Engine dies when it gets hot!

**Jfly13** · 06/12/07, 01:08 PM

The last couple of trips I have been on my 77 bronco starts dying on the trails after it gets hot. I was at Flat Nasty last weekend and by the end of the day Saturday it was daying constantly when I was at an idle speed on the trails. I have tried adjusting the screws on the carb ( stock 2 barrell motorcraft), I did get it to run pretty smooth, but I did notice that one of the screws would kill the engine when I had it all of the way in, but the other one would not. I don't know if this is right or not? The other thing that has changed is that when I bought it last October when ever I would start it the automatic choke would bump up the idle and I could bump it back down with the gas pedal. The choke no longer seems to be working. It is also hard to start when it is hot, but you barley have to touch the key when it is cold to start it. Any idea what I should look at first? I am not sure where to start. Oh, when it is "hot" my gauge reads around 190.

**70_Steve** · 06/12/07, 01:37 PM

Quote:

Originally Posted by eb4wd

The choke no longer seems to be working.... Any idea what I should look at first?

Fix the choke!

**Jfly13** · 06/12/07, 01:41 PM

I am very "carb dumb". I guess I just need to follow all leads and check all of the conections.

**deltarat** · 06/12/07, 01:46 PM

Could be the coil getting hot.

**70_Steve** · 06/12/07, 01:48 PM

Quote:

Originally Posted by eb4wd

I am very "carb dumb".

What kinda carb? Stock Motocraft 2v?

SaddleUp · 06/12/07, 02:06 PM

Before I opened this my first reply would be bad coil but if your choke is staying closed it will also cause it to die yet it will start fine when it's cold.

Rustytruck · 06/12/07, 03:15 PM

The motorcraft 2 barrel is prone to vapor lock its large float bowl in the front of the engine allowing heat to get to the fuel from 5 sides is a real problem when it gets hot. This has gotten worse with the newer blended fuels concocked in the last 10 years. The best you can do is make sure you are using the thick carb base gaskit. Its about a 1/4" thick with insulator rings at the studs. Make sure the float is set as low as it can and still run at speed on the freeway. Make sure the carb isnt running rich to start with use a vacuum guage to set the idle mixture screws to the highest steady vacuum reading at idle. If your carb has a bad power valve it can make the issues you are having. Another help is to have the engine suck under hood air using an aftermarket air cleaner. This allows more air flow from the fan with the engine consuming under hood hot air. I would start with a carb rebuild. Here in the hot deserts in california climbing at altitude with the fuels we are forced to use I couldn't solve the issues with the stock carb. After 20 years of the stock carb i finally changed to a Quadrajet it is a far better design for handling heat, altitude, and bumpy roads and its far superior to the motorcraft in these conditions. It has its own issues but when the environment turns ugly it is a far better solution. Next step would be fuel injection but i wont go there in an off road truck.

**Jfly13** · 06/12/07, 03:15 PM

Quote:

Originally Posted by 70_Steve

What kinda carb? Stock Motocraft 2v?

yes, it is a stock motorcraft 2v.

Sounds like I need to check my coil and choke. Is there any way to test the coil with out replacing it?

**Jfly13** · 06/12/07, 03:18 PM

Why would you not go EFI for an off road truck? Mine is 98% off road. My dad has a 5.0 efi I am trying to talk him out of. I thought that might be a really good upgrade. Installing it is a complete other story.

Rustytruck · 06/12/07, 03:35 PM

fear of component failure. You can always get carb engine running even very poorly but you can get home. With fuel injection too many components to fail and far too many components that when failed you dont get limp mode your just stuck with a steel rock. Living in So Cal you get such extremes in temperature sometimes in the same day its hard on electronics especially old ones. Granted fuel injection is the way to go for some just not for me. Once the quadrajet is properly set it works so good that you dont even think about needing fuel injection I cant say that about any other carb and i have tried and used most of them. Its just my preference and not a judgement on the fuel injection debate. All I can say is keep the truck simple and it will work well for you the more you complicate things the more stuff to go wrong.
and yes I do run my life like an old dinosaur.