Full Version: Double relay question on 74 1.8 liter
I’m excited to be back to the point of hooking up the wiring to the car after reinstalling the engine last night. Everything seems pretty straightforward up to this point except with the double relay. My 914 is a 74 1.8 L engine with fuel injection. My question is which side of the relay do I use? If it’s pointing down and I’m plugging in from the bottom do I hook too the left side or the right side? Currently I have it plugged into the left side but no power or anything hooked up to the car so I’m not worried about frying anything at this point I just don’t want to fry anything. Another question, why do we have a double relay if we only use one side? I appreciate the help thanks, Mike
QUOTE(Mcraneiowa @ Jul 2 2020, 01:44 PM) 
I’m excited to be back to the point of hooking up the wiring to the car after reinstalling the engine last night. Everything seems pretty straightforward up to this point except with the double relay. My 914 is a 74 1.8 L engine with fuel injection. My question is which side of the relay do I use? If it’s pointing down and I’m plugging in from the bottom do I hook too the left side or the right side? Currently I have it plugged into the left side but no power or anything hooked up to the car so I’m not worried about frying anything at this point I just don’t want to fry anything. Another question, why do we have a double relay if we only use one side? I appreciate the help thanks, Mike
Mike, both sides of the double relay are used with L-Jet. There should be two plastic connectors that plug into it side by side. Here's the wiring set-up for it. Not sure if it is different for '74 and '75. This came from a thread on TheSamba.com called Something like Double Relay Explained..In Color. Hope this helps.
Click to view attachment
The double relay will have one connection that comes from the engine harness. It will have a mix of colored wires on it. The other side will come from the fuel injection harness, and it will have all white wires.
If you don't have both the car will not run. There will be a big red wire on the harness side that attaches to the battery. The engine harness will have an extra yellow wire with a spade connector hanging out alone at the 12 pin connector.
If you don't have that, you have the wrong engine harness.
Take pictures and we can help better.
Clay
If you don't have both the car will not run. There will be a big red wire on the harness side that attaches to the battery. The engine harness will have an extra yellow wire with a spade connector hanging out alone at the 12 pin connector.
If you don't have that, you have the wrong engine harness.
Take pictures and we can help better.
Clay
QUOTE(ClayPerrine @ Jul 2 2020, 07:41 PM)
The double relay will have one connection that comes from the engine harness. It will have a mix of colored wires on it. The other side will come from the fuel injection harness, and it will have all white wires.
If you don't have both the car will not run. There will be a big red wire on the harness side that attaches to the battery. The engine harness will have an extra yellow wire with a spade connector hanging out alone at the 12 pin connector.
If you don't have that, you have the wrong engine harness.
Take pictures and we can help better.
Clay
Clay, thank you for the information. I was working late last night and just overlooked the other series of wires were kind of stuck down in among the spark plug wires. So I have both plugged in and hope to fire her up after several years of sitting. I really appreciate your help. The site is fantastic for helping some of us become familiar with our cars
QUOTE(Mcraneiowa @ Jul 3 2020, 07:49 AM)
QUOTE(ClayPerrine @ Jul 2 2020, 07:41 PM)
The double relay will have one connection that comes from the engine harness. It will have a mix of colored wires on it. The other side will come from the fuel injection harness, and it will have all white wires.
If you don't have both the car will not run. There will be a big red wire on the harness side that attaches to the battery. The engine harness will have an extra yellow wire with a spade connector hanging out alone at the 12 pin connector.
If you don't have that, you have the wrong engine harness.
Take pictures and we can help better.
Clay
Clay, thank you for the information. I was working late last night and just overlooked the other series of wires were kind of stuck down in among the spark plug wires. So I have both plugged in and hope to fire her up after several years of sitting. I really appreciate your help. The site is fantastic for helping some of us become familiar with our cars
Now that both plugs are connected, run some basic tests.
1. Disconnect the yellow wire from the starter and turn the key. You should hear the fuel pump running.
2. Manually open the air flow meter flap. You should hear the fuel pump running.
3. Get a noid light, plug it into each injector connector and crank the car. The light should flash.
If all that works, you should be able to star the engine.
QUOTE(ClayPerrine @ Jul 3 2020, 09:19 AM)
QUOTE(Mcraneiowa @ Jul 3 2020, 07:49 AM)
QUOTE(ClayPerrine @ Jul 2 2020, 07:41 PM)
The double relay will have one connection that comes from the engine harness. It will have a mix of colored wires on it. The other side will come from the fuel injection harness, and it will have all white wires.
If you don't have both the car will not run. There will be a big red wire on the harness side that attaches to the battery. The engine harness will have an extra yellow wire with a spade connector hanging out alone at the 12 pin connector.
If you don't have that, you have the wrong engine harness.
Take pictures and we can help better.
Clay
Perfect. This the point I am at. Will start this process tomorrow. Appreciate your knowledge more than you know.
Clay, thank you for the information. I was working late last night and just overlooked the other series of wires were kind of stuck down in among the spark plug wires. So I have both plugged in and hope to fire her up after several years of sitting. I really appreciate your help. The site is fantastic for helping some of us become familiar with our cars
Now that both plugs are connected, run some basic tests.
1. Disconnect the yellow wire from the starter and turn the key. You should hear the fuel pump running.
2. Manually open the air flow meter flap. You should hear the fuel pump running.
3. Get a noid light, plug it into each injector connector and crank the car. The light should flash.
If all that works, you should be able to star the engine.
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