7.3 Cold Starts

[powerstroke steveo]

Im having alot of trouble with my 2001 F-350 7.3. I have 6 inch stacks with a muffler on it. The weather is changing and the temps are low at night and it is giving me alot of trouble with my cold starts. Its been going below 20 every night and when i start my truck in the morning it has alot of trouble heating up. It makes super loud hissing noises right away but it is not constant, it does it on and off quickly. I let it warm up for 15 mins and when i pull away it does the hissing sound and takes all my power away. Im new to diesels and dont know where to start. Im going to purchase REV-X to add to the oil to help clean the injectors and i wanted to know if its worth buying? Any help would be great.

[sldghamr]

it's your exhaust back pressure valve closing. it cause the engine to work harder so that it will heat up faster, one side affect is some loss of power. i have disconnected mine.

[7.34ever]

not sure about the rev-x but you may have a bad glow plug or 2 that's giving you the starting trouble. the hissing noise is usually just the warm up valve but it's not supposed to do that once you're moving cause as soon as you touch the throttle it shuts off. not sure what that is.

i'd start with the glow plugs. if you need an explaination on testing them i'd be glad to help

[schafmeister]

Just sounds like the high idle to me. My truck when its real cold out does the same thing. Even after its warmed up it will go into high idle while driving when your not making no boost. Then when you give it gas it stops then goes back in.

[forddieseldoctor]

Originally Posted by 7.34ever

not sure about the rev-x but you may have a bad glow plug or 2 that's giving you the starting trouble. the hissing noise is usually just the warm up valve but it's not supposed to do that once you're moving cause as soon as you touch the throttle it shuts off. not sure what that is.

i'd start with the glow plugs. if you need an explaination on testing them i'd be glad to help

The exhaust back pressure valve can be activated by the pcm when you are cruising through town at low speeds and low power demand. I unplugged mine also simply because it irritated me by kicking in when it was partially warmed up.
I would definitely start by checking your glow plug relay. The best way that I've found is to hook up your meter leads on the 2 big lugs of the glow plug relay and cycle the key on with the engine cold. The voltmeter should read less then .2 volt. If it reads more then it is faulty.
And I would also replace your thermostat if it doesn't heat up to the middle of the normal range within a reasonable amount of miles.

[7.34ever]

Originally Posted by forddieseldoctor

The exhaust back pressure valve can be activated by the pcm when you are cruising through town at low speeds and low power demand. I unplugged mine also simply because it irritated me by kicking in when it was partially warmed up.
I would definitely start by checking your glow plug relay. The best way that I've found is to hook up your meter leads on the 2 big lugs of the glow plug relay and cycle the key on with the engine cold. The voltmeter should read less then .2 volt. If it reads more then it is faulty.
And I would also replace your thermostat if it doesn't heat up to the middle of the normal range within a reasonable amount of miles.

just for my info, if the gp relay was bad, would the truck even start in those temps?

[powerstroke steveo]

The exhaust back presure valve closes and opens constanly when i start it up. It makes weird noises. How can i disconect that so it dosent happen, id like the rev but not all the noise. And yes while i am driving it makes really loud hissing noises when i am easy on the gas, enought to where i have to pull over. I will check my glow plug relay. It runs fine once it is warmed up but that isnt untill its in the middle. Below that is alot of trouble.

[7.34ever]

might help if you plug in the block heater

[forddieseldoctor]

There will be a 2 wire connector connected to the solenoid on the front side of the turbo pedestal on the super duty 7.3. On the obs 7.3 it is on the intake side of the bottom of the turbo.
It will make a huge difference if you plug the block heater in and also change to a lighter weight oil such as 10w-30.