If I crack #5 and #6 injector lines at the injectors the fuel dribbles out at idle. I swapped #5 and #6 in into #1 and #2 holes. #5 and #6 still low on pressure. Injectors are new and have been checked 3 times. The injectors popped off at 380-390. Stock would be 260. So I eliminated the injectors.

Pump was rebuilt last month and bench tested.

Truck has rough idle and performance up to 1400 rpms. Above 1400 rpms truck screams.

With my 80 HP injectors could they be causing a issue with the stock DV's? Do DV's goe out individualy? Do high horespower injectors always require new DV's?

And are the DV's the main component that control pressure??

My local cummins shop as narrowed the idle problem to the pump with compression check, blow by test and timing all checked out good.

New lift pump, over flow valve and rubber fuel lines.....

Thanks.....

Dave

Thanks...

 

First thing that comes to mind is the gasket thickness and possibly more than one gasket in the hole. A broken spring in the DV could cause it too. If the plungers in the pump are worn, the higher opening pressures would cause the fuel to wash past the plunger instead of pushing it out. The pressures you stated don't sound familiar, is that in Bar or PSI missing one zero?

 

Hemi the pressure readings are in BARS. My local cummins shop did the test on the injectors. I had heard that you have to match DV's with Injectors? Not sure the truth to that....

Whats involved to change out the DV's? And do you have to reset the timing after the DV's install? I figure it would be the cheapest route to check first....

Thanks.....

 

ALL YOU NEED IS A special SOCKET, TO OPEN THE TOP OF THE BARREL, YOU CAN GET IT FROM pierdiesel.com for about 30 or 35.00

a vice grip wont do it

 

Like 12valve said you need a special socket. No you dont have to reset the timing. Just pull your injector lines off and then pop off the dv housing. Depending what pump you have you might have copper washers in there that are supposidly not reusable. And as far as matching the dv's to the injectors, I have never heard of such a thing and can see no reason for doing so.

 

Ok, so let me ask this.... How many things in the pump would cause #5 and #6 lines at the injector to have very low pressure at idle? And remember above 1400 RPMS truck runs excellent.....

Also when I drive the truck on the freeway for five to ten minutes and exit the freeway the truck will idle a little better for awhile.

Would the injection pump shop notices any DV issues when the bench tested it??

Thanks.....

Dave

 

As far as why the pump is acting up I am not sure, but they would have noticed if you had a problem with you dv's. When I had a bad pump I didnt even realize it. I had a stuck plunger and barrel and didnt even notice it although I now know why my truck ran the way it did.

 

DV's should match up with the injector and the volume of the inj line (length x ID). The DV has some affect on the start of injection, larger DV's will flow more fuel, but the main job of the DV is to control the end of injection. The valve of the DV has a seat to seal the fuel between the inj and the plunger, and just below the seat is a sholder that goes inside the barrel of the DV. The larger the DV, the larger the sholder is. When the plunger starts to flow fuel, it lifts the valve upwards until the sholder is above the barrel and flows fuel under pressure to the injector. When the flow stops, the spring pushes the valve closed. When the sholder covers the barrel and continues downward to the seat, that volume of travel pulls back the fuel inside the line and injector to stop the injection at the exact time it is supposed to end. Larger DV's have a larger sholder which retract more fuel to accomodate larger injectors and larger lines. This is called the retraction volume. If the volume is too small, you will have after injections that will inject or dribble fuel into the combustion chamber after the burn process is mostly over. This creats smoke only and no power or economy. If the volume is too large, it will cause cavitation (air bubbles) and cause poor start of injection, poor spray patterns, and coke up the spray tips causing them to drip and finally injector failure. Hope this helps you understand the need for correct DV's.
The only way to check the DV's is to remove them for inspection. When you do, be VERY observant of how it comes apart. If you put it in backwards you will hear a pop when you first crank it and a dead miss when it starts. Then you remove the inj pump and take it in for a new plunger and rebuild. Also make sure you are very clean and coat all the parts with diesel fuel before assembly.
Another thing you should do is check the valve lash. Sometimes they will close up or loosen up and cause a loss of power.