My 86' 6.9 L won't pump fuel to the injectors, I just put another injector pump on it and I am having the same issue. There is fuel being pumped to the injector pump, but from there nothing. Any help???

 

Take the return line and fitting out of the top of the pump. I ran into this again and it seems that if you have a motor that is sucking any air at all and especially if the bleed line from the filter base to the return line on the motor isn't there they won't start well if at all after replacing a pump. I think what happens is that the fuel foams up in the pump housing and it can't create any hydraulic head pressure.

Take that line and fitting off and crank the motor and see if you are getting good return fuel flow. It may start now. I have ran into this twice in the past six months. Both times the problem has been the fuel tank selector valve. I think that the valves were letting air in the fuel for awhile and that the arreated fuel finally got the pumps.

Also make sure you are getting the right amount of fuel to the injection pump. I have seen 3 or 4 6.9's that had fuel volumn issues and found that the lobe that drives the fuel pump on the cam was half worn off. Then you either fix the cam or put an electric fuel pump on the truck.

 

I took that line and fitting off and cranked the motor and I was getting a trickle out of the return fuel flow. I did have to replace the mechanical low pressure pump with an electric pump before this, and it puts off about 6 psi. Is that not enought psi? Any help?

 

5 psi to 7 psi is enough pressure for the lift pump but i am not sure of the volume needed. make sure the electrical wires are on the right posts or the fuse isnt bad to the ignition on/off terminal. you should hear the injection pump clicking with the someone working the key on - off.

 

check the fuel filter some time and types will collapse frams will for sure

 

If this is an old pump where warranty wouldn't be an issue. Take the top off the pump. See if it will start. If it does fuel will just leak out in the valley pan and you have to kill the motor by hand in the pump but it won't hurt anyhting and you can eliminate alot of possible problems.

Also if the pump got alot of air in it it can take alot of cranking to get the hydraulic head on the pump purged to get injection fuel out to the nozzles.

 

also if you have a filter before the pump like the little gold screw into the pump well take this out and put another filter in place some type that has a see tru this is a lesson i had to learn the hard way i have a filter from checker it is just a see tru 50 micron screen i change the screen to a 20 and have Had real good luck

 

did you leave the injector lines loose at the injectors to purge the air while cranking it over