Crank, no start

[justins81213]

Changed fuel filter, truck started up fine drove around for about 10-15 mins and hasn't started since and i don't hear my fuel pump coming on now. Have constant 12v to one pin on fp relay, relay ohms out at 70 something and inertia switch is reading 6 point something volts. Does this mean my fuel pumps bad or am i missing any other test? Any input is appreciated!

06 Ford ranger sport
3.0 2wd

 

[RonD]

inertia switch will only show the battery's 12volts for 2 seconds when key it first turned on, its a safety thing
After that it will show 5 to 8volts(no amps) from the computers Monitor circuit, while key is still on

So hook up volt meter to inertia switch again, and cycle key on and off as much as you want to see if you see the 12volts for those 2 seconds

FP relay looks fine, but it can still be broken inside if you don't see the 12volts with key on

New filter can be bad, extreme long shot, inside is now blocking fuel flow, but having a fuel pump failure just after changing the filter is as well
UNLESS............................
If you changed the filter because you were having fuel flow issues, then having the pump fail now won't be that much of a long shot, i.e. pump was already failing


You could do 50/50 test just to confirm its a fuel issue

 

[justins81213]

It was working fine before no hesitation no intermittent or anything. Going out to check for 12v at inertia switch now so let you know in a min on that as for relay just turn key on and make sure the 12v stays? Also is there any grounds by the filter i could've hit or anything?

 

[justins81213]

And what is the 50/50 test. Just saw that part?

 

[rumblecloud]

50/50+ spray starter fluid in the throttle body and turn the key. If it starts, and stalls then it's a fuel issue.

 

[justins81213]

Inertia switch is 12 then drops to 6.8 and relay has 2 points of 12v with key on

 

[RonD]

With key off you should have one 12v slot in fuel pump relay base, from fuel pump fuse
With key on there should now be a 2nd 12v slot, from PCM relay

The computer grounds the FP relay for 2 seconds as it boots up, then it won't ground it again until engine RPMs are above 400, cranking speed is 200rpms
But it will ground FP relay again if you turn key off and then on again

Yes, 50/50 test is the one that's been used since 1890's and the first gasoline engines
Manually put fuel into the engine
Try to start engine
If its starts and dies you know spark and spark timing is good, but there is no "self fueling"
If it doesn't start then spark issue(or compression)
50/50 and instant results on where to look next

 

[RonD]

If you don't HEAR the fuel pump run for those 2 seconds then its not getting the 12volts or is bad

Fuel pump is not quiet, should hear a HUMMMM from behind the cab
The ground and 12v wires for the fuel pump do run in the same frame rail as the filter, but there are no connections there to disturb, fuel pump is grounded in the cab near inertia switch, if I remember correctly

 

[justins81213]

I'm not hearing pump at all do you know where at by the inertia switch so i can rule that out while I'm at it? Don't mind replacing the fuel pump just wanna be 100% sure that's it

 

[justins81213]

So I'm looking at fuel pumps an my door sticker says my wb is 112 but when i look up fuel pumps for my truck i get wb of 111.5,.6, 117.4,.6 and 125.7,.9 it's this correct?

 

[rumblecloud]

I think the door sticker numbers are "close enough" numbers. So yours is 111.5 but referred to on the sticker as 112.

 

[justins81213]

I think the door sticker numbers are "close enough" numbers. So yours is 111.5 but referred to on the sticker as 112.

Thank you!