My 99 F-250 7.3 seems to have a fuel problem. It does not do it all the time, rather intermittently. It will run find for a week then will act up for a day. Suddenly it begins idling very rough, it will do this for an hour or two then run good again. Now it has started to die occasionally when I roll up to a stop, it always starts right back up. Now when I am driving it will occasionally hiccup, it will do it a few times over 10 minutes then stop doing it. I have changed the cam sensor and the ICP, neither fixed the problem. Does anybody have any ideas what might be causing these problems? Any help will be appreciated.

 

Moved to the 1999 - 2003 7.3L Powerstroke Diesel forum.

 

UVCH harness issue (50 cent mod) or other chafed wiring issue?

 

Well, the first 2 you already took care of, my 2nd two are checking the UVCH (Under Valve Cover Harnesses) and fuel pressure. Checking the UVCH's can be as simple as seeing where they connect and wiggling the connector to see if you can reproduce the symptoms of running rough, or you can get an ohm meter and pull the connection and ohm out each individual connection. I have to look up the range for that connector but I THINK it's anything below 6 ohms and you are okay.

As for fuel, I would check the fuel bowl and see how it fills up. First drain it by putting a drain pan under the drain tube on the passenger side of the bowl, turn the yellow lever on the back of the fuel bowl and let it empty then close the valve. Take the top off of the fuel bowl, and then turn the key forward and see how quickly the fuel bowl fills up. It should only take a couple of seconds. If it doesn't within within 3-5 seconds max, you may have either clogged in-tank screens, or a fuel pump on the way out.

The other thing you can do is hook a gauge to one of the test ports on the back of the fuel bowl.

I borrowed this image from Scotttahoe, I hope he doesn't mind. You can see here the post filter port that he put his sending unit into, as well as the yellow lever I mentioned above.



Edit: took me so dang long to put that together, Steve H got to it before I could post. Sorry to be redundant Steve.

 

Thank you guys for your suggestion to check the UVCH harness, I plan to do that tomorrow. I am hoping to get a little education, it seems to me that if say one cylinder has a bad lead in the harness that it would result in running rough and not necessarily kill the engine. I think that if there is a problem with the common then that would result in all four cylinders shutting down which I assume would certainly kill the engine. Another thought is that if there is a problem then why does it always start right back up? Thanks for any education that you can give me.

 

[QUOTE=HKusp;14204430]

I borrowed this image from Scotttahoe, I hope he doesn't mind. You can see here the post filter port that he put his sending unit into, as well as the yellow lever I mentioned above.



Not a problem thats what their there for.

Let me know if you need more.

 

Scotttahoe, I have checked the fuel fill in the bowl, it filled up very quickly, about 3 seconds. I am trying to understand the UVCH. Specifically, how a short or broken circuit on one injector could kill the engine and if so then why would it start right back up?

 

Do you have AE (Auto Enginuity)? If not where are you located? If you are close to me Lake Tahoe I could hook up my AE to read codes or someone here at FTE may be close and could hook your truck up.

So, we can check the fuel system off of the list... but never a bad idea to hook up a cheap gauge or, I went with a permanent setup on my dash to make sure you are in the 65psi range at an idle.

As for the UVCH, There is a wire loom that comes off of the main 42 pin connecter (big block of wires) and then leads to each valve cover. These wires send power to the fuel injectors and glow plugs. The plugs that enter each valve cover are known for shorting out / coming loose to say. Thats when the 50 cent mod comes into play. Many people on here swear by the 50 cent mod and yes it does do the trick but me personally I don't care for it as a permanent fix. You can order a new valve cover harness from Clay @ Riffraff and be done with it, If this is even the problem. That is where the 50 cent mod comes in to make sure that is what it is and it will only cost you 50 cents.

Here is a very good thread to read up on to learn a lot more about it.
https://www.ford-trucks.com/forums/9...50c-mod-3.html

Here is a pic of my fuel pressure gauge. Top is HPOP and bottom is fuel pressure.

 

When the connection on the UVCH comes loose, it takes out the whole bank of injectors. If a wire is chaffed and shorts on the metal valve cover or some bracket attached to the engine, it can do all kinds of things.