Fuel pump relay kicking off

[DonLawson84]

Other than the inertia switch, is there any other safety switches or pressure switches that cut power to the fuel pump relay? When I shut the truck off and try to start right up, the fuel pump relay will not kick on when ignition is on
1995 302

 

[L\Bronco]

Other than the inertia switch, is there any other safety switches or pressure switches that cut power to the fuel pump relay? When I shut the truck off and try to start right up, the fuel pump relay will not kick on when ignition is on
1995 302

Hey Don
no other safety switches other than inertia. The Pcm supplies ground to the fuel pump relay for 3 seconds on initial key on, then when it sees an ign signal (PIP). its power comes from the EEC power relay.
The EEC power relays go bad occasionally, plus, I've seen bad caps in the PCM cause the pump to not run sometimes. (Not exactly the same symptom as yours, but, you never know)
Does it start if you re-cycle the key?

 

[DonLawson84]

Most times will start, some times I cycle the key and never hear the fuel pump kick on. Looking into it more, the fuel pump relay is not engaging. I replaced that relay with same intermittent issue

 

[L\Bronco]

Most times will start, some times I cycle the key and never hear the fuel pump kick on. Looking into it more, the fuel pump relay is not engaging. I replaced that relay with same intermittent issue

One last question, when it won't start, does the check engine light work with the key on - engine off?
this will help with the diag.
Cheers

 

[DonLawson84]

One last question, when it won't start, does the check engine light work with the key on - engine off?
this will help with the diag.
Cheers

Yes, check engine light works. Also, when I pull relay 1 I can hear relay 2 clicking but it will not stay engaged

 

[DonLawson84]

Update:
Not getting power to fuel pump and only 10v to 85 & 86 (coil) on the fuel pump relay. Interia switch also metered closed. 20A fuse feeding pump has power.

 

[wyo58]

Update:
Not getting power to fuel pump and only 10v to 85 & 86 (coil) on the fuel pump relay. Interia switch also metered closed. 20A fuse feeding pump has power.

Hi Don,

The coil gets 12 volts on one leg and the pcm grounds the other terminal for 3 seconds. If your only getting 10 volts there I'd check that relay connector real close for a bad connection. I've seen and read both the EEC relay and the fuel pump relay have a tendency to corrosion because of where they are located in the engine compartment. It should be 12 volts.

 

[Ray_Bronco]

Other than the inertia switch, is there any other safety switches or pressure switches that cut power to the fuel pump relay? When I shut the truck off and try to start right up, the fuel pump relay will not kick on when ignition is on
1995 302

Other than the inertia switch, is there any other safety switches or pressure switches that cut power to the fuel pump relay? When I shut the truck off and try to start right up, the fuel pump relay will not kick on when ignition is on
1995 302

i have a 96 and there is a relay fuse indside on the drivers side that controls the fuel pump.. i am no way a mechanic so not sure if you tried this or if it will solve the issue

 

[L\Bronco]

Update:
Not getting power to fuel pump and only 10v to 85 & 86 (coil) on the fuel pump relay. Interia switch also metered closed. 20A fuse feeding pump has power.

Sorry Don, I've been off drag racing.
It only takes 4-6v to activate that relay coil, so I wouldn't focus there.
How did you check power at the pump?
If you have access to the pump connector,
-measure across the pump,(With the relay on)
-Then measure cross the positive side (with the relay on) (positive battery post to the positive side of the fuel pump)
-repeat on the ground side.
If you measure batt voltage across either side, leave the lead on the battery and move the other lead from the pump towards the battery terminal that the other lead is on. (activate the relay every time you measure)
When it changes from batt to zero across the side of the circuit you are on, the bad connection is between the last bad measurement and the good one.
Hope that makes sense.
Good luck.
Cheers