Won't start, fuel pump runs all the time

66_93

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93' 5.0 Automatic...This problem started 2 weeks ago...Would not start but the fuel pump keeps running. Try several times and sometimes pump would run a couple of seconds, like it should, cut off and the engine would start...This has gone on for 2 weeks...no codes and cannot pull codes when the ignition is on the fuel pump continues to run. Started once in this condition but ran rough and the check engine light was on...still no codes...have 40 psi at the fuel rail...yesterday, started it in the morning turn it around in the drive to replace the fuel sending unit...when I finished that project the Bronco never started again...and the fuel pump runs all the time...code reader won't pull codes...Tried the start by jumping the starter solonoid no key in ignition...didn't start...think she died

Thanks for any help

 

Rons beast

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No codes...or can't pull codes, and no injector action, may be as simple as a blown fuse for the power module. Check all the fuses. BTW..the fuel pump is supposed to run all the time with an injected engine.

 

miesk5

96 Bronco 5.0
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yo,

Check battery voltage; pull and have it tested for free, recharge if still good.

All symptoms lead to a bad FP relay; The Pump relay probably has the points welded. by Seabronc

Try swapping Horn Relay w/ FP Relay In Power Distribution Box (PDB); here is the PDB Diagram in a 96, sim to a 95; the PDB is Located under the hood on the drivers side fenderwell, behind the stock air cleaner location. See Relay #3; you can swap it temp w/da FP relay to verify if it is good, check for corrosion in socket & relay..."

Source: by miesk5

96pdb.gif

Relay 1 Relay PCM Power Relay

Relay 2 Relay Fuel Pump Relay

Relay 3 Relay Horn Relay

Relay 4 Relay Trailer Marker Lamps Relay

Relay 5 Relay 4WABS Relay No. 2

or,

Pump Runs w/Ignition Switch Off; The ign switch actuator and or switch needs to be adjusted. When the ignition sw is switched to the ON position, it turns the EEC Power Relay on. The EEC Power Relay provides power to the EEC-IV processor and the control side of the fuel pump relay. Power for the fuel pump is supplied through a maxi fuse in Power Distribution Box (PDB). From the high current fuse, current flow is through the fuel pump relay and Inertia Fuel Shutoff (IFS) switch to the fuel pump. Source: by miesk5 at Ford Bronco Zone Forums

Pump & Inertia Cut-Off Switch Wiring Diagram in a 95 (see #4) Source: by Seabronc (Rosie, Fred W) at Ford Bronco Zone Forums

 
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66_93

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Got it started last with ether. Fuel pump still runs in key on not running. Relay good. Check engine light on when started. Can not perform KOEO test as long as that fuel pump runs

 

miesk5

96 Bronco 5.0
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yo, Now swap PCM relay for horn relay.

And see if horn beeps or stays on.

If it does, then need to troubleshoot ckt in Ignition Switch & out to EEC (PCM) Relay and FP Relay

Ignition Switch Pin-Out Diagram & Continuity Testing (Logic Tables) in 92-96

Source: by Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/831772

Concentrate on Ign1 - R/LG

& following R/LG using Seabronc's wiring diagrams to troubleshoot;

From Ign Switch - shown @ left side of pin-out diagram

http://broncozone.com/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=5796

to PCM (EEC) Relay and to FP Relay, etc.. R/LG shown @ left side...

http://broncozone.com/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=5798

 
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BroncoJoe19

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Got it started last with ether. Fuel pump still runs in key on not running. Relay good. Check engine light on when started. Can not perform KOEO test as long as that fuel pump runs
miesk5 knows much more than me, and he is looking deeper into your issue than me, so if there is a conflict in advice, go with him.

As far as I know, if your fuel pump runs continuously with the key on, engine not running, or not being cranked, the problem is in one of three places.

1. the FP relay is stuck/fused ON.

2. someone left a jumper wire in the fuel pump test pin of the SelfTestConnector3.jpg self test data link connector in place, OR the wire to the fuel pump test pin that goes to the DLC is shorted to ground.

3. you have a bad PCM

 

66_93

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Checked all relays...same problem...Switch on engine not running...sometimes fuel pump cycles like it should, sometimes it doesn't...if it cycles off, bronco starts and run good. no check engine light. able to do a code check. everything is good...but if switch on engine not running, check engine light on, can't run test for codes and when I start it it runs very ruff, new battery, check grounds....seems to be failing more than not...

Thanks to everyone for your help...have learned a lot about this system because of you

 

miesk5

96 Bronco 5.0
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yo,

Did you swap the horn relay with the PCM relay?

then, will horn work properly?

Check the ign switch as shown above in;

Ignition Switch Pin-Out Diagram & Continuity Testing (Logic Tables) in 92-96

Source: by Steve83 (Steve, That dirty old truck) at http://www.supermotors.net/registry/media/831772

Concentrate on Ign1 - R/LG

 
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66_93

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Miesk5,

Relays are good...ignition switch checks out good...

Seems like whatever runs the fuel pump for a second when you turn the key to run is failing.

Wouldn't this be the ecm

thanks again for your time

 

miesk5

96 Bronco 5.0
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yo,

ok, as my pal BroncoJoe advised; check the wire to the fuel pump test pin that goes to the DLC; see if it is shorted to ground

DLC is labeled as "VIP DATA LINK CONNECTOR" LB/OR

Wiring Diagram in a 94 from EVTM



Source: by Mikey350 at http://www.supermotors.net/registry/media/874100



VIP DATA LINK CONNECTOR

in this diagram the VIP DATA LINK CONNECTOR is marked as "A" 926 FUEL PUMP RELAY GROUND LB/OR

 

BroncoJoe19

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66_93,

It is more likely a bad relay, or short to ground than it is a bad PCM.

The reason miesk5 asked you twice to swap the horn relay with the fuel pump relay, is becuase he knows that it could test good, yet still ocassionally get stuck ON.

It would be a costly mistake to replace the PCM if that is not the issue. THerefore it would behoove you to follow his advice first.

Good luck with it.

 

66_93

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Oct 7, 2011
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got it fixed...new computer

Thanks for all the feed back and help.

66_93

 

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