i have an 85 bronco and for some reason it will sometimes run for as long as i need it to.....and then when i turn it off it wont start again for a long time (multiple days)!!!!!! please help me!

 

I little more info if you please. Engine size (number of cylinders is fine), carb or fuel injection. Will it crank or do you get nothing (which could be an electrical failure).

 

it is a 351w, with a 4 brl holley carb, and yes it just cranks over and over!

 

Spark? Fuel? Compression?

 

RkyMtnMan has it right... that is the ignition triangle. (well actually is spark, fuel, oxygen but compression of the fuel and air makes the ignition actually do the work). If the problem is intermittent in the manner you described though, I'd be looking at electrical issues first. Weak or corroded terminals or connections can easily cause this kind of problem. Check for good voltage at the ignition coil. It should be getting battery voltage (at least +11.5VDC) with the key in the "run" position.

While fuel could be the issue, with a carburetor it's easy enough to check by pumping the throttle a couple times after cranking. Open the air cleaner and have a whiff. You'll know whether or not there is fuel getting down its throat.

 

ignition module, coil, ignition switch, wiring, fuel pump, carb, fuel filter... With out knowing what it has and doesn't have when it won't start will be just throwing parts at it hoping one of them fix it.

 

it has a brand new coil, new ignition wire, new fuel pump, and a brand new fuel filter...thats why im so confused!

 

When it wont start ..Pull off a plug wire put a screw driver in the end of the wire hold it close to a ground & see if you get a spark jump...Also remove air cleaner look down carb push throtle to see if is spraying fuel...Then at least you might find out where to look ..

 

Have you checked the battery cables? I had mine start to go bad, and even though they were TIGHT tight, there was moisture inside the connections that would keep it from starting. I could just *touch* the terminals, there'd be a spark, and it would fire up fine for a day or two. Just wasn't getting enough juice.

If nothing else, get a battery terminal cleaner and clean the posts and cable terminals. You'll at least know you're getting the juice you need.



Another thing to look at is your choke. Take your air cleaner off when the engine is cold, as in sitting for a day or two. If the adjustments are loose, your choke may be vibrating while driving, and then when it cools down, it closes COMPLETELY. I about tore my engine apart trying to find out why it wouldn't start when I had had it running five minutes before while working on something in a completely different part of the engine bay. Turns out the choke had just wiggled shut and the hold down screws were loose. It just cranked and cranked...


Just some quick glance things to check before you start really digging in.




PS: For future reference, it's always a good idea to make your subject something related to your issue. "Please please please" 't may not get you the help you need when "won't start again after turning it off". Secondly, if someone else has the same issue as you someday, they'll be able to find this article with the search function and may get the help they need without even needing to post.

 

When it won't start does it have spark, see Abandoned's post for the how to, does is have fuel, again see Abandonded's post for the how to, is there compression, help us help you.
It has a brand new coil, new ignition wire, new fuel pump, and a brand new fuel filter, only proves that you have been throwing parts at it and haven't got lucky yet so it is time to do some real troubleshooting.

 

yes the compression is fine, yes it has spark, and yah its getting fuel.

 

Then it will start unless the engine has jumped timing. And if that is the case, if it ever DOES start, it won't run right at all. The ignition trio is the key. If all three are present then the engine will run, period.

 

So when it wont start you know you have comp.. spark... & fuel but still wont start ..Right.???...When it runs its ok right ??? It could be the carb.. Stuck float or choke... You could have gas leaking in to the intake when the truck is not running...Flooding it out when you try to start...

 

If you have compression, spark, and fuel, then it should be able to start. If it had never run, and you were getting all three, I'd say it was a different issue, like timing, or something broken. But if it has run fine before, and now it's not and you're getting all three, you know all your internals are probably okay.

One thing you may want to try is to completely remove your ignition module (the box located in the engine bay on the driver's side wheel well) and have it taken down to a local parts store and have it tested. They should do it for free.

Other than that, take your air cleaner off and inspect your carburetor to be sure everything is opening up. If you're getting fuel, but no air, it will never start. If you're getting too MUCH air when it's cold, you probably won't be able to keep it running, if at all. Make sure your choke is only open about 1/8" when cold, especially if it's cold outside.

Do you notice a difference between days when it starts and days when it won't? 30 degrees when it won't, 45 degrees when it will? Raining? Etc.

 

Did you check compression on all 8? What was the PSI you are getting? Check the cap and rotor for wear, damage, and water also try starting it in the dark to see if you have any sparks arcing across from wires, boots, cap to metal parts. Have the ignition module checked like Abandoned said also check the connectors for corrosion. Let us know what you find.