Is it vapor lock, bad fuel pump, both, neither?

Last week, I had some issues with the Bronco stalling out when headed up off-roading. After it sat overnight, had no issues. Had no issues driving it home the following day from the mountains either (cooler temps most the day.)

Today-- was going to head to Boulder with it, hit a stretch of traffic on I-270 of stop and go where it started to run a little hot. The engine just sputters and then stalls. After the engine sits for about 10-15 minutes, I can start it back up and run it for about 1-2 miles before it goes back to doing the same thing. I would say I did this about 6 times before finally getting it back home. My fuel lines do run along the frame but there are stretches that are somewhat close to the exhaust. I have also noticed some fuel dripping from the carb (is this because of extreme pressure from evaporates?)

As the subject states-- my girlfriend hates me and the pony... I need some serious help figuring this out!!

-Eck

Intermittent problems are really tough to diagnose. I had a situation similar to you a few years ago (less one angry girlfriend). My suggestion is to really diagnose the problem, don't just start throwing parts at it. If you make changes, make one at a time, and see what happens. Patience will pay off.

First, I'd put a pressure gauge on your fuel line. Make sure you have 5-6psi when the truck is running well. I had a pump that was pushing 1 or 2 psi. The truck would run, but was failing when it got hot. I expect that the lack of pressure was making it easier to vapor lock. Similarly a high pressure EFI system is harder to vapor lock, because when fuel is under pressure, it raises the boiling point.

Next, make sure you have spark, when the truck won't run. A couple years later, with a new fuel pump, on the same trail, several hours from home, my truck started failing in a similar way. The pressure gauge was reading 1 or 2 psi, again. After a $500 tow bill, and a new fuel pump (all these were high end Edelbrock mechanical fuel pumps), the intermittent failure continued. I kept chasing an assumed fuel supply problem, temped in an electric pump, re routed lines, etc, nothing helped. Finally, I just let the truck idle away while I was at work, so it would fail where I had tools, not on the road somewhere. When it failed, I checked for spark, it turned out, in addition to my failing fuel pump, the magnetic pick up in my MSD dizzy was failing when it got hot. It was 10+ years old, so I'm not blaming MSD. The infuriating part was that just a few months before I had swapped cap, rotor, plugs, and even the little pads the advance arms rode on. The only part I didn't change was the magnetic pickup. I didn't really know it was a "part" it was hidden deep within the dizzy. So a $30 part was probably the real reason I had to tow the truck home. I bet I could have limped it home with the failing fuel pump. But combine the 2 bad parts, after each 20 minutes it ran, it wouldn't restart for 45 minutes or so. I killed the battery about 100 miles from home, and had to call in the wrecker.

http://www.summitracing.com/parts/sum-800115
http://www.summitracing.com/parts/sum-g1710

Do you remember the "chase" on national television? White broncos aren't supposed to go fast.... They just need a police convoy behind them

Thanks for the info Gunni. I think a fuel pressure guage is a good start. If the fuel pump is bad, would that cause this to happen only when it gets real hot like this?

Yes Keith-- I do remember the Chase. It would be nice if I could have helicopter surveillance at all times in case I do break down.

Today's fuel mixtures boil / vaporize at a lower point than the fuel in use when these cool ass rides were designed.

So when it is hot out it amplifies the problem which is most typically a result of fuel lines located too close to exhaust pipes, headers, manifolds, etc. all of this stuff just gets heat synced when it is hot out and the fuel boils / vaporizes.

The problem can be solved with a band-aid or a combination of band-aids.

The best answer is to use a pressurized fuel system, whether that is a electric fuel pump (need the 12 - 15 psi pump) with a regulator to suit your carb set up or switching over to EFI system which uses 40 psi.

You may try simply insulating the fuel lines and seeing if that helps. That could help with vapor lock. Moving the lines to the outside of the frame rail would accomplish the same thing.

When I swapped out my fuel tank, I put in hard lines and most of it runs on either the top or outside of the frame. The exhaust is pretty close to it where it comes out of the tank itself and then the line that runs into the engine bay probably gets pretty hot.

One question I have is where to actually install a fuel pressure guage. I read that the liquid filled guages can give you skewed results if the liquid in the guage gets too hot (ie- if it is located in the engine bay.)

Justin- did you end up getting an electrical fuel pump?

I am thinking of starting with a fuel pressure guage-- see where I am at with that. I wouldn't mind adding an electrical fuel pump either. Are they too difficult to wire/install?

Electric pump, easy to wire in... Just get a good pump, like the carter p4070

Nope, not yet. I've been debating around doing it now or waiting till I go EFI.

I don't know where to get a regulator... Summit I would think, I need to get one as well.
Summit has the p4070, there 80-90 bucks, free ship if you spend 100 . I had my pumps in 3 days.

Agreed with the carter, great pump, and every older tech I know recommends them for carbureted vehicles

Summit has them, Jegs too. If you want to buy local, check out On Track performance or AAI Speed.

I ran a liquid filled fuel pressure gauge mounted to my regulator right on my intake. I don't know how the heat affected the gauge reading, I always felt it was accurate. Anyways.

I've read that insulating fuel lines with a wrap type insulation can be a double edged sword. Once the line heats up, the insulation helps keep the heat in the line. I don't know if this is really a problem or not, just food for thought. If you feel your lines are too close to exhaust, you might build a simple sheetmetal heat shield to separate the line from the heat source. That way the heat doesn't build up under an insulated line.

