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94 bronco fuel pump no power??


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#1 1994eb

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Posted 19 December 2007 - 10:14 AM

My 94 bronco quit on me and the fuel pump is not running.
I checked for power at the pumpo and none.
checked for power at the inertia switch none.
swapped relay under hood still nothing.
Does any one know how the wires run to the inertia switch.? Thanks

#2 miesk5

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Posted 19 December 2007 - 12:05 PM

My 94 bronco quit on me and the fuel pump is not running.
I checked for power at the pumpo and none.
checked for power at the inertia switch none.
swapped relay under hood still nothing.
Does any one know how the wires run to the inertia switch.? Thanks

yo!
1st - Check da Fuel Pump Relay Socket for Corrosion
info;
When the ignition switch is ON, it turns the EEC power relay ON. (CK that relay too) The EEC power relay provides power to the powertrain control module (PCM) and the control side of the fuel pump relay. Power for the fuel pump(s) is supplied through a fuse link or high current fuse attached to the starter solenoid (battery side). From the fuse link or high current fuse, current flows through the fuel pump relay and inertia switch to the fuel pump(s). The fuel pump relay is controlled by the PCM.

When the ignition switch is turned ON, the fuel pump(s) will operate. If the ignition switch is not turned to the START position the PCM will shut the fuel pump(s) OFF after 1 second. The PCM will operate the fuel pump(s) operate the fuel pump(s) when the ignition switch is turn to START position to provide fuel while cranking.

After the engine starts, the PCM will continue to operate the fuel pump(s) unless the engine stops, drops below 120 rpm or the inertia switch is tripped.

in my archived BRONCO TECHNICAL

site; http://web.archive.o...s.com/index.php?;
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#3 1994eb

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Posted 19 December 2007 - 12:21 PM

Thanks for the reply!
Relay is ok, Where is the EEC? PCM?
I pulled the wire to the inertia switch , no juice.
Any wiring Diagrams for this 1994 bronco on line?

#4 miesk5

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Posted 19 December 2007 - 12:49 PM

Thanks for the reply!
Relay is ok, Where is the EEC? PCM?
I pulled the wire to the inertia switch , no juice.
Any wiring Diagrams for this 1994 bronco on line?


yw;
do ya mean where is da EEC (Ford calles it a PCM) relay:
should be below da FP relay in PWR DIST Box; have an owner's manual. will be in there.
Power Distribution Box Diagram by Rob
ck there for power.

Here is a Chilton diagram;
Fig. 16

Color codes are iffy @ times; as Seabronc has noted on a few occasions. Try for an e bay Ford Tech Cd; they are vg!

in my archived BRONCO TECHNICAL

site; http://web.archive.o...s.com/index.php?;
select a LINK, Right Click and and Hit Properties;

copy the second HTTP address

paste in a new browser to see the original page

96 Bronco, E4OD, Man Xfer Case & Hubs
Thanks to All Who Serve


#5 1994eb

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Posted 20 December 2007 - 07:01 AM

I just tested the pink wire out of the inertia switch and have power for a second when key turned on.
I guess the pump is shot since I have power to it.
I smacked the tank with 48oz. hammer and the pump came on.
Can you get just the pump or is it only sold with the sender and pick up?
Thanks

Edited by 1994eb, 20 December 2007 - 10:27 AM.


#6 PonyXpress

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Posted 11 January 2008 - 11:24 AM

90 bronco same problem. no power to pump. turn the key and it doesn't even make noise. checked inertia switch first. it was not tripped. replaced a perfectly good fuel pump. replaced a fuel pump relay. low voltage to inertia switch. used code reader, got a pcm code and a pcm ground code. had pcm reconditioned, replaced fuel inertia switch, new battery, turned the key and nothing happened. code reader still says pcm ground. have crawled all over looking for bad ground connections. can not find it. been down for over six months. any suggestions will be greatly appreciated as long as some a--hole doesn't say buy a chevy.

i found a fuel pump w/ no other components on ebay for about $50.

#7 BroncoJoe19

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Posted 12 January 2008 - 06:30 PM

<snip> low voltage to inertia switch. <snip> code reader still says pcm ground. have crawled all over looking for bad ground connections. can not find it. been down for over six months. any suggestions will be greatly appreciated (inappropriate comment snipped)


I took a look in my Haynes manual.
They list 10 separate grounds... A-J.

A. Starter mounting bolt
B. Right front of Engine compartment near the battery
C. Lower left front of engine
D. Right front of engine compartment on upper radiator support.
E. Left front of engine compartment Upper radiator support
F. Bottom of cowl panel
G. Rear of left fender apron
H. Behind bottom of right cowl panel
I. Left rear corner of cargo area near rear lamp assembly
J. Under center rear of vehicle on rear cross member.

Further reading through the schematics makes me suggest ground E or G as the first grounds to check.

If this works brother you owe me a beer :)
Good luck.
BTW.. IF you don't have one, you may want to pick up a copy of a Haynes repair manual or Chilton manual for your year truck.
joe
BroncoJoe19... I am not a professional mechanic, nor an engineer.
One should always obtain professional advice before attempting a repair or modification.

