1990 7.3 IDI will not stay running/IDI Down!

My IDI let me down today. She's stuck at the truck stop for the night but I need to get it going tomorrow somehow. I drove it to the truck stop about 2.5 miles from home after I cold started it and let it idle for about 10 minutes in about 40 degree weather to warm and it started and drove fine. I got to the truck stop and shut it down at the pump, filled up both tanks with fuel, checked the oil, and went inside and paid. I came back out let the glow plugs cycle and it started right up like normal, but when I was hooking up my aux cord to the stereo while idling it out of nowhere quit on me and wouldn't restart. It will start and run for a few seconds with the throttle to the floor but after that I have to wait a while before it will start at all again. There is some fuel around some of my return line caps. The return line to my filter housing is blocked off. Will a return line kit save my truck or are there other things I need to look at as well?

Thank you everybody in advance

did you purge the system of air with the schrader valve?

Yeah, the problem doesn't appear to be before the filter head. A previous owner had blocked off the return line to the filter head from the injectors.

IMO every IDI should have a fuel pressure gauge at the filter head.
it may a weak lift pump

sounds fuel related either as mentioned weak lift pump or air getting into the fuel system

Its definitely fuel related, looking like the lift pump or tank selector valve right now. Got it hooked up to a wrecker and home now, so the old girl is safe.

If you were going to put a fuel pressure gauge under the hood, would you put it between the filter and the ip? What kind of gauge and what kind of fitting would you need to adapt it into the hard line?


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On the filter head, remove the Schrader valve and put it there. Or tee in at that location.

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79jasper said:

On the filter head, remove the Schrader valve and put it there. Or tee in at that location.

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Click to expand...

your replace the schrader valve??
T into that badboy!
gotta have a way to purge when things go crazy!

Your filter head should have two ports you could tap into: the schrader valve and another just aft of it. Taping into the schrader valve port will give you pressure coming from the lift pump into the fuel filter. Taping into the other port, just aft of the schrader valve, will give you the pressure coming out of the fuel filter, the pressure going into the IP. To my way of thinking that is the more important pressure. If you have low pressure at that point, it's either a weak lift pump or a plugged fuel filter. Either one will give the symptoms you've described.

I have pictures on my other computer, my desktop, but I'm currently in Reno using the laptop. Maybe I can find them from a previous posting.



There, I found one which I had posted long ago. This picture shows the gauge tee'd into the schrader valve port. The other port is a bit further from the camera.

IDIoit said:

your replace the schrader valve??
T into that badboy!
gotta have a way to purge when things go crazy!

Click to expand...

Yeah lol that was more temporarily.

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With my turbo intake I don't have that kind of space, I'd need it to be much more compact


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Update for future reference. If your tank selector valve becomes stuck; turn your ignition on and start hitting the valve with a rubber mallet while flipping the switch on the dash back and forth. It may start properly functioning like mine did.

heres the "more compact" version

IDIoit said:

heres the "more compact" version

Click to expand...

Must have a hole in the hood?