Surging at idle and shaking.

[Farmer Rock]

Good evening folks, about 3 days ago, I went to warm up my f250 and I noticed that when the high idle shut off, it omly dropped to 900 rpm and fluctuating a lot, then it starting shaking like crazy (and that says a lot for an IDI lol). I just kind of brushed it off at time since I was too busy to look at it. It starts right up, and gets up and goes like it always does. I used the truck today, and it did the same thing. My immediate thought is air intrusion of course.The return lines aren't the newest, and I wouldn't be surprised if the O rings gave out. Either way I will install a new return line kit, but my concern is the shaking. I know in most cases that means a bad injector, but being that it shakes and surges at random times, I am convinced that is air intrusion. I would appreciate if anyone can confirm this for me. Thanks





Rock

 

[IDIBRONCO]

It may not help, but I'm pretty certain that leaking o-rings won't give you air intrusion while the engine's running. There is no way that air can get from the o-rings back into the high pressure fuel system. It would have to go through the return lines down to the tank. Once there, it should rise to the top of the fuel in the tank in the form of bubbles. Air intrusion comes from the suction side of the fuel system and these are under slight pressure while the engine's running.

 

[Farmer Rock]

It may not help, but I'm pretty certain that leaking o-rings won't give you air intrusion while the engine's running. There is no way that air can get from the o-rings back into the high pressure fuel system. It would have to go through the return lines down to the tank. Once there, it should rise to the top of the fuel in the tank in the form of bubbles. Air intrusion comes from the suction side of the fuel system and these are under slight pressure while the engine's running.

I didn't really think of it that way I guess. I did notice that one of the metal fuel lines before the lift pump is wet but not leaking. I just fixed a couple sections that were rotted out and sucking air, so I wouldn't be surprised if that is causing it. I really want to just replace all the fuel lines to start fresh, but that may be awhile.





Rock

 

[IDIBRONCO]

I didn't really think of it that way I guess. I did notice that one of the metal fuel lines before the lift pump is wet but not leaking. I just fixed a couple sections that were rotted out and sucking air, so I wouldn't be surprised if that is causing it. I really want to just replace all the fuel lines to start fresh, but that may be awhile.





Rock

That would be my guess. I can understand your situation. You probably still have a lot of snow on the ground and may have to repair it again just to make it through until spring/summer.

 

[Farmer Rock]

That would be my guess. I can understand your situation. You probably still have a lot of snow on the ground and may have to repair it again just to make it through until spring/summer.

Yeah, we still got some snow here, and where there isn't snow there is mud, so I have to wait a bit. I was really surprised how bad some of those lines were. I just can't stand doing stuff pieced together, but it is what it is.




Rock

 

[Farmer Rock]

I fixed the fuel lines yesterday and all is good now. When I pulled out the old lines they fell apart in my hands, so there will definetly be more to do in the near future.



Rock

 

[IDIBRONCO]

So it runs right again?

 

[Farmer Rock]

So it runs right again?

Yes, no surging or shaking like it did before, and it idle steady as it should. I am glad it was something simple.




Rock

 

[IDIBRONCO]

I'm glad that it was too.