I posted previoulsy about my 86' F-250 6.9L which had a hard start even after I installed new glow plugs. Then someone recommended that it might be the glow plug controller, and a switch is a good alternative to a new controller. Well, I tested the switch before I wen and drilled holes in my dash. The swithc didn't work I left the toggle on for about 6-8 seconds at first and then almost 30 at the end and, still it didn't start, not even a cough. So I talked to a diesel mechanic, and he said that it sounds to him like it is either the injector pump, or a fuel leak somewhere between the gas tank and the injector pump. He said to try the injector pump, simply runa dummy line from a gallon of diesel fuel to the injector pump with some plastic tubing, and then if the engine starts, you know that the leak is somewhere between the gas tank and the injector pump, but the fuel pump pumps the fuel at high pressure to the injector pump, so how would this work? Or does the fuel pump pump the fuel to the injector pump at low pressure? Help!

 

there should be a way to rig a fuel pressure gauge to the injector rail and get what you want from that. Seems a bit odd to have to rig up a fuel IV that way.

 

What the mechanic told you is correct. By connecting a gallon of diesel to the injector pump and GRAVITY ( the gallon can above the level of the injector pump ) feeding the diesel you eliminate all problems downstream. And yes the fuel lift pump supplies diesel to the injector pump, thru the filter, at low pressure-I think at about 5psi. You can test this by fitting a pressure guage to the valve outlet on the filter body and cranking the engine. Should read about 5psi. If you gravity feed the pump make shure the diesel is perfectly clean and crack open one of the injector diesel lines to bleed air out of the system as you crank.

 

How much fuel is in the fuel tank your using, if it is below 1/3 full then connect a line from a small diesel fuel can to the lift pump inlet (RH side of the engine below filter). Crank engine for 15 seconds, bleeding the filter Schrader valve while cranking. When the filter is full go for a start, if you suspect a GP problem plug the block heater in for an hour or 2 then attempt a start.

You can test the lift pump.........

Do pressure and flow test on the fuel pump at the Schrader valve on the filter (FSS- fuel shutoff solenoid disconnected). Remove the tire valve core and hook a hose and pressure guage on it should see 4-6 psi when cranking. Then do a fuel quantity test same place, should see 1/3 pint in 10 seconds of engine cranking, route fuel to a suitable container with a hose.