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Hi all, I recently bought an 86 F-350 with the 6.9 IDI, and it has a ticking noise and blows white smoke out the exhaust. I suspect it's a stuck lifter but wondered what everyone here thinks.
I can't hear it very well from the engine bay but it's very noticable out the exhaust. Also I can hear it from under the truck but I wonder if that might be an exhaust leak. It gets louder, more like a knock, when I shift into drive (auto trans). Here's 2 videos that capture it pretty well.
I'm thinking of opening up the valve covers and running it to diagnose further. Assuming I can identify the problem lifter should I just replace the one or do them all while I'm in there?
I was told it has a new ip but the injectors are not new. Any chance it could be an injector? I'm going to replace them all in the near future anyway.
Any input is appreciated. The goal is to make it into a reliable daily driver for years to come so I don't mind putting some time and money into it.
Last edited by ac0xr; Mar 1, 2025 at 04:49 PM.
Reason: fix youtube links
What is your oil level at and how long since it was changed? Had a 86 6.9 and it would do that when the oil got to low. Yea it went through lots of oil and once in awhile I would forget to check it and it would start doing what yours is doing. Always carried a couple of gallons with me just for those times. It was a well wore out engine.
Check compression and while you have injectors out have them pop tested. Give you a pretty good starting spot and you will have a better idea how to proceed.
The white smoke is caused by unburnt fuel. Either the IP, injectors or both. If it were bad valve related, the smoke should be very blue, but I've not heard a bad injector sound just like that either. You can check for a bad injector a few ways; one is feel them once the truck is up to temp. A stuck one will be much hotter than the others. The hard line right on top of it will be way hotter. Another way is to use a large screwdriver and put the working end on the injector body and your ear on the handle. A good injector will have a clean, sharp "click" to it.
I think that ticking sound is valve noise, and if you didn’t have the pop-like noise from the exhaust I wouldn’t really worry about it- as it is 40 years old.
But since you have that pop-like noise at the tailpipe, you could loosen the fuel line at each injector one at a time and check the noise at the tailpipe (each time) to see if it changes the sound or removes the sound or the smoke, this might help you isolate the cylinder.
Thanks everyone for the replies. Oil level is good so I don't think it's that, I have not changed it since I bought it though. Compression test is a good idea, I'll do that.
Reading through your comments, my plan is to first to try to identify a bad injector by feeling for a hot injector/line, and listening with the screwdriver trick. If that works then I'll replace the injectors and ip. If I can identify a bad injector is there a reason to get them pop tested or is it best to just start over with new ones?
If that doesn't work I'll crack injector lines and if I can hear a difference then I'm assuming that would point to a valve train issue on that cylinder. I guess I could also swap injectors between the problem cylinder and another cylinder to double-check that it's not an injector issue. If it's not then I'll remove the valve cover and examine the lifters/push rods/rocker arms. Really hoping it's not a valve issue where I'd have to pull the head but I guess we'll see.
Hoping I'll get a chance to work on it this week, thanks again and I'll update the thread with my findings.
No, you'd just want to change all the injectors if mileage/age is unknown. Regardless as to the tick noise, the IP and or injectors is the cause for all the white smoke. When it comes time to replace them, don't try and skimp on the price. You'd be sorry. Those IP's sold online for hundreds less than most trusted sellers; there's a reason for that. Use a reputable local shop or a trusted online source.
No, you'd just want to change all the injectors if mileage/age is unknown. Regardless as to the tick noise, the IP and or injectors is the cause for all the white smoke. When it comes time to replace them, don't try and skimp on the price. You'd be sorry. Those IP's sold online for hundreds less than most trusted sellers; there's a reason for that. Use a reputable local shop or a trusted online source.
Thanks, yeah I'm planning on getting them from R&D IDI. I've heard a lot of good reviews for them.
I got a little time to mess with it today. I got it up to operating temp and listened to all the injectors with a screwdriver. It's a little hard to describe but some of them had a clean, sharp click sound while others were more muffled. None of the injector lines/top of the injectors were hot, some were maybe a little warmer than others.
Once it was warmed up the white smoke almost all went away. I did individually loosen the injector lines and engine RPM decreased with each one. None of them made a difference with the pop-like noise out the exhaust or the ticking sound from under the truck.
Also, once it was warmed up the knocking sound when in gear also went away.
I'll get the new pump and injectors ordered. Not sure what my next step is for diagnosing the valvetrain issue. I was really hoping cracking the injectors would help me isolate it to a specific cylinder.
The engine sounded pretty normal to me. But the exhaust pipe has a weird pop. Do you have any exhaust leaks?
Not that I'm aware of, but I didn't look too closely. I'll double check.
I got a chance to pull the valve covers today. Nothing really jumped out at me. The rocker pedestals on cylinder 7 seemed to have more oil/sludge around them then the other cylinders. Not much though.
I also cranked the engine from the solenoid (with the key off so it didn't have fuel) with the valve covers off, and everything seemed to be moving as it should.
I think my next steps will be compression and leak down tests.
I didn't test cylinder 8 as at that point I figured 7 was my issue and I don't know if I could've gotten the tester in the glowplug hole with the turbo on.
I then did a leakdown test on cylinder 7 and with 100psi in it's holding around 10psi and I can hear/feel it coming out the tailpipe so looks like it's an exhaust valve problem.
If you identified the noise coming from the exhaust during the cylinder leak down test you could always remove the heads and try to lap the valves and knurl the guides. Once the heads are off you MAW have them redone the right way though.
