Help Needed skip on cylinder 8

[Potentialbuyer]

I have owned my 2000 F350 7.3 automatic 4door long box for about 8 months with out any problems. I have done some routine maintenance that included changing air, transmission, and fuel filters, fluids (engine oil, p/s fluid, ATF). I used Motorcraft filters and engine oil (15-40). Trans fluid is Amsoil. I also add .5 oz two stroke oil per gallon of fuel to protect the injectors. The truck has 167,000 miles on it and is completely stock.
I noticed a slight skip a few weeks ago and today I did some tests including KOEO, KOER, injector buzz test, and cylinder contribution test. I had a P1249 and P0470 continuous codes and a P0470 KOEO code. These codes are exhaust pressure and waste gate codes that shouldn't contribute to the skip. Cylinder contribution showed cylinder 8 was weak. Injector buzz test passed. From this information, I believe that there is an internal injector problem or a base engine issue.
I looked all over the PCED to find what is the best way to do a compression test but I couldn't find the procedure. I would guess that there is an adapter for the glow plug hole and you need a diesel compression gage. What is the spec for a good engine? I will compare cyl 8 to another cyl but I would like to know if I am in the ballpark. I doubt there is a base engine issue because it has never used any oil, it starts when it is below zero without being plugged in, and there is no smoke from the tailpipe.
Is there a way to check the injectors without removing them? This problem started gradually. I found some TSB's but none of them provided a solution. I would appreciate any help.

 

[DaveBen]

We had another guy who tested his 7.3 and he got around 450 psi. That sounds right to me, but I have not tested a 7.3.

Dave

 

[Potentialbuyer]

Could this be fuel issue? I used to use TCW3 two stroke oil but a friend gave me some old 40 wt ski doo oil that I have used for the past few tankfuls. This stuff was made before the TCW3 rating existed. I don't know if that would matter. It still is a petroleum based 2 cycle oil. Are there any fuel additives that may help if there is an injector problem?

 

[BIG JOE]

You might be getting some injector nozzle Coking (?) from the Ski-Doo oil if it's not an Ashless type oil.

Try a "Hot" ratio mix of Power Service Diesel additive... for a few tanks to see if it clears up any ?

Joe

 

[dpantazis]

X2 on what BigJoe sez. try to use ASHLESS 2 cycle oil.

could you be describing cackle as your skip? there was a TSB for some issue that spec'd the use of a long lead injector for number 8, but I don;t think that is your problem.

dp

 

[dpantazis]

X2 on what BigJoe sez. try to use ASHLESS 2 cycle oil.

could you be describing cackle as your skip? there was a TSB for some issue that spec'd the use of a long lead injector for number 8, but I don;t think that is your problem.

dp

 

[Potentialbuyer]

It is definately a skip. It has a slight shake at idle and the exhaust tone has changed when going down the road. It doesn't feel like a completely dead cylinder but there is one that is doing less work than the others. MPG is down and i noticed less power on hills too.
I appreciate the input but can you explain what a "hot" ratio of Service Power Diesel additive is? Does the "long lead" injector pertain to the wiring of the injector? If so wouldn't it have failed the buzz test?
Also. do I really need to use two cycle oil in the fuel? Last year this was all the rage but from reading some of the threads now it may not be so critical and the injectors won't be damaged from Low sulfur fuel.
Thank you for the help.

 

[Tail_Gunner]

There was a fuel starvation problem with #8 injector which manifested itself as the "cackle" sound and drove the development of the long lead fuel injector. They were more treating the symptom instead of the cause with the L.L. injector.

If you've not yet done so, you might try shimming the fuel pressure regulator. That will raise the fuel pressure a bit to help out that #8 in case it is a fuel starvation issue.

 

[BIG JOE]

There was a fuel starvation problem with #8 injector which manifested itself as the "cackle" sound and drove the development of the long lead fuel injector. They were more treating the symptom instead of the cause with the L.L. injector.

If you've not yet done so, you might try shimming the fuel pressure regulator. That will raise the fuel pressure a bit to help out that #8 in case it is a fuel starvation issue.

X2.

That was going to be my next.. Try This. For all the same reasons TG mentions.

 

[Potentialbuyer]

I will get some washers and shim the pressure regulator. If this corrects the problem, is this a band aid for future fuel system/injector problems?
Thanks