change was the location of the pickup tube so it went into the bottom of the front cover to make a shorter path rather than the backing plate after being drawn through a portion of the block from the bolt on type 1983 pick up tube.
This picture shows the thickness of a T/C pump gear to be 15mm rather than 11.5mm for the pre-1984 truck oil pumps.
Pump speed in rpms in regards to the discharge rate is twice engine rpms as the silent shafts turn at 2x engine rpms and the same chain drive gears also turn the oil pump.
Here are the two "high" volume oil pumps and the only difference is where the oil is drawn in and these are the only two pumps you have to choose from
Some problems addressed in the change of the oil pump were from some noise on start up and it was addressed in a TSB when they also added a short rubber stick to go inside the timing chain plunger spring to take up some space so the pump wouldn't have to fill that cavity with oil first even though they already made the new pickup tube to have a shorter path to draw the oil up from with sump with.
That TSB is here:
http://www.b2600turbo.com/images/tsb%2009-09-85%20pg1.jpg
http://www.b2600turbo.com/images/tsb%2009-09-85%20pg2.jpg
The 1983 style pickup tube is shown further up on this page in the TSB to replace the 84-89 service manual pages.
The same type steel gears that turn in this aluminum oil pump housing are also the same as the front bearing on the upper silent shaft and while some seem concerned that silent shafts fail simply because they turn at 2x engine rpms they don't seem to care at all that their oil pumps do. That type thinking would tell me those same people must believe that their oil pump is going to fail too -funny they don't isn't it?
The 2.0 liter engine addresses the oiling for the front bearing surfaces and the oil feed location change for the rear bearings on the silent shafts that the 2.6 didn't receive but this is a different topic. If interested those TSBs are here:
http://www.b2600turbo.com/TSBs/bs%20oil%20groove.jpg
http://www.b2600turbo.com/TSBs/20%20block%20chg.jpg
http://www.b2600turbo.com/TSBs/20%20oil%20pump%20chg1.jpg
http://www.b2600turbo.com/TSBs/20%20oil%20pump%20chg2.jpg
Part numbers, 1984-1989
md061314 driven gear
md061313 drive gear
md021563 relief plunger
md050299 relief spring
