This weekend, on my 2003 Excursion 6.0, I decided it was time to go ahead and bite the bullet and do the famous "blue spring mod" on my fuel system. I wasn't having any issues with it, but thought since the truck is 21 years old, heck, why not go ahead and do some preventative maintenance? The weekend before, I installed the Glow Shift fuel pressure gauge, wired it all up, and it's working. Fuel pressure hovered right at around 60psi, and under heavy throttle would drop down to maybe 53 for just a second and then immediately come back up. After installing the blue spring upgrade from Sinister Diesel, there was absolutely no difference. Not that I think the current numbers are an issue, but based on other people's experiences, I was fully expecting at least a 5psi, if not 10psi improvement.

Also, as a side note, I paid extra for the blue billet housing that Sinister gives with their kit, but was unable to use it because it's too bulky to allow the pressure sensor to plug into the fuel bowl and tighten all the way, so I ended up having to re-use the stock housing. Not really a problem, but it's not as pretty, and I could have saved my money.

 

Could have this spring mod already been completed by a previous owner?

Rob

 

I wondered the same thing, but the spring in it was not blue, and the components all looked original. The plastic seat that the plunger sits in (early 03 models) was broken, and the little plastic relief orifice also easily broke upon removal. All o-rings looked old and original.

 

FWIW, my '05 6L shows 72+ at idle for fuel pressure with the blue spring upgrade done 12 years ago.
Perhaps your filters are in need to replacement, or your fuel pump is tired.. ?

 

Bingo!

This is a common thing I MAKE customers do when they come to me for major repairs on their 6.0: a new Motorcraft HFCM and blue fuel spring. They're often shocked and how much more power their truck has and how much smoother it runs. The problem is that the manifold on the HFCM often gets plugged up with rust and gunk. While the engine runs and it appears fine, it's not running its best. Yes, you can clean it but chances are the pump is tired and needs to be replaced anyhow.

 

you may very well already have had the blue spring installed...or a version of it. Your post reminds me, I've had the IH package sitting on my garage workbench for 6-7 months. Need to install on this rig. When I was shopping for my kit, the China knock-off pictures didn't show a blue spring. I had to dig a bit for an actual kit vice reproduction

When I installed mine the 1st time, pre-spring my fuel pressures would drop to ~50 psi on anything more than slight throttle. After, she ran at least 65psi on everything except full throttle (PCM was tuned HOT). never less than 60psi even WOT. But that was a 9,000 mile motor quite a few years ago. Toreador/Misky likely have the root issue pegged. Pump maybe getting tired.

 

The spring itself does get tired over time. Mine was done before 5 years before I got my Excursion in 2008. Around 2015 or so, I replaced the spring with a new one and it solved the problem I was having on mine.