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1915cc backfires at highway speeds and dies
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Kindredz
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PostPosted: Mon Jan 16, 2017 2:08 pm    Post subject: 1915cc backfires at highway speeds and dies Reply with quote

73 super beetle with newer 2 year old 1915cc with Empi dual 34 epc carbs. Drives great for last couple of years, starts easy runs around town with no problems. When i drive on highway for about 30 minutes at 65-70mph it starts to act like its running out of gas and putters, then when gas applied backfires. more gas more boging down and backfires more until it dies. immediatly restarts up and runs again for about 20 minutes and dies again. if sit for 15-20 minutes runs again for 30 minutes and dies again. I have adjusted the valves, rebuilt the carbs floats. installed a new electronic fuel pump, new fuel filter. did timing and new dist cap. last time it died i removed the air filters and white smoke came out, but the j tubes do squirt fuel. checked the fuel filter and no fuel in it. as i restarted it, i gave gas and fuel started to fill up the fuel filter about half way. It use to run on highway no problem, even installed the hood extenders. Has all tins in place and new seals.

lost!
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ps2375
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PostPosted: Mon Jan 16, 2017 2:25 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

Is tank vented? Either via vent line or filler cap.
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williamM
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PostPosted: Mon Jan 16, 2017 2:29 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

Would throw a condenser at the ignition- if that does not work- go through the scientific- fuel/ fire/ compression test. get back to us
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VERTED71
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PostPosted: Mon Jan 16, 2017 2:37 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

williamM wrote:
Would throw a condenser at the ignition- if that does not work- go through the scientific- fuel/ fire/ compression test. get back to us


X2....I had a similar issue a while back, turned out to be the points or condenser. I say or because I changed them both at the same time.

Good luck.
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Starbucket
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PostPosted: Mon Jan 16, 2017 3:05 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

Sounds like rust/crap in tank blocking fuel pick-up, is the filter clean and when was the last time it was changed? Might be old cracked rubber lines leaking air. Back firing usually means lean fuel/air mix or timing way off (you didn't remove the wires from the cap before this started did you?). Think back what was changed before this started. Good luck trouble shooting you will get a lot of help here.
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Tim Donahoe
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PostPosted: Mon Jan 16, 2017 3:20 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

x 3 on the condenser.

Tim
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miller0358
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PostPosted: Mon Jan 16, 2017 3:36 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

X-4 on the condenser. Text book symptom. Jeff
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vamram Premium Member
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PostPosted: Mon Jan 16, 2017 3:52 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

What kind of a fuel pump are you using?
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Kindredz
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PostPosted: Mon Jan 16, 2017 5:11 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

vamram wrote:
What kind of a fuel pump are you using?


I'm using this
2-3.5

https://www.summitracing.com/parts/mrg-42s?seid=sr...gQod2UgJTg
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Kindredz
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PostPosted: Mon Jan 16, 2017 5:13 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

williamM wrote:
Would throw a condenser at the ignition- if that does not work- go through the scientific- fuel/ fire/ compression test. get back to us


i have a 09 with electronic ignition pertronix, no condenser
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Kindredz
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PostPosted: Mon Jan 16, 2017 5:14 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

ps2375 wrote:
Is tank vented? Either via vent line or filler cap.



the tank is stock 73 super, the filler cap is the basic metal vw cap, don't believe its not vented. as for a vent line i would have to look.
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Kindredz
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PostPosted: Mon Jan 16, 2017 5:19 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

williamM wrote:
Would throw a condenser at the ignition- if that does not work- go through the scientific- fuel/ fire/ compression test. get back to us


i checked the plugs no oil, changed to new. compression came in at 110-115 all around. had a regulator on the fuel line set at 1.5, moved it to 3. checked valve spacing, all at .006 but #2 was tight(couldn't get spacer tool in-between) and needed adjusting. still stalling once driven on hwy for 30+ minutes.
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Kindredz
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PostPosted: Mon Jan 16, 2017 5:26 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

