Help rewiring carburetor

[fuzzhead_smurf]

I bought a '74 710 wagon off my friend, but he wasn't very good at wiring, and the car wouldn't start when I bought it due to a short to ground. I found where the short was, but I had to disconnect the wires leaving the carburetor as they were the culprit. I know that one wire is from the choke, one is from the vacuum solenoid, and the third is from something else (I don't know what it is). I need to know where to hook each of those things up, and what is the best way to do it. I finally got the darn thing to crank but now it won't start because the carb isn't wired up right.

[LenRobertson]

Hey, a 710 goon is my current dream Datsun. I'm envious!

 

I think the third wire goes to the fuel shutoff solenoid. This is a kinda long plug-like thing screwed into the side of the carb. A 19mm wrench fits it, so it will be easy to find. There should be a pigtail wire coming from this solenoid (I've seen this wire broken off before, too). The wire it plugs into is hot when the key is in On position (maybe all three wires are; can't remember). When the key is turned to Off, the solenoid shuts off the fuel to the idle circuit in the carb, to prevent the engine running on after the key is off. So if this solenoid isn't getting power, it probably won't start. As a test, you can even try a jumper wire from the pos. battery post to this solenoid, and see if it will start.

 

I think the three wires should have different ends, or color code wire, or something to tell you which goes where. Maybe someone with a decent memory will post and give you more info.

 

Len

[datzenmike]

The red wire is for the idle cut solenoid. The blue wire is for the choke heater. Both can be tied together and run from any ignition ON/Run position on the fuse box. The 710 should still start without either but wont idle or run well. The third wire is probably from the BCDD solenoid.

 

I finally got the darn thing to crank but now it won't start because the carb isn't wired up right.

 

Pull the coil wire and hols near ground while cranking..... got spark??

 

Look down the carb and pump gas.... see gas squirting???

 

 

If YES to both it should start and run.

[fuzzhead_smurf]

I got the fuel cut-off solenoid hooked up and it works properly. I havent hooked up the BCCD or BCDD or whatever it's abbreviated to, or the choke. I tried hooking the choke up to a wire that had 12V when the key is "ON" but the wires immediately started melting. I don't know if the particular wire I chose had too much current, or maybe the choke is bad (I opened it up and it looks ok inside - not sure how to test it though). Someone else told me to wire it to the + side on the ignition coil. I'm going to try it as soon as I charge the battery.

I also tried testing all three mystery wires with a DVOM. I found that the B/W wire is hot when they key is "ON" and the other two don't seem to do much of anything at any time, which is confusing the hell out of me. I usually get a reading of about .02V when I test the connection.

Also, I don't have a red wire. I have a B/W, a B/G, and a blue one. Everyone (and a few books) keep telling me to hook the choke up to the blue one, but as I said above, I don't think the blue one is getting the correct power supply. What kind of voltage/amperage is the choke supposed to receive? I read that there is a choke thermostat relay somewhere in the car. If someone knows where that is, I would be very grateful.

[fuzzhead_smurf]

I've also noticed that the car seems to be out of gas, which is pretty important. However, there is still fuel visible through the sight glass on the carb. But, when I press the throttle, no gas squirts in. Now I've moved from a wiring problem to a carb problem. Any suggestions?

[fuzzhead_smurf]

ArrrgggH! Now I'm confused. When the choke is wired to the ignition coil, the car makes this horrible churning sound when I try to crank it. When it's not connected, the car cranks fine. Help.

[LenRobertson]

I'll try to post more later, but leaving for work right now. Does all the wiring look more or less stock, or has some of it been redone with crimp-on connectors, etc.? Knowing makes it easier to guess if something is wired wrong.

 

If you have gas in the float bowl, but none squirts out into the carb throat when you pump the throttle by hand, it is probably the accelerator pump. You can search carb posts for more info, or if you have a book of some sort, look that up.

 

Len

[banzai510(hainz)]

is there a choke relay for those cars?

 

Fuck it and just adjust the choke plate where it stays open and dont use the choke(pull the wire). its nice if they work but not essential

[fuzzhead_smurf]

About 99% of the wiring looks stock, but in a few crucial places there's some "modifications" if you can call them that. There's a bit of mystery stuff under the dash, and like I said, the original connector was stock, but I don't know what it went to. I'll post an image of what was actually done to it to cause the short. Maybe that will help. The stock wires are on the left. They were B/W, B/G, and Blue. The "mod" is on the right. All three went to the carb. I'm thinking that the BG and Blue wires are ground wires because the have no voltage. The BW wire is hot.

