I have a 1999 F150 4.6. Went to start and it cranks really strong but doesn't fire.

This is what I've done:
Checked inertia switch behind kick panel, which didn't need resetting.
Tested with ohm meter both fuses # 10 & # 18 in dist box both good.
Test for 12V in relay socket #301 go 12V on 2 pins.
Removed fuel filter, cranked to see if fuel came out, NO fuel, replaced with new filter.

I'm assuming it is my fuel pump.
Have I missed anything?

Any help appreciated.
Kenny

 

Check the inertia switch behind the passenger side kick panel.

 

Sorry forgot to add that I checked the inertia switch.

 

What 2 pins did you get + VDC on and what state was the key in when you tested ?

Did you bench test the relay to see if it was working correctly ?
- Alternate is to swap with another full size ISO relay like the trailer tow battery charge relay.

The fuel pump will not run if the system has had the key cycled without the truck being started.
- The fuel system is smart enough to know the fuel rail should have pressure on it, if the truck has not run. if the relay is bad, the truck cannot ID this.

 

With key off pin 30 has 12v
With key on pin 30 & 86 has 12v

On relay
pin 85 to 86 cont
pin 85 to 30 open
pin 87 to 30 open
pin 87A to 30 cont
pin 87 to 86 open

How do you get the pump to run if the key has been cycled without the truck being started?

Just swapped relay with brand new on I had in my trailer tow package, same part # as one removed. No start either.

Also noted fuse #10 has 12v with key off and nothing on fuse #18 until key to on position. I assume this normal.

Thanks SScully

 

Put a gauge on the fuel rail and check to see if it has pressure.

 

I don't have a fuel gauge, but if I cranked the motor without the fuel filter in place and nothing pumped out wouldn't that create no pressure on fuel rail?

 

You don't necessarily need a gauge - you can hit the Schrader valve with a screwdriver tip and see if any fuel sprays out.

Stand outside the truck by the gas door and have someone turn the key to the ON position - don't try to crank it - and you should hear the fuel pump run for a couple seconds to prime the system. If you don't hear anything, the fuel pump is shot or you do have an electrical issue.

 

glc, I turned the key to on and pushed on valve on fuel rail and fuel did come out. It didn't seem very strong. So for the hell of it I cranked it over and it fired up and started running. Have no clue why!

All I did prior is disconnect the negative lead to clear things and had the charger on battery for about 40 min cause I was cranking it and it may have been a little low. Went out and tried what you suggested with screwdriver in valve and gas came out so I tried to start it and everything seems to be good.


The only thing I really did was replace the fuel filter but it still didn't start. I'm really at a loss but happy she's running again!

Thanks to all for the helpful inputs. Wish I could really help someone else on this problem but I'm confused.

 

Anyone have a guess or reason why the truck started after all the testing I did?

Did disconnecting the battery and charging up the battery have an effect that caused it to start?

Did the original failure to start get cleared when I disconnected the battery?

I'm not trying to look a gift horse in the mouth but I hate when things start working and not knowing what I did that caused it.

Kenny

 

You were half way there, you also needed to apply ground and power to terminals 85& 86 to activate the relay to see if it was operational.



the truck does not blindly cycle the fuel pump. You did remove pressure from the system when you removed the fuel filter, but go some pressure back again when you cycled the key ( else the schrader vale would have had nothing on it ).
The only way to check this is to pull the fuel pump relay and momentarily jumper the normally open contacts without the key or if the truck has been cycled to the on position without starting.



You might have had carbon in the relay socket and / or a questionable relay that replacing it did the trick.

It might also be something on the fuel pickup in the tank that moved away.

You also disconnected the battery, so the truck forgot that the fuel pump had been run without starting the truck.
- This series does not know pressure, it keeps track of key on start to see if it should keep doing it ( I think 3 or 5 is the number of key cycles without a start that will time out the fuel pump ).

If it does the same thing again, try removing the fuel pump relay and jumpering the normally open contacts. you should hear the fuel pump run. Don't just leave the jumper installed.

If you do not hear it run, try smacking the bottom of the fuel tank with a rubber mallet.

This is what I found with my 2001 when I had a crank no start issue a decade ago.
https://www.f150online.com/forums/v8...e-my-cure.html

 

SSCULLY, thanks for the informative explanation and help on directing me in the right direction. I'm glad I took my time testing before jumping in and dropping the tank.

Thanks Again,
Kenny

 

Years ago, I bought a used 89 Ford Escort GT for my 16 yr old son. One day it wouldn't start after sitting in the driveway. I found out the fuel pump wasn't running. So, I reset the inertia switch. No help. After resetting it a couple more times, the pump ran and it never failed to start again!!!!?????

 

Roadie, I did check that but I wasn't sure how far up the red button is when it's set off. I pressed it down but didn't seem to move at all. I really learned a lot from all the help here.
Kenny

 

After starting & running perfect for 4-5 days I went out yesterday to use the truck and the same thing. Turns over like always but doesn't start or sputter.

Popped the hood went to check for fuel in the rail first without key on and nothing. Turned key on but not to start and checked for fuel and nothing.

In the power dist box I pulled fuse #2 & #18 which both were good, reinstalled them. Cranked the engine and after a few seconds it fired up as usual.

It's almost like after I parked the truck after driving it, it turns off the fuel pump.

Any suggestions, I'm at a loss now.

Kenny