The Diesel Stop banner

21 - 37 of 37 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter #21
I found some information about the adjustment to altitude. Here it is:
"There are some variables that affect the readings obtained from compression testing. They are cranking speed, altitude, temperature, worn camshaft lobes, and high performance long duration profile camshafts. The cranking speed needs to be maintained the same for each cylinder. This may mean jumping your battery to maintain the speed. The effect of the two camshafts above is the same, one of lower readings. Compression data is usually based on 14.7 atmospheric pressure and 59F at sea level. There are factors to compensate for the different altitudes and the corresponding temperature differences. These are as follows:
1000' = .9711
2000' = .9428
3000' = .9151
4000' = .8881
5000' = .8617
6000' = .8359
7000' = .8106
8000' = .7860
The equivalent compression reading for a cylinder that should be 350 PSI by the data at 5000' would be 350 x .8617 = 301.595"
After some research, though, it seems like even 350psi at sea level is not good. Most things I see say about 400 psi is where it should be.
 

·
Registered
Joined
·
3,500 Posts
Something doesn't sound right....

You left the shop and it ran great for a few days until you ran it low on fuel - then started getting worse and worse.....

I think there is more going on - you should be able to get it back to the way it was running after it left the shop - unless the compression has dropped further - might want another compression check...

Also, when you get it warmed up and with the truck running, open the oil fill and do you have a stream of smoke or a puffing and how strong is it? can you flip the cap over and set it on the fill hole and it will stay there or will it get blown off.

probably some more things to check, but i think there are few more things to do first like find the leak and check your fuel pressure. Get a flashlight and look in the valley at the top of the engine - is there fuel in it?
 

·
Premium Member
Joined
·
7,913 Posts
I am new to reading glasses and learning how to keep them at hand I apologize.
Look at it this way the compression is the needed component.Higher elevations make it harder to get the thin air in there,benefit turbo.but at the end of the compression stroke that pressure is what it is regardless of what it took to get enough thin air in the cylinder at the beginning of the stroke.
 

·
Registered
Joined
·
3,500 Posts
I have seen both mentioned - but don't have the shop book handy.

400psi +/- 10%
or 350 - 400

You do need to account for altitude - as you have done.

Regardless - the truck ran fine with the values that were recorded. Something else has happened in the meantime - or, as was mentioned, the compression has gotten worse - but I don't believe that since "it sounds" like you did not have a huge concentration of gasoline to diesel.
 

·
Premium Member
Joined
·
7,913 Posts
Never dealt with it up there.
350 down here is pretty weak I am not crazy about less than 375.
RT.and others hear have been on this forum for along time and probably more experienced with elevation factor posts and might know but I believe at end of day it's what that guage reads and of course how an engine that gives those readings handles the thin air.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #26
Something doesn't sound right....

You left the shop and it ran great for a few days until you ran it low on fuel - then started getting worse and worse.....

I think there is more going on - you should be able to get it back to the way it was running after it left the shop - unless the compression has dropped further - might want another compression check...

Also, when you get it warmed up and with the truck running, open the oil fill and do you have a stream of smoke or a puffing and how strong is it? can you flip the cap over and set it on the fill hole and it will stay there or will it get blown off.

probably some more things to check, but i think there are few more things to do first like find the leak and check your fuel pressure. Get a flashlight and look in the valley at the top of the engine - is there fuel in it?
I just flipped the cap over on the oil fill tube and it did not lift up at all. It vibrated around, but there was no visible space between the cap and the fill tube. And how would you go about checking fuel pressure? There are probably a few places with different pressures that would have to be checked, right?
 

·
Registered
Joined
·
15 Posts
Discussion Starter #27
I am new to reading glasses and learning how to keep them at hand I apologize.
Look at it this way the compression is the needed component.Higher elevations make it harder to get the thin air in there,benefit turbo.but at the end of the compression stroke that pressure is what it is regardless of what it took to get enough thin air in the cylinder at the beginning of the stroke.
And no problem about your glasses! Haha, I understand
 

·
Premium Member
Joined
·
7,913 Posts
Flywheel has an old join date so he is informed and experienced how to calculate it.
The number I gave you 300 to 400 came from my factory book.
The references to different values are for this and other diesels down here by sea and how they perform at those numbers.
Good luck and know this happened to countless others.I have almost done it more than once and have since painted my gas cap yellow.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #29
Flywheel has an old join date so he is informed and experienced how to calculate it.
The number I gave you 300 to 400 came from my factory book.
The references to different values are for this and other diesels down here by sea and how they perform at those numbers.
Good luck and know this happened to countless others.I have almost done it more than once and have since painted my gas cap yellow.
Hey, thanks a lot! That's good to know your numbers came from your factory book. I couldn't find anything other than hearsay anywhere else, so that's really good to know. The darn fill handle at the gas station was green, so I didn't even read the label.

Does anybody happen to know why 2 brand new cps' would make it run much worse?
 

·
Registered
Joined
·
3,500 Posts
That's a good sign about the oil fill. If you have serious blow-by, the cap would flip off.

However, that does not mean that you don't have burnt exhaust valves - however, I think you need to address the things you know are wrong and flushing a tank can stir up a bunch of debris - depending on how they did things.

