7.3 won't start; fuel problem?
 

I have an 89, F250, 7.3. I think it was running out of fuel on the front tank right after starting, although wasn't quite on Empty, and switched to rear tank, but ran rough, died and started hard...like it was loading up on fuel. Got it home, now will start, but dies right away, like no fuel. When I switch tanks now from front to rear, the fuel gauge doesn't change anymore. It just started doing that with the problem. I tried to tap on the fuel solenoid in front of the front fuel tank while a buddy switched the tank switch back and forth to see if it was stuck, but didn't hear anything. Any ideas???

Due to a problem with the fuel pickups in the tank breaking off at 1/4 tank you are lucky to get that low....... so yours may be ok in that respect.

You could have air in the injection system..... symptoms are it starts, then quits with a hard restart......

visit..... Ford diesel 6.9 7.3 IDI do the clear hose test. Any fuel leaks on the fuel filter or return line orings, actually anywhere on the fuel system.

If you can't hear it switching tanks I would start with fuses. You should put a few gallons in the other tank and run a pressure and volume test at the schrader valve.
If it starts for a few seconds and dies then hard to start but runs good when it finally starts it is usually in the return lines, if it continues to run bad and dies it is usually in the fuel delivery somewhere.

Cowboy another thought what is the temps where you are.

It's cold now, but was mild when the problem occurred, so ice in the line wasn't the problem. My first concern is why the fuel gauge doesn't change when I switch tanks. Where is the fuse(s) for the fuel system?

Earlier, the fuse for the auxiliary fuel tank was blown, but I had replaced it with no difference. Is there any other fuse besides the block to the left of the steering column? What would be the symptoms if the tank switch solenoid in front of the front fuel tank was bad? That's what I'm guessing, but would that also cause the fuel gauge not to change between tanks?

With KOEO you should be able to hear a faint ziiip when you change the fuel switch. If the tank switch solenoid is bad it won't change the gauge either. The fuse for the fuel switch is in the under dash box to the left of the steering column, I don't recall wich one it is. If the fuse is good and you can't hear the zip sound when you change the switch the tank change valve could be your problem. I was lucky enough to have 2 go bad on my 85 in about 3 months. When I got my first one from the Ford dealer the parts guy said that they had never sold one, the second one was warrenteed.

Funny Farmert when I was running my shop I changed countless ones on chevys but now that you mentioned it I can't remember changing one on a ford, and they are probably built in the same place. Different specs probably.

When is the last time you changed your fuel filter? If you sucked some crap up from the empty front tank, you may have plugged it up gunk and need to change out the filter before you destroy your lift pump. I don't usually hear anything when I switch tanks either, but then again the truck is usually running when I do that. As far as the fuel gauges, I have the same problem, but that's because both the senders in the tank are screwed, I can only tell when my rear tank is almost empty as the needle starts to bob around a little.

Oops... sorry delete.

I ordered a new fuel tank selector valve from Advance (first ordered one from AutoZone, but had the wrong terminal type, so returned it, then checked online at Advance, and looks like the same valve as AZ, but has a different terminal end to change on the wiring) but then checked the voltage at the switch and it's getting 12v, but unhooked the connector at the valve and don't get any voltage at any of the slots. Is there an inertia switch, relay, or another fuse between the dashboard tank switch and the valve on the frame? Don't want to go to expense of the valve, if that's not the problem. '89 f250, 7.3 diesel

Key on and power will be on position 2 or 3 depending on which way the tank switch is turned.

Read this post, it will answer many of your questions.
https://www.ford-trucks.com/forums/9...el-gauges.html

I plugged the new selector valve into the terminal and now the fuel gauges work, so I think the valve was the problem. Now I need to hook up the fuel lines to the valve, but the Ford lines don't hook up to the valve lines (new valve made by AC Delco). Directions say to cut the fuel lines and put gas tubing over line with clamp, but with plastic fuel lines, I'm afraid it won't hold. How do you connect the Ford lines to the new selector ports? Looks like the AC valve is the same as the Pollack valve I've heard of. Will gas tubing work for diesel fuel to connect to the valve. Does anybody carry adapters to connect Ford gasline ends to fuel hose (connect to Ford end with a barbed nipple to connect hose to)? Does the diesel have too much pressure at the valve for gas hose?

It is sucking there on the suction side not much pressure but my vote would be to get the correct valve as every splice you have is just another place to have air problems.

its all low pressure.
the IDI (InDirectly Injected) engine,just uses a low pressure fuel system from tanks to the IP pump.
simply strip back the outer layer on the stock lines.strip it back a good 4-6 inches,then your fuel line will slide right over it.then just clamp it.-dont over tighten,just enough to hold it good.
she wont leak.

if your worried about air intrusion,install an electric pump and put that old common IDI problem behind you.:D