[hairy_apple]

I bought a 1990 7.3 IDI about a month ago. It broke down three days after I bought it... driving home from work, it was like someone shut the key off. Just instantly dead. No sputtering, no power loss, nothing. No warning at all. Just off.

I thought I had run out of fuel at first, however I don't believe that is the case anymore. I have fuel coming as far as the injector pump, but don't seem to have fuel past that... at least not much. A small amount maybe, but not enough run or start. Not even close. I seem to lose pressure if it sits for a while after cranking, however I also have lines on and off trying to find where I have fuel to so I think that is most of the reason for that. I even went as far as to get an electric fuel pump and just run a line into a fuel gas and a rubber hose to differant parts to make sure I KNEW it had fuel moving through the lines.

Any ideas what else I can try? I know the lifter pump is working. I know the gas tanks are supplying fuel. I don't know much at all about the injector pump or how it works and I have no idea how to start testing it or how to check it. When I turn the key on, it buzzes and then clicks a few times. I don't remember it doing that before it broke down. I did take a voltage meter and check all the wires going to it DO have power with the ignition on.

It ran GREAT before that day. No issues at all. I really am starting to wonder if I made a big mistake buying this thing. Any one have any ideas what else I can do this weekend. I'm pretty much ready to break down and call a tow truck and take it to a shop next week.

 

[standbypowerguy]

Same thing happened to me the day I bought mine. I got that sinking feeling of "oh crap, what did I just get myself into?" A few hours of searching this forum and troubleshooting later, I learned that the truck had indeed run out of fuel because of a broken in-tank pickup assembly. This is a common problem with the these trucks, the crappy plastic parts become brittle over time, then break or fall apart. If your symptoms occurred with the level near 1/4 tank, my first bet would be a broken pickup. Google "hutch mod" for the fix. It's for a later truck, but works similarly on these early rigs.

Other possibilities include a clogged fuel filter, a failed lift pump or IP, but they are less likely than a broken pickup. The first thing I suggest is to switch tanks or add 5 gallons to the one you're on, then have a friend crank the engine while you bleed air from the shrader valve on the top of the fuel filter. While you're at it, check the lift pump volume once you see pure fuel. The pump should deliver at least 1/3 of a pint in 10 seconds of cranking.

BTW, don't crank the starter for more than 15 seconds without allowing a 2 minute rest between crank cycles. This approach allows the windings to cool and will keep you from burning up the starter.

If it doesn't start once you've got pure fuel at the shrader valve, try cracking a couple of injector line nuts, one each on the DS and PS, then crank again. This wil allow air to escape the IP quickly and the truck should fire on the other six cylinders. Once running, tighten up the loose line nuts. Don't worry too much about fuel seepage, it's minimal at idle and even less while cranking.

 

[hairy_apple]

I have about half a tank now in the front tank and about 5 gallons in the rear. The truck seems to have OK flow from the lift pump and out of the filter. I did not actually messure it, but it seemed like an OK amount out of the line, but when I tried to get fuel from the bleeder valve not so great. Lots of sputtering and air and never solid fuel.

Does the truck just shut off like that with an IP failure? I would have expected some kind of sputtering or it running bad or something else.

Sadly, it's pouring rain today and sounds like tomorrow is going to be worse, so I have to wait to mess with anything else. Any other ideas I can look into before I take it to a shop next week?

 

[cdnsarguy]

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

If there is a problem with the lift pump and you are changing it, ensure the new pump comes with instructions as to correct installation procedure if it is the newer model pump with the almost straight arm.

Check for power at the FSS (fuel shutoff solenoid) spade terminal.... key on...it is on the front drivers side of the IP. If you remove and replace the spade terminal, power on... you should hear a click.

 

[chuckster57]

I have fuel coming as far as the injector pump, but don't seem to have fuel past that... at least not much. A small amount maybe, but not enough run or start. Not even close

While your turning the engine over with the starter, if you have a line loose at an injector you not going to see much fuel at all.

I know the lifter pump is working

Are you sure?? did you do the flow and pressure test? If you search the IDI forum for "FUEL FLOW TEST" it will be spelled out for you.

but when I tried to get fuel from the bleeder valve not so great. Lots of sputtering and air and never solid fuel.

Sound like either the lift pump is not working, or you might have a supply line that is letting air into the system...Maybe a crack in the rubber line?

Does the truck just shut off like that with an IP failure?

yeah it would, but it would also just shut down when you turn off the fuel supply. that's how these engines get stopped. there is a fuel shut off solenoid in the top of the IP and when you turn the key off, fuel quits flowing and the whole shootin match shuts off. gotta remember that diesels need fuel to keep the cylinders hot and since it takes 400 PSI and heat to make the fuel go boom...

 

[rotaryboots]

I think you were talking about having power to the FSS on the IP, but if not, definitely check that. Typically when these trucks start to run out of fuel the engine stumbles a bit and then speeds up for a couple seconds, then dies. A failing IP doesn't usually die like this, once the IP is running, it usually keeps running. Its when they are hot, worn out, and the engine is turned off, that they don't develop enough pressure to run the engine again. I'm leaning toward something being wrong with the fss, but then again, you're saying you're getting fuel to the injectors...sort of. With that shraeder valve out, you should be getting a powerful stream of fuel out of it; if not, then keep looking from the filter back.

You mentioned getting an electric pump. Did you bypass the entire fuel system from before the fuel filter and try to run the engine that way? You might even wanna try hooking up the electric pump to a "jerry can", temp tank, (gas can) and then directly to the pump. That would eliminate the possibility of something being wrong before the IP.