Sat for a month, Fuel pump wont prime

[Acgallen]

Another problem after the other. When i go to turn my key i hear silence, whereas a month ago it would prime and start. Its a rebuilt 306 5.0 that would cut out at higher rpm's, so i replaced the fuel pump a few days ago and still no priming. Im getting to the point where i think wiring a switch to turn the fuel pump would be better, but im not ready to give up lol. The relay is relatively new, the inertia switch is good, and fuze didn't blow either. Sounds to me like i have a grounding problem but my grounds are sanded and tight. Am i missing one possibly? My connector at the frame rail is pretty beat up as well, ill attach a picture. Megasquirt and a harness is my last resort.

 

[RonD]

You can use jumper wire in the Fuel Pump relay's socket/base to send fuel pump 12volts directly

Confirming either pump issue or its not getting 12v and good ground, pump doesn't run
Or a relay activation issue, if pump runs

You can test 12v wire to pump with OHM meter, should see 2 to 6 ohms if pump motor is connected to 12v wire and a good ground

 

[Acgallen]

You can use jumper wire in the Fuel Pump relay's socket/base to send fuel pump 12volts directly

Confirming either pump issue or its not getting 12v and good ground, pump doesn't run
Or a relay activation issue, if pump runs

You can test 12v wire to pump with OHM meter, should see 2 to 6 ohms if pump motor is connected to 12v wire and a good ground

I was hoping you would find this post Ron. Ive combed through a bunch of your replies to other threads. I will try jumping it through the relay. Its a brand new pump so im hoping nothing wrong with it. I did try it turning it on yesterday, heard a faint click 2 ish seconds after turning the key, which usually happens when its working. Thank you for the reply.

 

[Acgallen]

You can use jumper wire in the Fuel Pump relay's socket/base to send fuel pump 12volts directly

Confirming either pump issue or its not getting 12v and good ground, pump doesn't run
Or a relay activation issue, if pump runs

You can test 12v wire to pump with OHM meter, should see 2 to 6 ohms if pump motor is connected to 12v wire and a good ground

Sorry for not replying earlier, i broke my leg. The relay was getting 12v, i jumped the relay and heard the click after 2 seconds, but no pump sound

 

[RonD]

FP Relay socket should have 4 or 5 slots, only 4 are used
Key off
One slot should have 12volts, thats from the battery, always has 12volts, if not then a fuse or fusible link is blown
Remember that slot, this is the 12volts with 20amps that powers the fuel pump

Key on
Test the other slots, should now have a 2nd slot with 12volts, that's from the EEC/PCM Relay 12v only with key on, and low amps, only for activating the relay

That leaves 2 unknown slots
One is from computer, the ground that activates the relay
The other goes TO the fuel pump motor

If you have a 12v test light hook it to battery positive and one of the unknown slots
Turn on the key and see if it lights up for 2 seconds
If so thats the slot for the wire from computer
If not then its most likely the slot for the wire TO the fuel pump

So test the other slot for the 2 second light up to confirm

Once you have ID the 3 slots, 12v full time, 12v key on, and Computer ground, the remain slot goes TO fuel pump

You want to jumper the 12v full time slot to the TO Fuel Pump slot, and fuel pump should come on, if not then no 12v at fuel pump so wire or fuel pump issue

 

[Acgallen]

FP Relay socket should have 4 or 5 slots, only 4 are used
Key off
One slot should have 12volts, thats from the battery, always has 12volts, if not then a fuse or fusible link is blown
Remember that slot, this is the 12volts with 20amps that powers the fuel pump

Key on
Test the other slots, should now have a 2nd slot with 12volts, that's from the EEC/PCM Relay 12v only with key on, and low amps, only for activating the relay

That leaves 2 unknown slots
One is from computer, the ground that activates the relay
The other goes TO the fuel pump motor

If you have a 12v test light hook it to battery positive and one of the unknown slots
Turn on the key and see if it lights up for 2 seconds
If so thats the slot for the wire from computer
If not then its most likely the slot for the wire TO the fuel pump

So test the other slot for the 2 second light up to confirm

Once you have ID the 3 slots, 12v full time, 12v key on, and Computer ground, the remain slot goes TO fuel pump

You want to jumper the 12v full time slot to the TO Fuel Pump slot, and fuel pump should come on, if not then no 12v at fuel pump so wire or fuel pump issue

followed the steps. Tan/Blk is always 12v hot. Green is fuel pump wire. The Blue/Or reads 0v both with key on and off. Red wire shows .25 v. There is no power to the inertia switch, but when i jump 12v to fuel pump wire it reads 12v. I jumped the green and tan slots but still no fuel pump. Brand new fuel pump as well.

 

[RonD]

Yes looks correct
From older wiring diagrams
Red is key on 12v from EEC/PCM relay
Blue/orange(red) is ground from computer
So those 2 wire run the relay part, low amps

Yellow/black(Tan/Blk) or black/yellow should be full time 12volt power, 20amps
Green/yellow is OUT to fuel pump, well out to inertia switch then a pink wire from inertia switch OUT to fuel pump

So if there is a jumper wire from(Tan/Blk ) yellow/black to Green/yellow then inertial switch should show 12v in on green wire and 12v OUT on pink wire
Fuel pump should come on, key on or off wouldn't matter

 

[Acgallen]

Yes looks correct
From older wiring diagrams
Red is key on 12v from EEC/PCM relay
Blue/orange(red) is ground from computer
So those 2 wire run the relay part, low amps

Yellow/black(Tan/Blk) or black/yellow should be full time 12volt power, 20amps
Green/yellow is OUT to fuel pump, well out to inertia switch then a pink wire from inertia switch OUT to fuel pump

So if there is a jumper wire from(Tan/Blk ) yellow/black to Green/yellow then inertial switch should show 12v in on green wire and 12v OUT on pink wire
Fuel pump should come on, key on or off wouldn't matter

The red wire with the key on and off gets from .2-.3 volts. Leads me to think the EEC relay is bad, or worse.

