Engine from purring to racing in a single day

[Datsui]

This winter I replaced the carb and fuel pump and managed to plug all the vaccuum leaks, getting the engine down to a almost silent 600rpm (about) at idle. She stayed like that for maybe three weeks of light use and now is back up to a high racing (2500+ rpm) at idle. The only thing I did was change the oil (Mr Lube, from the barrel oil) and got a new air filter during those three weeks.

 

I've tried adjusting the idle mixture screw and is seems to do nothing and the throttle screw is completely backed off with slack in the cable at idle. Any ideas what I should look for next??

 

Ds

[TENDRIL]

im assuming its the 210 goon?

 

 

choke adjustment? , wd40 or 3-in1, the linkage...

[datzenmike]

Replaced carb with what?

 

 

Secondary sticking slightly open?

Stuck on choke fast idle cam?

[datsunaholic]

Sounds like either the choke is stuck close/partially closed (leaving it in high idle) or a vacuum line came off again.

 

To check the choke, take the air cleaner cover off and when it's warmed up AND racing, look at the choke butterfly. Should be perfectly vertical. The choke mechanism is what also controls the high idle. If it's not vertical (if it is partially closed), you can open it manually, and while holding it hand-cycle the throttle to see if it kicks down off high idle. If the idle drops down to normal, that means somthing's not right in the linkage. If you cycle the throttle again (without holding the choke open) and it goes back to high idle, then usually that means the electric choke heater isn't hooked up or is't badly adjusted. If the idle stays down and the choke stays open, but the problem returnd after you let it cool off it's sticky linkage.

 

Now, if none of that works, see if you can manually close the throttle. Sticky linkage, or a piece of gasket sticking into the throttle bore can cause the throttle plate to stay open all the time.

 

If none of the ablve gets the idle speed down, start looking for vacuum leaks again. Maybe you knocked a hose off doinng the filter change. I've also had the vacuum secondary (on a Hitachi carb) "Hang" open due to sticky linkage.

[Datsui]

Hey guys, thanks for the advice.

 

I soaked the carb (Hitachi '81) down in cleaner and let it sit for 20 mins. Everything seems to be working on it, except when idling the primary is wet with gas and it's definitely burning rich.

 

The choke seems to work fine, it's never fully vertical at idle and when I do flip it open the car dies.

 

I also noticed an oil leak around the #3 spark plug. I pulled the plug once before a long drive (nice brownish/grey) and after (black and fouled). Could they somehow be related?

 

I also checked my vacuum and it's a steady 16, so there aren't any new leaks :D

[datsunaholic]

it's racing because the choke is partially closed. It dies when you open the choke because you have the main idle screw turned too far out. It's fouling plugs because of the choke... oil on the OUTSIDE of the plug doesn't foul them, unless it takes the place of the circuit (from saturating the plug wire) and then the plug doesn't fire.

[Datsui]

Hey guys, thanks for all the insights. I spent a whole lotta time bashing my knuckles on this one and it turns out it was a partially blown fuse! The 10amp "engine" fuse to be exact. It would work sometimes (like at high rpm, I'm guessing more volts to bridge the gap?) but fail at idle. So long story short (bad pun) it looks like some road brine got up and shorted a cracked wire to the engine.

 

So now it's 1) check fuses 2) check vacuum 3) search internet 4) post on Ratsun :)