Resurrecting a $900 1986 with 7.3idi swap. Fuel?

Greetings all, first post here.

Picked up a 1986 F-250 that had a 89 7.3idi swapped into it for $900. Been parked & not running for over a year. The story goes that the original 6.9idi died and a 89 7.3idi was swapped in. PO says it ran for a couple of weeks after the swap, but then it died and he parked it.


First things first, disable the glow plugs and find out if it starts on ether. Then figure out if it’s getting fuel.

[Tl;dr at the bottom]

Ok, so I disabled the glow plugs by pulling the electrical caps off and tucking away. Then I tried starting it using a generous spray of ether and reaching in the window to crank it over. Not happening - the truck turns over and spins like it isn’t registering that I’m spraying ether and it doesn’t look like there’s smoke coming out of the manifold pipes.

Then I cracked all of the injector cap to see if there’s fuel getting to the injectors. There wasn’t - I cranked the motor with all 8 lines loosened and not a drop of fuel was spraying out of the injector caps.

Then I checked the Schraeder valve at the fuel filter head, and fuel was spraying out of the valve when I cranked. So we know the fuel pickup/mechanical pump is getting fuel up to the fuel filter inlet side.

So far we’ve isolated the problem to be between the fuel filter/filter head, and the injector lines. It is possible the injector lines are blocked. It’s possible the injector pump needs servicing. It’s possible that the fuel filter is clogged. It’s possible that the fuel filter head is full of gunk and junk.

Its odd that the truck didn’t start on ether. It is possible that the engine has low compression and needs a compression check. My theory on why the truck doesn’t start using ether is because the ether doesn’t carry enough energy by itself to start the combustion, like when it can’t mix with diesel. each motor is particular and maybe this one is pickier than others when it comes to fueling.

I noticed that the intake manifold has a ton of mud and debris on the inside, so I think the intake should come off before that debris gets sucked inside.

It also looks like the glow plug controller at the back of the motor is completely absent


For now I’ve ordered a replacement fuel filter - the Napa one. I’ve also ordered a new Delphi fuel injector return line and refresh kit. Does anyone know if the Delphi comes with the Viton and not rubber O rings?








Tl;dr:

No fuel at injectors. Glow plug controller unhooked. Won’t start on ether. There is fuel at the shrader valve.

Welcome to the club. You're on the right track. Don't go overboard with the ether, just a little shot on the air filter will do.

Do a fresh fuel filter, the ether probably needs diesel with it to make it happen.

Jesus Freak said:

Welcome to the club. You're on the right track. Don't go overboard with the ether, just a little shot on the air filter will do.

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Thanks for the warm welcome, happy to be here. Seems like a good community

Jesus Freak said:

Do a fresh fuel filter, the ether probably needs diesel with it to make it happen.

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That’s what I was thinking. The NAPA filter should be here in the coming days.

In the mean time I have some reading to do with the 86 and 89 electrical diagrams and make heads of the wiring mess.

The voltage regulator is missing.

SkylabTech86IDI said:

That’s what I was thinking. The NAPA filter should be here in the coming days.

In the mean time I have some reading to do with the 86 and 89 electrical diagrams and make heads of the wiring mess.

The voltage regulator is missing.

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So the previous owner used the "solid state" system from the 88? I would have left it as it was with the old style, oh well. Post a picture of the alternator if you can. If the previous owner was that excited about putting in a different glow plug control he may have done a 3G alternator upgrade, that's a pretty common thing and it's internally regulated.

I would bypass the fuel tanks for now, run it out of a jar or bucket of some sort. The tanks may be full of garbage. Had that happen on a 1988 my old man and I picked up dirt cheap not running. New tanks and she ran just fine.

Your fuel filter head is off of a van, for what it's worth. The truck engine will have the fuel filter behind the alternator.

Nero said:

I would bypass the fuel tanks for now, run it out of a jar or bucket of some sort. The tanks may be full of garbage. Had that happen on a 1988 my old man and I picked up dirt cheap not running. New tanks and she ran just fine.

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I didn't want to burden you too much, but since Nero mentioned it, I'd drop the tanks and clean them out before I "depended" on the truck. I just did that to my tow truck before I started driving it and boy I tell you what, I don't have to wonder about my fuel system....... and that's a good thing with a diesel.

Jesus Freak said:

Your fuel filter head is off of a van, for what it's worth.

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Again for what it's worth, International also used that type of filter head.

Nero said:

I would bypass the fuel tanks for now, run it out of a jar or bucket of some sort. The tanks may be full of garbage. Had that happen on a 1988 my old man and I picked up dirt cheap not running. New tanks and she ran just fine.

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That’s a good plan. I went ahead and ran a clear hose fuel line from a diesel can and it hooks up to the steel line that wraps around the back of the motor.

Jesus Freak said:

So the previous owner used the "solid state" system from the 88? I would have left it as it was with the old style, oh well. Post a picture of the alternator if you can. If the previous owner was that excited about putting in a different glow plug control he may have done a 3G alternator upgrade, that's a pretty common thing and it's internally regulated.

Click to expand...

Here’s a picture of the alternator, the existing wiring, and the missing voltage regulator and 2 relays on the passenger inner fender well.

Yeah, that's a regular alternator. The solenoid on the side wall is for the starter, the one above the tire is for the glow plugs. I thought it looked like you had the solid state controller but it looks like you have the old style glow plug system like is supposed to be there. It really sucks cleaning up wires!

It sure does. My electrical trouble shooting skills are a work in progress, but I have a multimeter.

Given that it’s still running the old style system, it sounds like I need to go get another voltage regulator and plug that in asap.

Is there a wiring schematic that I should be following to help make heads of what wire should go where and to know the expected voltage?

i know there’s diagrams in these Truck Manuals but I admit that I’m not sure how to read them or which one I should be reading.