I know that this is going to be a "preference" type question but I am looking at getting the electric fuel pump and have a couple of questions. Some of you guys have said to get a fuel pump that pushes around 15psi and then regulate it down to around 5-6 psi. On the flip side, some of you guys have really suggested the Carter P4070 which is a max of 6psi. What would the advantage be of running the higher psi pump and regulating it down as opposed to just running the Carter?

Also-- it looks like both of these options come with the regulator-- Keith, you said you thought I would need a regulator, but it looks like maybe I don't?

http://www.jegs.com/i/JEGS+Performance+ ... 4/10002/-1
http://www.summitracing.com/parts/crt-p4070/overview/

The advantage to the higher psi pump is that the higher the fuel pressure, the less likely it is to vapor lock.

If you use a pump rated to 6 psi, you don't need the regulator, but it would be more prone to vapor lock.


Sent from my C771 using Tapatalk 2

I meant pressure gauge, not regulator... It's what happens on 3 hrs of sleep a night. If your lines are on top of frame or better yet outside of frame, with the 4070 I doubt you will vapor lock again.

Did this happen before you swapped tanks?
How much original fuel line is left?

How new is the mech pump? Diaphragm could be shot?

Just more things to look at

I am not sure how old the mech pump is. I don't mind investing into an electrical pump either way but I am hoping that fixes the problem. I did not have this issue prior to replacing the tank and fuel lines, however, I never really drove it in really hot temps or on any trails. The only other thing I can think of is the fuel filter that came with the tank could be clogged?
P8190001.JPG

The only place that the exhaust is close enough to the lines is right out of the tank where I have the filter set up. The rest of the way it travels to the top of the frame and then outside before going to the fuel pump. I did not re-use any "old" line-- I have used new rubber line to piece the hard line together.

If you want, I can order an extra guage when I place my order Keith.

To me that exhaust looks WAY to close to the fuel line. You might try a header wrap on the exhaust and an insulation wrap on the fuel line, but I wonder if that would work. I'd reroute the fuel line (doesn't look possible) or the exhaust. Unfortunately, rerouting the exhaust looks like the only (and somewhat expensive) option.

I bet with the old tank the fuel line was much further from the exhaust. So changing tanks probably caused the situation. That is the hard part of adding mods to a Bronco, no two are alike and one mod can cause unexpected problems with another mod.

I would recommend going to a large single exhaust dumping out behind the right rear tire, that left side pipe is way to close, you could do the header wrap like gunni said but I wouldn't wrap the line

Any idea what re-routing/reconfiguring the exhaust would run?

Yes, I will take a gauge... Like previously said the line is too close right out of the tank. Re configure that pronto,,, especially with the plastic filter. How are you planning to re route the line even with an elec pump?

At a minimum I would think about300-500 to reconfigure the exhaust, I paid 600 for mine and I had most of the parts and material until the state made me put on cats.....

You've got a welder and can do it yourself. I can show you how to make a merged collector, they're neat. It's the route I'm likely to go since I have to lose my long tube headers for my full width swap. It isn't hard, just fiddly and time consuming. I'll second the vote for a single pipe out the passenger's side. I'm planning on 3", maybe 2.75".

So my plan of action at this point is to:

Add a Carter P4070, and fuel pressure guage.

I think the single pipe option is the route that probably makes the most sense as long as I don't lose power. I just can't see anywhere else to route the driver side tail pipe away from the line. I believe my set-up is a stock 302 so the BCB kit would probably work. Justin-- what would it take to build/weld one (parts cost)? I don't think I am up for doing it myself unless I have someone helping me with it (Justin, if you have the time and desire.. I would gladly accept your assistance.)

I don't think you need to worry about loosing power with a 2 into 1 system. I switched from a cheapo dual exhaust, to a 2->1 and can't tell the difference. I'd do it yourself. I'd call BCB and confirm it works with your drivetrain set up and go for it. No one could confirm it worked with hp axles so I didn't do it. Wish I could/would have.

My friend built his exhaust from a mandrel bent kit for his 60's hot rod Chevy p/u truck and it looks super sweet. I didn't know the kits were available or I'd have done my Bronco myself. $800+ and I didn't even get mandrel bent tubing.

Carter pump is a good one, I'll probably switch to one soon as my LP pump for my EFI. Another friend is running one as his only pump on his 79 Cherokee and it hasn't had a problem. Its a little loud, you can hear it run when you turn the key on, but once the motor is running you can't hear the pump at all.

I'd be happy to help! Not sure on cost. A few hundred bucks, probably. Mandrel bends will flow a bit better but cost more. A compromise would be to buy the BC kit, then weld or modify as desired. Not sure what they want for shipping it, that could tip me towards saying diy was absolutely the better way.

Add to your plan of action a 90* brass barbed elbow and get the fuel line away from your existing exhaust. It's hard to see what your options are, but an elbow will help get it out of the way faster.

There is a place in the 'Springs that sells exhaust wrap cheaply. It was expensive everywhere else.
http://www.siliconeintakes.com/

Also, with the mounting of your pump, I believe it is recommended to mount the pump as close to the tank as possible. They are designed to push fuel, not pull it.

Those guys are in CS, huh. That is funny I've had them bookmarked for about 6 years when they were recommended for parts for a DIY cold air intake for my 300C. Never realized they were so close. Their exhaust page is pretty cool. Lots of good stuff there.