Fuel Pump Problem

[freedom5]

My '87 2.9 has been running like a dream until today and it wouldn't start. I couldn't hear the fuel pump come on so checked the fuel at the shrader fitting - no fuel. I then checked the inertia switch - it had not tripped nor has there been any reason for it to. Next step was to check the fuel pump relay. It is the original 27 yr old and was full of crud and corrosion. I bought a new relay but the pump still wont come on. I have a wiring diagram but age has faded all of the wires except the red one.

Can I hot wire the pump temporarily to see if it will activate? I hate to remove the pump and then find it isn't the culprit.

Please Help - Freedom5

 

[RonD]

Have a look here: http://www.therangerstation.com/tech_library/OBD_I.shtml

You will see the diagram of the OBD test connector, it is usually on drivers side near firewall, but can be on passenger side.

In the diagram the Fuel pump port is labelled
The way the system works is that the Computer Grounds the Fuel pump relay to Close it, sending power to the inertia switch and then fuel pump(s), I think '87 has two pumps.

That fuel pump port is spliced to the computers Ground wire for fuel pump relay.
So if key is on, and you Ground that port you should hear Fuel pump relay close(click).
Just put a wire in that port and put other end on the engine or Negative on battery.

If you don't hear the click then fuel pump relay(green base) isn't getting power from EEC relay(brown base), EEC relay closes when key is turned on, sending power to computer(EEC), fuel injectors, ignition, and fuel pump relay.

If you hear the click but not the fuel pump(s) then check the Blue Fusible links, there should be two, one for EEC power and one for Fuel Pump power.
These connect to the battery or starter relay.

If you have a test light then you can check if inertia switch has power after putting in the ground jumper and hearing relay click closed, check both connections on inertia switch.

The high pressure pump is in the frame rail under drivers seat area, low pressure pump is in the gas tank.
There is a splice near the high pressure pump where Ford tied into the lower pressure pump's power wire from inertia switch, this splice can corrode.
high pressure pump was add for fuel injection, low pressure pump was there for carburetor engines.

Power for fuel pump
Battery-------20gauge fusible link------ fuel pump relay------inertia switch------fuel pumps

If you are getting power to inertia switch don't forget to check fuel pump grounds, they are often on the frame near high pressure pump.

 

[freedom5]

Have a look here: http://www.therangerstation.com/tech_library/OBD_I.shtml

You will see the diagram of the OBD test connector, it is usually on drivers side near firewall, but can be on passenger side.

In the diagram the Fuel pump port is labelled
The way the system works is that the Computer Grounds the Fuel pump relay to Close it, sending power to the inertia switch and then fuel pump(s), I think '87 has two pumps.

That fuel pump port is spliced to the computers Ground wire for fuel pump relay.
So if key is on, and you Ground that port you should hear Fuel pump relay close(click).
Just put a wire in that port and put other end on the engine or Negative on battery.

If you don't hear the click then fuel pump relay(green base) isn't getting power from EEC relay(brown base), EEC relay closes when key is turned on, sending power to computer(EEC), fuel injectors, ignition, and fuel pump relay.

If you hear the click but not the fuel pump(s) then check the Blue Fusible links, there should be two, one for EEC power and one for Fuel Pump power.
These connect to the battery or starter relay.

If you have a test light then you can check if inertia switch has power after putting in the ground jumper and hearing relay click closed, check both connections on inertia switch.

The high pressure pump is in the frame rail under drivers seat area, low pressure pump is in the gas tank.
There is a splice near the high pressure pump where Ford tied into the lower pressure pump's power wire from inertia switch, this splice can corrode.
high pressure pump was add for fuel injection, low pressure pump was there for carburetor engines.

Power for fuel pump
Battery-------20gauge fusible link------ fuel pump relay------inertia switch------fuel pumps

If you are getting power to inertia switch don't forget to check fuel pump grounds, they are often on the frame near high pressure pump.

Thanks Ron - I'll give it a try tomorrow. In the meantime I will look up the reference you gave. Hope you have good Holidays.

Freedom5

 

[freedom5]

Thanks Ron - I'll give it a try tomorrow. In the meantime I will look up the reference you gave. Hope you have good Holidays.

Freedom5

Tried to bring up the web site referenced and got "can't find it". Will try again.

 

[RonD]

Don't copy and paste the link just click on it.

OR
Up at the top of this page below the top banner are Links.
Home | Discussion Forum | Tech Articles | Other Articles |

Click on Tech Articles
Lots of good stuff here, it is a "been there done that" info page

Find Charging & Ignition Systems
Click on it

Under Computer click on EEC-IV (OBD-I) Diagnostics

That's the page I linked

 

[freedom5]

Thanks to RonD and other research I got from the web I have solved the problem and found I did not have to replace the fuel pump. I found a bad connection which took care of things.
Again - thanks to Ron his advice has always been accurate.

 

[RonD]

Good work

Thanks for the update