Fuel pumps keep running

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Shadow_D

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Ok folks time for my issues again...

I tried to search for my old post about this problem but couldn't find it.

Problem is, when the key is off the fuel pump will run on it's own. Ive been told to look for a bad ground or a shorted wire but I haven't found one yet. I've also had to replace the relays under the hood a few times over the years (6 or more times, I've lost count).

Someone also told me to look at the wiring under the brake booster but I just haven't had a chance to check yet.

Any other ideas?

 

miesk5

96 Bronco 5.0
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YO D,

I think I replied to that other post with this;

Fuel Pump Runs w/Ignition Switch Off; "...If it stays running with the truck off, then most likely you have a bad fuel pump relay; EEC Relay hanging closed; If the EEC relay goes bad, it could be sending the signal to the fuel pump relay to turn the fuel pumps on;

One easy test for this is: Without the key in ignition, bump the starter over with the starter relay using a screwdriver. If it is the EEC relay, the truck will start without the key in the ignition..."

Source: by sackman9975 (Scott), Redwagon & miesk5

What Brand are those relays? Ck for socket/relay contact corrosion.

Here is the sequence to troubleshoot the wiring

EECFPrelay.JPG


I don't have a 90 wiring dia, but here is a Wiring Diagram in an 89 5.0, 5.8 & 7.5

Source: by my pal here, Seabronc@ http://broncozone.com/topic/20547-fuel-pump-wont-shut-off/

His reply to a SAME Q about; "...Seems the fuel pump does not want to shut off when the ignition is off. This is what was draining the battery..."

Seabronc replied; "...

The relay probably has the points welded. Here is a diagram of the circuit...."

See LINK for the diagrams

 
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Shadow_D

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miesk5: Yea I remember you did reply but I just couldn't find the old post.

Those are the relay's I've replaced several times so something is causing them to short out, maybe a chaffed wire somewhere???

I guess I'll need to dig around under the hood to see if I can find this thing.

One thing that I might not have mentioned and forgot about until just now, about 3 or 4 years ago (truck hasn't been driven more than 500 miles in the last few years) my neighbor stopped me when I came home to tell me that my horn started blasting in my truck and had been for over an hour. When I investigated it the horns were hot and smoking so I pulled the battery. I checked everything and couldn't find a reason, replaced the now burned out horns and it hasn't done it since...

 

miesk5

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yo,

If yu have a multimeter and can use it; here are the diagrams;

Wiring Diagrams & Component Location Diagrams in 86-96 Bronco & Fords; Agree and enter year, make/model, etc.

Source: by Airtex at http://www.showmetheparts.com/airtexts/

go thru the year, make, model eng type Drill

then select:

Wiring & Component Locations

Engine

Fuel Controls

Part1 1; this will give you color codes of the wiring from IGN Switch to EEC Relay and then on to

EEC and FP Relays

I assume you have to remove NEG cable and prob + batty cables so batty doesn't drain and FP runs forever, right?

So with KEY off..

Put meter in 0 to say 50 volt DC range

Black (-) Meter lead on Good Ground on engine

Re (+) meter lead on the RED/Light Green (R/LG) wire at EEC Relay

re-connect battery

if you have 12 V DC on that RED/Light Green, then

EDIT

Check IGN Cylinder

=============

 
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miesk5

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If no 12 V at that RED/Light Green.

The RED ® wire from that EEC Relay then goes to FP Relay and that carries the 12 volts to close the FP relay

So, with Battery still connected

FP should not be running so far

Connect meter + lead to that Red wire To FP relay

Have someone turn key to start; Should get 12 Volts there

turn off engine & remove key

if 12 volts is still there; then EEC relay is hanging up (cloded)

 
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Shadow_D

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yo,

If yu have a multimeter and can use it; here are the diagrams;

Wiring Diagrams & Component Location Diagrams in 86-96 Bronco & Fords; Agree and enter year, make/model, etc.

Source: by Airtex at http://www.showmethe...s.com/airtexts/

go thru the year, make, model eng type Drill

then select:

Wiring & Component Locations

Engine

Fuel Controls

Part1 1; this will give you color codes of the wiring from IGN Switch to EEC Relay and then on to

EEC and FP Relays

I assume you have to remove NEG cable and prob + batty cables so batty doesn't drain and FP runs forever, right?

So with KEY off..

Put meter in 0 to say 50 volt DC range

Black (-) Meter lead on Good Ground on engine

Re (+) meter lead on the RED/Light Green (R/LG) wire at EEC Relay

re-connect battery

if you have 12 V DC on that RED/Light Green, then

EDIT

Check IGN Cylinder

=============

Well thats part of the problem... They don't always run. every once and a while I will walk by the truck and they will come on for a few seconds then shut off like they are trying to keep pressure. after a day or so the battery is dead...

See why I've been beating my head against the wall :lol:

 

miesk5

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ok,

Hook Batty up

insert key in IGN Cylinder..don't turn it

shake it. violently

if nothing happens, reach down to the switch itslf at the base of the column. Manually push the switch back and forth through the different positions. Push it all the way forward (or down) and see if it will engage the starter. If it does, then your ignition rod is probably bent, which can be remedied quite easily.

 

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