Isolating TD42

Post by **WHITEWIZARD** » Wed Jul 25, 2007 6:53 pm

Can anyone tell me how to isolate a TD42 properly and safely?
As at the moment i am only isolating the negatives and as it is a diesel it probably will still keep running under it's own compression (please correct me if i'm wrong)
Thanks

Post by **MyGQ** » Wed Jul 25, 2007 6:55 pm

A Diesel will keep going if its got fuel, thats why there is a Fuel Cut Solinoid on the diesel pump that stops the pump getting fuel and stops the engine. This is pisitive activated and earthed through the injector pump to the motor. you need to isolate this to shut the engine down once its going. works on the same principal as a petrol motor, if you cut the power to the coil, the engine just stops

Post by **WHITEWIZARD** » Wed Jul 25, 2007 7:06 pm

So is it the fuel cut solinoid, is what cuts out when you turn the ignition off normally? or is it something different?

Post by **nayto** » Wed Jul 25, 2007 7:06 pm

some small diesels will use an air shutoff, usually as an emergency only but as MyGQ said easiest and safest is fuel shutoff solenoid

Post by **WHITEWIZARD** » Wed Jul 25, 2007 7:08 pm

As i am not TD42 mechanically minded, is there any chance on info where this fuel solinoid is?

Post by **killer_garden_gnome** » Wed Jul 25, 2007 7:10 pm

if u isolate the negative the engine will still turn off, yes the pump is earthed to the motor but the motor is still earthed to the battery, if u isolate it ur are breaking the circuit

Post by **nayto** » Wed Jul 25, 2007 7:28 pm

WHITEWIZARD wrote:As i am not TD42 mechanically minded, is there any chance on info where this fuel solinoid is?

its on the pump itself mate, iv got no photo but im sure someone on here will post 1 up for u.......

Post by **WHITEWIZARD** » Wed Jul 25, 2007 7:39 pm

f u isolate the negative the engine will still turn off, yes the pump is earthed to the motor but the motor is still earthed to the battery, if u isolate it ur are breaking the circuit

Correct me if i'm wrong , but with diesels that can run under there own compression therefore still running the pump, this will still supply diesel still and keep running? I am confused as some will say the suggestion above and some will say solinoid. Can some one set me straight please as i don't really want to do it twice?

All and all thank you for your inputs

Post by **killer_garden_gnome** » Wed Jul 25, 2007 7:48 pm

if u isolate ur negative battery earth ur effectivly cutting all power to the car so in turn ur cutting power to the fuel solenoid so the motor can compress all it wants but it wont be getting fuel

Post by **badger** » Wed Jul 25, 2007 7:54 pm

this would be true except the fuel cut solinoid is in the fuel line from the tank and therefore the pump may spin but no fuel will get thru and the motor will stop spinning very quickly once the fuel supply stops.

best bet if you wanna isolate a td42 is to put the switch in line with the wire from the ignition to the relay for the solinoid

if i could find a wireing diagram online atm id show u wich one

Post by **WHITEWIZARD** » Wed Jul 25, 2007 7:54 pm

OK, so what i have done already (isolating the negatives) is ok?

if u isolate ur negative battery earth ur effectivly cutting all power to the car so in turn ur cutting power to the fuel solenoid so the motor can compress all it wants but it wont be getting fuel

Thank you for your input, but as there is so much confusion on this topic and so many ideas you just don't know what's right. Thanks again and i will leave my set up as i got it, till someone says it's wrong.

Post by **killer_garden_gnome** » Wed Jul 25, 2007 7:55 pm

ifu have it already done cant u just try it?

Post by **WHITEWIZARD** » Wed Jul 25, 2007 7:57 pm

this would be true except the fuel cut solinoid is in the fuel line from the tank and therefore the pump may spin but no fuel will get thru and the motor will stop spinning very quickly once the fuel supply stops.

best bet if you wanna isolate a td42 is to put the switch in line with the wire from the ignition to the relay for the solinoid

if i could find a wireing diagram online atm id show u wich one

Thanks badger, this does make sense too i will take this into account

Post by **WHITEWIZARD** » Wed Jul 25, 2007 8:01 pm

ifu have it already done cant u just try it?

It does sound stupid, but i just didn't know exactly what it would do, if i did loose fuel and IF it kept running it would run dry of diesel and i would have to re prime it (that's what i thought anyways) as mine had trouble last time re-priming and it is only for emergency too. I'm a little picky like that, I probably should try though

Post by **killer_garden_gnome** » Wed Jul 25, 2007 8:05 pm

i dont see why it will pump dry, as soon as u cut the power the fuel will cut and the motor will stop, it cant run on compressed air only, and if for some reason the circut to the pump is still complete it will simply keep running, but it wont

Post by **WHITEWIZARD** » Wed Jul 25, 2007 8:10 pm

A Valid point.

Post by **ozy1** » Wed Jul 25, 2007 9:33 pm

uponspeaking to an auto elec, i was advised not to put a kill switch on the negative, as this could damage diodes in the alternator, not sure on the alts in the gq but was advised against it,

on mine i run a continuous dudy solenoid on the positive of the battery, so once the solenoid is open nothing gets power, only thing left live in the truck is a small trigger wire

Wed Jul 25, 2007 10:23 pm

the single wire going to the back of the injector pump controls the solinoid and this solinoid is what shuts the car off when you turn the key to off
so if you cut this wire no power will go to the solinoid therefor stopping any fuel from being pumped into the motor it wont run dry etc, as this is how you are supposed to stop the motor by shutting power off to the solinoid
anothe option is to use a big solinoid as suggested but for accessories only , i wouldnt run the starter through it or any heavy current drawing items

Post by **ozy1** » Wed Jul 25, 2007 10:32 pm

its aford not a nissan wrote:the single wire going to the back of the injector pump controls the solinoid and this solinoid is what shuts the car off when you turn the key to off
so if you cut this wire no power will go to the solinoid therefor stopping any fuel from being pumped into the motor it wont run dry etc, as this is how you are supposed to stop the motor by shutting power off to the solinoid
anothe option is to use a big solinoid as suggested but for accessories only , i wouldnt run the starter through it or any heavy current drawing items

the one i use is a continous duty 300Amp item, i run starter and all throught it, and have not had any dramas since fitting it back in march

Post by **WHITEWIZARD** » Thu Jul 26, 2007 3:39 pm

Thanks for you input fellas at least it's pointed me in the right direction

Post by **MissGU** » Fri Jul 27, 2007 1:10 pm

Micheal
Call Aaron

He did mine & he'll tell you exactly what you need to do

Post by **WHITEWIZARD** » Fri Jul 27, 2007 4:40 pm

Thanks, I will call him

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