My son's 85 Bronco II stopped running a while back. It will start sometimes, but only runs for 30 seconds or so, then dies. We changed out the alternator, battery, [font=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif][font=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]spark [/font][font=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]plugs[/font][/font], air filter, [font=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif][font=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]fuel [/font][font=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]filter[/font][/font], distributor cap and just a few minutes ago, the [font=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif][font=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]O2 [/font][font=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]sensor[/font][/font]. Still nothing. We did get it to start today by pouring a little gas in the carb (I know, not a good idea)...started right up, then died about 30 seconds later. I'm not the most mechnically inclined, but I can't figure out what to do next! By the way, when it DOES start, it runs real nice and smooth (for the 30 seconds!). HELP!

 

so, you have spark - that's good - did you try changing the fuel filter? or checking the pressure of the fuel line? have no idea what it should be at, but if you get a reading, you can at least rule it out, from someone that knows what it should be.... if you have fuel at the carb, all the time, then a rebuilt carb is most likely what you'd need, since it sounds like the choke is not working right - but, I bet it's a fuel supply problem...

if you have no fuel pressure, and you changed the filter, then it's a new fuel pump you need most likely... which is in the tank, and not super easy to do yourself... but you can do it if you had to.

Might also be a vapor lock situation - caused by poor vaccum... don't ask me how to test for it, but I would check all your vaccum lines, just to see if they are all connected, etc...

they make a special carb cleaner too... I'd try soaking the carb in that stuff, and see if you get it to work right - if that is the problem... I think it's fuel related, or vaccum - I would look there first... if it never started, you'd know it was a spark issue... try shooting some of that carb quick start in there, and see if it will run (better to use than gas) -

You can check the choke too, with the air cleaner off, and if your son puts the metal all the way down, you should see the flaps move and stay moved... although, in 85, they may have changed the choke to an electronic choke, where it is set by the PCM, but the PCM may not be setting it correctly...

 

looks like it could be a bad fuel pump,a carb that is varnished,or an electrical problem causing the fuel pump not to come on. have you checked to make sure the inertia switch hasn't tripped?

 

72, there's no inertia switch since the '85 is carbed, thus has a mechanical fuel pump.

CMW, it sounds like the problem is that fuel isn't getting into the engine, so that points to a fuel filter, bad fuel pump, or bad carb. Also, when you take into account the fact that the '85 has one of the most complicated and unreliable ignition/fuel management/emissions systems in the world, there is a whole list of variables that can enter into the equation. However, since it runs when you pour gas in to the carb directly, I'd focus on the fuel syste, first. Then, if you don't live in an emissions regulated area or California, do a search on the Duraspark mod which will make your son's life simpler and the truck much more relaiable.

Good luck!

 

rw..sorry,that was my fault..you are right that a carb engine does not have the inertia switch! guess i was tired the other night!

 

Thanks to all that's replied! Not sure what happened to the initial message...it has all kinds of other stuff in there (about the font, etc).

We replaced the fuel filter...with no luck. So we're lookig at the fuel pump. I can see it, I just can't figure out how to get TO it!. Is there some kind of test I can do to see if the pump is bad (before we remove it)?

Again, thanks for your help!!

 

unhook the fuel line going to your carb. try starting the engine but be careful because if it is good it will spray gas everywhere. so make sure you have plenty of rags handy to catch the gas.

 

Okay, tried unhooking the gas line...tried to start and it sprayed gas. Looking at the carb...when I fully step on gas pedal, the flap just barely opens, is that good?

 

you should get full movement of the flap - did you try spraying the flaps and hinge with carb cleaner? really let it soak...

so you have fuel - you have spark - must be carb -

one thing you can try too to be sure you do have spark after it dies, is to disconnect a plug wire, and see if it arcs when you try to start it - if it doesn't, could be a bad Ign Coil that is cutting out, but I'd bet it's the carb, since you said it always fires up after you dump some gas in there....

I'd run some GOOD carb cleaner throughout the fuel system too - short of just replacing the carb, which is what you might have to do...

 

Get someone to replace the O2 sensor. Mine ran great for exactly 55 seconds and then sputtered and died. New O2 sensor was the fix. Mine was an 86 FI, but its the computer that looks for a certain code or something. Its worth a shot.