 

Also, I removed the carburetor and I'm in the process of fixing and cleaning it. I'm concerned that the linkages may have been messed with and the float might be sticking.

[LenRobertson]

Your wiring pic looks like something that shouldn't work, but who knows? I need to look at my cars tomorrow and see if any have something like the connector on the left. It doesn't look familiar, but I'm just getting back to working on Datsuns after a winter away from them.

 

One thing on your carb, since it sounds like you have a non-working accelerator pump, there is a tiny ball and spring that works as a one way valve, under the pump plunger. If someone has been messing about in the carb, they may have lost this ball. Or if you don't know it is there, you will be the one to lose it. It is tiny! I've had Dead Datsun carbs where gas dried out, and the ball was stuck shut. A little spray carb cleaner and a poke with a skinny tool, like an ice pick, will free it up. If you blow carb cleaner or compressed air down the accel. pump bore, wrap a rag around the opening so the ball doesn't blow out.

 

Was your 710 running recently, or is it a typical Datsun that sat for years? Dead ones are a lot of fun to bring back to life, if you don't mind some frustration. If it a more or less running car with a glitch or two, diagnostic ideas are different from those for a dead-one-has-been-sitting-for-years. Let us know a little more history, please. Always love any Datsun story.

 

Len

[fuzzhead_smurf]

Haha, the wiring pic DIDN'T work. It was the reason the car was dead.

The car was running regularly only a few months before I got it. Then the previous owner did something to the wiring causing a short and killed the car. I bought it not running and fixed the short, but I guess not running for a while killed the carb. I'll post more info as I get some.

[fuzzhead_smurf]

Turns out the carb is shot. The accelerator pump doesn't work, the linkages are damaged, there's a major air leak, and one of the diaphragms is trash. Looks like I'm buying a new one.

[LenRobertson]

Turns out the carb is shot. The accelerator pump doesn't work, the linkages are damaged, there's a major air leak, and one of the diaphragms is trash. Looks like I'm buying a new one.

 

It's good to hear you are making progress. When you say "new one", are you thinking Weber 32/36? That is what almost everyone uses. I don't know if replacement original Hitachis are even available anymore. If they are, I think they are lots more $$ than a Weber. But if money is tight, rebuilding your carb is probably doable, or get a junkyard carb and combine them. If you need parts, someone here on Ratsun probably will have the things that don't come in a carb rebuild kit. If you have the $300 or so for a new Weber and adapter, you will likely be happier in the long run. But I don't know what the smog check situation is in your location. Probably that has been covered in past posts here. I don't know if Cali smog regs are county by county or what. Or maybe your '74 is so old it is exempt. Keep us posted. Still envious of your 710! Gotta be worth the time you are putting into it.

 

Len

[fuzzhead_smurf]

I was planning on a weber - just saving up some cash for it. Also, I don't have to worry about smog since the car is before 1975.

[kgrantkey]

is there a choke relay for those cars?

 

Fuck it and just adjust the choke plate where it stays open and dont use the choke(pull the wire). its nice if they work but not essential

 

If it's a standard shift this is the easy way. Keep in mind you gotta pump the gas a couple times usually on cold engine to start easy.

 

I've never had a webber but if i ever need to buy a carb for mine thats the way i'd go.

 

 

I've heard others say wire any 12V w/ign.on to the choke, just make sure it's 12v and not the 9v from the coil if you got a ballast resistor. My elec. choke relay is bad, so i've got it disconnected. I put a carb on the bench and used a 12v power supply with .5 amp output to my choke to watch how long it took to open and i can say the choke will get hot, but if the resistance is high enough you'd think it shouldn't melt wire.

 

I think choke bi-metal resistance is 15-25 ohm so you should never get more than about .9 amp current to the choke. If you got less than 15 ohm resistance it's shorted or bad.

 

Many people do away with the BCDD. Remove it and the solenoid and block it off. It may cause emission problems in Cali though.

[fuzzhead_smurf]

Just bought a weber 32/36 kit. Waiting for it in the mail.