My F150 all of a sudden started running terrible. One day it was fine, the next day it was like this.
Will not idle unless you constantly pump the throttle. SEEMS starved for fuel, but I could be wrong. Does nothing to indicate an ignition problem.
Will run down the road, but poorly. Replaced fuel filter and nothing changed.
Truck has 306,000 miles. Injectors serviced once at 170,000. Otherwise no engine parts replaced.
I have a Haines manual but no code reader and reading all that stuff with sweeps of a needle on a volt meter is not something I look forward to.
Wondering if someone can point me to a shortcut. I'll buy a code reader if I must. Did check the MAP sensor voltage and the output is only 2.5 volts and the manual says it should be about 5. However I checked my '94 which is running fine and it is only 2.5 also.
The in tank fuel pump was replaced at 170,000. Truck is right in the middle of the shop and I need it out of there to get another in.
Any help would be most welcome. MOST welcome.

Thanks, Lynn.

 

Hi Lynn. I'm just guessing at this, but my first guess would be another bad fuel pump. Second guess would be the fuel pressure regulator. This is easy to check if you have a pressure gauge; you simply screw it into the schrader valve on the fuel rail. Good luck.

 

Thanks for the tip. Is the Schrader valve just screwed in to 1/8" female pipe thread? I can just remove it and screw in a gauge? If so what pressure range gauge do I need? I have several. But I'm guessing the one range I don't have might be the one I need.
Thanks again. Lynn

 

[updated:LAST EDITED ON 01-Mar-02 AT 10:01 PM (EST)]Lynn you don't have to read the sweeps on a volt meter hook it up and then read the check engine light flashes from drivers seat. I too suspect a fuel delivery problem. You can short the fuel pump test lead in the EEC-IV connector and test fuel pressure with out having the engine running. And I don't think you can unscrew the schader valve. I cheat on the fuel pump test. I was able to buy a Ford Fuel injection cleaning kit and I hook it up and this bypasses the in tank pump plus it gives the truck inquestion an injection cleaning.

 

[updated:LAST EDITED ON 01-Mar-02 AT 10:21 PM (EST)]Could it be with a Schrader valve I could just use a good tire gauge to check the pressure? My manual is at the shop 3 miles away or I would look and see what the fuel pressure is supposed to be. Would be great if I could. And then I wonder if it is low how to tell if it is the regulator or the pump?

With all your help I think I'm getting closer, thanks, Lynn.

 

>Truck has 306,000 miles.

well there's your problem.......

 

Hi Lynn, I've never heard of anyone using a tire gauge on the fuel rail. Not a bad thought, but I'm sure gas would be going everywhere. The gauges screw on, as I recall pressure is around 30lbs at the rail. A good way to check the high pressure pump, let's just say a easy way, is to let the system pump up and then disconnect the fuel filter, use a rag to block the spray. You'll recognize the 60lb spray (watch out for your eyes!) A shop wouldn't recommend this, but then this is a way to check it without any equipment.

 

Lynn, I would not try the tire pressure gauge route unless you want to try for the human torch record. The fitting on the fuel rail takes an adapter fitting to be used with a gauge, I just bought one to test my 90 and it came with an adapter fitting for the ford rail fitting ( cost $29.00 at Pep Boys ). Don't try to remove the valve from the fitting as it will not come out easily and you might wreck it and then you might have to spring for a new fuel rail. The fuel pressure should read 50 to 60 pounds with the engine off and 40 to 50 running, remove the vacum line from the fuel pressure regulator and the pressure should rise to the 50 to 60 pound reading.My system doesn't seem to hold any pressure after it the engine is shut off but that might be an indication of another problem such as a leaking check valve in one of the pumps. The pressure is set higher on the I6's ( normal ford pressure is around 40 ) because of the tendency of the fuel to boil in the fuel rails.

Bob / stractor