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Power surges after 2500 rpm

10640 Views 27 Replies 6 Participants Last post by  1dieselman, 
Plywood
Well, I did a search and I can't find anything that is the same as my problem.

What happens is, at 2500 rpm, if I increase the throttle there is less acceleration than there should be, then at maybe about 2600 rpm, the truck will surge up to about 3000 rpm without a change in the throttle.

Seems like it happens only when the truck is warm, and maybe been on the highway for a while, but I also don't rev it that high when cold so I am not 100% sure of that.

I am guessing the IP or lift pump, but IP is the only thing that makes sense to me.

Has anyone experienced the same thing or have any ideas?
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Plywood
Thanks guys, I had no power cord for my laptop yesterday, nothing like starting a thread and then dissappearing, eh.
I just changed the fuel filter.
I have not done the lift pump, but I should have since I just had to replace the vacuum pump, oh well thats easy. Thinkin' about going electric anyway.
I think the idea that the lift pump sucks air after 2500 rpm makes sense, although it seems like the longer it's been running the worse it gets??
My tanks are low though, so I will fill them and see if that makes a difference, hadn't thought of that one.
I've been meaning to pick up some clear line, I had some on there before I put the return line kit on.
I did have an air leak in the return lines so everything from the filter inlet cheerio to the return line at the back of the engine has been done.
I guess I will try some clear line, then electric lift pump, then IP, starting from the cheapest.
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Plywood
Well, I filled the tanks and no change on either tank.

When I got the rear down about 8 gallons it started to make a few poofs of blue smoke on the highway, I switched to the front and no change, then after it sat it was fine and hasn't had any puffs since. I think that was a separate issue like sucking some gunk from the tank, happened just once a couple months ago.

Now it's back to the same surge problem on a full front tank.

I've never ran out of fuel before, and my gauges are a little off so I don't really know about that. How much do they hold? Are they all the same?

The truck idles perfect most of the time, but every so often it will idle goofy enough to rock the truck back and forth a little.

I picked up some clear line, but I'm not sure that I will see any bubbles since it dose it more when warm on the highway and at a high RPM, but I will try that.

Not really great weather for working on it outside right now.
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Plywood
Yeah, that sounds most like it to me right now also.
I was planning to install an electric lift pump and that line, but I may do one at a time just for the sake of diagnosis and everyones collective knowledge here.
I hate it when I do two or three things at once and I don't know what fixed it.
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Plywood
No I haven't.
Right now I am trying to decide what electric fuel pump to use.
I picked up some clear line, but it was 1/4 inch, and I looks like I need 3/16 which I haven't found yet.
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Plywood
OK, so I put the clear line on.
It runs down the highway good for about 10 minutes and the starts to surge, after more driving it will sometimes puff blues smoke.
So I got home and revved it up and it runs like a gasser missing on a cylinder or two, and pukes blue smoke that smells like diesel.
No bubbles what so ever, not even tiny ones.
I put a pressure gauge on the filter, and it says about 4.5 psi at idle, and when I rev it up high it goes down to about 2.5 psi, do ya think that is too low?
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Plywood
Did I reach the summit of dieselstop knowledge?
I have learned oodles here, I appreciate everyones help.
Tis always my destiny to have a problem know one can explain eventually.
I stopped by a local IP shop, I can drive right to it, just wish I could think of the name, they have been incredibly selfless and helpful.
Dude gave me a 16 oz bottle of stanadyne fuel treatment free, maybe he felt bad that he was stumped as well.
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Plywood
The fuel treatment dosen't seem to have done anything so I went ahead and bought a Facet Dura-Lift.
Was $114 and some change, I told the guy I worked for Freightliner and it ended up being $97. Hee Hee.
Picked up a 30amp relay and such, I don't really think it is the problem, but I want to do it anyway so what the hay.
Will update, I think it's the injectors but who knows.
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Plywood
I have the Dura-Lift in and it works good, but here's the thing.
Now that I have clear line before the filter, low and behold I can see bubbles!
I still don't see any from the filter to the return line or from the IP to the return line where I had the clear line before.
It seems to be running fine in the driveway (I didn't have a chance to drive it yet) but if the air bubbles are going in the filter it seems like I should be seeing some coming out, I can't imagine the IP is pumping those to the injectors and it is running alright.
I suppose the injectors return some air to the tank also.
I guess I will replace the line before the Dura-Lift and see if there are still bubbles, when I got the truck it had a newer rubber line with a great big clear line wrapped around it to protect it, but now that I have pulled an end loose it is like your typical old rubber line that dosen't instill any trust.
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Plywood
Wasn't the lift pump.
Got it on the highway and same old thing.
Pulled off and revved it and I couldn't see a single bubble and same problem.
I think the bubbles I was seeing before were just from having the fuel line disconnected for the lift pump swap.
Oh well, I am still glad I got the Dura-Lift in, but I guess it's injector time.
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Plywood
I wouldn't doubt it one bit, if it's not the injectors then I will have to take the IP in.
The injectors looked like they were original and the IP had a Stanadyne Reman tag and the injectors of course are cheaper so I thought I'd try them.
I'll let you know the result in case somone is having the same problem.
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Plywood
Got the injectors in, at first it smelled a whole lot better and seemed like it ran a little better, but once on the highway it started smoking and surging again, bummer bummer bummer, seemed worse on the smoke actually.
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Plywood
That's a good idea for diagnostic that I hadn't thought of, but I would be afraid to do that and have to find a whole new pump or something.

I'll just take the IP in I guess, not much left it can be really.

The smoke is kind of blue, so I thought about the CDR, but the smoke smells just like diesel and not a bit like oil, so it just can't be the whole problem.

Once the pump is rebuilt, the fuel system will be new from the new electric lift to the cylinder. I'm not getting any air intrusion anywhere now so I just have to fork out the dough I guess.

Thanks for the help and ideas and I will update when there is news!
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Plywood
Low and Behold it was the IP!!!
Not that I doubted it.
Apparently there was a broken spring washer next to the thrust washer, allowing the shaft to move back and forth, causing the governer weights to do something and so on.
The advance piston was wore out also, anyway for $385 I got a complete overhaul and calibration and it runs perfect.
At least I didn't go to an Auto Parts store and pay them $1200 to send it to the same place!
Goes to show you never know, the smoke was sure looking blue to me, but it was diesel that was makin' it.

Thanks to everyone for their input!
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