ThePog Posted August 23, 2023 Share Posted August 23, 2023 Hey y'all I am looking for something to act as a fuel cutoff for my X1/9. Currently the fuel pump runs when the key is on regardless if the engine is going, and as I am doing the rewiring thing I thought i might as well do things right. I have found this that might work, although it is spendy; https://www.trademe.co.nz/a/motors/car-parts-accessories/other-accessories/listing/4289397427 Or this, also kindof spendy. https://themetricnut.co.nz/store/index.php?route=product/product&product_id=1724 Is there anything else I should be looking at? Potentially I could wire a standard relay to the oil pressure warning light circuit as a cheap fudge, I don't know if this is really a good idea or not. Thoughts? Quote Link to comment Share on other sites More sharing options...
locost_bryan Posted August 23, 2023 Share Posted August 23, 2023 @kws had the same challenge with his Marina, there's a very detailed description of his solution with photos and everything on his build thread Quote Link to comment Share on other sites More sharing options...
RUNAMUCK Posted August 23, 2023 Share Posted August 23, 2023 I bought some relays off aliexpress. They had two "power out" wires. (Could be an earth trigger if so desired) one was live when the relay was energized, and one was live when the relay was not energized. We're going to fit one to dads Car, run a 12v+ feed off the key to the switching side, and a 12v ground off the oil pressure sensor. So the fuel pump wont pump gas until the motor gets oil pressure. Conversely if the vehicle suffers a series upset/crash/etc, and the driver is unable to manually turn off the key. Then the power supply to the fuel pump will stop as soon as the engine oil light comes on. Not as fast as a modern vehicle with EFi. But if the driver has injuries preventing them from exiting the vehicle under 5heir own power, it prevents a small fire becoming a very very big one. Quote Link to comment Share on other sites More sharing options...
ThePog Posted August 23, 2023 Author Share Posted August 23, 2023 22 minutes ago, locost_bryan said: @kws had the same challenge with his Marina, there's a very detailed description of his solution with photos and everything on his build thread It could be this but the pump would still run all the time, it is reasonably loud. I saw something somewhere which was some sort of switching if/then logic gate. Quote Link to comment Share on other sites More sharing options...
ThePog Posted August 23, 2023 Author Share Posted August 23, 2023 37 minutes ago, RUNAMUCK said: I bought some relays off aliexpress. They had two "power out" wires. (Could be an earth trigger if so desired) one was live when the relay was energized, and one was live when the relay was not energized. We're going to fit one to dads Car, run a 12v+ feed off the key to the switching side, and a 12v ground off the oil pressure sensor. So the fuel pump wont pump gas until the motor gets oil pressure. Conversely if the vehicle suffers a series upset/crash/etc, and the driver is unable to manually turn off the key. Then the power supply to the fuel pump will stop as soon as the engine oil light comes on. Not as fast as a modern vehicle with EFi. But if the driver has injuries preventing them from exiting the vehicle under 5heir own power, it prevents a small fire becoming a very very big one. Yea this is pretty much what i had in mind. Quote Link to comment Share on other sites More sharing options...
kws Posted August 23, 2023 Share Posted August 23, 2023 1 hour ago, ThePog said: It could be this but the pump would still run all the time, it is reasonably loud. I saw something somewhere which was some sort of switching if/then logic gate. Yeah my pump is wired to run all the time with key on, but is quiet enough I'm not bothered by it on my car. The inertia switch is my safety in case I put the car on its roof or something. 1 Quote Link to comment Share on other sites More sharing options...
RUNAMUCK Posted August 23, 2023 Share Posted August 23, 2023 https://www.aliexpress.com/item/4000151271784.html Must have bought the 5 pin one? Quote Link to comment Share on other sites More sharing options...
GregT Posted August 23, 2023 Share Posted August 23, 2023 You can sidestep some of the aggro. A fuel pump from a bike - specifically one of the big Hondas or FZR Yamahas on carbs - will have an automatic cutoff which is backpressure sensitive. IE it only pumps when the float chambers need fuel and cuts when the float needles hit the seats. Volume shouldn't be a problem as they're used on sidecar outfits using Methanol. 2 Quote Link to comment Share on other sites More sharing options...
