EFI vapor lock....SOLVED!!!!

[Gregg]

I vapor locked a little over a week ago. It was only in the 80s and after an hour or so on the highway I sputtered out and died. Its happened before. I pop the hood, let the pressure out of the tank by slowly removing the gas cap, wait 15+ minutes and try to get home.
This time, after 15 min, I drove it to a gas station and filled it up with cool gas (it was at 1/3 tank). That seemed to do the trick and finished the 40 minute uneventful trek home.

I've got a couple questions:
1. I thought I already had a vented gas cap but it's not working now. There's quite a lot of pressure in the tank. It's it recommended to have a vented cap for efi?

2. I only have one external pump by the tank that pushes it up to the injectors but it seems like the fuel stays in the engine bay and heats up way too much before returning to the tank. I've read a little on a LP pump to an accumulator and then a HP pump to the injectors. Does anyone have a diagram or link how it is set it up?

Thanks.

[ZOSO]

answer is swap to intank pump. I had the same issue as you. went intank and it all went away.

[Eck]

I have exactly what you mentioned in option 2 and have never had an issue. Got the accumulator setup from BC Broncos with a LP pump before it and a HP right after it.


Sent from my iPhone using Tapatalk

[Viperwolf1]

I don't think the cap is a problem. Pressure in the tank would not create vapor lock. It's the vacuum between the tank and pump inlet combined with the high fuel temp that's causing the vapor lock.

There's a few ways to make it better. In tank pump is cleanest solution but possibly most expensive and requires either fabrication or new tank. Pusher pump and accumulator works good but will require a little wiring, plumbing and space management. Just use a good pusher pump like a carter p4070. Other ways to Band-Aid the situation are to move the HP pump lower and closer to the bottom of the tank, put a cooler in the return line to cool the tank, and keep the tank full.

[Jesus_man]

I had similar issues. Not convinced it was vapor-lock per-say. When I bought the bronco, it had a holley red pump at the tank, and the factory HP fuel pump from the 95 F250 engine donor in the engine bay No accumulator. Worked great until I rebuilt the engine (you can find my thread). I replaced the Holley pump with the Carter unit and still had problems. the HP pump would get HOT! In the end, I moved the HP pump to the fuel tank, eliminating the LP pump and it's been great since.

So...if you're fuel tank is under a vacuum, a vented cap should help because then your pump isn't working against a vacuum. If you want to experiment, I suppose you could drill in a pinhole in the gas cap and go for a ride on a hot day.

[Gregg]

I already picked up a new vented gas cap. After looking over at CB.com there seems to be a lot of different opinions regarding the accumulator. Looks like the in tank is the best way to go but also more $$$ than I planned. OR they are back ordered. I'll entertain the accumulator for now.

1. Would the correct order of stuff go:
Tank, filter, LP pump, accumulator, HP pump, injectors
2. The filter and LP pump be close to the tank
3. Could the accumulator and HP pump go where the aux tank is
4. Assuming the return lines stay as is.

Thanks!

[Viperwolf1]

I already picked up a new vented gas cap. After looking over at CB.com there seems to be a lot of different opinions regarding the accumulator. Looks like the in tank is the best way to go but also more $$$ than I planned. OR they are back ordered. I'll entertain the accumulator for now.

1. Would the correct order of stuff go:
Tank, filter, LP pump, accumulator, HP pump, injectors
2. The filter and LP pump be close to the tank
3. Could the accumulator and HP pump go where the aux tank is
4. Assuming the return lines stay as is.

Thanks!

1-3, yes. The return line will need a T to connect to the accumulator.

[Gregg]

Will this Holley Red pump from my carb days work:
https://www.amazon.com/Holley-12-801-1- ... B00029JC5S

I just got a HP filter like this:
https://www.ebay.com/itm/Genuine-Ford-F ... 2430714477

I have the 95 ish F150 (dual tank) inline HP pump from the JY

As for the accumulator....What would suggest?

Cool.

