I found a 1984 F250 with the 6.9L IDI diesel for sale at $650. The seller says it was running fine until it suddenly died on the road. He suspects a solenoid issue, but I want to be sure before pulling the trigger.
I own a pressure washing company, so a 3/4-ton diesel could be useful for carrying large amounts of water. If I don’t use it for work, I’d like to build a rig (maybe for junk hauling) or flip it for a profit.
The truck doesn’t come with a topper, and I’m aware of potential odometer rollback issues with the 5-digit display.
What should I check before buying? Could this be a simple fix, or am I looking at a bigger issue?
Be careful with the 5-digit odometer. My old man sold his with 420k miles, and I saw it listed later with ‘280k miles.’ If it’s in NW Ohio, I’d be suspicious.
Merlin said:
Be careful with the 5-digit odometer. My old man sold his with 420k miles, and I saw it listed later with ‘280k miles.’ If it’s in NW Ohio, I’d be suspicious.
Not in Ohio, and no topper. But yeah, I’ll keep that in mind when checking the odometer history.
@Hollis
6.9L IDIs are all mechanical, so the only solenoid involved in shutting the truck off is the fuel cutoff solenoid on the injection pump. If it lost power or failed, the engine won’t run. Other possibilities:
Clogged fuel filter
Injection pump failure (rare but possible)
Air intrusion in the fuel system
Quick checks before buying:
Have someone turn the key while you put a finger on the fuel cutoff solenoid. You should feel a ‘click.’
Crack the fuel line on injector #1 and crank the engine. If no fuel comes out, the injection pump isn’t working.
Check the fuel filter and look for air bubbles in the lines.
If all of that checks out and it still won’t start, it could be low compression, which is a bigger issue.
Kiran said: @Darcy
That’s super helpful. I’ll try those before deciding. If I see bubbles in the fuel, does that mean there’s a loose connection somewhere?
Yep. If someone recently worked on the fuel system, a line could be loose or cracked. The engine-driven fuel pump on the passenger side should be pulling diesel, not air.
Check the fuel pump’s output by loosening the outlet line—if no fuel comes out, you’ve got a supply issue. If fuel does come out but nothing reaches the injectors, it’s likely the injection pump.
I’ve had two 6.9 IDIs. They’re reliable but slow as hell without a turbo. I used to tow with one and it was painful. I upgraded to a 7.3 Powerstroke and it was night and day.
But if you’re just hauling water tanks and not in a rush, it’s a solid engine. Just be prepared for some frustration if you’re used to modern diesels.