I have a 91 f-250 w/ 7.3 diesel. It has fuel to the inlet of the injector pump, but no fuel will come out of the pump on the injector side even with all of the injector lines disconnected. With power on I have voltage at all electrical connections. Do I need to replace the injector pump, or is there a filter built into the inlet pressure regulator that could be plugged?

you may have a fuel tank strainer some sort of filter which filters the fuel coming out of the tank
not fuel filter more of a strainer type
see with your manufacture

See id it is actually pumping fuel and if so see if the glow plugs are getting hot.

Maybe it causes by the following problems:

Fuel System Failure

1. Air in the fuel system
This is a common problem that a diesel generator fails to start normally.
Solution: Check whether the fuel oil pipe connector is loose or not, and ensure that the air is cleared from the fuel system. Loosen the bleed screw bolt on the diesel filter, and then use the manual oil pump to pump the fuel until the air bubble is gone.
2. Fuel Line Obstruction
Solution: Check whether the pipeline is smooth or not.
3. Fuel Filter Clogging
Solution: Clean the filter or replace the filter element
4. The Handle Position of Fuel Injection Pump Is Not Correct
Solution: The handle position should be pushed to no-load when starting the diesel generator set. Rotation speed is about 700-900r/min.
5. Fuel Injector Problem - Little fuel injection or fuel injection is not atomized
Solution: Remove the fuel injector, connect it to the high pressure oil pump, pry the fuel injection pump plunger spring and observe the spray condition. If necessary, wash the injection pump.
6. Oil Supply Problem - Oil transfer pump doesn't supply oil or the oil supply is brokenly.
Solution: Check whether the oil inlet pipe is leaked or not and the filter screen on the oil inlet pipe connector is blocked or not.
More information at article.
https://www.dieselgeneratortech.com/diesel-generators/why-diesel-generator-fail-to-start.html

if its an early 02 then it would be the fuel return valve that you want to change and they're pricey. If its a late 02 then it could be an injector stop ball issue and that's even pricier. so figure out if you have common rail injection or vp44 pump with lines from the pump to the injectors

Here is some reasons and solutions for diesel generator fail to start:
1. There is air in the fuel systems
Check if the fuel line connection is loose and remove air from the fuel system. First unscrew the exhaust screws on the injection pump and the fuel filter and pump the oil with the hand pump until there are no bubbles in the spilled fuel. After, tighten the exhaust screw. Pump oil again, when there is return oil in the tubing, then tighten the hand pump. Loosen the nut of the high pressure tubing at one end of the injector, pry high injection pump plunger spring seat, when there is no bubble in the fuel out of the nozzle, spin the nut, then pry a few more times, so that each cylinder injector is filled with fuel.
2. The fuel line is blocked. Check if the pipeline is unimpeded.
3. Fuel filter block. Clean filter or replace filter.
4. Oil pump does not supply oil or intermittent oil supply. Check that the inlet pipe is leaking, and that the filter screen on the inlet joint is blocked. If no oil is supplied after removal, the intake pipe and oil pump shall be inspected.
More reasons and solutions, please see at:
https://www.dieselgeneratortech.com/generator-sets/Why-My-Diesel-Generator-Set-Fail-to-Start.html

The injector pump on your diesel will only dribble fuel when the starter is the only thing turning the engine. things to check:
1) make sure that there is fuel pressure at the fiter. Have someone turn the starter on and at the same time, push the Schrader valve ( looks like a bike tire valve). If there is pressure, the fuel will spurt out. NO pressure, probably the fuel pump has gone out. If there IS FUEL PRESSURE

2) make sure the fuel shut off solenoid (FSS) is working. It is the electrical connection on the top of the Injector pump on the drivers side in the front. With the key on you should be able to hear a "click" when you disconnect and then reconnect. There isn't a filter in the supply line from the filter to the IP.

