Do get me started! (93 Bronco)

[Calxurn]

Hi all,

I've got a 93 Bronco, 5.0, EFI, 165K miles.

After letting it sit for almost five months, it wouldn't start. Engine cranked, but I noticed the fuel pump had suddenly become quiet. It had been squealy for a while, and several people told me it sounded like it would go soon. So I figured that was the problem, and I replaced it. Still nothing. So I replaced the relay (yes, I know I should have done that first). Still nothing. No sound from the fuel pump, just a few clicks from the engine compartment, which I've read is normal. I checked the inertia switch, and it had not been tripped. Red button was down, but I lifted it and pressed it down again, just for the heck of it.

I've read a few posts that led me to believe it could be the EEC, or PCM. But others have stated that it is extremely rare for them to go down. I do get the Check Engine light when I turn the key, and I understand that's a good sign in terms of the PCM still being alive.

I've also checked all the fuses, and they're all good.

One thing I've not seen on the boards, and something I can't seem to find the part for:

When I replaced the fuel pump, I noticed there had been a bit of melting around one of the female ports in the wire harness that attaches to the fuel pump interface, where it attaches to the fuel tank. I've looked up "wire harness for 93 Bronco fuel pump", but the images don't match what I've got. The wire harness has four female ports in a line. Maybe I'm looking up the wrong part description. But maybe it's not even the problem?

Thanks, everyone!

Mark

 

[miesk5]

yo C,

WELCOME!

Hopefully, the terminals are ok within the connector; in other years some have eliminated the connector and hard wired. Try this

Grounding the FP lead at the Diagnostic Link Connector (DLC) will allow the pump to run continuously with the ignition switch on.

The DlC is located in the engine compartment on the driver's side just above the wheel well, (between the fire wall and the air filter box) it looks like this picture

http://broncozone.com/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=6766

by BroncoJoe

Connector C441 Pin-Out Diagram in 92-96 at tank

http://broncozone.com/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=11736

Source: by miesk5

http://www.thedieselstop.com/faq/9497faq/maint/vra/images/a16317a.gif

Operational Sequence: When the ignition is switched to the ON position, it turns the PCM (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 high current **** fuse.

If the horn(s) work ok now, try swapping the horn relay for the PCM (EEC) Power Relay; if no change, then swap it for FP relay and check for corrosion within relays' sockets.

Power Distribution Box Diagram in a 93;

Source: by Troll Banned (Bronco Rob, BroncoRob)





From high current **** fuse, current flow is through the fuel pump relay and Inertia Fuel Shutoff (IFS) switch to the fuel pump. The IFS switch is a safety device used to shut off the fuel pump in the event of a collision. If the IFS switch is tripped, it must be reset by depressing the white or red button on the top of the switch. The fuel pump relay is controlled by the EEC-IV . When the ignition switch is turned to the ON position, the fuel pump will operate. If the ignition switch is not turned to the START position, the EEC-IV will shut the fuel pump off after approximately one second. The PCM will operate the fuel pump when the ignition is in the START position to provide fuel while cranking.After the engine starts, the PCM will continue to operate the fuel pump unless the engine stops, engine speed drops below 120 rpm, or the IFS switch is "tripped." Note: Grounding the FP lead at the DLC will allow the pump to run continuously with the ignition switch on..." READ MORE

Wiring Diagram in a 94 (SAME for your 93) from EVTM, partial; from **** Fuse U in Power Distribution Box (PDB) through PCM Power Relay Coil & **** Fuse O in PDB through FP Relay to Inertia Fuel Cut-Off Switch (IFS)



Source: by Mikey350

If you still have the No start, but starter cranks engine over as normal;

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

http://broncozone.co..._mode__threaded

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.

Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accessories/lights, etc.

Make sure A/C is off and transmission is in Park (automatic) or in Neutral for a Manual & release clutch.

Do Key On Engine Off (KOEO) portion first.

Look Codes up in my broncolinks.com site using the new Search function.

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.

Run it around to heat the engine up and shift thru all gears incl Reverse. Then turn off all accessories/lights, etc.

Make sure A/C is off and transmission is in Park (automatic) or in Neutral for a Manual & release clutch.

Do Key On Engine Off (KOEO) portion first.

Look Codes up in my broncolinks.com site using the new Search function.

 

[miesk5]

yo,

I forgot to incl this;

Testing; "...A better test is to check the fuel pump relay when cranking the engine over. Not the 2 second run after the key is turned on, but while cranking the engine. If the fuel pump relay kicks on when cranking, the TFI & Stator are good..."

Source: by Ryan M (Fireguy50) at oldfuelinjection.com

 

[miesk5]

yo,

I forgot to incl this;

Testing; "...A better test is to check the fuel pump relay when cranking the engine over. Not the 2 second run after the key is turned on, but while cranking the engine. If the fuel pump relay kicks on when cranking, the TFI & Stator are good..."

Source: by Ryan M (Fireguy50) at oldfuelinjection.com