Hey guys!
i have a 1998 F-700 with the 429. it starts out good but when it warms up it will loose power and start running very poorly, it runs at idle ok but as soon as you hit the gas it dies out. we have changed the fuel pump, filter and a regulator but that did nothing for the situation. i was told it may be in the ignition so we changed the distributor from the advice from another mechanic but that didn't fix it ether. so after that we put a fuel presser gauge on it an went for a drive when it happened again the gauge read 18 to 20 psi and when its runnig good its at 32 to 40 psi. so it seems to be loosing fuel presser. what do you guys think?

 

Have you looked in the fuel tank to see if something could be at times restricting flow? Sounds like you've covered the rest of the fuel bases.

 

have you replaced the fuel preasure regulator.,if so,like other reply,check tank for debrie

 

jpr38057 thats my next step we are going to drain the tank check that out.

guss36 we did replace the regulator, didnt help it

 

Let us know what you find out.

 

will do, it will be monday befor we get at it again.

thanks!

 

Had one that was doing the exact same thing. There is a electronic box on the passenger side fender- Change that. Should be available at napa.

 

Did you locate the problem?I have a 98 F700 with the same engine which runs great untill i hit 1/4 tank of fuel.Then it will barely idle and have no power untill i put in some more fuel then it runs excellent

 

There are rubber seals in the fuel pump/pick up assy. that can go bad and cause a leak in the fuel system which will give bad pressure, dual tanks? You replaced the fuel pump on one side, try switching sides and see if the problem goes away. Fuel injected or carburetor?

 

No dual tanks on F700 with a gas engine unless it was done after the fact.

 

my '91 f-700 has dual tanks, saddles under each door.I guess the upfitter could have put them on?

 

Is yours gas or diesel?

 

Gas, 429 fuel injected. Both the fuel lines and tanks look oem but still could have been put on by the upfitter.

 

Found a pic from the 91 f700 truck shop manual showing dual fuel tanks, guess mine are oem after all.

 

I'm looking for information on the passenger side fuel tank sending unit. What ohm's resistance would the sending unit be for a 1980 F-600? I am trying to change an F-600 Derrick Truck from propane back to gas and was told that I need to know what ohm resistance the sending unit needs to be? Any info on this would be appreciated

Tim