I own a 1994 F350 with the same engine you have. These engines are very basic and easy to work on. Just post up a reply of what you find. If you need, I can paste the full fuel pump test. At this point let's not blame the IP yet.

crack on of the injector pipes and see if its got fuel coming up ,if no fuel then either no diesel in tank or the transfer pump has packed up and this year has the lift pump built into the pump so fitting a non return valve on the inlet and return sides will help if the valves in the pump are weak ,as close to the pump as possible does the trick ,also check for a perished or porous pipe on the inlet side of the pump ,look at the top of the fuel tank especially as this is the most obvious place they go as its not seen very often ,whatever the problem is its because its drawing in air

Hi,

if the diesel does not start on the starter mtr, are you tow-starting it?
There are a couple of other bits of info required. I say that, because if the engine isn't turning over fast enough on the str mtr then it will not start. If it has got the cranking speed, then the injector pump isn't getting enough fuel to pump to the injectors.

However, that theory is null and void if the engine fires with a 'bump / tow' start

QUICK INITIAL TEST:

Remove the cap from the fuel tank.
Slacken the OUTLET fuel pipe union on the Fuel Lift Pump.If unsure trace the fuel inlet pipe back from the fuel injection pump.

Have a helper crank the engine and check for fuel coming from the slackened union.

No fuel or little fuel? Problem between fuel tank and lift pump, or Lift pump is faulty.

Check fuel supply pre-filter for trash etc. Also check vent hole in the fuel tank cap, it must be clear. If no vent in fuel cap, check tank and ensure that if a vent is fitted that it is CLEAR of any obstructions.

Have you checked the throttle position on the start sequence?

What diesel engine is in the vehicle? It should have a 'lift' pump to bring the fuel from the tank to the injection pump.If the 'lift' pump is not working correctly, or if there is an air leak between the fuel tank and the 'lift' pump then it will not be pulling sufficent fuel from the tank to the injection pump. The injection pump merely compresses the fuel and sends it to the injectors. If the vehicle was allowed to run out of fuel, was refilled and then will not start when cranking, you may have air in the injection pump.

Do you know the difference between a DPA injection pump and an inline injection pump? DPA pump works like a distributor in a gas engine. They are also notoriously fickle as regards fuel requirements / supply.

As you are in a somewhat remote location I would advise you to get a length of hose, suitable for transferring diesel from a 1 gal container to the engine. Locate the fuel "lift' pump and slacken the pipe union on the outlet side, (the feed to the injector pump") Go to the primary fuel filterand slacken the inlet fuel pipe union, but do NOT remove the pipe from the primary filter .. Remove the pipe from the LIFT pump outlet, and be careful with it. Depending on the type of union, you can either slide an end of the length of hose which you have on hand, over the pipe end and clamp it with a screw type hose clamp, (Jubilee type). As you have already slackened the fuel pipe at the primary fuel filter. Move the fuel inlet pipe at the lift pump, with now attached hose untill it is clear of local obstructions.

Now, using a funnel, or whatever, pour a cup or two of diesel into the hose from the LIFT pump end. Secure the hose in a high vertical position, (use the bonnet / hood and a piece of sash cord / mechanic's style wire). Go to the inlet fuel pipe at the primary fuel filter and check id fuel is coming out of the union which you had slackened. If fuel is apparent, secure the union.

Now, the usual way to do the next step is with a helper, it makes it a lot easier. It also depends upon whether you have a DPA type injection pump or an inline.

If you have a DPA pump, (identified by the fact that all the injector lines are situated around the body of the pump at one end, hence the Distributor Pump Assy name.) then you will have to bleed the pump assembly. There are normally TWO bleed screws on the unit if it is of CAV origin. One is normally located on the front side of the pump casing quite evidently visible. It is small, I think 3/16 wrench, or the metric equivalent. However, there is a smaller bleed screw on the pump casing usually located on the engine block side..

That is the one which people tend to miss, and end up having great difficulty in bleeding the pump correctly.

If you cannot find the smaller bleed screw, do not despair. Open the FRONT bleed screw and instruct your helper to start feeding diesel fuel down the hose. Do NOT remove the bleed screw completely to speed up the bleeding process. You will find, as a lot of people have, that you will drop it, and have a hard job finding it, as it seems to be reluctant to fit back into the threaded hole it came from!

