Ahh, Stranded and Fuel Pumps don't prime/turn on!!!!!!!

Mylesofsmyles · Feb 21, 2015

Truck ran great all morning....died on a scary road...just sputtered, stalled and died.

Spark good...clearly NO FUEL!

Did what I could, road side, and got it running and drove to safety.

After further diagnosis....I confirmed both Fuel Pump Relay and EEC Relay both work as they should....even swapped Fuel Pump Relay to confirm.

At Key On....NO FUEL PUMP PRIMING!

How did I get it running....jumped ground from battery to Red Diagnostics Port, to force pumps on.

So, with my diagnosis, I assumed it'd be the ECU....story there is a few months ago, I swapped in a used Manual Trans ECU from eBay....it's worked great. Being used, I assumed it went bad, so I swapped in my known good Auto ecu, when I got home....CAR WILL NOT START on Auto ECU....and will now only start on manual ecu, if I jump ground to said connector....

Any help would be much appreciated...this '85 2.3L EFI Ranger is kind of my daily transportation.

Mylesofsmyles · Feb 21, 2015

I'm scratching a hole in my head wondering what I missed...

I followed this guide...

http://easyautodiagnostics.com/ford/4.9L-5.0L-5.8L/fuel-pump-relay-tests-1
&
http://easyautodiagnostics.com/ford/4.9L-5.0L-5.8L/eec-power-relay-tests-1

Everything checked out, BUTTT.....

Testing the HIGH CURRENT (12V+), pin #4 of FUEL PUMP RELAY shows no change from key On to key Off...It's ALWAY HOT!

Could it be a bad ignition switch, or related, wiring?

Mylesofsmyles · Feb 21, 2015

^

Nah, I overthank that last part....

When I jumped that one wire on the test port to ground...right on the batt, the truck ran.

I drove it 16 miles home.

So, why isn't my fuel pump getting it's switched ground?

Mylesofsmyles · Feb 22, 2015

I hate hunches...

Going to get a new ignition switch today, and try that....don't know what else to do!

Someone must have a clue.

RonD · Feb 22, 2015

When you Ground the OBD I Fuel Pump slot you are doing what the computer does on exactly the same wire.
This means ignition switch is OK, EEC relay is OK, Fuel Pump relay is OK.

So issue is in the computer OR its connector/wire

Diagram here of the computer connector: http://www.auto-diagnostics.info/ford_eec_iv
Pin 22 is the Fuel Pump activation connection.
Unhook battery
Always Unhook battery when removing or reconnecting computer's connector.
Hook battery back up and then turn on the key
Check pin 22 on connector for 12volts(battery voltage), if no or low voltage then wire is bad, broken connection
The power for the fuel pump relay comes from the EEC relay, and a relay is just a coil of wire, so will show up on pin22 as 12v, if you ground pin22(like computer is suppose to), fuel pump relay activates and pumps come on.
Pin22 and the OBD I connector's Fuel Pump slot are spliced together.

Other thing to check is that there are 4 or 5 Grounds the computer needs, they are not shared inside the case, you could have a loose Ground that is used for the Fuel Pump circuit.
Look at diagram for the Ground Pin numbers and check each one, I think 16, 20, 40, 60 are grounds

Mylesofsmyles · Feb 22, 2015

Swapped ECU, again...with my old, original unit. Truck took a second, but fired right up.

Seems nominal now....

Guess that manual ECU I bought was bad.

All signs were pointing towards the ECU yesterday, don't know why it fooled me yesterday, and didn't start after swapping.

Ahh, Stranded and Fuel Pumps don't prime/turn on!!!!!!!

Mylesofsmyles

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