Low Voltage Electrical Connection Cleaning
It seems like 70% of most early Z car problems are related to poor electrical connections. Usually the contacts have corroded and this "opens" the electrical connections.
- a poor connection is in the EFI harness usually causes the engine to run rough and either rich or lean.
- a poor connection in the battery, alternator, fuse or fusible links harness can cause many unusual things to happen: gauges showing false readings; batteries not charging; batteries over charging; lights dimming or instrument lights dimming when electrical devices are activated.
- a poor connection in the ignition system can cause: poor spark; no spark; or even ignition circuitry failure
Here are some photos of common electrical connections that should be inspected and cleaned:
IMPORTANT HIGHLIGHT: This is the first item to clean and it is the most common cause of running rich The Coolant Temperature Sensor connector and it's bullet connectors at the end of it's pigtail:
Curled up pigtail with problematic coolant temp sensor on left and bullet connector on right
Detail of bullet connectors at end of pigtail. Just pull apart to clean.
Here is what actually happens when connectors corrode:
This is a fictional circuit that has a fuel pump connected to a battery and a connector in the circuit.
- The battery's job is to maintain +13V.
- The amount of current drawn is determined by the load on the battery, in this case the only load is the resistance of the pump (1.86ohms). (pretend the wires and connectors are perfect conductors and have no resistance)
- So the resistance of the pump is what "draws" current from the battery. In this example 1.86 ohms draws 7Amps at +13V (Ohm's Law I =V/R = 13 / 1.86)
Now a poor connection is introduced in the connector and it's resistance increases by only 1ohm.
- The battery's job is still to maintain +13V.
- The amount of current drawn is still determined by the load on the battery (which has now increased by 1ohm) (1.86ohms + 1ohm= 2.86ohms). In this case the load is the resistance of the pump AND the resistance of the connector corrosion. You can also see that this results in lower voltage applied directly to the pump. It has dropped from 13V to 8.5V!!
- So the resistance of the pump AND the connector is what "draws" current from the battery. In this second case it is 4.5A (Ohm's Law I =V/R = 13 / 2.86). The corrosion causes the current through the pump to drop from 7A to 4.5A.
So if you look at the specs for a typical fuel pump.....
- For 7 Amps ~ 70gallon per hour @ 45psi
- For 4.5Amps ~ 70gallon per hour @ 15psi
Bottom line: Fuel pressure and/or flow decreases because of a corroded connector!
Sensor and EFI Circuit Corrosion
It is important to realize that corrosion can cause the same problem in sensor circuits. For example, a corroded air temperature sensor in the AFM may fool the ECU into thinking the temperature is lower than it actually is: (sensor resistance increases as temp decreases). This will result in the ECU into thinking the the incoming air is colder and denser thus it will add too much fuel and cause the engine to run rich.
Likewise, corrosion on the water temp sensor will fool the ECU into thinking the engine is colder than it actually is thus it will add too much fuel and cause the engine to run rich.
Corrosion on the AFM connections can make the engine run rich OR lean depending on which connections are corroded.
Corrosion on the Oil Pressure Sender connections can make the gauge read lower than it actually is.
Corrosion on the Thermotime switch connections can make the car run rich for a longer period after start up.
Corrosion on the Aux Air Regulator connections can make the car idle faster for a longer period after start up.
Corrosion on the Boost Control Decelleration Device connections can make the car idle faster.
Corrosion on the EFI grounds or EFI power cables can make the EFI system unpredictable.
Corrosion on the injector connector can make make a cylinder run lean.
Those annoying temp sensor bullet connectors:
Here are the connectors that are 1' upstream from the temperature sensor and thermo-time switch.
To my surprise the previous owner also had a 330ohm resistor in series with the temp sensor. I had assumed he simply soldered them together as most do however, after finally opening up the mile of electrical tape, I found this! FYI, The resistance at operational temp of 170°F should be 290 to 360ohms.
How to clean electrical connectors:
DISCONNECT THE -NEGATIVE BATTERY TERMINAL BEFORE REMOVING/DISASSEMBLING OR RECONNECTING/REASSEMBLING ANY CONNECTOR!!!
Most connectors can be cleaned with an abrasive... but, some connectors actually have an electrical plating on the contacts so an abrasive is not recommended for plated contacts.
Here are a some examples of abrasive cleaning
This brass ground ring has been half-cleaned with sand paper. Sand paper is great when you have easy access to the part.
The other side of the brass ground ring has been half cleaned by scraping with a knife. This method is great when the part is not easily accessible.
The brass ground ring has been completely cleaned with a small file. (My fav tool).
A small wire brush or a dremel tool with wire brush attachment can also do the job..
Remember to also clean the other half of the connection. It could be a bolt, locking washer and nut, connector pin, etc. (Wire brushes work great for bolts).
When the contacts are plated, simply using a contact cleaner is best. An old tooth bush helps do the job. If the connector's plated pins are very corroded, then you may have to scrape them with a knife. Be sure to follow up with a final contact cleaner squirt as it coats and protects the metal. Don't forget to do both parts of the connection.
Alcohol (rubbing alcohol, isoproponal, etc) is good for a quick fix but it does not have metal protectants so it is not the best solution. Electronic control cleaners such as the MG Chemicals product work great, however; most recommended is Caig Deoxit. It cleans, deoxidizes and protects.
Here are two connectors that were cleaned with Caig Deoxit and a brush. (Before and After shots). It is difficult to see but the pins went from dull greeny-brown (left) to shiny silver (right). You can also see how the Deoxit oily film covers everything evenly.
Tune Up Grease is an electrical insulator developed for high voltage connections (distributor, coil and plugs). It is not recommended for sandwiching in low voltage connections as it prevents conductivity, however, after the low voltage connection is cleaned, sprayed with Deoxit and reconnected, Squirting Tune Up grease on the outside of the connection acts as a good way to prevent water from working into the connection and beginning the oxidizing process. It also helps keep the Deoxit oils inside the connection as the engine temp can evaporate them. Use this stuff after reconnecting.
Fusible Link "Refreshing" Details
Disconnect fusible link
Clean blade connection using an abrasive method from above (file, knife,sandpaper)
Lower left blade has oxide scraped off
Scrape oxide from inside of connector where it contacts the blade. No need to worry about the outside.
Gently pinch connector lobes so that it firmly grips the blade.
Spray with Deoxit and reassemble