So I’ve had 100s of obs fords, but every one is a gasser, I just made a deal on a 6.9 bullnose, for 500$. Thing is it doesn’t start, now I have fixed a lot of issues on a lot of trucks so I’m confident in my ability, but never have I worked on a diesel this old. (86)
I guess it’s having a fuel issue from what the kid was saying but he doesn’t have much information on it. And when it comes to the diesels I’m clueless.

what I’m asking for is a quick paragraph explaining the functions of this motor, Is it mechanical fuel pump? What’s the injection system like? Relate it to a 12v because I’ve worked on 1 of them. I’m just looking to see what kind of headache I get myself into before I go shake kids hand.

I’m thinking I’ll use this truck to pull my travel trailer, it’s 4500lbs, 20ft long, and my current 351w barely tugs it along.

 

Welcome to the Forum, surprised no one answered you yet.

Well for $500 you can`t go too wrong, buy it.
You didn`t list where you live (state), it could be a pile of rust, or in good condition
body wise.
These IDI engines (6.9/7.3) are good dependable engines, they will always get you there.
They are not the fastest ones out there, compared to todays electronic Diesels.

The injection system is mechanical, as well as the Fuel Pump that has a lever going into
the engine to run it.
There is one wire that operates the Injection Pump to turn it on and off.
If the kid has a fuel issue, probably has air in the fuel lines and does not know how to
purge it. If he changed the spin on fuel filter and didn`t fill it first and just cranked on the
starter to fill it, he has air in the IP and hard lines to the Injectors.

There is a Shrader Valve on the filter head, push in the valve stem (looks like a tire valve)
while cranking over the engine to see if fuel spurts out. If not, the filter is low of fuel. If so
unscrew it and top it off with a bottle of ATF and replace it. ATF won`t hurt anything, the
engine will burn it ok.

Loosen some of the hard fuel lines at the Injectors, (5/8" wrench) to purge out the air. When
you see fuel start coming out when turning the engine over, tighten each one up. Just snug
them up.
You may have to top off the filter a time or 2.

If the Glow Plugs don`t come on, then you will have a problem starting the engine. The engine
will need the heat from the GP`s to start.
The GP Controller on the 83 - 86 6.9 is on the rear drivers side. They can fail, and as I have read
will fail and burn out the plugs . (I wired mine manual in my 86 with a toggle switch)
The GP Relay is behind the Pass side Battery on the flat part of the inner Fender. Listen to hear if
it clicks when the key is turned on. If not then the Controller is bad. You can jump the Relay, pull the
purple wire off the small post and use a jumper wire from Batt + to this small post. Just touch the post
about 8 seconds, (don`t screw on the wire) this should activate the plugs if they are good.

A way of testing the plugs, is use a test light. Pull the wires off each plug, connect test light to Batt+
and touch each plug on the top. If good light will come on.

The kid may have been using Starter Fluid, if so, make sure the GP`s are disconnected.

I bought my 86 with 192K, now up to 312K and have had it 7 yrs. Engine has run great for being NA,
except for usual stuff like WP, Alt, Starter, GP`s. Rebuilt the front end (king pins, tie rods, steering box,
Springs and Shocks) Drive Line, Clutch, Brakes, tires etc..... Hey it`s an old truck, neglected and
abused by prior owners.
Also it is a 4-spd and 3:55 Diff.
I an get 20 mpg out of her empty, loaded is another story. Depends on gear ratio, and manual or auto
trans and Diff.

The one you are looking at, expect to have to do some maintenance to be road worthy.
It will drag around your travel trailer, but don`t be in a hurry.



I know nothing about the Cummins engines except the 12V were also mechanical to about 93 or 96.
I test drove one when they first came out, thought I was in a rocket compared to my Datsun 720 KC.
Think that was in 1990.

Charlie