420 C questions

[420C+VANBRUNT]

Have been working on 420C engine... New to me, aquired non running.. Have too low oil pressure! Gears in pump have play between teeth. Parts book shows both gears... Idler and drive drive gear and shaft shown as one piece. My pump drive gear is keyed to shaft. Is this original part or something someone has manufactured to repair pump? Gears fill cavity in pump but there is play between teeth! Thank you for any insight

 

[Jim.ME]

Here again, the Service manuals you have been told about before would answer these questions.

The pump shaft and pumping gear are not to be dissembled. You only remove the driven gear that mates to the camshaft gear. The parts book shows the pump shaft with the gear on it as one part and the idler gear as a separate part. The pump drive shaft and pumping gear will be one piece. and the idler gear that mates with it needs to be replaced as well. You may have trouble finding parts or even a complete good used pump.

The spec for between the teeth of the gears inside the pump is .0005"" to .002".

The spec for clearance between the gear faces and the lower cover is .002" to .006".

And there is a procedure for timing the oil pump gear to the camshaft so that the distributor is in the location it was originally. It will run if it is not timed by the procedure; but you will have to figure out where the plug wires belong and not just go by where any picture shows #1 plug wire as the distributor shaft has an offset tang drive that matches into an offset slot in the pump's gear which is driven from the camshaft gear.



edited to correct punctuation for .006"

 

[JOCCO]

Only other thing i can add is on that I would look for a replacement oil pump. Do check for a pressure relief or adjustment on engine. some 40/430 and maybe 44o parts will work too.

 

[Jim.ME]

Only other thing i can add is on that I would look for a replacement oil pump. Do check for a pressure relief or adjustment on engine. some 40/430 and maybe 44o parts will work too.

The pressure relief is in that pump as shown in the parts drawing. It is adjusted with shims behind the spring and was discussed in a previous thread about his oil pressure problem. It only limits maximum pump pressure not system pressure. Beyond wear in the pump causing low oil pressure, the system has a bypass filter that needs to have all the parts and be assembled correctly or pressure will be lost. Bad bearings, including camshaft bearings, are the other key areas where system oil pressure losses can occur in those engines.

 

[JOCCO]

The pressure relief is in that pump as shown in the parts drawing. It is adjusted with shims behind the spring and was discussed in a previous thread about his oil pressure problem. It only limits maximum pump pressure not system pressure. Beyond wear in the pump causing low oil pressure, the system has a bypass filter that needs to have all the parts and be assembled correctly or pressure will be lost. Bad bearings, including camshaft bearings, are the other key areas where system oil pressure losses can occur in those engines.

I was implying if he thought a pump was bad I would look for a replacement vs. rebuild/machining. Yes my next move was bearing issues. and one must keep in mind leaky pickup tubes or distribution tubes. It has been awhile since I been into the oil system on one of them. Also one must be on the look out for what someone ahead of him has done. IE tinkered with the oil pump.