These are notes from my business partner who handles our trucks. We have been working on this one for some time and we've just about hit a dead-end with it.

If anyone could read over these notes and let me know if you have any thoughts, I'd surely appreciate it!

This truck ('99 E450 box van with 7.3 PSD) has been looked at by several shops and "mechanics" over the past 4 years and NO ONE has been able to figure it out. Normally it will not act up when at the shop and with limited codes being thrown. A solution has eluded everyone.

Symptoms

Intermittent dramatic power loss
Sounds like it is running on 2 cylinders
No power to the point of not moving
Heavy smoke and fuel smell when running poorly
NO check engine light when the vehicle is running poorly
Low/high fuel pressure codes and transmission gear shift codes are only stored codes
More common when under 1/2 tank of fuel


Attempted repairs and things checked

Injector buzz test......nothing
Cam shaft sensor replaced several times
Fuel filter changed on several occasions while being looked at.
Fuel tank dropped and cleaned
Fuel pump replaced
Fuel pick up removed, cleaned, checked flow and replaced.
Transmission replaced .....that was an expensive miss diagnosis! That shop is now closed...I wonder why?


Other recommended possibilities

Bad injectors
Bad computer


We have 5 of these 7.3's..........a couple have displayed symptoms similar. One was fixed with a replaced injector, and 2 were fixed with new or cleaned tank, pick up and pump.

 

Did you delete the mixing chamber or just clean it. Ive read when you reinstall it something goes wrong and could start sucking air. JMO I thik it must be tank related if it only does it at certain fuel tank levels

 

I had the same thought, David. Sounds like a fuel supply problem. SunBum, would the company be willing to purchase an electric fuel pressure gauge that can be mounted in the cab? That way you could monitor the fuel pressure while driving to see if there is a problem with fuel delivery. But if you were sucking air you may still have pressure but not adequate fuel. I'm not sure how this situation would affect the gauge pressure. You don't want to plumb in a regular gauge 'cause you don't want the chance of high pressure fuel being sprayed around in the cab....

Another thing you could do is use a diagnosis tool to monitor the engine performance while driving to see what is going on. Some here use Auto Enginuity which is used with a laptop computer. This will do more than just show codes. You see what the different components of the engine are actually doing and the info can be logged to be printed out. It sounds like you would have use for this since you have quite a few vehicles.

 

Have you checked the UVCH, (Under Valve Cover Harness)?

They are notorius for the little clip getting weak and the harnesses loosening. Pull the valve covers and check the harness at the top/back of the head. You can take a quarter and grind down one edge flat to the top of Washington's head. Slide it under the little tab to hold it in the locked position. The grinded edge is so the valve cover goes back on correctly.

If you do a search on here for "50 cent mod" you will find instructions and pics. Cheap fix if it works. If not, then it's a cheap fix you wont have to worry about later. 50 cents a truck and about an hours work.

 

I also say get the AE for the lap top, that way you can quit the guessing game, and you can make sure of HPOP and fuel pressure's.

 

I have read all the responses and will forward the info to my partner. I sure hope we can get this thing fixed. Our trucks (when they are on the road) are gone 300-400 miles away for a week a time. Needless to say, this truck has been parked for a couple of years, but we sure could use it back on the road. Thanks again for the help.

 

Defacing currency is a federal offense.

 

Paying $40 for a plastic chip to do the same thing should be a federal offense.

 

I'm not getting this part. The truck PCMs don't monitor fuel pressure. Do the vans?

I've had the dreaded UVCH problem and it throws all sorts of codes. My vote is also on a fuel problem. The little mixing chamber and filter screens may be clogged and need to be cleaned or replaced or deleted. Below are some pictures of mine. Just because the tank has been "dropped and cleaned" doesn't mean the real problem has been addressed.

 

I already have a guage on my fuel system and I know I'm getting tons of air in the lines. I can see it through my Raycor fuel filter/separator and the fuel pressure will still read, it just won't be very consistent. I've been having these similar problems with my truck since I bought it about 6 months ago. I have a couple of threads on this site and if they're posted by me, "bulla", they pertain to the issue similar to yours. The only difference is that mine does it all the time, whether the tank is full or empty. I'd recommend the ITP kit and just delete the mixing chamber altogether. You'll need to put an inline filter between the tank and the fuel pump to keep the trash out of your pump. Also get rid of the quick-connects on top of the tank and go with good ol fashioned hose clamps. I'm only stuck on this tank issue since u say it only happens at certain fuel levels.

 

Looks like that mixing chamber and / or those little screens might have been the culprit. We found both (one from a sending unit that we replaced in another truck, and one from this van) clogged. We've already swapped the one out from this van and it has stopped acting up... at least for now!

Thanks again!