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Old 01-01-2019, 02:42 PM   #1
rb92673
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Default LH2.2 Fuel Injection Relay Elimination / Removal

I want to remove the factory fuse box in my dedicated Lemons race car. I think I have it all figured out except for the last relay I have, the Fuel Injection Relay. Car is 85 740T LH2.2. All wiring not essential to the running of the car in a race has been stripped out. Charge overpressure switch was missing on my car and is just jumpered.

I am fine with the fuel pumps running all the time, I understand that the relay is supposed to stop the fuel when the engine is turned off. I have the wiring diagram, but I don't fully understand it.

This is what I understand:
12v+ Power goes in through 30.
During running, 12v+ power goes out 87/2 to the fuel pumps and injectors.

This is what I think I understand:
When running 12v+ power goes through 87/1 to pin 9 on LH2.2
When not running 12v+ power goes through 85 to pin 9 on LH2.2

So I should be able to provide 12v+ power to:
Green and Pink wires coming out of 87/2 for fuel pumps and injectors.
Blue-Yellow wire going to Pin 9 on LH2.2

What I don't know what to do with is the red wire going from 86/1 to pin 21 on LH2.2 or,
yellow-black wire through the overboost to 17 on LH 2.2. Are these needed to be connected to the LH2.2 anymore if I direct wire as above?

Thanks for your help. I searched for about an hour and could not figure it out.
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Old 01-01-2019, 03:04 PM   #2
dl242gt
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The relay has a control side and a load side. You just need to disonncect the relay from the computer and wire it stand alone so a switch will turn it on and off. That would be done with the control side of the relay. You can wire the control side of the relay to a switch and ground to turn it on and off.

Note: I don't recommend what you are doing. It's kind of a fail safe and works fine as a circuit and will give you some safety should you crash the car and can't turn the key off. So if it's working fine. I would keep it the way it is since it turns off the fuel when the engine is not running.
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Old 01-01-2019, 03:23 PM   #3
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Originally Posted by dl242gt View Post
Note: I don't recommend what you are doing. It's kind of a fail safe and works fine as a circuit and will give you some safety should you crash the car and can't turn the key off. So if it's working fine. I would keep it the way it is since it turns off the fuel when the engine is not running.
Thanks for the reply.

I have thought about this a bunch. The original fuse box is in poor shape and in a very bad location after all the interior and dash are gone. The car has a master kill switch and a 4 liter fire suppression system both of which can easily be reached by the driver or a course worker. In the event of a fire or crash, kill switch should immediately go to the off position. If driver see's a fire they have the option of engaging the fire suppression system which has two nozzles pointed at the engine and two at the driver. Fire suppression should only really be used if the driver needs an extra couple of seconds to get out of the car. There is also a hand held bottle in the car.

I could re-use just the relay from the original fuse box, but it is another potential failure point and I would have to figure out a good way to mount it.
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Old 01-01-2019, 04:41 PM   #4
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The relay stops fuel when the motor stops running like when you wreck the car, otherwise it keeps pumping fuel onto the car that is on fire that you are trapped in. Understand?
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Old 01-01-2019, 04:59 PM   #5
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The relay stops fuel when the motor stops running like when you wreck the car, otherwise it keeps pumping fuel onto the car that is on fire that you are trapped in. Understand?
Yes.
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Old 01-01-2019, 05:04 PM   #6
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If you plan to eliminate the fuel pump relay you're going to need a safeguard to make sure the fuel pumps stop when the engine stops. It only takes about 30 minutes for the fuel pumps to discharge the battery enough that the car won't start without a jump.

One safeguard would to use a oil pressure switch in the system, that way the engine would need oil pressure to trigger a relay.
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Old 01-01-2019, 05:12 PM   #7
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Quote:
Originally Posted by rb92673 View Post
I want to remove the factory fuse box in my dedicated Lemons race car. I think I have it all figured out except for the last relay I have, the Fuel Injection Relay. Car is 85 740T LH2.2. All wiring not essential to the running of the car in a race has been stripped out. Charge overpressure switch was missing on my car and is just jumpered.

I am fine with the fuel pumps running all the time, I understand that the relay is supposed to stop the fuel when the engine is turned off. I have the wiring diagram, but I don't fully understand it.

