Howdy,

I have a 93 F250 7.3L diesel.
It idles at about 700 RPM and there is a noticeable shake or vibration, when you raise it up to 1000 RPM the vibration is so bad I can feel it in my teeth. Raise it up over 1300 RPM and it smoothes right out. The truck has lots of power, on start ups it only blows a tiny amount of black smoke and it goes away.
I changed the fuel filter hoping that would fix the problem but it didn't, and the air filter is clean. I bled the air out at the fuel filter but I didn't notice anything.
Could I have an injector doing something funny? I replaced them almost exactly a year ago.
About three months ago I replaced the injection pump and everything had been running fine until about two weeks ago.
I took it to ford to have the timing checked and have them figure out the vibration. All they did was check to see that the little lines lined up on the injection pump and then told me that for the age of the truck it was running good, they charged me 90 dollars for that
The only other thing I have replaced recently is the CDR valve, but I don't see how it could cause a vibration like this.
So any ideas on what could be causing the vibration and how important is it to have the injection pump dynamically timed?


Thanks,
Gr8ride

 

It sounds like a nozzle (injector) to me. One little bit of dirt, or a weak spring will cause it to act up. Also may want to check the o rings under each return cap (may not be leaking but may be sucking air). Doesnt sound like a timing problem to me.

 

The caps aren't leaking, but I would like to know how check to see if they are sucking air in??

Thanks agian,
Gr8ride

 

They won't suck air till you shut it off. The next day it would start, then die, and be hard to get going again.

Loosen your inj. lines one by one and see if you can narrow it down to one cylinder.

 

The cylinder on the passanger side closest to the firewall had the least affect on the engine when I loosend it. So I replaced that injector with a brand new one, and it runs exactly the same if not a little worse. Did I get a bad injector or is there something else wrong?

Thanks,
Gr8ride

 

I'm going to go out on a limb here and stick my nose in where it don't belong if you don't mind. How about valves? I haven't worked on a diesel in a while but that is mostly what a tune-up consisted of was making sure the valves were all readjusted.

 

How many miles on the engine? Check the compression on that cyl. If it's OK, maybe the new pump has a problem already. We got a pump from texas once that ran worse than the old one. Make sure the advance piston on the bottom driver's side of the pump comes all the way out when the pump is at idle. If it is hanging up, run some lubrication additive and see if it helps.

 

The truck has 160,000 miles on it.

 

Well I think it was a really really bad tank of fuel. I switched tanks and it's idleing alot smoother today. I also went to a diesel shop today and he looked it over and said it's a good running truck, so all is well.
Thanks for the replys guys.


Gr8ride

 

Do me one last favor, remove the air filter housing while it is running and listen for a popping or a loud compression noise. If so then it could be bad lifters. A normal intake should sound very low pitched and very even.

I had two lifter roller flatten out and wipe the cam lobes off and it did the same thing you are saying.

 

Hi fordiesel69,

I took the air cleaner off today and listened for any of the sounds you where talking about. I didn't hear anything unusual, It sounded pretty good.
I filled the tanks up again and put in a little more rotella dfa then I normally would and it's running real good now.
Thanks for the posts.

Gr8ride

 

Thats great to hear. Sometimes these injections pumps can cause some very annoying things, if your fuel does not have enough lubricant, it can cause the internals of the pump to malfunction. All kinds of symptoms.

The all tyme classic for me is that when you let you foot off the gas, she stalls out, I keep up on the additives and no problems at all.

If you don't have the money for the expensive additives, use powerservice. I use it all the time and it really works great.

 

Since we are on the additive topic I have a question.
Is there any harm in running the winter formula all year around?
The summer formula boosts the cetane by up to three numbers, but the winter formula boosts it by five numbers. I like the winter fomula better, but is it going to hurt the engine by running it year round?

Gr8ride

 

Just so you know, winterized diesel is nothing more than a blend of No 1, and No 2 fuel. Which of course results in a thinner fuel which does not provide the proper lubrication, and does not provide as much BTU's per gallon. So the end result is worn out injections systems and less fuel economy.

Using a winter fuel additve is actually better because the manufacture takes this into consideration and makes sure there are plenty of lubricants in the additive.

As long as you use, a TRUE diesel additive, you cannot go wrong. You may also use, marvel mystery oil, seafoam, 2 stroke oil, and straight motor oil safely. Do not use multi viscosity oils and do not use any kind of ATF unless it is from the 1950's. The friction modifiers will ruin the internals of the pump.

 

Thanks for the info, that helps a lot.

Gr8ride