So I stalled twice today due to vapor lock... I had a very similar issue in Moab the last day when it finally got hot out.

I am running a mechanical fuel pump at the moment that is less than a year old. All of my fuel lines run nowhere near the exhaust line and is pretty far away from the headers running in the engine bay. The lines are cool to the touch until you get past the mechanical pump and it runs up to the carb. It is then very hot as is just about everything else inside the engine bay (not sure there is anywhere else to run the fuel lines to keep it any cooler at that point.)

My plan is to put an electrical fuel pump (Carter P4070) on back near the fuel tank tomorrow. When I was in Moab, the trail fix to the problem was to put a high pressure (35psi) pump on it and we wired it to the light switch. Whenever I started to vapor lock, I would hit the light switch and the pump would blow fuel past the vapor and like magic, I was up and running again. I am hoping that the Carter low pressure pump will suffice in combatting the vapor lock issues I have been having. Any other thoughts (OTHER THAN SUGGESTING I GO EFI)?

Also, I find it extremely hard to believe that someone hasn't figured out how to run a carb on a Bronco and mostly avoid these issue every time it gets above 90 degrees. Do I need to run some sort of charcoal return cannister? Does anyone have any other things they know will help in my issue?

-Eck

Wrap your line from the mechanical pump to the carb loosely in aluminum foil. Sounds ghetto but works.

And install a phelonic spacer between your carb and your intake manifold.

I don't know what firewall wrap is. The key is to wrap loosely to provide an air barrier between the foil and line.

It's not a pretty fix but it works. I've been running mine like that for probably 3 years and don't have vapor lock anymore.

I think maybe braided lines or some sort of real insulation might be key.

They also make a heat defective sleeve that fits loosely around the fuel line.

Is the fuel line steel or rubber ?

Steel is better.

It's rubber in the engine bay.

I ran an Edelbrock carb & mechanical fuel pump for 15 years and didn't vapor lock. I did use a pressure regulator that returned unused fuel to the gas tanks. I think that makes a big difference. without return lines, the unused fuel just builds behind your carb or pressure regulator & gets hot. You'd have to run return lines & a 6 port valve, if you are using both gas tanks. You'll have to do it to go EFI in the future, so consider it time well spent.

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Buy a few feet of 3/8" metal brake line, bend & flare up a line from the pump close to the carb. It might take a few adapters to get from the pump outlet to the brake line.

Insulation around the fuel line can have negative consequences. Once the heat is in the fuel it can't get back out. You should be able to run uninsulated metal line, with minimal rubber hose.

You mentioned a charcoal filter for the gas tanks. You don't need that (unless THEY check for that type thing), but you do need tank vents. There has to be a way for air to replace the gas you are pulling out of the tank.

The gas caps we use are listed as "vented". I think this is just for pressure differential due to temperature rise/fall. I don't think they can keep up with the motor using up fuel. The stock system used vents, some through charcoal, depending on the EPA rules. I noticed large pressure releases when I wasn't using a tank vent. It didn't become a problem, but I added vents before it could.

So I just have the one 23 gallon tank. What does it require to run return lines and where do the lines hook up?

If it's vapor lock it's happening between the tank and the pump. That's when the fuel is under a vacuum and it boils at lower temps. Putting the electric pump at the tank will put most of that fuel line under pressure and raise it's boiling point.

Another option is to go with a different pump. I run a jegs on my 79 that is 15psi. Then run a regulator right at the carb. Dont have any more vapor lock issues. Just remember like Phil said. fuel boils at higher temps the higher the pressure.

I just put on a Q Jet carb and a Carter electric fuel pump, all new fuel injection rubber lines and steel lines underneath. Clear fuel filters at each tank and one by the carb. No issues so far.

One thing people forget is that when your crawling or 4x4ing, the mechanical fuel pump is going to get heat soaked from the engine and that also can cause the vapor lock.

I like to keep things simple on the Bronco and like the idea of a mechanical fuel pump, but electric is the way to go in this situation.

J.E.

Installed the electric pump yesterday and used some steel hard line for part of the engine bay. I routed the line as far away from the block as I could so I'm hoping the combination of the two will so the trick. If not, I'll have to keep throwing other ideas at it. Thanks for the suggestions.

In the long run switching over to just an electric pump may be the cure to your woes. I don't know why you've had so many problems with vapor lock, but it'll get at least 5 feet of fuel line out of the engine bay.

I'm not sure, but do I see 3 filters? There is a screw in filter on the inlet of the pump, in addition to the 2 larger silver filters. I don't see anything wrong with 2 filters, one before the pump and one before the carb. But 3 is overkill.

The rubber line will heat soak and retain heat more than steel line. I'd minimize the rubber hose, and maximize steel line. And keep the line far from exhaust & headers.

If you change out the pump get a Carter P4070 pump.

What Gunni said. I'll also add that you should reduce the amount of fuel hose in the engine compartment. Take the shortest route to the carb. Then the fuel will have less time soaking in engine bay heat on its trip to the carb.

Both Gunni and Digger are correct. I will add also that in researching and posting up about this topic, it seemed that each person had a different fix and a different result/experience with vapor lock. I had changed my line to steel lines most of the way, re-routed my exhaust away from the lines and was still getting vapor lock on hot days and usually when sitting still for a period of time (traffic or wheeling). I had a couple of see through fuel filters along my system and I was able to pretty much determine that the fuel was vaporizing in the engine compartment within a few feet of the carb.

I would start with the small stuff-- how long have the filters been in there? Maybe change those. I also think that taking the most direct path with your fuel line while still staying away from the hottest parts of the engine (headers) is your best bet. You could also try doing this with steel fuel line for most of the way and that may help.

I will be honest-- I never really solved completely my vapor lock issue. My last time with it, was in Moab in the middle of a trail on a Saturday morning. That was not fun! I have since switched to EFI and have had ZERO problems and it makes driving the Bronco so much more worry-free...

Good luck!

Gunni, Digger, Eck. Thank you for the input. I'll start with some clear filters, takinging out the one at the pump and minimizing the line in the engine bay. Then trying steel line, new pump etc.... EFI....

Brett. Copy that on the regulator. Is there one you recommend? Maybe one that goes well with that Carter P4070 pump.

I talked to a fella today at a tire shop that has a bronco. He thought he had vapor lock. Same symptoms. He was all stock under the hood except for the ignition coil. He put a stock coil in and his problems were gone. I'm by no means stock but something else for me to look in to before resorting to EFI$

Appreciate all the help!

Hmmmmm, which tire shop? You may have been talking to B.O.B.

With respect to clear filters.............don't get the glass ones...........they like to break and leave gas pumping onto hot engine

I remember having to result to popping the hood on the trail to let the heat out. I did end up cutting in vents on my hood and that helped quite a lot. But you may not want to do that. You can also cut holes in your inner fenders to release heat as well.

Insulating the line can help since there will be cool fuel pumping thru the lines.

But truthfully, 99.9% of the time EFI corrects the issue.