Please help diagnose 7.3L I'm considering buying.

[bnorman]

Hi all. I'm looking to buy a super duty for towing. I've looked at a lot of 6.0L trucks, but not as many 7.3L ones (because of high miles). Anyway, I test drove my first 7.3L (76k miles) today and have some concerns:

1. After the engine was warmed up, 3 out of 3 cylinder contribution tests came up with P0284 (Cylinder 8 Contribution Balance Fault).
2. The engine seemed very sluggish compared to the 6.0L trucks I drove (with the same crewcab/longbed configuration). I realize the VG turbo must add a little pep to the 6.0L coming off the line, but this thing was a complete dog compared to the 6.0L trucks I drove (at all speeds).
3. Even towing a 8000# 5th wheel up a steep mountain road (at 2500 RPM), the turbo seemed to be topping out at 10-12 psi of boost. This is based on the MAP sensor, which was about 12 psi at idle and maxed out at 24 psi.

Things that seemed ok:

1. A block leak check (blue liquid sensing for exhaust in the coolant) came out clean (unlike half the 6.0L trucks I tested, probably beginning EGR leaks).
2. The injector buzz test passed (and sounded ok to my untrained ear).

Given that I'd rather not have to work on this truck immediately, would you walk away?

Thanks!
Ben

[Codum]

I can only comment on item #2. I have a 6.0 and a 7.3, 6.0 is a lot quicker than a 7.3 and will get better mileage, put 8,000 pounds behind it and I think the 7.3 pulls better. 7.3 will be cheaper in repairs and routine maintance too!

[jesilvas]

Originally Posted by bnorman

Hi all. I'm looking to buy a super duty for towing. I've looked at a lot of 6.0L trucks, but not as many 7.3L ones (because of high miles). Anyway, I test drove my first 7.3L (76k miles) today and have some concerns:

1. After the engine was warmed up, 3 out of 3 cylinder contribution tests came up with P0284 (Cylinder 8 Contribution Balance Fault).
   
   Cam sensors throw this code. The injector is fine.
   
2. The engine seemed very sluggish compared to the 6.0L trucks I drove (with the same crewcab/longbed configuration). I realize the VG turbo must add a little pep to the 6.0L coming off the line, but this thing was a complete dog compared to the 6.0L trucks I drove (at all speeds).
   
   It's a 7.3. Yes, it's slow.
   
3. Even towing a 8000# 5th wheel up a steep mountain road (at 2500 RPM), the turbo seemed to be topping out at 10-12 psi of boost. This is based on the MAP sensor, which was about 12 psi at idle and maxed out at 24 psi.
   
   The MAP might be bad or have a cracked line going to it. If it said 12PSI at idle, that's odd. The EBP will read 15PSI on a dead engine, but that's the pressure of 1 ATM. Sounds like the MAP might be messed up or something. No big deal.
   

Things that seemed ok:

1. A block leak check (blue liquid sensing for exhaust in the coolant) came out clean (unlike half the 6.0L trucks I tested, probably beginning EGR leaks).
2. The injector buzz test passed (and sounded ok to my untrained ear).

Given that I'd rather not have to work on this truck immediately, would you walk away?

Thanks!
Ben

What's the price for 76k?
What you listed, there's nothing wrong with it.

[Codum]

Got any pictures of it and yes what's the price, with 75k miles hard to believe the motor has issues, but then again I don't know what it's been doing, miles may be low, but the owner be one of those guys wo let it idel all day, thus hours could be higher than mine with over 400k miles?

[bnorman]

Originally Posted by jesilvas

It's a 7.3. Yes, it's slow.

Ok, good to know; thanks.

Regarding the MAP, I should have mentioned we're at about 6000 feet elevation, so the 11.7 PSI reading made sense. What kind of boost should the turbo be producing under heavy load?

The asking price is about $15k (white, supercrew, longbed, xlt, SRW, F350). That's over even NADA retail; I wouldn't be inclined to pay over $13k for it even if I wasn't worried about the motor.

[Codum]

Has it been taken care of? With that low of mileage it should look like new, if it has then I agree $13,000 is about right for that truck.

[bnorman]

Originally Posted by Codum

Has it been taken care of? With that low of mileage it should look like new, if it has then I agree $13,000 is about right for that truck.

Appearance is very good for a 13 year old vehicle. I guess the 7.3 was just a little bit of a letdown after driving the 6.0 trucks. (Yes, I know it would be less of a letdown 200k more miles down the road. )

The other issue I forgot to mention is that it smelled pretty strongly of diesel exhaust in the cab even with the windows up and the A/C on. And there didn't seem to be a "recirculate" option on the HVAC controls. Is that typical for this era of truck? I didn't notice it in the 6.0 trucks. I think it would get pretty old on long drives.

I guess I'll take another look and specifically:

1. See what color CPS it has.
2. See if I can coax PERDEL data out of my AutoXray or ScanTool.
3. Try to read the "boost" PID directly rather than inferring from the MAP (although maybe it's equivalent?)
4. Crawl around under it more and see if I can see an exhaust leak.

Any other ideas? Is there any good way to tell if the turbo is spooling up properly? I can't hear it over the deisel.

I suppose a leaking up pipe would explain both weak turbo boost and exhaust smell in the cabin...

[jesilvas]

Max AC recirculates the cab air.
The exhaust smell could be an exhaust leak or just the wind blowing wrong.
Boost is read from the MAP.