Plus if you just slack it, you will not run the risk of cross-threading it when you try to re-fit it.

Ok, have a gallon jug or similar, securely sitting on the wing / mudguard /fender filled with diesel on the lift pump side where you have secured your hose.Ensure that the hose fitted to the fuel line to the main fuel filters and hence to the injector pump is fully primed and then place it into the gallon jug of fuel on the fender /mudguard etc.
Get your assistant to crank the engine, and it should start. You now know that the lift pump / line tfrom fuel tank to lift pump is definetly faulty.

You might well check the fuel line Pre-filter which is normally situated between the fuel tank and the lift pump. If it's full of sediment, it will not allow free flow of fuel. Likewise check the main fuel filters for blockage, plus check a fuel /water separator if fitted.

Is the engine fitted with heater / glow plugs? If it is, and they are not working, the engine will not start even on a warm day. Check the wiring to them etc. There should be an indicator in the cab to show if they are on or not.

If they do not work, and you have checked them with a meter etc, Disconnect the wiring to them. Get a can of Diesel start, which consists primarily of ether and have your helper crank the engine. Whilst the engine is cranking, spray a SMALL amount of the starting fluid into the main air cleaner. If the engine starts, well and good. If you do not have starting fluid, spray a little WD40 onto a piece of rag and hold it in the main
air inlet cleaner. If all is well the engine will fire up. Do NOT use gasoline / petrol, as a starting aid, the engine may very well give a very large bang and self distruct!! Do not jam the rag into the air inlets the engine will ingest it and you will have a BIG problem. Do all the above AT the MAIN air cleaner.

Checking for fuel at the injectors entails SLOWLY slackening the injector farthest from the injection pump, whilst someone cranks the engine. The injector must be tightened when the fuel is under pressure, other wise air will be sucked in and that cylinder may well have a "miss'. just a reminder::))

Last but not least! Check the DPA pump and ascertain which type of stop control is fitted. Some have an electric solenoid so check the wiring to it and ensure that it has a full operating stroke. Disconnecting the wiring to the off /on solenoid when the engine is stopped, then, turning the ign on and touching the wire to the connector on the pump should result in an audible click. Some of those DPA pumps on / off solenoids work in reverse. The power is applied to the solenoid when the engine shutdown switch is activated. Through a relay operated by engine oil pressure, the power is held to the solenoid long enough to shut the engine down. With the engine shut down, oil pressure drops and the relay is opened and power is disconnected from the solenoid. Likewise check if it is a mechanical off/on cable operated lever. if it has worked loose etc, then it will hold the "no fuel' position when trying to start.

I hope this gives you something to work with. Before closing, are you aware that you could rig a 12V auto gasoline pump to supply fuel to either the lift pump or the main fuel filters if you find that the lift pump is indeed faulty but that obtaining a replacement locally may prove to be difficult. If you do fit a 12 V auto gas pump to the fuel system, you will be able to bleed the entire system at the DPA injection pump as the 12V pump will push the fuel all the way through the system. A word of warning on that issue, make sure the fuel return line from the DPA injection pump can handle the flow from the 12V gas pump. if not then you will have to fit a pressure reducer in the outlet side of the 12V pump. they are sold in auto stores, and some pumps actually have them fitted.

This is NOT good! You can try bleeding the fuel system first. More than likely, air is trapped in the fuel lines, injector, and injector lines. Bleed at the fuel pump, (On the fuel pump to injector pump side), then the injector pump, then each line.

(You have to loosen the fitting to each line to each part, then when the air is bled out, and fuel comes through steadily, close it)

I also suggest an attorney to resolve the problem, as there may be damage. Pistons could have holes in them. Do a compression check.

Usually diesel's have 16:1 ratio compression. Today's gasoline engines have anywhere from 8:1, to 8.5:1, to maybe 9.0:1, (Maybe)

I'm willing to bet though, that you just have air in the system, and it needs to be fully bled out.
There is NO half stepping on this!
You have to start at the source, loosen each fitting, bleed the air out, and continue on down the line.

You said you have fuel flowing from the inlet line of the injection pump? But not at the injector lines?