Not antique but close, 955K no fuel pressure

Check the bypass valve out first....if that isn't it you probably have a worn out transfer pump. Try low pressure air to the fuel tank to see if you can build some pressure for bleeding. Normal fuel pressure is 15 psi max. Check with a real gauge.

PS. Your 1968 model qualifies as "antique".....range is now up to 1970.

Excuse me,
what it is and where the bypass valve is found?:help:
Also my 1973 951c with the new filter ago this way!The engine start(not quickly even at 20°c, start good only hardly out) but the pressure gauge run at middle green at high rpm and in the limit yellow-green area at low rpm; at very low idle the gauge is at 3/4 yellow area.
😖orry:

On the 3304 the bypass is mounted in the lower RH corner of the fuel injection pump housing, right next to the transfer pump. Purpose is to limit the build up of fuel pressure from the gear type pump. Max pressure on these is 30 psi.

If by chance you have the D330, the bypass is on the bottom of the transfer pump, just behind the primary filter....Hex plug with long spring.

What do you intend for "RH"? Do you have some photos?
Can be the bypass valve to cause me this drawback?
Thank you very much!

Sorry, RH is right hand....when facing the fuel injection pumps.

The bypass/pressure relief valve can become troublesome if any foreign material gets stuck in the valve/seat. It's more common on units that didn't have a prefilter but should be checked if you are experiencing fuel pressure problems.

I can probably find a picture out of the service manual but I need to know whether your engine is the D330 or 3304 (43V,48V or 78P) engine.

Mybe you need to just pull the throttle back all the way to trip the shut off then push forward and start.

Hi Team,
about this era Cat put a oil pressure retracted rack limiter on their engines. This means you can not get full fuel rack for easier starting in really cold weather until the engines has been cranked long enough to build up oil pressure to retract the limiter piston.
Also as "zip" said you sometimes need to really pull the governor lever back to get past the stop detent to the fuel rack on position. Sometimes you need to push the lever to shut-off then pull it to the on position after the oil pressure has built up and whilst still cranking so as to allow the limiter piston to unjam from against the governor mechanism and then move back to the retract position to get the rack to full fuel.
Sometimes the rack can stick if there is water in the fuel and the engine has not been started for a long time, especially if you are not getting past the limiter position as the limiter only allows enough governor spring tension to be energised get to about a fast low idle until it retracts.
We used to encounter this on first starts after a rebuild on the Dynomometer at The Dealers, we always pressure pre-lubed, from a seperate reserviour, the engine lube system before the first start to charge the system and reduce cranking time.
Usually as long as the fuel system is primed--no air--the fuel injection pump will pick up fuel to get a start, you really only need good fuel pressure to get maximum power from the engine.
Hope this helps.
Cheers,
Eddie B.

Hi!!Thanks for answers!
what do you intend for "Rack"?Excuse me but I don't know well the English....
Old Magnet my engine is a 3304 pc 48v series!

A rack is a bar with gear teeth cut in it so it can make other round gears turn when pushed or pulled. The plungers in your fuel pump have gears on them and the governor is connected to the rack to increase or decrease the amount of fuel injected into the cylinders to match the power needed.
Later Bob