85 fuel problems
CF Community Team
Joined: Oct 2004
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From: Cape Cod, Mass.
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There is a fuel pump relay on the firewall in the engine compartment.
Team Owner
Joined: Jan 2003
Posts: 20,293
Likes: 240
From: Summerland B.C. Canada
When are you testing for voltage ??
Power is only there for 2 seconds unless your cranking or running.
Take 12 volts and insert the wire into terminal "G" on the ALDL connecter. That should send power to the fuse until the 12 volt wire is removed. Helpful when diagnosing.
My schematics are for 86 and not accurate enough for your 85.
Hopefully someone can post the 85 fuel delivery electrical schematic.
Power is only there for 2 seconds unless your cranking or running.
Take 12 volts and insert the wire into terminal "G" on the ALDL connecter. That should send power to the fuse until the 12 volt wire is removed. Helpful when diagnosing.
My schematics are for 86 and not accurate enough for your 85.
Hopefully someone can post the 85 fuel delivery electrical schematic.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
The main fan turns on at 228 F from temp measurement of the sensor that is on the front of the block under the MAF. Check the connectors on this sensor, they eventually degrade. Look at what the scanner says the coolant temp is compared to the dash coolant temp, they should be close. Ground the grn/wh wire on the fan relay with the ign on, this should close the fan relay and the fan motor should come on. Fan motors also don't last forever.
Intermediate
Joined: May 2008
Posts: 36
Likes: 0
From: Katy TX
On the fuel gage problem, you might have left the fuel gage sender unit disconnected or the sender unit lost its ground connection. Both conditions will give you FULL indication on the gas gauge. The pink colored wire from the sender unit should be ~ 0 Ohm on empty and 90 Ohm with the tank full. With the pink wire from the sender grounded, the gas gauge should read EMPTY.
On the fan problem, I have attaced the cooling fan wiring diagram from my ’85 service manual. Hope it helps you, -good luck!
CHART C-12A, FAN CONTROL CIRCUIT
• The cooling fan is totally controlled by the ECM, based on
inputs from the coolant sensor and the A/C pressure fan switch.
The fan should run if coolant temperature is greater than 106°C.
• Battery voltage is supplied to the fan relay on terminal D
and ignition voltage to terminal C.
• Grounding CKT 335 (relay terminal B) will energize the
relay and supply battery voltage to the fan motor.
• The ECM will remove the ground to CKT 335 if vehicle
speed is over 35 mph.
• When A/C is used the fan control switch will open when
head pressure exceeds 233 psi (1600 kPa) and this input causes the
ECM to ground Circuit 335.
• If a Code 14 or 15 sets, the ECM will turn on the cooling
fan.
• The fan override switch is used for engine cooling if the
ECM fails.
On the fan problem, I have attaced the cooling fan wiring diagram from my ’85 service manual. Hope it helps you, -good luck!
CHART C-12A, FAN CONTROL CIRCUIT
• The cooling fan is totally controlled by the ECM, based on
inputs from the coolant sensor and the A/C pressure fan switch.
The fan should run if coolant temperature is greater than 106°C.
• Battery voltage is supplied to the fan relay on terminal D
and ignition voltage to terminal C.
• Grounding CKT 335 (relay terminal B) will energize the
relay and supply battery voltage to the fan motor.
• The ECM will remove the ground to CKT 335 if vehicle
speed is over 35 mph.
• When A/C is used the fan control switch will open when
head pressure exceeds 233 psi (1600 kPa) and this input causes the
ECM to ground Circuit 335.
• If a Code 14 or 15 sets, the ECM will turn on the cooling
fan.
• The fan override switch is used for engine cooling if the
ECM fails.