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#8 PonyXpress

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Posted 12 January 2008 - 10:43 PM

I took a look in my Haynes manual.
They list 10 separate grounds... A-J.

A. Starter mounting bolt
B. Right front of Engine compartment near the battery
C. Lower left front of engine
D. Right front of engine compartment on upper radiator support.
E. Left front of engine compartment Upper radiator support
F. Bottom of cowl panel
G. Rear of left fender apron
H. Behind bottom of right cowl panel
I. Left rear corner of cargo area near rear lamp assembly
J. Under center rear of vehicle on rear cross member.

Further reading through the schematics makes me suggest ground E or G as the first grounds to check.

If this works brother you owe me a beer :)
Good luck.
BTW.. IF you don't have one, you may want to pick up a copy of a Haynes repair manual or Chilton manual for your year truck.
joe

Thanks Joe, those are the first places I'll check.

#9 Seabronc

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Posted 13 January 2008 - 07:31 AM

My 94 bronco quit on me and the fuel pump is not running.
I checked for power at the pumpo and none.
checked for power at the inertia switch none.
swapped relay under hood still nothing.
Does any one know how the wires run to the inertia switch.? Thanks


If by checking for power you used a voltmeter, why did you change the relay? Did you have voltage on one contact (yellow wire) and not on the other (Dark green wire with Yellow stripe)? The pump relay depends on the PCM relay picking it, so you need to look for two things at that point,
1. that you have 12v on the fuel pump Red wire (pick voltage for the fuel pump relay)
2. that you have 12V to the contact that supplies it to the fuel pump (the yellow lead to the fuel pump relay)

If you have both then ground for the pick coil is controlled by the Power train control module. Check to see if you have a ground on the light blue with orange stripe wire that is connected to the fuel pump relay.

The following is in bold for a particular reason, it is for general consumption and not directed ant any one in particular.

These problems are relatively easy to trouble shoot if you spend a few Bucks on good documents and a multi meter. The manuals I'm talking about are the factory SERVICE MANUALS, not Chiltons or Haynes they SUCK, and are a readers digest version of a complete set of manuals that are about 4 inches thick in total. The very first service manual to get is the EVTM (Electrical and Vacuum Troubleshooting Manual), cost any where from $10.00 to $25.00 on eBay. That investment in your truck can save you literally hundreds of dollars in buying the wrong components. After that you can get the Body and Chassis manual, the engine manual, and the Emission diagnosis Manual. There is also a Lubrication manual but it is not as informative as the others. The total investment in all that can be any where from about $100.00 to $200.00. Well worth it in savings on good parts expense and mechanic fees. Beyond that you need a bit of a mechanical aptitude (the more the better). If you can't troubleshoot without throwing money at the truck then find a good mechanic that you can trust and I'll guarantee you he will be less expensive than you replacing good parts and getting totally frustrated.

Off my soapbox, sermon is completed, you may all go home now and do exactly what you were doing before I started preaching :D

By the way 1994eb, I have some pictures of the pages in the EVTM, but not on this computer. I'll post them for you later. They are different than the 1990 diagrams. It is a little more complex than for the 1990.


Good luck,

:)>-
Fred

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#10 Seabronc

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Posted 13 January 2008 - 04:04 PM

Fuel pump diagrams as promised. They are from a 95 EVTM but should be the same.

Good luck,

:)>-

Attached Thumbnails

  • Power_Distribution_033.jpg
  • Power_Distribution_035.jpg
  • Power_Distribution_052.jpg
  • Power_Distribution_069.jpg

Fred

Parts replacement is not trouble shooting, replacement follows trouble shooting

Broncos are MPVs not SUVs

Engines run on fuel, or steam

Motors run on electricity, hydraulic fluid, vacuum, or air


Communication: I know you think you know what I said, but what you need to know is, I didn't say what I meant.

Some of my pictures at Supermotors http://www.supermotors.net/212

#11 starviewer

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Posted 08 July 2009 - 07:44 AM

I have similar problem on the 91 bronco. I see 6.8 volts on the initial switch output and 12 volts on the in side. I pulled the relay and still see 6.8 volts. Pulled the initial switch and still see 6.8. I am now tracing the harness wire. There may be a problem in the design of that harness. Good thing it is a short trip from relay to initial. DK Green/ yellow stripe wire. Without relay, there should be no power there.

#12 regarrr

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Posted 13 July 2009 - 03:59 PM

My fuel pump wouldn't kick on either last year. Turns out it was the yellow wire on the relay mounted to the back of the air box. Turn the key to on but dont start it. Jiggle that yellow wire and see if you can hear the pump. Mine is still a little loose, I'm terrible with solder, but I have it zip tied in place now.

Edited by regarrr, 13 July 2009 - 03:59 PM.

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#13 Steve83

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Posted 14 July 2009 - 09:18 AM

...the initial switch...

It's "inertia". ;)

Posted Image

...the relay mounted to the back of the air box.

Those relays are a big problem. The best solution is to chop 'em off as described in this caption & the NEXT few:

Posted Image



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