When i jump the yellow/black to Green/yellow the inertia switch pink wire is hot. Pink/Blk reads hot when it goes into the frame on the drivers side towards the fuel pump. There is a grounding wire (Blk/white) there which is grounded to the fender.

Still hearing a click 2 seconds after the key is turned, but when i jump the wires the fuel pump wont activate.

 

[RonD]

So there is no 12v or no ground at fuel pump connector, or bad fuel pump
40 years ago "new" meant "tested and working"
"New" now means "YOU test it, and we will swap it if it doesn't work"

For the EEC power OUT, the red wire, test the red wire at IAC Valve or any of the fuel injector's red wires they all get 12v from EEC relay when it turns on

EEC relay can have same layout as the FP relay
Has a full time 12volt wire with fuse, 30amp
And a Red wire OUT that powers several engine systems

It has a full time ground
Then gets 12volts from Key On, ignition switch, to activate it

 

[Acgallen]

So there is no 12v or no ground at fuel pump connector, or bad fuel pump
40 years ago "new" meant "tested and working"
"New" now means "YOU test it, and we will swap it if it doesn't work"

For the EEC power OUT, the red wire, test the red wire at IAC Valve or any of the fuel injector's red wires they all get 12v from EEC relay when it turns on

EEC relay can have same layout as the FP relay
Has a full time 12volt wire with fuse, 30amp
And a Red wire OUT that powers several engine systems

It has a full time ground
Then gets 12volts from Key On, ignition switch, to activate it

Could a bad EEC relay be a cause of cutting out at WOT? The whole reason i was chasing what i thought were fuel issues was because the truck cuts out above 3-4k Rpm when driving in any gear. This whole swap has so many headaches

 

[RonD]

No, EEC relay wouldn't cause that

Cutting out above 3,000rpm can be the REV Limiter, the computer "thinks" transmission is in Neutral or Speed is at 0MPH
If will cut off fuel to injectors until RPMs are lower, so engine won't stall just has limited RPMs

Exhaust blockage limits RPMs, engine is a self powered air pump, so if old air(exhaust) can't get out, then "new" air(with fuel) can't come in, so RPMs are limited, this varies in RPM range based on the blockage

Yes, fuel pump flow could also limit RPMs, weak pump, dirty fuel filter, failing Fuel Pressure Regulator

 

[Acgallen]

No, EEC relay wouldn't cause that

Cutting out above 3,000rpm can be the REV Limiter, the computer "thinks" transmission is in Neutral or Speed is at 0MPH
If will cut off fuel to injectors until RPMs are lower, so engine won't stall just has limited RPMs

Exhaust blockage limits RPMs, engine is a self powered air pump, so if old air(exhaust) can't get out, then "new" air(with fuel) can't come in, so RPMs are limited, this varies in RPM range based on the blockage

Yes, fuel pump flow could also limit RPMs, weak pump, dirty fuel filter, failing Fuel Pressure Regulator

Wired my second new fuel pump up to a separate relay circuit, got it to send fuel. Of course i dont have spark now though. My guess is the EEC relay. Its gonna take a week to get here, none around me.

 

[Acgallen]

No, EEC relay wouldn't cause that

Cutting out above 3,000rpm can be the REV Limiter, the computer "thinks" transmission is in Neutral or Speed is at 0MPH
If will cut off fuel to injectors until RPMs are lower, so engine won't stall just has limited RPMs

Exhaust blockage limits RPMs, engine is a self powered air pump, so if old air(exhaust) can't get out, then "new" air(with fuel) can't come in, so RPMs are limited, this varies in RPM range based on the blockage

Yes, fuel pump flow could also limit RPMs, weak pump, dirty fuel filter, failing Fuel Pressure Regulator

I at least got it to start! Bad EEC relay was the culprit, ill let you know tomorrow how it runs.

 

[Acgallen]

No, EEC relay wouldn't cause that

Cutting out above 3,000rpm can be the REV Limiter, the computer "thinks" transmission is in Neutral or Speed is at 0MPH
If will cut off fuel to injectors until RPMs are lower, so engine won't stall just has limited RPMs

Exhaust blockage limits RPMs, engine is a self powered air pump, so if old air(exhaust) can't get out, then "new" air(with fuel) can't come in, so RPMs are limited, this varies in RPM range based on the blockage

Yes, fuel pump flow could also limit RPMs, weak pump, dirty fuel filter, failing Fuel Pressure Regulator

Well it ran better than it did before, still cuts out after 4k rpm. Its 4k on a 4.0 V6 tach so im not sure what the equivalent is for a 5.0. When driving, increasing from 3k rpm it will start to pop a little, then passing 4k rpm it sounds like i hit a rev limiter. It holds good temp and oil pressure, drove fine under 3k. Is this a tuning problem? I have brand new plugs, wires, dizzy, stock rebuilt injectors. It has straight pipes on it with each side having an o2 sensor. Any help would be appreciated, want to see what this thing has.