'96 7.3 PSD- Complete Miss or Just Weak Injector?
#1
'96 7.3 PSD- Complete Miss or Just Weak Injector?
Hi, guys, first post here. Great forum, I've learned a whole lot in a few days.
Last week I bought my first diesel- '96 F-250 CC SB 5-spd 4X4 with 150k miles. It was a real sweet find, I bought it from the original owner and it was babied and decently maintained- no mods whatsoever, stock airbox, etc. The Garrett turbo still has the factory barcode stickers on it, lol.
The only problem I could find with it is what feels like a misfire or weak cylinder. The engine always starts after 1 or 2 seconds of cranking, doesn't smoke at all, and idles smoothly- it doesn't sound like the YouTube videos when guys pull one injector connector at idle. It has very little blowby, even when cold. But under load, especially at low RPMs, it feels like one cylinder is missing. If you accelerate to 3K RPMs or so, the vibration continues all the way up. As soon as you let off the pedal, it's as smooth as glass decelerating and being spun by the drivetrain- wouldn't you feel bad compression in one cylinder here? It sort of seems like the more fuel you're demanding from the injector, the more obvious the miss. I don't have anything to compare it to, but it feels like the engine is making pretty good power overall- I would expect a completely dead cylinder to have more effect, both in vibration and loss of power. After all, the original owner was (apparently) driving like this and didn't notice it at all.
Also, I believe this truck has the 2-stage injectors, since it was originally sold in CA in '96. Is that right? And would it be possible for the injector to only pulse the first (small) pulse and not the second?
I found one UVCH male connector melted with the GP pin totally gone and the injector pin looking iffy, so I was really hoping that would be the problem. I figured I might as well replace all the weak links at once, so today I replaced both VC gaskets and all harnesses under the VC, all GPs, the burned male connector, and the camshaft position sensor. Unfortunately, it runs exactly the same as before, lol. I also had noticed that it was running really cool, like on the cold peg on a 70-degree day, so I put a new thermostat in it today and now it warms up right.
I've only run 1/4 tank of fuel through it with the Kleen in there, so it hasn't had enough time to do much.
Has anybody seen this kind of symptom? Do diesel injectors get "dirty" and fail to put out high fuel volumes? Could running with a stuck-open t-stat for a while affect an injector? If a couple tanks with Kleen don't change anything, what should my next diagnostic steps be?
Thanks in advance, guys. The help is appreciated.
Last week I bought my first diesel- '96 F-250 CC SB 5-spd 4X4 with 150k miles. It was a real sweet find, I bought it from the original owner and it was babied and decently maintained- no mods whatsoever, stock airbox, etc. The Garrett turbo still has the factory barcode stickers on it, lol.
The only problem I could find with it is what feels like a misfire or weak cylinder. The engine always starts after 1 or 2 seconds of cranking, doesn't smoke at all, and idles smoothly- it doesn't sound like the YouTube videos when guys pull one injector connector at idle. It has very little blowby, even when cold. But under load, especially at low RPMs, it feels like one cylinder is missing. If you accelerate to 3K RPMs or so, the vibration continues all the way up. As soon as you let off the pedal, it's as smooth as glass decelerating and being spun by the drivetrain- wouldn't you feel bad compression in one cylinder here? It sort of seems like the more fuel you're demanding from the injector, the more obvious the miss. I don't have anything to compare it to, but it feels like the engine is making pretty good power overall- I would expect a completely dead cylinder to have more effect, both in vibration and loss of power. After all, the original owner was (apparently) driving like this and didn't notice it at all.
Also, I believe this truck has the 2-stage injectors, since it was originally sold in CA in '96. Is that right? And would it be possible for the injector to only pulse the first (small) pulse and not the second?
I found one UVCH male connector melted with the GP pin totally gone and the injector pin looking iffy, so I was really hoping that would be the problem. I figured I might as well replace all the weak links at once, so today I replaced both VC gaskets and all harnesses under the VC, all GPs, the burned male connector, and the camshaft position sensor. Unfortunately, it runs exactly the same as before, lol. I also had noticed that it was running really cool, like on the cold peg on a 70-degree day, so I put a new thermostat in it today and now it warms up right.
I've only run 1/4 tank of fuel through it with the Kleen in there, so it hasn't had enough time to do much.
Has anybody seen this kind of symptom? Do diesel injectors get "dirty" and fail to put out high fuel volumes? Could running with a stuck-open t-stat for a while affect an injector? If a couple tanks with Kleen don't change anything, what should my next diagnostic steps be?
Thanks in advance, guys. The help is appreciated.
#2
#5
#6
Yeah, it does have the DMF. I took a look at it today and it looks ok, no broken springs that I can see. But I was thinking about it today and I realized that what I'm experiencing feels exactly like the flywheel is out-of-balance... Does that happen on these trucks? When I shut the engine off it does make quite a clatter, maybe the DMF is going bad.
#7
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#8
OK, I had mine go bad last year and replace it with valair lots of people use them here. I am adding a couple of links to for you to take a look at.
https://www.ford-trucks.com/forums/1...l#post11306691
https://www.ford-trucks.com/forums/1...-slipping.html
https://www.ford-trucks.com/forums/1...l#post11306691
https://www.ford-trucks.com/forums/1...-slipping.html
#9
Well, I'll be ---, that must be what it is. Mine rattles all over the place when you wiggle it by hand, and those other symptoms are right on too. Good enough for me, I'll throw a little more $$ at it and see what happens. Thanks for the links and info, it's surely appreciated. I'll update the thread just for information's sake once I get it changed out.
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