Whats wrong?

[BahamaBlueFord]

I have a 1970 Bronco 4x4 302, ive owned it for 8 years. always ran pretty well. lately, the truck will start up, runs great, i'll move it. leave it sit, start it up. the third time usually wont fire.. nothing just spins over. First time this happened, a few weeks ago, i shot some either down the carb. fired right up. happened again 2 weeks later. nothing at all, then again the other day in the driveway. If i leave it sit an hour or so, then it fires right up. each time i have not touched the pedal so im not exactly flooding it. It has a new coil, new brain box, spark plugs with less then 1000 miles, new wires, new valve/oil pan gasket. temp usually runs about 155-165 operating depending on weather. any help would be great

 

[m_m70]

fuel filters good? fuel pump?

 

[patterdale]

It could be sucking crap up in the tank plugging the pickup tube. The hour or so cool down would give it time to clear up a enough to run for a while. When it does it look in the carb and move the accelerator linkage. You should see it squirt fuel in the throat. If it doesn't you need to work your way one component at a time back to the tank. Also check for spark. The coil could be acting up when it gets warm or the new brain box. It can also be the pickup coil in the dist. Any of these can run for a bit and then cut out.

 

[Chief Master Sergeant]

Mine was doing something similar and a new fuel pump cured it.

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[NDFess]

sounds like a clogged filter....

 

[kaharp]

If it has a PCV valve on the oil filler cap, try changing it. Mine was doing similar things and I changed the PCV and it corrected it. If the PCV valve is bad, it is basically a big vacum leak and the engine won't draw the fuel it needs to start...they cost about $3.00...

 

[BahamaBlueFord]

fuel does squirt into the carb at all times, nice and strong. so i dont really think its the fuel pump. ive run my old brain box and the new one. same results. is the pickup coil easy to replace in the distributor. thanks

 

[DonsBolt]

do you have the issue when the truck is hot. Say after you have been driving then shut it off, then try to restart it?

I know the alcohol in the fuel they sell now a days does a number on the needle and seats in the carb.

First off what carb are you running

few things could be your fuel level is to high in the bowl or bowls, so when it gets hot and you shut the truck off, the heat from the engine makes the fuel in the bowls expand as it heats up. So when the fuel expands it floods the carb.

could be the needle and seats are getting corroded from the alcohol and not shutting when the fuel bowl fills up, giving you the same symptoms of your fuel level set to high.

I had issues before I went to efi where every few months my needle and seats would get stuck, and my fuel bowls would overflow. A quick removal of the bowls(holley carb) cleaning of the needle and seats would cure my problem for a few months. Then all of a sudden it would do it again, and I would have to clean them again.

Carbs don't like the alcohol in the new fuels we have now. Some goodl fuel stabalizer made for the alcohol blends we have now, or star tron does a world of good if your still running a carb

 

[BahamaBlueFord]

It does happen after the engine heats up. Its the stock carb, have no clue if it has ever been redone. When this has happened, ive checked the carb and it has been pretty full of fuel.

 

[patterdale]

fuel does squirt into the carb at all times, nice and strong. so i dont really think its the fuel pump. ive run my old brain box and the new one. same results. is the pickup coil easy to replace in the distributor. thanks

It's been a while but if I remember correctly it isn't a whole lot harder than replacing points and no gap to set.

 

[suckerpunched]

I had the same symptoms with a holley carb on a streetrod. when I shut it off hot, the fuel in the carb would get hot and boil which would result in fuel running into the intake and flooding it. In my case i could hold the pedal down and crank it, it would start and run fine. I talked to carburetor guy who builds race carbs, he said it has been a fairly common problem in the last 10 years or so. As fuel is changing it seems to boil at a lower temp (which is probably great for EFI). He advised trying to insulate the carb from heat via installing a phenelic spacer between the carb and intake. I did, and in my case, cured the problem. You may not have room for a spacer depending on your setup, if not, I have run thick gaskets that are about 3/8" thick. Also I could hear the fuel boiling in the carb after I shut it off.

 

[BahamaBlueFord]

Tonight i just let the truck sit and idle. it reached 155, i shut it off. waited a bit, went to start it. nothing. I gave it gas, steam rose from the carb. Boiling? I also checked for spark and nothing. it has a new fuel filter now, new coil and brain box. ran with old/with new. same results. Also it starts awesome at cold start, no pumping of the gas pedal in summer. runs awesome. Then heats up,spark disappears and fuel boiling/flooding maybe? Could the Distributor be going bad? timing chain?

 

[suckerpunched]

when the no start condition occurs, it will still start and then continue to run if you give it a shot of ether right. If so, it must have some amount of spark. It also sounds like its getting enough fuel, If it squirts fuel when pump the throttle and it won't fire on that, I would think is must already have too much fuel in it (flooded) or a weak spark maybe. When it does start on ether, does it blow any black smoke out, or run rough for a few seconds? have you tried holding the throttle wide open (do not pump it) and cranking for five seconds or so? this usually will let enough air through to clear the flooded condition.

 

[BahamaBlueFord]

The first time it happened, the truck did start on ether. Since then when the problem happens , it does not work. Also, feathering the pedal seems to help a bit. Putting the pedal too the floor does nothing to help. The night i started it on ether, it ran rough for a few seconds then was fine. Truck doesnt blow any black smoke.

 

[suckerpunched]

I'm still leaning toward flooded condition, but you could probably rule out the spark issue by visually verifying it. I have a spark checker gizmo that plugs on in between the plug and wire, you can see the spark through a clear plastic portion of it. just crank the engine over while watching it.

 

[BahamaBlueFord]

Do you think a new carb would help?

 

[Justafordguy]

I think you need to verify spark first. If it's losing spark then a new carb won't help at all. Next time it won't crank check it for spark. You can test it with a good extra spark plug, just take one of the plug wires off a plug and put it on your test plug. Be sure the test plug is grounded to the engine somewhere.

 

[BahamaBlueFord]

I figured out i was i losing spark after it heated up, so i went and replaced the distributor figureing the stator went bad since everything else is replaced. If i dont have the distributor placed correctly, will it still produce spark? just be out of time. Also,one of the wires from thr alternator was frayed very badly, i fixed that as well. any help would be good, as of now, i have no spark at all.

 

[Justafordguy]

The distributor will spark even if it's out of time. Check power at the + side of the coil.

 

[BahamaBlueFord]

Whats the best way to test for power at the coil?