Popping through intake on cylinder #2, 2014 F250

BrunoWilimek · February 5, 2018

Customer was driving when he heard a bang, then had no power. I did a relative compression test and found #2 cylinder was low. An actual compression test shows zero compression in cylinder #2 and popping heard through the air intake. Truck has been modified with a tuner, exhaust is straight pipe and has AFE air cleaner and ducting. EGR system is still in place. The glow plug came out OK and tip looks good. I drained the oil and fished through it with a magnet and found no metal. Truck has almost 300,000 km on it. I just replaced the low pressure fuel pump, secondary fuel filter and fuel pickup recently and removed an aftermarket inline fuel pump/filter/separator from ahead of the factory pump. The low fuel pressure warning message had been coming on for a year before that, until one day the owner killed the batteries trying to start it. He has an aftermarket oversize fuel tank as well as a bed mounted tank. The reason for the aftermarket fuel pump/filter/separator was that he was using his own special blend of bio-diesel in it. Has anyone run into an intake rocker problem on the 6.7? I am thinking if I go further, that I want to lift the cab to ease access to the head. What are your thoughts on that?

mchan68 · February 5, 2018

If it's popping through the intake, that leads me to believe the exhaust valves are not opening up on that cylinder. Removing the cab is probably the best approach.

forddieseldoctor · February 5, 2018

4 hours ago, mchan68 said:

If it's popping through the intake, that leads me to believe the exhaust valves are not opening up on that cylinder. Removing the cab is probably the best approach.

+1 for the exhaust valves not opening.

Keith Browning · February 6, 2018

Either exhaust or intake will do that. A damaged or stuck ipn intake will cause low compression and popping from the intake BUT exhaust valves not opening will cause a more severe pop noise from my experience.

Bruce Amacker · February 6, 2018

Bruno says it has zero physical compression, if the ex valves were stuck closed he'd still have compression. I'm thinking something more sinister, sounds like the rt VC is coming off for a look. Maybe a stuck/broken/bent intake valve? Put shop air into the GP hole? You'll probably still have to have the VC off to verify the valves are closed......

Other than that, I agree- if the ex valves are stuck closed it will pop back strongly into the intake manifold when the intakes open.

BrunoWilimek · February 6, 2018

Thanks for the replies. When time permits(shop very busy this week)I am going to remove the VC. Have to do it with only a partial cab lift as per service manager.

BrunoWilimek · February 7, 2018

Just got VC off. Several loose rocker arms, loose pushrods, low pushrods(1 inch gap to rocker arms), several rocker arms almost off their valves. Calling it for a complete engine at this point. Also found the rubber boot for the AFE air cleaner to engine duct was rotted at the flexible bellows, with a hole in it and gritty dirt inside next duct. This is the second AFE inlet boot that has had this issue. Don't know the root cause, but suspect the performance chip was at least partially at fault.

Edited February 7, 2018 by BrunoWilimek
More info added.

jw33 · February 7, 2018

Why only partial cab lift?

BrunoWilimek · February 14, 2018

Just got VC off. Several loose rocker arms, loose pushrods, low pushrods(1 inch gap to rocker arms), several pushrods almost off their valves. Calling it for a complete engine at this point.

On 2/7/2018 at 5:59 PM, jw33 said:

Why only partial cab lift?

Service manager wanted to avoid having truck in 2 pieces as customer stated he was going to put a Cummins in it if it needed a motor. He changed his mind, now have cab fully lifted and new motor here, just waiting for install kit that is back ordered til the cows come home. I did pull the head and found the cause, though. The roller lifters flat spotted on the cam and when clearances got too great, lost contact with the pushrods/rocker arms.