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Wxman25
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Joined: March 17, 2018
Posts: 44
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 Posted: Sun Jun 29, 2025 12:46 pm Post subject: 1971 fuel pump question |
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Hello I have a 71 and I'm having hot start issues (vapor lock). So I bought a electric fuel pump. The question is are you supposed to wire the "trigger" wire to the negative on the coil?
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VW BAY BUS 1971 don't know original color.
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67rustavenger
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Joined: February 24, 2015
Posts: 11101
Location: Oregon
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| Posted: Sun Jun 29, 2025 1:14 pm Post subject: Re: 1971 fuel pump question |
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| Wxman25 wrote: |
| Hello I have a 71 and I'm having hot start issues (vapor lock). So I bought a electric fuel pump. The question is are you supposed to wire the "trigger" wire to the negative on the coil? |
No, that will make is so the engine will not start due to grounding the - side of the coil.
The safe thing to do is, on Amazon look for a Revaluation Fuel pump relay.
That relay, when installed correctly will run for three seconds after the key is set to the on position, then turn off the E-pump, the pump will restart when it senses engine RPM.
There are other ways to install a relay for an E-pump. But the Revaluation relay is dead simple and safe should you, God forbid be involved in an accident.
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SGKent 
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Joined: October 30, 2007
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Location: at the beach
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| Posted: Sun Jun 29, 2025 1:16 pm Post subject: Re: 1971 fuel pump question |
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I fail to see how an electric pump will solve a vapor lock problem. Electric pumps with FI systems do it by increasing the fuel pressure from 2 psi or so on a carb to 40 - 100 on a FI system. They also add a return line so the fuel is constantly flowing thru the hose and back to the tank. That keeps cooler fuel in the line. On my 1971 when it was 100+ out, I added segments of rubber hose around the steel lines in the engine bay to keep heat transfer down, and added a phenolic spacer to the carb base to slow the transfer of heat into the carb. If you can get ethanol free gasoline, it will vapor lock less than fuels with ethanol in them. Also when you park, park with one side facing the wind if you can so the air blow thru the engine bay.
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lil-jinx
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richparker
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Wxman25
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Joined: March 17, 2018
Posts: 44
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| Posted: Mon Jun 30, 2025 8:37 am Post subject: Re: 1971 fuel pump question |
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| SGKent wrote: |
| I fail to see how an electric pump will solve a vapor lock problem. Electric pumps with FI systems do it by increasing the fuel pressure from 2 psi or so on a carb to 40 - 100 on a FI system. They also add a return line so the fuel is constantly flowing thru the hose and back to the tank. That keeps cooler fuel in the line. On my 1971 when it was 100+ out, I added segments of rubber hose around the steel lines in the engine bay to keep heat transfer down, and added a phenolic spacer to the carb base to slow the transfer of heat into the carb. If you can get ethanol free gasoline, it will vapor lock less than fuels with ethanol in them. Also when you park, park with one side facing the wind if you can so the air blow thru the engine bay. |
Thanks for the advice but still no luck. I wrapped the fuel lines in the heat barrier stuff that looks like tin-foil. I also put an additive in the fuel for ethanol star- something. I don't remember. The only thing I don't have that you suggested is the phenolic spacer. I'm having trouble finding those.
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VW BAY BUS 1971 don't know original color.
Should I do a shag interior? |
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SGKent
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Joined: October 30, 2007
Posts: 42562
Location: at the beach
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| Posted: Mon Jun 30, 2025 1:42 pm Post subject: Re: 1971 fuel pump question |
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| Wxman25 wrote: |
| SGKent wrote: |
| I fail to see how an electric pump will solve a vapor lock problem. Electric pumps with FI systems do it by increasing the fuel pressure from 2 psi or so on a carb to 40 - 100 on a FI system. They also add a return line so the fuel is constantly flowing thru the hose and back to the tank. That keeps cooler fuel in the line. On my 1971 when it was 100+ out, I added segments of rubber hose around the steel lines in the engine bay to keep heat transfer down, and added a phenolic spacer to the carb base to slow the transfer of heat into the carb. If you can get ethanol free gasoline, it will vapor lock less than fuels with ethanol in them. Also when you park, park with one side facing the wind if you can so the air blow thru the engine bay. |
Thanks for the advice but still no luck. I wrapped the fuel lines in the heat barrier stuff that looks like tin-foil. I also put an additive in the fuel for ethanol star- something. I don't remember. The only thing I don't have that you suggested is the phenolic spacer. I'm having trouble finding those. |
what are your symptoms? Do you have the rubber strips around the engine?
