Ok I found out my injection pump is not out. so they say. [undecided] but they said that the governors in the pump are letting the fuel pressure get to high and blow the seals out of the pump ??? They figure just rebuild the pump but if its only the gov. then why can't that just be rebuilt? &gt;<br>DM01

 

There is an orifice in the pump that is calibrated to determine the internal pressure vs. rpm. It is possible that this is clogged, and keeping fuel from venting from the pump through the return line.<br><br>However, other than allowing the enigne to over-speed, there is nothing in the governor assembly that could be causing the internal pump pressure to get too high. I might try a different shop.<br><br>How did they determine that the internal pump pressure is too high?

 

thats the whole thing they sent it off to Cummins of Cincinnati and they said the pump was putting out too much pressure. I wish I had the time to take the pump to another place. I need the truck back.<br>DM01

 

Well, I'll make an honest effort to help here...then, when I'm done, I'll apologize for complicating things....

The low pressure stage or vane-type supply side pump draws fuel from the tank (lift pump in our case). It delivers a virtually constant flow of fuel per revolution to the interior of the injection pump. A pressure control valve is fitted to ensure that a defined injection pump interior pressure is maintained as a function of supply pump speed.
Using this valve, it is possible to set a defined pressure for a given speed. The pump's interior pressure then increases in proportion to the speed ( the higher the pump speed the higher the pump interior pressure). Some of the fuel flows through the pressure regulating valve and returns to the suction side. Some fuel also flows THROUGH the overflow restriction (return) and back to the fuel tank in order to provide cooling (our pumps are entirely cooled by diesel fuel ONLY) and self-venting for the inj. pump.
The high pressure side of the pump MUST have continual/uninterrupted supply of fuel with NO vapour bubbles.

** Pressure control valve**... is a spring loaded spool-type valve with which the pumps internal pressure can be varied as a function of the quantity of fuel being delivered. IF THE PRESSURE INCREASES BEHOND A GIVEN VALUE, THE VALVE OPENS THE RETURN PASSAGE (overflow restriction or fuel return) SO THAT THE FUEL CAN FLOW BACK TO THE SUPPLY PUMP'S SUCTION SIDE. If the pressure is too low, it closes the return passage. The springs initial tension can be adjusted to set athe valve opening pressure.***
maybe a problem here???? should be fixable.

***High pressure stage*** ... the pump &quot;plunger&quot; is responsible for supplying the high pressure fuel to the delivery valves and subsequently the fuel lines to each cylinder.
The control collar which rides on/around the plunger determines the the effective stroke of the plunger. It does this by opening and/or closing a relief passage during the plunger stroke. If load is constant or increasing, and the RPM warrant it, the plunger maintains high/max fueling/pressure until load or RPM trigger the governor to kick in and reduce the fuel supply pressure and volume.
As a side note here.... for those of us who have changed the governor spring itself, a bench test would likely result in diagnosing internal pressure problems unless the shop knew of our intentional modification.
One of the things that can make a difference in the internal pressure of the pump (supply side) is the KSB solenoid. When this is activated it literally doubles the internal pressure from roughly 4 bar to 8 bar (1 bar =14.7psi +- ).
Remember, the pressure of the supply side has a direct impact on the pressure in the &quot;head&quot; or high pressure side based on RPM's.. right...
One of the more common problems with our pump is the small plate and o-ring seal on the lower back side of the pump. If pressure is raised to high, or for too long the plate/o-ring fail and fuel leaks.

So, you've got the control valve setting on the supply side as a possibility, the governor circuit eg: counter weights, plunger, control collar, KSB shut off of return fuel that raises the internal pressure from 4 to 8 bar, possibly a sticky or sticking delivery valve(s), plugged return or overflow restriction, and probably some others I have missed....

Ok, this is were the apology come in ..... I got a headache now...
BTW a good shop can fix these things in house unless it's going back under warranty.

Bob.

 

Wow I feel smarted already : thanks for all that you need a beer? I do. well the pump is on its way to Daves Diesel in Muncie IN tomarrow. He seems to think he can fix it cheaper than a rebuilt pump. Thanks guys <br>DM01