I recently acquired a 1985 Econoline Van with a newly rebuilt 6 cylinder and AOD 3-speed with Overdrive. Through extensive research (I am totally unfamiliar with Ford 6 cylinders) I have discovered it has the TFI type distributer with no built in mechanical or vacuum advance. It also has the "feedback" Carter YA carburetor. I understand that ALL timing advance is done electronically by the "computer". The previous owner said it was running fine, then one day it suddenly started running very sluggish with no power.
I have checked the compression and all cylinders are between 110 and 125 lbs. My manual does not say what normal compression for this engine is, just that they should all be within 80% of each - which they are. Are these normal readings for a 4.9 inline 6?
I also checked manifold vacuum with a vacuum gauge and found it 10 inches at an idle with timing set at 10 degree's. I have checked all hoses and can not find any vacuum leaks. 10" of vacuum seems very low to me - especially with a rebuilt engine. Anyone have specs on what vacuum I should expect on a carbureted 6 cylinder in good condition?
I finally discovered yesterday - after maticulously setting and making sure that the initial timing was correct - that there is no timing advance when engine speed is increased! It stays at 10 degrees no matter what the RPM! I have no clue as to where to go from here. Assuming all the wiring between the distributer and EEC unit is ok, what component is most likely the problem? The Chilton manual is basically useless in this area.
Any help would be greatly appreciated.

Thanks,
Tom

 

Tom, I have 85 F150 with the 4.9L. Check and make sure that the "spout" connector is plugged together. It is a little connector about 3 inches or so away from the TFI module. Your TFI ignition module should be right on the distributor. What make sure the timing is set for 10 degrees below TDC. Also, when you set base timing, make sure this "spout" connector is disconnected, for, with this connected it will automatically advance the timing.Hope ths helps
Rich

 

Thanks for the tip, Rich. I have made sure the connector you mentioned is connected, and have even checked the continuity from the TFI module all the way to the EEC connector and there is a solid connection. I did some investigating while I had the EEC connector off and discovered that the +12 volts to the EEC unit (pins #57 and 37) were missing with the ignition switch on! EUREKA! This voltage is supplied through a relay called EEC POWER RELAY but I have searched till I am blue in the face and cannot find that relay! If someone reading this knows where that relay is located, please let me know. Once I find the relay, I can do some more checking and determine why there is no voltage to the EEC unit. My only other recourse is to untape the cable harness that carries those 2 wires till I find where they go. Not a real fine option.

Tom

 

My EEC Relay is under the dash right next to and inboard of the computer.

'84 F150
YFA F/B
SROD
"Ex" => Bone Stock