should my 1989 f-250 with 5.8 start with the vaccum line removed from the fuel regulator?

 

Yes it will start and run with or without the vacuum line hooked up
all the vacuum does is lower the fuel pressure when under a light load

 

thanks frend this thing is driving me crazy terible milage black smokes no power when its cold it back fires bad out the tail pipe untill it warms up i have replaced the mapp censor the engine coolant censor and throtle position censor no codes

 

When you disconnect the vac line to the FPR, it will go to full pressure, which on the 5.8 would be around 45 PSI. That pressure is too high for idle, and will cause some of your symptoms, if the FPR itself is not failed. Remove the vac line, and ground the Fuel Pump Test pin on the DCL. Turn on the key (preferrably on a cold engine to avoid flash fire) to run the pump continuously, and check the vac line coming off the FPR for fuel. If you find fuel coming out that line, the FPR is shot. Replace it.

At idle, with no intake leaks, the intake vacuum should be around 20 in. Hg. At WOT, the vacuum approaches 0. I.E. with the line disconnected, it will think the truck is at WOT all the time. At 20 inches vacuum, it knows the truck is idling The pressure is proportional to intake vacuum. More vacuum, you need less fuel, because you have less air coming in the plenum. Reduce pressure. At less vacuum, you need more fuel if that air is SUPPOSED to be coming in.

If you don't find the FPR leaking, check the intake closely for vacuum leaks. Disconnect everything except the MAP sensor from the intake, and see what your vacuum is. If it's below 16, you've got an intake leak somewhere. Put the hoses back on one at a time, and keep testing between each hose connection to see if there's a sharp drop in vacuum when something gets hooked back up. You could do this with the engine idling, and putting the hoses back on one at a time to see what makes it drop. There's LOTS of places for vacuum leaks. When you're disconnecting stuff and capping it off, don't forget the vapor purge cannister line between the venturis of the throttle body. That solenoid valve can stick open and cause grief. If the cannister's full of fuel, that would mean a check valve at the tank is probably stuck open, allowing it to pull raw fuel into the cannister.

 

hey thanks old paint im gona print your reply off and cary it to my shop and pinn it to the wall this ole truck belonged to my dad and its been doing this for several years dad was sick most of those years and only carried trash to the dump` about once a week with it the transmission went bad and the e4od was chuncked cause of a 1700 price tag i got another drive shaft and put a c-6 in it people try to tell me that is what is wrong with the engine but that just aint the case cause it was messing up years before the trans went out .dad passed away july 06 and now its mine and i sure would love to get the old thing running better anyway thanks for letting me "bend your ear"

 

Sorry to hear about your loss.

Working on an old Ford can be good therapy, though, especially when it was inherited from the one you lost.

Don't give up on the old truck. It just wants some attention.