ThePog Posted August 23, 2023 Author Share Posted August 23, 2023 Ah I just bit the bullet and ordered the relay from the Metric Nut, $140 to not get burned alive kindof makes sense. 1 Quote Link to comment Share on other sites More sharing options...
sheepers Posted August 23, 2023 Share Posted August 23, 2023 LPG safety switch's are quite handy for this task. 2 Quote Link to comment Share on other sites More sharing options...
cubastreet Posted August 24, 2023 Share Posted August 24, 2023 Just don't leave the car standing long enough to dry out the float bowls or it won't start again. Quote Link to comment Share on other sites More sharing options...
ThePog Posted August 24, 2023 Author Share Posted August 24, 2023 48 minutes ago, cubastreet said: Just don't leave the car standing long enough to dry out the float bowls or it won't start again. The one I bought runs for 3 seconds on power on, the stops til it gets a signal from the coil. Should be perfect. 3 Quote Link to comment Share on other sites More sharing options...
Nominal Posted August 24, 2023 Share Posted August 24, 2023 A fiat starts in less than 3 seconds? 2 Quote Link to comment Share on other sites More sharing options...
ThePog Posted August 24, 2023 Author Share Posted August 24, 2023 13 minutes ago, Nominal said: A fiat starts in less than 3 seconds? Obviously it primes for 3 seconds then waits for a minute of churning. Then it probably cant tell if the weak coil signal is actually the car running so never turns on... 1 Quote Link to comment Share on other sites More sharing options...
ynot Posted August 24, 2023 Share Posted August 24, 2023 Hi I just put an off/on switch in feed to fuel pump in the racing X. You soon realise you forgot to turn pump on!! Quote Link to comment Share on other sites More sharing options...
kws Posted August 24, 2023 Share Posted August 24, 2023 5 hours ago, ThePog said: The one I bought runs for 3 seconds on power on, the stops til it gets a signal from the coil. Should be perfect. that sounds good, its the reason i didn't put mine on an oil pressure switch or the likes, as I want to prime the fuel system before starting as my car sits for a bit between starts. 2 Quote Link to comment Share on other sites More sharing options...
Doug Hill Posted August 24, 2023 Share Posted August 24, 2023 The part is a Bosch T0068 relay, 7 pin tachometric jobbie. Common to a lot of fairy early injected cars and only needs an analog/old fashioned coil signal Quote Link to comment Share on other sites More sharing options...
gibbon Posted August 25, 2023 Share Posted August 25, 2023 I used an oil pressure cutout and bridged the relay on demand with a "prime" button that sortof doubles as a security system because it's a repurposed aircon button 2 Quote Link to comment Share on other sites More sharing options...
RUNAMUCK Posted August 25, 2023 Share Posted August 25, 2023 ^this is what we wanted to do with the old boys car. The whole point of an electric pump is not having to crank it for 20 seconds to refill the carb bowls. Quote Link to comment Share on other sites More sharing options...
vk327 Posted August 25, 2023 Share Posted August 25, 2023 tachometric relay is the best setup for safety common in alot of 80s efi cars (bosch jetronic era) the tachometric relay is used to supply battery voltage to the entire EFI system and it does this via two different methods. Initially when the engine is cranking, supply voltage from the starter circuit is used to energise the relay. When the engine is running the relay contacts are held closed by sufficient primary ignition signal pulses delivered directly from the ignition coil negative terminal. Having the relay energised in this way also acts as a safety precaution because if the engine stops, the fuel pump and EFI system power supply would then be turned off. The tachometric relay consists of seven terminals, which are connected and marked as follows: Relay Pin 30 – Battery supply: Connect to battery positive usually via a fusible link. This circuit should have battery voltage at all times. Relay Pin 15 – Ignition supply: Connected to ignition key on circuit. This circuit should have 10-12 volts whenever the ignition is on. Relay Pin 1 – Ignition coil signal: Connected to the ignition coil negative terminal & is used to hold the relay contacts closed when engine running. Relay Pin 50 – Starter signal: Connected to the starter circuit and is used to energise the relay when cranking. Should have 12 volts when starter is engaged. Relay Pin 31 – Relay earth: Connected to ground and voltage should be less than 0.3 volts at all times; with a resistance to ground of less than 5 ohms. Relay Pin 87 – Power supply to EFI system: Connected to all EFI related components, which require a 12 volt, supply. Whilst cranking or running, battery voltage should be present. Relay Pin 87b – Power supply to fuel pump: Connected to the positive terminal of the fuel pump. With the engine cranking and running, battery voltage should be present. common part numbers Bosch: 0280230005, 0280230006 Wehrle: 51 223 909 1 1 Quote Link to comment Share on other sites More sharing options...
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