Yet another 12ht swap, help needed with vacuum hoses

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Jul 28, 2016
Hi all, doing a swap in my 75 series from the standard 2h to a 12ht engine. Most of it is going as expected however now I'm at the wiring and vacuum hose stage and need some help with identifying where a few things go. From the vac pump on the alternator, the hoses on the 2h went from the pump to a vsv then to what i assumed was aircon idle up on the butterfly valve. As you can see in the pics I've got an extra hose coming from the solenoid at the throttle down near the alternator. I'm not sure if that is meant to attach to the alt, if so there doesn't seem to be anywhere to lead it back to. There is another vsv laying about in the other photo that also goes to the solenoid but doesn't use the alternator. Can't seem to find any solid info on the hose setup so if someone is able to help that would be great. Hopefully all that makes sense. Also if anyone knows what the green plugs are for that would also be good to know. There's a red wire inside it that runs back to another vsv underneath the glow screen, everything seems to be connected to everything, it's a bit of a nightmare to work out.
If you go to my 12ht engine rebuild thread in the diesel section. I have the pluming side manual pages there it helped me get mine sorted.
Thanks mate, was starting to get a little frustrated with the darn thing!
Not that hard to work out also the green plus is located top front left on the 2h and the same thing is located bottom right near the bell housing on the 12ht so you need to make a longer wire to go around the firewall to the female plug. :)
That wire in the pic is a fusible link wire not the oil pressure switch I was on about above.
Cheers oz, got her all hooked up with that info. Seemed to have developed another issue though, engine now runs fine when primed, but only for a few minutes then stalls and needs to be primed again. I'm guessing air is getting in somewhere but can't figure out where. What's the best place to start looking?
How old is the primer pump on your engine this normally give problems have you got it screwed all the way in after priming.
Brand new bosch primer, tried the old one from the 2h also with no success.
All you can do is work your way back from injectors through the fuel system replacing hoses until you find the leak. I would run a clear line like all posts suggest from pump to filter to determine where the air may be entering the system and work from there.
Turned out to be the feed pump piston inside the fuel feed pump. Spring was completely destroyed making the piston not come back out. Replaced with the 2h pump and all is good now in that regard.
Great news glad to hear your on top off it bet your happy with the grunt of the 12ht engine. :)
Huge power difference over the old slug 2h. Never needed her to go fast but being able to merge safely is definitely a bonus! Thanks for your help mate
Welcome mate
My old girl loves to cruise around 95 KPH so just picked up a low K 5 speed with a good fairey overdrive. Happy days can split ever gear in any range. :)
Had the opportunity to get a fairey when I bought the engine but couldn't justify the extra $2k at the time. They do love to sit on about 95 though, was pretty much the top speed on my old 2h!
The 12ht is a great engine but at 2800 rpm she's sitting around 130 kph. I don't fell happy using the extra fuel and having the engine work so hard so I tend to back off to around 1800 to 2000. I'm hopping the fairey will give me the best of both worlds with a better cruising speed 120 kph while keeping the tachometer around 2200rpm. Time will tell I suppose.

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