So I recently picked up a garage kept, fleet maintained, 1999 F-450 Crew Cab, 4x4, Auto, w/ 9' EBY Aluminum flatbed, 4.88 gears, 63k miles (not a typo, it was a former airport firetruck). It was manufactured in 1998 so I assume its the Early 99 engine. Just finished a round trip from Norfolk, VA to Philadelphia, PA with a 18' 10,000lb gvwr car trailer in tow to pick up 16 IBC/Tote tanks (100 lbs each) and a small 4 wheeler. There is a decent amount of sail area (think extra tall enclosed 18' trailer) but not more than 5000 lbs including weight of trailer. The truck was a total dog towing the load especially on any sort of grade/hill (and they are hard to find on the Eastern Shore). I keep the speed limited to 60 mph due to the 4.88 gears but I could not maintain speed on very mild of hills. Coming out of the Chesapeake Bay Bridge/Tunnel it dropped down to 50 mph with the pedal on the floor.

NOTE: The outside temp was in the upper 90s and I had the A/C on MAX. The clutch driven cooling fan would not disengage until the truck was cruising over 50 mph. Truck showed no signs of overheating. I know neither of those factors help but I feel like it shouldn't be that noticeable with such a light load.

The whole point of this truck was to massively increase my towing capacity compared to my old 7 cylinder (burned valve) IDIT. So far it's barely out classed it. I can't imagine how slow it would be if I took it up to the rated 18,000 lbs towing capacity (not happening anytime soon but I'm heading that direction eventually). The truck seems to run fine. Only known issues: 3-4 shift is a little sloppy but torque converter fully locks up, overdrive on/off button doesn't work (starting that project tomorrow), and batteries are getting old (battery light comes on when rpms drop. It starts fine so I don't care).

Am I just expecting too much or should I suspect an issue? Boost leak maybe? I'm currently mulling over the idea of swapping in 4.30 gears (better mpg, higher top speed, lower rpm = longer engine life) and a mild tune for towing then replace the trans with a built unit when it finally bites the dust. I just don't want to further neuter the already lack luster performance.

Any thoughts are greatly appreciated.

 

You shouldn't have that much trouble with the load. Start with the basics, fresh air/oil/fuel filters, fresh oil, check the exhaust backpressure valve isn't closing, make sure all the boots aren't cracked or loose and stick a good scanner on it.

 

If you start fine probably not the batteries fault, Takes alot to start these trucks alt may be suspect. Sounds like you have issues for sure I pulled a 27' enclosed trailer from MI to WA over several passes, weighed around 11,000lbs last time then pulled back empty 4,000lbs. It was very easy empty. About to head back. That is with 3.73 gears as well so it should be easier with your gears to stay in power. Check for boost leaks, up pipes. Get the charging system looked at this truck needs power to run right.

 

Air filter, fuel filter, engine oil and filter, trans filter/flush/fill were all done in last 2k miles. I'll take it down to Twisted Diesel to have it scanned if I don't find anything obvious in the daylight. I should probably install a boost gauge while I'm at it since I just discovered how easy it is to tap off the MAP sensor.

 

Fuel pressure gauge too, especially if it was a chassis cab with a steel tank,that could be part of it. Also check the up pipes to the turbo for signs of soot and consider building a boost leak detector.

 

Agreed on making sure the basics are covered. Fuel pressure good, no exhaust leaks or you won't be making much boost.
These trucks have a screen on the inlet of the fuel pump that restricts flow. Truck will idle all day long and register good fuel pressure at idle.
Soon as you put a load on it and fuel demand goes up, then the fuel pump cannot keep up with demand and the fuel pressure drops off to near zero and there goes your towing power.
My cure was to put a Bosch fuel pump at the end of the fuel pickup, and eliminate the fuel pump on the frame rail.
What that did for the truck was to enable it to pull 13k up a 4% grade without having to shift down. 6 % grade shift down once. Stock tune with stock injectors 4.88 rear axle F550 ZF6 4x4

 

1999 Ford F550+ 4x4 - Fuel Pump In the Tank

 

The early 99's have 120cc injectors if I remember correctly. That said, with 4:88 gears, you should not have any trouble pulling the load you had.

 

I wonder if it is detuned, since it was an airport vehicle. We had an old Dodge on the farm with a gas 300 and 4:88 gears, and it could pull a small planet off its axis.

 

This could be a bad ICP sensor. There are too many question here, so I will offer my usual suggestion: Get a logging scan tool, and the answer may pop up like a prairie dog.

 

I forgot about that possibility. The F450's and 550's are detuned compared to the 250's and 350's from the factory.

 

I thin that Dan has your problem figured out. Metal tanks with paint, bad idea. Plastic, stainless replacement, good idea. Get rid of in tank screens, good idea. External pre-tank filter, good idea.

And your idea to get it scanned, good idea. The possiblility that the HPOP is going bad with such low mileage is pretty slim. Much more likely that the screens are plugged from sitting around-bio sludge forms and clogs the screens over time from condensation forming in tank. This stresses the fuel pump. Your pump could be on it's last legs.

Get that alternator rebuilt, it will fry stuff (like the $$$PCM$$$)if you don't. That light should never come on, even with bad batteries.

Although bad batteries will stress the alternator as the load on start-up is transferred almost fully to the alternator.

If you don't mind getting a little dirty, pull the drivers side inner fender and check that all important IDM for water and proper sealing of the external holes. Do not use any Silicone type one to seal the IDM. That is the silicon that smells really strong like acetic acid. It will give off fumes that eat up electronics, electrical parts, brass, copper.

Larry

 

i had similar experiences as you with my 210k mile 99, my turbo was dusted really badly, if i put any kind of pressure on the turbo to work it would pshhh and bypass and it would have to start building boost all over. not saying this is your problem but it would be a good start to see what kind of shape the turbo is in. i recently did a ton of maintenance repairs on my truck and have been driving it for the last couple of days and it is day and night difference better. i am driving to california monday and bringing back a 19ft travel trailer so i will report back on my thread how the towing goes with all the maintenance repairs done.

 

Good to see you posting again, kwikk.

 

I just thought of something (other than detuning) that has a high likelihood - steel tank? If so, they are starting to slough the inside coating right about now. This "oatmeal" clogs the fuel pick-up.