Starbucket wrote:
Sounds like rust/crap in tank blocking fuel pick-up, is the filter clean and when was the last time it was changed? Might be old cracked rubber lines leaking air. Back firing usually means lean fuel/air mix or timing way off (you didn't remove the wires from the cap before this started did you?). Think back what was changed before this started. Good luck trouble shooting you will get a lot of help here.


fuel filter changed last spring, does look dirty(will pick one up).
checked the timing and discovered that my pully is the one with a notch(front) and a v notch(rear on pully) at 5*Atdc and had set the timing last spring at the v notch. Tis was wrong! So I measured 7/16 from the notch on front of pully to make it 7*btdc and retimed. still stalling
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williamM
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PostPosted: Mon Jan 16, 2017 8:19 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

can you run round and check the fuel bowl after it stalls easy way is mirror and look for accelerator pump out put.- can also remove the brass plug above and to rear of adjustment needle- but have rag to soak it up.

Solid state ignition module fail too. If listening to the radio your ignition is on- that can over heat that system-- wiring the coil backwards can have the same --

Best way to set timing is with a good TDC mark and an adjustable timing light-

run up to 2800 rpm and set to 28 degrees. let idle fall where it may.
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Dougy Dee
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PostPosted: Tue Jan 17, 2017 5:43 am    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

Pertronix requires a full 12 volts or it will crap out as you are describing.
Either your battery or gen/alt/voltage regulator is failing.
Edit: could also be battery connections corroding or moisture under the Pertronix plate.
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andk5591
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PostPosted: Tue Jan 17, 2017 7:45 am    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

Quote:
checked the fuel filter and no fuel in it.


Anybody read this? Tank vent is first thing to check - Second thing is (as mentioned) crap clogging the spigot and also you can have crud in you main fuel line.

Here's a test. Disconnect your fuel line at the carb and run a hose into a gas can. Turn on ignition (disconnect your hot lead to coil) and the pump should start pumping fuel. Should have a nice steady stream - do it for more than a couple minutes to see if the flow drops.
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DeathTrap
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PostPosted: Tue Jan 17, 2017 8:51 am    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

Them little fuel filters plug without notice.

Just slime or invisible coagulants from various fuel blends not mixing well or dislodging slime will plug the filter and with no noticeable indications.
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williamM
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PostPosted: Tue Jan 17, 2017 4:55 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

they can also appear empty, but they are just vapor locked and passing fuel.
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Starbucket
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PostPosted: Tue Jan 17, 2017 5:34 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

Check all wires going through the firewall or along the back and front of the motor for any rub through. On my 70 Ghia I had a wire drop down between the motor tin to body rubber seal and it rubbed through just enuff to barley short the wire so that the motor would slow down and backfire and finally lose all power and die, sit for a min. and it would fire up and run till the same thing would happen again. Had me stumped for a long time but finally stumbled on it.
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Kindredz
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PostPosted: Tue Jan 17, 2017 8:42 pm    Post subject: Re: 1915cc backfires at highway speeds and dies Reply with quote

andk5591 wrote:
Quote:
checked the fuel filter and no fuel in it.


Anybody read this? Tank vent is first thing to check - Second thing is (as mentioned) crap clogging the spigot and also you can have crud in you main fuel line.

Here's a test. Disconnect your fuel line at the carb and run a hose into a gas can. Turn on ignition (disconnect your hot lead to coil) and the pump should start pumping fuel. Should have a nice steady stream - do it for more than a couple minutes to see if the flow drops.


thanks for reply.
i removed tank, added all new lines from front to carbs. added new electric fuel pump(4-7lbs) with regulator at 3. new fuel filter moved from engine bay to above the wishbone under car. tried your test, olde pump flowed fine, changed to new one anyway. everything ran great but when i gunned it, next time i applied gas it bogged down? to much pressure now and flooded?
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