This is what I understand:
12v+ Power goes in through 30.
During running, 12v+ power goes out 87/2 to the fuel pumps and injectors.

This is what I think I understand:
When running 12v+ power goes through 87/1 to pin 9 on LH2.2
When not running 12v+ power goes through 85 to pin 9 on LH2.2

So I should be able to provide 12v+ power to:
Green and Pink wires coming out of 87/2 for fuel pumps and injectors.
Blue-Yellow wire going to Pin 9 on LH2.2

What I don't know what to do with is the red wire going from 86/1 to pin 21 on LH2.2 or,
yellow-black wire through the overboost to 17 on LH 2.2. Are these needed to be connected to the LH2.2 anymore if I direct wire as above?


Thanks for your help. I searched for about an hour and could not figure it out.
On LH 2.2 you would only need to add a ground to 86/1 of the relay, maybe through an oil pressure switch. Still not recommended. There are options to use to add a second relay between the fuel pump relay and the pumps. Think you need to look at Dave Barton's site. http://www.davebarton.com Search for Mods Using Relays.

Last edited by lummert; 01-01-2019 at 05:29 PM..
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Old 01-01-2019, 05:15 PM   #8
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Quote:
Originally Posted by lummert View Post
One safeguard would to use a oil pressure switch in the system, that way the engine would need oil pressure to trigger a relay.


https://www.summitracing.com/parts/hly-12-810
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Old 01-01-2019, 06:50 PM   #9
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This device will do it electronically. It cuts the fuel pump when engine revolutions stop: http://www.revolutionelectronics.com/Fuel_Pump.html
It's also on Amazon if you want to read customer reviews. I have not used one.
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Old 01-01-2019, 06:54 PM   #10
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Quote:
Originally Posted by lummert View Post
On LH 2.2 you would only need to add a ground to 86/1 of the relay, maybe through an oil pressure switch. Still not recommended. There are options to use to add a second relay between the fuel pump relay and the pumps. Think you need to look at Dave Barton's site. http://www.davebarton.com Search for Mods Using Relays.
Thanks for the link to Dave's site. I found a diagram to replace the Volvo relay switch with a standard automotive relay. Pumps will still turn off as per Volvo design and I can get rid of the stock fuse box.

I like that oil pressure switch too. Might be good to add on later to kill the engine in the event of low oil pressure.
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Old 01-01-2019, 07:18 PM   #11
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Quote:
Originally Posted by dbarton View Post
This device will do it electronically. It cuts the fuel pump when engine revolutions stop: http://www.revolutionelectronics.com/Fuel_Pump.html
It's also on Amazon if you want to read customer reviews. I have not used one.
Dave B.
Thanks. I think I can do it with all the factory wiring to the ECU with two standard relays.

Volvo Relay - Standard Relay
First Relay
30 - 30
30 - 85
86/1 - 86
87/1 - 87


Second Relay
30 - 30
87/2 - 87
86/6 - 86
85 - 85

It was nice for Volvo to keep the standard numbers for an auto relay. I would add some fuses in there somewhere, I got to think about that.

Thanks for the help everyone.
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Old 01-01-2019, 07:52 PM   #12
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Btw I wasn't disagreeing with getting rid of the fuse box and bad wiring. Just was saying you can use the stock relay setup to have some safety for racing.

In reading your post I'm glad you have addressed important safety concerns. Most of them count on the driver being awake and or the track worker getting there fast. If you aren't awake you can't shut anything off. If the closest track worker is far away. Well you get it. Have a good time!
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Old 01-02-2019, 12:17 AM   #13
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Quote:
Originally Posted by dl242gt View Post
Btw I wasn't disagreeing with getting rid of the fuse box and bad wiring. Just was saying you can use the stock relay setup to have some safety for racing.

In reading your post I'm glad you have addressed important safety concerns. Most of them count on the driver being awake and or the track worker getting there fast. If you aren't awake you can't shut anything off. If the closest track worker is far away. Well you get it. Have a good time!
Itís all good conversation and suggestions. Even though itís Lemons racing, I take safety seriously. I am putting some of my best friends in the car, so the pushback on eliminating it entirely is appreciated.
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