Ford 6.9 IDI sat for 25 years, 72k kms but has issues.

Also if I replace the lifters do I also have to replace the cam or is that only in flat tappet engines?

Only way to know if the cam needs replacing is by looking at the lifter roller. If it is froze or shows a flat spot. then the cam needs replacing. normally the cams are fine in these idi engines. In fact the same cam is in every 6.9 or 7.3 engine. Even the same cam in the turbo 7.3. At this time I have 4 cams here. Two are new oem cams with the gears and thrust plates installed. Thats how ford sold them. the other two are used spares. Ebay is full of them too. The early 6.9 had issues with lifters and ruined cams but that was fixed when they made needle bearing roller lifter.

Thank you! I did look at the lifters when I had the valley pan off they are the needle bearing type and they all seemed to be free without flat spots so it's probably not a cam. I added some seafoam to the oil today going to let it sit for a while and try to run it see if there's any improvement.

So I think I have it narrowed down to a lifter, rocker, spring, or valve on one cylinder. Is there any way to definitely tell which one it is?

The gushing oil points to the lifter. The oil feed is bypassing the lifter and going straight to the rocker without pumping the lifter up and uncovering the bleed off orifice.

Voodoo in a can might work, but there is a way cheaper method. A cup or two of kerosene in the oil will unstick a load of stuck parts. Add it to the oil, start the engine and let idle for 5 minutes. Revving is only asking for trouble, and it won't make anything unstick faster. Change oil and enjoy unstuck parts, or change oil and replace permanently stuck parts.

Thanks Knucklerdragger!

I added Seafoam earlier and changed the oil with no effect. I might try kerosene as well (it NEEDED a lot of oil changes, sitting 25 years had turned the oil to sludge).

A question about lifter diagnosis: I had the valve cover off and the gushing oil has stopped now, but when I put my thumb on the rocker attached to the lifter in question I felt like I could limit the travel of the rocker by pressing a bit. I am not sure if this is in fact what was happening or not, sometimes you imagine things because you want them to be true. Is there a more scientific way to test for a collapsed or soft lifter? I have a dial indicator on a magnetic base at my shop, I'm thinking I can measure the travel of the lifter in question and compare it to another to see if it is going as high? I'm not sure how feasible it is to read a dial indicator on a motor while it's running though. Anyone have any ideas?

Something I noticed too is the loud clapping through the intake is intermittent and seems to be somewhat of a pattern. It always seems to chuff out the intake and I'm not sure if that's normal or not, but every minute or so it will start making a louder clapping out the intake for 15 to 20 seconds that sounds like someone beating a drum or clapping their hand over the mouth of a cup. Could this be the lifter going through cycles, or the valve rotating through bad spots?

Thank you to everyone who has taken the time to read and reply!

The sound coming out the intake may be bad lifters or really worn valve guides. When guides wear badly sometimes the valves can't complete a seat on the valve seats. so it pops out the intake. It just depends on how the valve lands on the seat if it seals properly is what I saying. From the sound of this engine non care that the previous owner felt it could do without.

Cracked the injector from the suspect cylinder and it seems to be bleeding air non stop.
6.9 idi: https://youtu.be/HViU_5VwFa4

Is my IP possibly hooped?

On further investigation I cracked ALL the injectors and they all made a difference in engine RPM. I could not definitely find one that changed the intermittent intake popping though. All the rockers seem to be rocking with none that look to be too different. I'm stumped!

I have a spare injection pump I could swap in but I might be spinning my wheels.

I put a piece of clear hose before the last filter and I am getting no bubbles, my earlier suspicious were wrong.

changing IP wont tell you anything.

if its a bent valve, a leak down test will tell you instantly.

Thanks IDIoit! I've never done one before but I assume you just remove a GP, thread in a fitting along with a valve and pressure gauge and pressurize it to 80 or so PSI and shut it in? Listen for where the air escapes? Intake = intake valve, exhaust = exhaust valve, coolant = head gasket, anything else?

^^^^^ Crankcase = compression ring. Coolant may = cavitation.

If you've got sludge problems with the oil yet, a little Kerosene will do wonders in breaking it up and sending it through. Plus you'll help clean some internal components, free oil valleys of sludge, and generally clean things up. Just make sure you do a very good job of changing the oil afterwards and when you think you have things clean enough, a little Lucas Oil Stabilizer is wonderful in the oil.


And if you are still getting a steady stream of air to the injectors, you need to track down that area where you are getting the air intrusion.

opusd2 thank you! This is my third oil change, there was quite a bit of crud in it and it is still pretty black. At this point I might add some kerosene and try to clean up everything a tad bit better. I'm still researching it!

No air leaks, it was just an illusion I think. Checked again recently.

I am starting to suspect my lifters are not the problem but it's in my valves. I think from sitting so long it might be a bit corroded or gummed up. I am going to remove the valve springs and check for sticky valves and turn them while applying a bit of upward force and dribbling some clearner down the valve stem. Hopefully I can clean up any gunk that might be on the valve seat if there is any. That is my next project while I wait for a leak down tester (small town woes).

Thanks all for contributing to this thread!

Just a note about removing valve springs to test the seats as you say. Make sure the piston is at top dead center. If you drop a valve in a cylinder the head is coming off to get it back. At top dead center there is about 80 to 90 thousands clearance between the valve and the piston so it can't drop far. Just find a way to make sure the piston is up at the top.