These people had some different ones on ebay. I think that one for a 34-pict-3 or 34 ICT will work. You will need a gasket top and bottom, and maybe longer studs. https://www.piercemanifolds.com/
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richparker
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Location: Durango, CO
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| Posted: Mon Jun 30, 2025 5:50 pm Post subject: Re: 1971 fuel pump question |
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Hot start issue is likely caused from fuel boiling in the bowl rather then vapor lock. When hot, put the gas pedal to the floor while cranking and it will start. This is a know Issue with ACVWs, VW even put out a bulletin on the issue. This was recently discussed in depth in one of the beetle forms. You should put the mechanical fuel pump back on with all new fuel lines. I use 1/4” FI fuel line from Autozone.
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richparker
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SGKent
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| Posted: Mon Jun 30, 2025 6:26 pm Post subject: Re: 1971 fuel pump question |
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I looked for the phenolic spacers. no luck other than one in europe that was about $70 USD to get it here and it is not worth that. They used to come in the carb kits as throw aways. You might ask Tim at Volksblitz if he has one. It will help with heat soak. You need a gasket on the top and bottom, and maybe longer studs. You can also slide a piece of aluminum can between one side of the heat exchanger tube and exhaust to stop the heat riser from working when it is really hot, and that will help a little too. Make sure you have good rubber seals around the engine so the heat below the engine stays there and doesn't rise into the engine bay.
Follow what Rich says too. FWIW putting in an electric pump will not solve a heat soak problem. Also make sure that the float level is correct and not high.
These fit a 34 ICT and may work. A gasket goes above and below them. Maybe need longer studs. Ask Tim at Volksblitz if he knows.
https://classiccarbs.co.uk/product/weberdellorto-i...tlecamper/
This one has gaskets adhered to it already.
https://www.dellorto.co.uk/shop/vw-carburettor-kit...or-spacer/
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Abscate
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Location: NYC/Upstate/ROW
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| Posted: Mon Jun 30, 2025 8:47 pm Post subject: Re: 1971 fuel pump question |
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Wishing you well this week, SGK.
I’m overseas at moment, thinking of you.
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SGKent
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Location: at the beach
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| Posted: Mon Jun 30, 2025 9:29 pm Post subject: Re: 1971 fuel pump question |
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| Abscate wrote: |
Wishing you well this week, SGK.
I’m overseas at moment, thinking of you. |
thank you.
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airschooled
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Joined: April 04, 2012
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Location: West Coast, USA
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| Posted: Tue Jul 01, 2025 12:12 am Post subject: Re: 1971 fuel pump question |
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No amount of thermal tomfoolery will stop the heat from getting into the engine compartment fuel/lines. Plastic spacers, space shuttle wrap, and 12v gadgetry have all come and gone in this forum, and a few proven fixes have stuck around.
"Vapor lock" is a buzzword that is thrown around so often by people who mean different things that it's lost all meaning. Like the bar that's so crowded, nobody goes there anymore. Let's define what's happening in your engine.
Flooding. If you hold the accelerator to the floor while cranking, and never let up, it will eventually start with a cloud of dark smoke.
Fuel starvation. You can pump the pedal all you want, but nothing gets it to start. A spoon of gas down the carburetor throat gets it to start instantly.
Which is it? 
My go-to's for flooding:
Keep the heat out of your fuel. Your '71 fuel line from the tank to the pump, by design, goes close the the #3 exhaust manifold and heater dump tube. If you're an inch off the factory routing, you're adding a significant amount of heat to the gasoline before it even enters the hot engine compartment. Then you have a metal fuel line to the pump, make sure it doesn't touch the heat risers.
Keep the fuel pressure down. The last picture of your engine in your gallery is from 2019, where you have a no-name generic fuel-pump-shaped-object. Let's ignore the fact that the lower fuel line looks like it's crying for help. I would check the fuel pressure and confirm it is less than 3psi with the engine running.
