2021 F550 Engine Problem
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1st Gear
Joined: Feb 2026
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2021 F550 Engine Problem
Hello everyone,
Got an issue with a 2021 F550 6.7. It started shutting off and was brought to the shop. When you tried to start it, it sounded like the starter was knocking and the batteries were low. It had codes for low oil pressure and cyl 5 glow plug. It had a rough idle, and then I noticed it had no boost pressure. We tore into it and changed the glow plug and injector in cyl 5. Replaced the turbo because it was locked up and cleaned all the piping. We went to start it, and it sounded like the batteries were low and the starter was bad. Replace both. Now, on most key turns, it just knocks like the starter. One out of 10 turns, it sounds like a screaming/whining sound. There are a few times it has started, idled roughly for a few seconds, and then shut off.
This is the only Ford we have in our fleet and was trying to get some ideas on where to start before we tear back into it or haul it to Ford. I have added some videos, but they are not the best.
Any advice would be greatly appreciated.
Got an issue with a 2021 F550 6.7. It started shutting off and was brought to the shop. When you tried to start it, it sounded like the starter was knocking and the batteries were low. It had codes for low oil pressure and cyl 5 glow plug. It had a rough idle, and then I noticed it had no boost pressure. We tore into it and changed the glow plug and injector in cyl 5. Replaced the turbo because it was locked up and cleaned all the piping. We went to start it, and it sounded like the batteries were low and the starter was bad. Replace both. Now, on most key turns, it just knocks like the starter. One out of 10 turns, it sounds like a screaming/whining sound. There are a few times it has started, idled roughly for a few seconds, and then shut off.
This is the only Ford we have in our fleet and was trying to get some ideas on where to start before we tear back into it or haul it to Ford. I have added some videos, but they are not the best.
Any advice would be greatly appreciated.
Mountain Pass
Joined: Aug 2025
Posts: 121
Likes: 64
Sounds expensive to me. Have had similar issues in the past with a bad starter on a tractor but that was just trouble starting it. Once started was good to go. With how rough that idle sounds im assuming something internal has gone bad. Especially with the low oil pressure coming on im expecting a bearing and its wanting to seize. Im no expert but just doesn't sound good to me and not sure what else it really could be. Only thing I've had issues before once with a bad ground to the starter also but id doubt it again with how rough the idle was and not wanting to run.
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