[Gunnibronco]

BC Broncos makes an accumlator, but you can do it yourself like I did. Not sure it's too much cheaper, but it works.

viewtopic.php?f=5&t=3874

And yes everything you posted should work.

Mount the filter between the HP pump and motor. I've added a real basic filter between the tank and the LP pump. Any 6 psi carb pump should work.

I've been running this type of set up since I went EFI and it works fine. I've debated going to HP only or intank pump but it has never happened.

[Viperwolf1]

I don't know about Holley pumps but I do know that any LP pump doesn't always work. It has to flow at least as much fuel as the HP pump. That is why I mentioned the carter pump above. I know they work. It would really suck to do all this and end up with exactly the same result.

[Gunnibronco]

I don't know about Holley pumps but I do know that any LP pump doesn't always work. It has to flow at least as much fuel as the HP pump. That is why I mentioned the carter pump above. I know they work. It would really suck to do all this and end up with exactly the same result.

I'm sure Viperwolf is right. I'm running the Carter pump now. I started with a cheapo generic pump when I went to EFI and it worked. I swapped to the Carter pump because I was concerned with the cheapo pumps life expectancy. I didn't know about the flow rate issues.

Sent from my E6910 using Tapatalk

[red75bronco]

Go in tank and never worry again.

[Gregg]

I'm about to start ordering parts.
Other than how much fuel it holds and size, what would be the reasoning between a 1 qt and .5 qt accumulator?
https://bcbroncos.com/shop/fuel/fuel-pu ... ly-bronco/

Also, if the accumulator has a filter on/in it, do you need a filter between the accumulator and injectors?
Would it be overkill to put a fuel cooler before /after the accumulator as the fuel goes back towards the tank? Something like:
https://outlawspeed.com.au/shop/dp13310

Thanks.

[Eck]

I’m guessing an additional HP filter is overkill but that is what I did.

I’m guessing the larger the accumulator, the more the fuel can cool before delivery?

Here are a couple of dirty pictures for your viewing pleasure of my setup.





Sent from my iPhone using Tapatalk

[Gunnibronco]

I've been running fine with a smaller filter. I'm not sure how much you would need.

I read to install the filter between the HP pump and motor in case the HP pump fails, it can send pieces of the damaged pump into the motor if not filtered.

[Viperwolf1]

Larger accumulator hangs down further. I run the shorter one.

[Gregg]

Thank you for the advice and Pics. I ordered the parts and I have this weekend to hammer this out.

Wiring.....

Can I use the existing power supply to the HP pump, split it to power the LP pump too? Seems too easy....

Thanks!

[Gunnibronco]

Wiring.....

Can I use the existing power supply to the HP pump, split it to power the LP pump too? Seems too easy....

Thanks!

That's what I did, running Mustang EFI.

[Gregg]

I got all the parts and will doing this on Sunday. Thanks for the suggestions.

On my 15 minute drive home on Thursday I parked the Bronco for 15 minutes and ran back out for a quick errand. 5 minutes into the errand it started to sputter and backfire. It didn't die but I had to really gas it to keep it running. When I got home I felt the fuel lines, filter and pump and none of them were hot and the fuel pressure guage was at 35 psi. It's only happened when the weather has been 75 degrees or so. Sucks because it's beautiful Bronco driving weather. Ideas?

[Eck]

Not sure how any of these suggestions would matter if specific to warmer temperatures but...

- fuel filters?
- check all the injectors are opening and aren’t getting clogged.
- air filter is clean


Sent from my iPhone using Tapatalk

[Rox Crusher]

My guess is injectors or fuel pressure regulator

[cw72]

Unfortunately I didn’t see this but I have an accumulator sitting in my garage.

I had a very similar issue. Ended up with a low pressure puller, a reusable filter, high pressure pump. In tank has dynamats. Had to redo the plumbing inside the tank because they dumped in the same area not allowing the return fuel to cool in the bulk. I’ll attach a picture.


