Hard starting 4.9l

[mitcha]

I have a 1990 ford f150 fwd w/300-6. You must pump the gas repeatedly to get the truck to start unless it is completely warmed up. Sometimes it then runs fine, but other times it will quit every time you put it in gear until it warms up a little. Also my fuel milage is down to around 10 mpg. I have done a complete tuneup and have a new O2 sensor coming. Any ideas?
Mitch

[mustangmike351c]

check the tps

[mitcha]

Thanks. I'll check it out and let you know.

[rhandwor]

Check your fuel pressure regulator vacuum line if leaking replace it. Otherwise do a pressure test on the system.

[mitcha]

Quick update. The O2 sensor seems to have helped some, I don't have to pump the gas. It takes a few seconds of cranking to fire up and then dies but on the second try it usually stays running. I am going to check the TPS and ECT this weekend. I've had this truck since it was new (1990) and have never replaced any sensors. Even with the problems I've been having I have never had a check engine light. What gives?
Mitch

[dandycamp]

I have a rough running 1990 ford f-150, 4.9 2 wd,, I replaced plugs, wires , cap, n rotor.. when i unhook the vacum to my fuel pressure regulator It runs a heck of alot better.. I didnt know it would run without this vacum line hooked up......Would I have a bad fuel pressure regulator??.. also there is some type of heavy black ground wire on the right side lower engine, If your facing the front on the engine "drivers side" well its unhooked and I dont even know where this should be hooked after it comes off the engine block..If you get a chance to look at yours could you let me know thanks.

[rhandwor]

I would say you have a week fuel pump or a bad regulator. Borrow a pressure gage and tell us the reading both with and without the regulator. Look at the ground wire should it go to the negative terminal. Somebody might have changed it and used a different length cable. It surely won't run without one.
If its a lot smaller reply so I'm sure what your talking about.

[dandycamp]

I dont know if its a battery ground cable, Its on the other side of the block, It was unhooked for weeks, I grounded it to the body, but no change in the way its running, also i drove it with that regulator vacum line unhooked, It still ran the same. I have the high pressure fuel pump off another truck I had like this one. It wasnt bad, so I'LL try it on this truck. do I need a special gauge to check to check fuel pressure? Thanks I'LL post what it took to fix it.

[rhandwor]

They have a fitting on the fuel rail it is about the same size as a tire valve stem. If you have an old bicycle tire pump or an old r-12 freon hose not being used check if it will fit. You could remove the valve stem push a 3/8 inch fuel hose over it with a clamp and a pressure gage installed in the hose.
You can buy a gage with connector at the parts store. This is the safer way to test.