HELP!!!- I'm losing my mind!

[Highoctanefever]

My 7.3 idi ran great when it was cool outside. Ever since it's gotten warm it will start great but only idle for a min or 2 before it turns off. By turn off I mean no hesitation- it feels like I turned the key back to turn it off. Any ideas????

 

[icanfixall]

Welcome to the forum. Sounds like might be several different problems. Try this idea. Run a jumper wire from either battery positive directly to the large spade connector on top of the injection pump. Just squeeze the connector to remove it. Now you have power going to the injection pump shutoff solenoid and not going thru th ignition switch. Go ahead and start the engine and see if it continues running. If it does then you have a bad ignition switch. They are cheap and easy for most to replace too. No be aware the engine will not shut off when this jumper wire is connected. You have to pull it off the battery for the engine to stop running. If this does not fix it you probably have a fuel line sucking in air. Most of our fuel tank suction heads break off and then the last 1/4 tank of fuel can't be drawn out. So make sure you have more than 1/4 tank of fuel.

 

[Highoctanefever]

I tried the jumper wire with the same results. I also pulled the sending unit and replaced the broken shower head with a rubber hose and brass T, still same results. I have now replaced the fuel filter, all my O rings, acorns and all return tines (clear hose with no air in lines) with the same results.

 

[tbrumm]

If it is only shutting down when hot, it might be possible that the coil windings in the fuel shut off solenoid is "opening up" when hot and not keeping the solenoid lever engaged in the pump to keep the fuel "on". This is one of the less likely possibilities though. Very often these are symptoms of a bad ignition switch or short in the column harness. It doesn't sound like the pump is getting hot enough for a "heat soak" problem if it is shutting down within a couple of minutes of starting. Sounds more like an air intrusion problem as Gary stated above.

 

[Agnem]

To find out if the fuel shut off solenoid is your issue, carry a test light with you, and as soon as the truck shuts off, pull the wire off the IP, and connect your test light ground probe to the positive battery post, and then touch the test light to the contact on the IP. If the solenoid has opened, it will not light. It should light brightly and not be dim either. If that checks out OK, you may as well put the wire back on and verify you have power there, by grounding the test light and touching the IP contact to verify it lights as well.

 

[Highoctanefever]

Today I replaced the lift pump and found the previous owner had run the inlet rubber hose goofy so it would collapse and starve the motor of fuel. Runs like a flaming rabid cat now!

 

[OLDBULL8]

HELP!!!- I'm losing my mind!

Sure is nice when you find your mind. Ya, these old SUCK - SQUEEZE - BANG - BLOW can be a mystery at times,diagnostic patient is the key to success to keep/get them running. All they need is air and fuel.

Welcome to the OB. The greatest IDI info forum on web.

 

[icanfixall]

Glad you found the issue. After reading all of this I figured it was a fuel issue. Some so called mechanics should never be allowed to touch anything mechanical like our simple idi engines. Really not much this forum hasn't seen here either. If we didn't need electrical power to operate the fuel shutoff solenoid all we would need to start our diesel idi is fuel and air. then a down hill roll to bump start. A manual fuel shutoff will take care of the fuel solenoid too. many semi engines from the 60 and 70 era had them..