What tank do you have?


Sent from my iPhone using Tapatalk

[mickphatmac]

Might be worth checking your timing. It's quick and simple. I had a "vapor lock" situation, or so I thought? Turns out my timing was way off. Throw a timing light on it.

[Gregg]

I got everything plumbed and wired. I primed the fuel line a few times to fill up the ACCUMULATOR and fired it up. It was running just fine minus the significant leaking from the ACCUMULATOR brass threads. I continued to tightened them but I couldn't stop the leak. I called BC Broncos and they sent me a new one.
I was cautious (again) to gently snug it and then progressively tighten it until the the leaking stopped. Well, I couldn't tighten it enough. Literally, I have worked it in a vice and I've got it as far as I can physically turn them, and they both still leak. I'm at a loss and I'm tired of smelling like gasoline. Am I missing something?
BTW- BC Broncos was super cool about the replacement.

[Eck]

Did you try using some rtv or Teflon on the threads?


Sent from my iPhone using Tapatalk

[Gunnibronco]

Regulator leaking or accumulator fittings?

If you are sealing the accumulator fittings they are pipe thread and need a sealant. I'd use a thread paste or yellow teflon tape, or both. The yellow tape is for corrosive fluids or gases (liquid propane) and tougher than the white teflon tape.

The regulator looks like an oring seal. I've never swapped mine so I don't know myself.

[Gregg]

Regulator leaking or accumulator fittings?

If you are sealing the accumulator fittings they are pipe thread and need a sealant. I'd use a thread paste or yellow teflon tape, or both. The yellow tape is for corrosive fluids or gases (liquid propane) and tougher than the white teflon tape.


The regulator looks like an oring seal. I've never swapped mine so I don't know myself.

Sorry, I meant accumulator (fixed post). The posts I read said they are NPT threads and shouldn't need sealant and not to use teflon. However, I'd entertain the idea of the yellow teflon tape.... or this:
https://www.permatex.com/products/threa ... d-sealant/

[Gunnibronco]

Regulator leaking or accumulator fittings?

If you are sealing the accumulator fittings they are pipe thread and need a sealant. I'd use a thread paste or yellow teflon tape, or both. The yellow tape is for corrosive fluids or gases (liquid propane) and tougher than the white teflon tape.


The regulator looks like an oring seal. I've never swapped mine so I don't know myself.

Sorry, I meant accumulator (fixed post). The posts I read said they are NPT threads and shouldn't need sealant and not to use teflon. However, I'd entertain the idea of the yellow teflon tape.... or this:
https://www.permatex.com/products/threa ... d-sealant/

Weird advise about NPT threads not needing sealant. To me NPT threads are one of the only places you should be using sealant. This is from working on pools and spas and gas lines for years.

If the linked Permatex sealant is specifically rated for gas it should be fine. Many products aren't.

I used the yellow tape and Rectoseal paste and it's been good for years.

Sent from my E6910 using Tapatalk

[Gregg]

Thanks Gunni and Eck. I wrapped the threads with the yellow tape and seems to be holding for now. No leaks.

Took it for a test drive around the neighborhood and it wasn't good. Lots of sputtering on acceleration. Idles fine.
32 psi on the fuel pressure gauge.
Yes, the hoses are hooked up correctly.
No kinks in the hoses.
Both pumps are getting power.

What else should I check?

[Eck]

Thanks Gunni and Eck. I wrapped the threads with the yellow tape and seems to be holding for now. No leaks.

Took it for a test drive around the neighborhood and it wasn't good. Lots of sputtering on acceleration. Idles fine.
32 psi on the fuel pressure gauge.
Yes, the hoses are hooked up correctly.
No kinks in the hoses.
Both pumps are getting power.

What else should I check?

Did you ever pull the injectors to check those? If you are getting fuel pressure, I’d think the issue is after that which would lead me to believe it could be the injectors. Could be either getting stuck closed or open or clogged.


Sent from my iPhone using Tapatalk