yoeddynz

(was) Yoeddynz's 1968 Viva + Mazda V6. New owner ! Welcome Guzzi rat.

Recommended Posts

Hi.. its been a while. I blame a rusty old Hb wagon and a needy cat taking all my attention.

So i had been discussing some fuel issues with this car in the DIY fuel injection thread. I'd found the main problem but Ive continued on with some other work so an update was possible. (Please ignore the next wall of text if you'd already read the stuff id written in the above mentioned thread over the last two days.)

Well then..back to this old thing. Here comes lots of words...

For ages, actually since I put the V6 in, my current fuel pump arrangement has been like this...

20170319_195837_1.jpg

But for quite some time it has been a bit noisy especially when its hot outside. One time when arriving at my parents place in Blenheim on a stinking hot day (maybe 35 degrees..not Aussie hot but hot enough! ) and moving the car about on their hot asphalt the engine started idling lean. I felt the surge tank and it was really bloody hot. What I figured back then was that the hot fuel returning from the fuel rails was going back into the surge tank and the engine was not drawing enough at idle to bring in fresh cold fuel from the tank. This is possibly compounded by the fact that the surge tank is filled by a low pressure high volume Carter pump I had been using when the car had the Rotary.

So on that day I ended up making the fuel table richer at idle to compensate and that worked fine for when the day was hot as but usually it just means the idle is too rich.

I finally had got around to putting the Viva up on the hoist and having a look at things.  I decided to add a tee to the return line went from the regulator on the rail to the surge tank. I then ran a line direct to the the return on the main tank and connected the overflow from the surge into the spare input on the tee.  This did not work. In fact the pump was way noisier and engine ran lean. So I tried running the return straight back into the main tank and blocked off the overflow. I figured the surge tank would still fill up as any air would get drawn through.

But no.. air does not sink...

So that didn't work either.

I've connected it back the way it was as I was in dire need to go for a strop over the hill to show off the car to my cousin. I took a photo and this what its currently like- you can see the brass tee I'd added when mucking about...

P1110369.jpg

After doing more research (that would be looking at stuff on google..) I have noted that almost all surge setups are like mine. So they all have the same potential issue of rising fuel temps within the surge tank. To me it makes more sense to have the return to the main tank.. so long as you have a lift pump that will always keep up with demand and keep the surge tank full. But the surge will still require a overflow to purge air out and that needs to go to the same return pipe on the main tank.

I don't think I can run the return from the rail into a tee on the overflow line that goes from the surge to the tank because the higher pressure would override the lift pump pressure and prevent it filling the surge.  Man that's a tricky one to type..or picture.

I figured I could add a second return into the main tank and run the rail return into that?  All I know is that I need to stop the hot fuel going back into the surge. I don't really require a huge surge tank as the car does not see any D1 hardcore action. But if the main tank is low its nice to know I wont get any starvation out of a tight set corner heading up Takaka hill for example.

 

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now