1987 bronco 2 2.9 won't start

[Broncobgr]

If I jump the relay it will start and run fine. I changed the relay and it still will not start or turn the fuel pump on. Any one ever have this issue? Can I just jump the relay permanently????

 

[adsm08]

Well there are three or four relays on an 87. A starter relay, a fuel pump relay, a PCM power relay, some had a WOT relay. Which one are you talking about?

I assume fuel pump, in which case you can, but it is ultimately unwise to do so. I would look into seeing why the PCM is not closing the fuel pump relay.

 

[Broncobgr]

I have diagnosed this thing for hours and tried numerous attempts at fixing it. Why would it be unwise? This thing had a mouse nest in it at one time so it would surprise me if there is a wire frayed or something but I can't take a week off work to try and chase that down. It would prob be faster for me to rerun wiring for it all. I'm just wondering if this is a common problem with a common fix and if not can I just bypass it.

I also use to have to spray starter fluid in it to start but when I bypass the relay it starts right up. Thanks to all for any and all help, it is extremely appreciated

 

[RonD]

You still haven't said what relay you are "jumping"?

I assume it is not the Starter relay, passes power to starter motor/solenoid.

As said there are two other main relays:
Brown base is the EEC relay, when you turn the key on this relay should click closed and pass power to the EEC(computer), spark system, fuel injectors, and fuel pump RELAY(not fuel pump itself).

The other relay has a Green base, the fuel pump relay, it gets power from the EEC Relay but has no Ground so doesn't close, the computer Grounds this relay, so computer controls fuel pump operation.

If there is a 3rd relay with Black base that is for air conditioning compressor clutch power, it will cut power to AC compressor clutch when you press gas pedal to the floor, wide open throttle(WOT), this gives you extra power which computer assumes you need at WOT, so it is called the WOT relay.

"Jumping" EEC relay will cause battery to go dead, since devices would be getting power when key was off.

"Jumping" Fuel Pump Relay would leave fuel pump on all the time, and cause battery to go dead.

So which relay are you "jumping"?


As a side note go here: http://www.therangerstation.com/tech_library/OBD_I.shtml

2nd picture is the OBD connector usually found near drivers side firewall, engine side, could also be passenger side, depends on where they located computer in your vehicle.
It is loose, just hanging in the wire loom.

In the drawing you will see Fuel Pump slot labeled, this slot is the Ground for the fuel pump relay, it is spliced to the computers control wire for the fuel pump relay.
With key on, engine off, if you Ground that slot the fuel pump relay should click closed and fuel pump should start.
If it is the fuel pump relay you are talking about this is a safer and better way to "jump it", fuel pump will go off with the key.

 

[Broncobgr]

It is the fuel pump relay I'm referring too

 

[Broncobgr]

Ron D. I used the diagnostic connector under the hood like you said for the fuel pump and bingo!!!! It works great. I haven't drove it yet but it ran and idled good. If this works, I will have to say- you are a Bronco God!!!! And thanks a ton

 

[RonD]

If that works but computer doesn't run the fuel pump relay then I would check the Ground wires around the computer, internally the computer doesn't share Ground connections, so one loose or corroded ground wire may only effect 1 system.

Good look at computer here: http://www.auto-diagnostics.info/ford_eec_iv

Pin 22 is the control wire for the Fuel Pump relay, it will show 12volts with key on/engine off(no jumper) if wire is good all the way to computer connector.

0volts are the computer Grounds, check that they are Grounds, use an OHM meter.

Driving with that jumper in place removes a safety factor in the fuel system.
The computer monitors engine RPM, if RPMs fall below 400 computer would shut off fuel pump, stop Grounding Fuel Pump Relay.
Say a fuel line broke, engine would stall(no fuel) and pump would shut off, preventing fuel from being pumped all over the ground.
Now say the fuel line broke because of an accident..................so very good safety feature

There is an Inertia switch on the fuel pumps 12volt power wire, if there is a sudden stop or rollover this switch "should" cut fuel pump power, "should" of course is the key word there.
Just a heads up