If you have starvation when hot, that could be a binding pump rod or aftermarket pump seizing up. Probably harder to diagnose overall, but it's also more rare and usually solved with restored/OG parts.
If you have an electric kit, providing us a link to the kit is the ONLY way anyone here can answer your question.
Robbie
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Abscate
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| Posted: Tue Jul 01, 2025 12:40 am Post subject: Re: 1971 fuel pump question |
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Go to Bill for a beautiful rebuilt fuel pump rather than a piece of silver cheese crap. Cry once, then dry your tears in your smoothly running car
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wcfvw69
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Joined: June 10, 2004
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Location: Arizona
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| Posted: Tue Jul 01, 2025 5:53 am Post subject: Re: 1971 fuel pump question |
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In my experiences the "vapor lock" of over heat of fuel to the pump or pump itself getting to hot is caused by improper routing of fuel lines like Airschooled pointed out. I often see the steel fuel lines feeding the fuel pump either touching or too close to the heat risers or other hot ancillary items in the engine compartment. The other issue is an engine that is running too hot. Have you checked your oil temperatures? There's plenty of threads here that discuss hot engine temperatures or hot engine compartments that have great suggestions on how to resolve that.
The OP needs to find the root issue that is causing his suspected vapor lock vs. changing to an electric fuel pump as a band-aid. I ran a 1971 bone stock dual port engine in my old 1970 bay bus in HOT Phoenix. I never had an issue with vapor lock or other stock mechanical fuel pump issues. We have to remember there were millions of stock VW's on the road back in the day running the original fuel pumps in hot parts of the country w/out the issues the OP is having.
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Wildthings
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| Posted: Tue Jul 01, 2025 6:05 am Post subject: Re: 1971 fuel pump question |
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You can buy gaskets for the heat riser pipes that have a significantly smaller hole in them that greatly reduce the flow of exhaust gases through the tubes and thus the amount of heat reaching the carb.
I just run ethanol free gas during the summer months to combat this problem, and typically get instant hot restarts, whereas with ethanol laced fuel I end up with 30 seconds of cranking with the pedal down, followed by a minute or so of rough running. |
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Wildthings
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| Posted: Tue Jul 01, 2025 6:22 am Post subject: Re: 1971 fuel pump question |
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| wcfvw69 wrote: |
The OP needs to find the root issue that is causing his suspected vapor lock vs. changing to an electric fuel pump as a band-aid. I ran a 1971 bone stock dual port engine in my old 1970 bay bus in HOT Phoenix. I never had an issue with vapor lock or other stock mechanical fuel pump issues. We have to remember there were millions of stock VW's on the road back in the day running the original fuel pumps in hot parts of the country w/out the issues the OP is having. |
The ethanol boils out of the bowl after a hot shut down and ends up causing the engine to run puke rich while cranking and for a minute or so after start up. Different states have different fuel mixtures as well. The gas sold in Arizona is much more heat tolerant than the gas sold in Oregon.
On my VW Thing, I cut a hole in the engine compartment door behind the license plate and use a computer fan to blow outside air at the carb. I have a thermostat attached to the fan shroud that causes the fan to come on once the engine stops and the engine fan quits sucking cooling air into the engine compartment thus letting the temperatures rise. The fan may run up to 30 minutes or so when it's 105°F out. |
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Wildthings
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| Posted: Tue Jul 01, 2025 6:28 am Post subject: Re: 1971 fuel pump question |
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| Maybe 6-8 years ago, hot start problems got discussed and I think it was Busdaddy that added a bleed to the line between the fuel pump and the carb to bleed off pressure after a hot shut down so that the fuel boiling in the line isn't pushing past the needle valve into the bowl. |
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busdaddy
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| Posted: Tue Jul 01, 2025 7:40 am Post subject: Re: 1971 fuel pump question |
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Yes I did, and it did help somewhat when combined with a lower float bowl setting, but I still got the odd long crank start after 20 minutes sitting when shut down hot. I even tried a solenoid valve at the carb inlet, same result.
Fuel isn't formulated for carb systems anymore, it's designed to be kept under pressure in a FI system and vaporise easily now, there's only so much we can do to combat that.
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