Since you had fuel issues, and now potentially fuel related problems based on the leak and the cause, find the leak.

Then see how it drives.

Then check the fuel pressure:

http://www.swampsdiesel.com/site/how_to_pdf/pdf/fuel_pressure.pdf


You may just want to take it to the shop and see what they say - they can probably measure the fuel pressure in 10 minutes...assembling the parts and making a kit and installing will take you a bit of time. They might be able to check a few quick things and get you back on the road.

At the same time - you can have a quick discussion about the compression numbers and find out.

My guess is you are leaking fuel out of a pressure line and your fuel pressure is down - probably on one side.

Did you look in the valley yet?

You could even have multiple issues, but you gotta start by finding the leak.

Also - try to find somebody on here that can run diagnostics - and has an Autoenginuity or similar. That might give us some more data to go on.
 

·
Premium Member
Joined
·
7,913 Posts
Yep good sign there.I thought more about it.so an engine up there putting out 300 in the clouds is going to do 350 down here.Wow I really hadn't thought that.
Still lower range numbers but will work for sure.
A leaking line will give you issues for sure as I earlier stated.I was not trying to give you a heart attack.Finding out compression is really first step after gas.Find that leak.Get a proper fuel pressure gauge fitting installed on fuel bowl.Have it tested after leak is fixed and record it for future reference.
You asked about multiple places to check for fuel pressure.If you have stock set up there are also test ports on head at opposite ends of fuel entrance.Cross over kits utilize that port.
There are check valve fuel inlet fitting with screens in them.It is possible to get debris on the screens from trash in fuel that didn't get filtered for some weird situation that arose.Sometime pieces of the vibra lock oring on the fuel supply line get on the screen from it crumbling upon the line being removed at one time.
 

·
Premium Member
Joined
·
7,913 Posts
I would do a compression test for sure.A leak down will pick up a valve issue but is a little more work than just doing a running compression test with a high range high quality disel guage like a snap on,after recording cranking reading.The rocker really puts that lateral force on the valve guide.This method will show a worn guide and how the compression is lost there with it shifting while running.This condition is hard to pick up with just a crank reading or a leak down test.I have mentioned this in the past,so this time I have found a video to refer to .The guy goes by dieseltechron.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #34
Okay, so I did some looking around by the fuel bowl and I definitely have a fuel leak. I touched the back of the fuel bowl, my hand got wet and smelled like diesel. I believe it is coming from the fuel filter cap because the fuel bowl is slightly dusty on the outside, except for the entire back side, from immediately below the cap all the way down. It's clean like the fuel has been leaking from under the cap and cleaned the dust off. While the truck was running, I looked at the back of the fuel bowl and couldn't visibly see it leaking, so it must be a pretty slow leak. Every time I park somewhere, there is at least a 5" diameter spot that looks like oil below my truck. After finding this leak, I now realize that it is actually fuel that runs down the valley and picks up some old oil along the way, making it dark like oil. After consistently parking on my driveway, there is a huge spot on the concrete (about 3' x 3'), and it is much lighter in color towards the outside, like it's fuel, not oil. I don't know why I didn't think of it before.

Is it possible that such a slow leak from the fuel bowl could be creating spots like that everywhere I go, or is it more probable that I also have another fuel leak from somewhere else, also?

Also, could a leak from the fuel bowl be causing all of my issues: rough idle/knock, terrible fuel mileage, and white smoke on cold start?

Btw, thanks a lot for helping me through this!!!
 

·
Registered
Joined
·
3,500 Posts
Sounds like the fuel filter gasket got installed upside down and / or it got kinked up and is causing a leak - or the cap is not tight.

(Or something cracks or the drain o-rings are leaking.....)

You can get a new filter / gasket and replace it or just inspect the one you have. You should be able to see if the gasket got bundied.

The gasket should be installed with the wide flat part down on the aluminum bowl and the tapered part against the cap. Lube the gasket with some fuel prior to setting it in the fuel bowl groove. then tighten the cap buy hand. Then I take two crescent wrenches - one I open up and put the wretch part ingot he grooves of the cap, and while pushing down on the so it doesn't jump out, I turn it with the other one. There appears to be a positive stop - just try to be smooth with it so it is all one motion. You could also just try to tighten it as it sits.

Wipe it all down and cycle the key a few times to fill the bowl.

------
If the fuel drain orings are leaking, you will need a repair kit from dieselorings.com to replace the orings. If this has never been done, it is common.


I doubt this the issue as a leak that slow will not affect the pressure enough - even if you already have other pressure issues.


But take it one step at a time.
 

·
Registered
Joined
·
1 Posts
Fixed this problem

I was having this problem with my 7.3l excursion, and I did an oil change (3k mi.). I found that I only had around half the total oil in the engine. Yikes!!!!
Not sure where it went. No detectable oil leak on the engine, no oil drips in driveway, no smoke from tail pipe (even on cold starts).
I went to Shell T6 5-40 oil. There's no noise nor loss of power at start up/cold anymore. Pretty scary. Crossing fingers that everything is okay now.
 
21 - 37 of 37 Posts
Top