95 3.0 Fuel Pump stays on, or "flickers" the relay on and off.
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Joined: Apr 2019
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From: Loranger, La
95 3.0 Fuel Pump stays on, or "flickers" the relay on and off.
My ranger seems to prime the fuel pump fine , but it resets quickly and sporadically. Occasionally it will just stay on. The Schrader valve on the fuel rail seems to be getting plenty pressure (! I am aware until I rent or buy a fpg to test it I won't know for sure.) When I unplug the fuel pump relay there is still a whining sound over the intake manifold/ under the coil pack. When I put the relay back in the clicking/flickering continues. The truck ran fine and just didn't fire one morning. Am able to get a sputter from starting fluid. Any advice on which circuits to test and how much voltage I'd be getting per would be a huge help and time saver. Thanks in advance, Kenny.
Welcome to the forum
Pull out fuel pump relay
Key OFF
Test each slot in relays, now open, base/plug in
Only one slot should have 12volts <<<< from fuel pump fuse, 20amp
Remember which one it is
Now turn on the key
A second slot should now have 12volts <<<< this is 12volts from PCM relay, full 12volts, if its lower then you have a corroded wire
Automotive relays all use the same base structure, like this: http://www.gtsparkplugs.com/images/m...iring-840x.jpg
Slots 85 and 86 are used to activate the relay, slots 30 and 87 pass the power to the device, so either 30 or 87 will have 12v key OFF
85 OR 86 will have 12v key ON, find out which one
The OTHER one will be the Ground wire that runs to the computer, the computer GROUNDS that slot to activate the relay, for the 2 seconds or full time once engine starts
So IF........85 or 86 has a good steady 12volts with key on, then hook volt meter up to battery positive and the GROUND slot, turn key on and you should see 12volts when computer grounds that slot for 2 seconds.
If you ever wondered where the screwy numbering for automotive relays came from its from DIN 72552 designations
Pull out fuel pump relay
Key OFF
Test each slot in relays, now open, base/plug in
Only one slot should have 12volts <<<< from fuel pump fuse, 20amp
Remember which one it is
Now turn on the key
A second slot should now have 12volts <<<< this is 12volts from PCM relay, full 12volts, if its lower then you have a corroded wire
Automotive relays all use the same base structure, like this: http://www.gtsparkplugs.com/images/m...iring-840x.jpg
Slots 85 and 86 are used to activate the relay, slots 30 and 87 pass the power to the device, so either 30 or 87 will have 12v key OFF
85 OR 86 will have 12v key ON, find out which one
The OTHER one will be the Ground wire that runs to the computer, the computer GROUNDS that slot to activate the relay, for the 2 seconds or full time once engine starts
So IF........85 or 86 has a good steady 12volts with key on, then hook volt meter up to battery positive and the GROUND slot, turn key on and you should see 12volts when computer grounds that slot for 2 seconds.
If you ever wondered where the screwy numbering for automotive relays came from its from DIN 72552 designations
Last edited by RonD; Apr 29, 2019 at 06:39 PM.
Thread Starter
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Member
Joined: Apr 2019
Posts: 2
Likes: 0
From: Loranger, La
Thanks for the quick help. I'll have to check it when I get back to it tomorrow... It's just hard to get a good reading when it's cutting on and off so quickly. Maybe continuity would be easier to pinpoint, dunno.
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