1974 280 M110 fuel pump (and oil pump?) drive gear not functioning

After purchasing and installing a new fuel pump, I discovered that the gear/shaft/eccentric that drives the fuel pump is not moving.

Currently I have the pump out and with the LF tire off, I can see into the hole and the part that drives the fuel pump is motionless when I'm cranking the engine.

I can't move it with my finger. I pulled the plugs and gently rotated the engine back a little bit and it did not move then either.

I fed gas directly to the carburetor and it will run.

I can't find any diagram in the factory service manual that mentions the fuel pump. I have found the distributor and oil pump drive diagrams, but don't see any mention of the fuel pump.

Just went out and cranked the engine over and it appears I have no oil pressure, but the distributor still turns.

Does anybody have any relevant BTDT?

Thanks,
Ed

[mbshop]

most likely the bushing on top of the drive gear is worn
and the drive gear slipped out. you'll see the cap on the bushing
on the left front side of the block.

george

[mbdoc]

The early M110 engines had drive gear failure & so MB modified those gears in 1976! The process for replacing thar "matched" set of drive gears will take a GOOD technician at least a DAY.

They do drive the oil pump & you also have no oil pressure!

Does this require the removal of the cylinder head?

I recall seeing in the service manual that the gear or at least the shaft comes out of the top of the cylinder block just next to the cylinder head, if you remove the intake manifild.

I'm trying to gauge whether I want to try to tackle this job myself or not.

Thanks.

[mbdoc]

The cyl head doesn't have to come off BUT the intake does. Also the a/c compressor must come off so that you can remove the chain tensioner. Very labor intensive!