Any Mustang Guru's Here? It's a EEC4 riddle...

[Mylesofsmyles]

My love for the Lima 2.3 has led me to a fox mustang convertible....

It's a 1990....
2.3 w t5

only runs when i jump power to fuel pumps...

i need help figuring out why i need to jump pumps.

This place has always been so helpful, when I've needed help with my 85 2.3 ranger...not sure where to go for a 2.3 Fox mustang source.

Thanks,

Myles

 

[don4331]

I assume you have done all the standard checking of fuses.

Power to pumps can be interrupted by the 'accident' switch tripping. Have you tried resetting that?

 

[RonD]

Where are you "jumping" the pumps at?

Yes, between the engine compartment and the fuel pump is an inertia switch, this switch will pop open in a collision or rollover, it can be reset but needs to be replaced if it ever "trips", because once it opens once it can't be fully reset, small bumps can trip it again.

Ford uses a relay and the computer to run the fuel pump(s)
Fuel pump relay will be in the engine compartment, it will have a Green base.
This relay passes power to the inertia switch, the power is from a 30amp fuse or Fusible link.
Find the Fuel Pump relay, pull it out of the Green base, key should be off
Test for voltage in the base's slots
1 slot should have 12volts, that the 30amp fuse or fusible link power, it is on 24/7.
If no 12volts is found fuse or fusible link is bad.
That power is the Load/Fuel pump power that passes thru the relay when it closes

Now turn the key on
Check slots again, another slot should now have 12 volts, that's the power for the relays coil.
When key is turned on this relay's coil gets 12volts but has no Ground so doesn't close.
The computer controls the ground.

Not sure where it is on the Mustangs but there will be an OBD1(EEC4) test connector, usually in the engine compartment on the main wiring harness by the firewall.
It isn't mounted to anything it just hangs from the harness

Look here for what it looks like: http://www.therangerstation.com/tech_library/OBD_I.shtml

In the second drawing you will see the Fuel Pump slot in the OBD1 connector.
That slot is the Ground for the fuel pump relay's coil, it is spliced to the computer's wire that should activate the fuel pump relay by grounding it.

So..............if you turn on the key, and then put a jumper wire in that slot and Ground the jumper wire the fuel pumps should come on, if relays coil has 12v and the fuel pump relay "clicks" closed and the fuel pump fuse is good.
If pumps still do not come on then you will need to find the inertia switch, can be in the truck or passenger compartment.
With key in and Ground jumper in place(and grounded), check for 12volts on BOTH sides of the inertia switch.

 

[Mylesofsmyles]

I was jumping at the relay...from constant hot right to fuel pump

I need to find the inertia valve....and I'll test it

I'll also check the relay wiring as you've suggested...though that's what I did yesterday and all signs seemed good


I'll also consider the OBD1 port to see what I learn as well.

Thanks for the suggestions.

 

[RonD]

If pump works by jumping at fuel pump relay then inertia switch is fine.

When key is off there should be only that one slot in relay base that has power
With key on there should be 2 slots that have power now, that other slot's power is from the EEC relay, if there is no 2nd slot with power then you found the problem, that wire is bad, or EEC relay is or EEC fuse is(30amp)

 

[Mylesofsmyles]

EEC relay seems okay. I tested and it seems okay, based on the tests I performed.

EEC fuse...where?

 

[Mylesofsmyles]

Should the pumps prime with key on? They don't.

 

[RonD]

The OBD1 connector was mentioned just as a means of grounding the FP relay to test if the Ground wire is connected to relays base.
You can of course try to read codes using that connector but probably won't help with this issue.

Yes, fuel pumps should come on for 2 seconds when key is turned on, then won't come on again until engine RPMs are above 400.

That's each time the key is turned on, so you can turn key off and on repeatedly, won't hurt any thing.

When EEC(computer) starts, CEL will come on and it will Ground the FP relay for 2 seconds, then wait for RPMs to get above 400.

If EEC isn't powering up then FP relay won't be Grounded.

EEC relay passes power from a 30amp fuse in engine fuse box or from a fusible link hooked to battery post of starter relay(solenoid).
EEC relay's coil is grounded to inner fender and gets power from ignition switch when key is turned on.

 

[Mylesofsmyles]

Not sure if this helps us along...the only thing I need to do is jump fuel pumps, with ignition on, and it'll run...

Is that an indicAtor that I'm powering the EEC?

 

[RonD]

Yes, EEC Relay would need to be working for EEC to have power, it also powers fuel injectors, spark system and fuel pump Relay, so test if you have 2 slots with power in the FP relay base when key is on, if only 1 slot has 12v then you have a broken wire in the FP relay base

 

[Mylesofsmyles]

Tested both FP relay & EEC relay...all systems "nominal"

...except for, there's no grounding signal at FP relay connector. OUTPUT from EEC computer CONFIRMED...

It's not making the signal from the connector under dash, passenger side....to the driver footwell connector....

May need to do a wire repair...

So, i'm going to get to the bottom of this.

 

[RonD]

Did you find the OBD1 connector?

That has the Ground wire for the FP relay, use a jumper and test if it is working to Ground relay.

A relay's coil(activator) is just that, a coil of wire, so in this case, when key is on one end of that coil of wire will get 12volts, so the other end of the coil wire will also show 12volts, it is just a wire so passes voltage.
But the voltage is just "sitting there", not "flowing".
Like hooking up 1 contact on a light bulb up to power, voltage is there but no light, in order to get voltage "flowing" you need to Ground the other contact, then bulb lights up, or in this case relay activates, closes.


Wiring for FP relay

EEC4(pin 22)---------/------------------(ground)FP relay(12v)---------EEC relay
OBD1 Port-----------/

When key is on, and replay is plugged into it's base, pin 22 at EEC should show 12volts, that means the wire from the FP Relay to the EEC is OK.
Fuel Pump slot in OBD1 connector should also show 12volts if key is on as that slot's wire is spliced into the Pin 22 to FP relay wire.

The EEC4 also needs good Grounds, it has several Ground wires, which are not shared internally, just FYI.
The EEC4 will Ground pin 22 internally when it wants the fuel pump relay to close.
So pin 22 is not a "testable ground" except for those 2 seconds just after key is turned on.


Here is a diagram of an EEC4: http://www.auto-diagnostics.info/ford_eec_iv
To test if all it's ground wires are good