Heater core replacement/idle problems

[mensch53]

First post for a long time lurker. I bought a 73 Ranger a month or so ago and have been doing a bunch of work on it. I'm hoping you guys can help with a weird problem.

Not long after I brought it home, my heater core blew up. I bypassed it by connecting the hose from the intake to the water pump. Everything ran well.

I decided to replace the heater core, which, of course, meant rebuilding the heater box, replacing the dash pulls, new seals, etc. Everything went back together correctly and seemed to be working properly.

The problems started when I hooked the new heater core up again. I hooked up the hoses (with the temp valve closed), started it up, then pulled the knob to open the temp valve.

Engine immediately died.

I realized I probably should have filled the hoses and new heater core with coolant before starting the engine, so I did that.

Ever since, the engine will start up from cold and run briefly (2-3 minutes), but will eventually die. It wont idle well.

I have a manual choke on this truck - it doesnt seem to have any effect on how well the engine runs. No matter how much I play with the choke, I can't get the engine to idle/run as it did before this project.

I've tried burping the cooling system. I don't seem to have overheating problems.

I just cant figure out why the cooling system would mess with the idle.

Any ideas? What am I missing here?

 

[DirtDonk]

It's not. No way that some air in the system, or even a lack of coolant in the new part of the system is messing with your engine. Just not happening.
Now, once it's been running for awhile, air pockets and such can mess with your temperatures, but even then they won't effect like you're talking about.
Especially since it sounds like all of this is happening cold anyway, because the engine just is not running long enough.

Go back to the heater control cable you pulled. Is there a wire or connector running anywhere near it? Either under the dash or on top of the engine? If not, then it was likely just a coincidence. A strange one to say the least, but it pretty much has to be.

If it's not something obvious, then perhaps all the messing with the heater plenum and such under the dash was the culprit. You might have smashed some wires or pulled a connector.
Or else something in the carb or ignition just decided to give up the ghost at that moment.

The fact that the choke does not seem to do anything is suspect. If you can physically close off the choke valve, it should literally choke the engine off and kill it. Even with it almost closed, the engine should load up and just burble and sputter and not want to run right. Once it's opened up some, then it clears up and runs as you'd expect.
Because that is not happening, we might suspect that not enough fuel is getting through the carburetor to be burned, but it's usually not that simple unfortunately.

Sorry I don't have any specific things to look at yet. Just keep digging and see what you find that might be a new fault.
Things like the points getting wet from the coolant getting on top of the engine maybe? Do you still have points, or is it converted to an electronic distributor?

Good luck. Hopefully you find an easy solution

And welcome to CB finally too, you lurker you!

Paul

 

[SHX669]

Did you possibly mix up/ swap around the cable control for the choke with the temperature control cable ?

 

[Viperwolf1]

On some years the heater hose has a little cradle on the side of the choke spring housing. The hose is supposed to sit in there and help warm the choke spring in addition to the heat stove tube coming from the exhaust manifold. You may not have that hose in the cradle or the heat stove tube may be damaged.

 

[ransil]

check the vacuum lines, might has pulled one off or damaged one and now you have a vacuum leak.

 

[mensch53]

Yeah, I can't imagine how the two would be related, but good to know I am not crazy.

Given that it's basically impossible for one to have caused the other, I am going to call the cooling system done and start at the beginning with the idle problem.

At this point, it looks like the carb is not getting enough fuel, so I will start with a new fuel pump and go from there.

I appreciate all the help and great suggestions.

 

[Seventee]

Did you possibly mix up/ swap around the cable control for the choke with the temperature control cable ?

'zackly my thought too, only way it makes sense.

 

[mensch53]

'zackly my thought too, only way it makes sense.

Great thought, but no. I didnt touch the choke cable. I put a new temp cable in the dash, ran it through the firewall, and attached it to a new temp valve.

New fuel pump is in and the carb is being cleaned. Running better all the time.

Thanks for the help!

 

[mensch53]

Figured I should close this out in case anyone is interested. Turns out it was, as expected, two completely separate problems. A new fuel pump, carb rebuild, and a tune, and the Bronco is running like a top. And now that it is cold, thankfully the heater is in great shape. Thanks for all your help on this.