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vapor lock

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RoyS Avatar
RoyS Roy Sperbeck
deptford, NJ, USA   USA
MGA vapor lock issues

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wyatt Avatar
wyatt Silver Member Wyatt W
penguin point, drift ice, Antarctica   ATA
...do you have your heat shield on, where is your fuel line running, are you sure its vapor lock? need more info

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RoyS Avatar
RoyS Roy Sperbeck
deptford, NJ, USA   USA
Ok the car will stall out sitting in traffic and it has spark ,it has a Mikuni 40mm side draft, manflow headers a heat shield between the carb and exhaust .the fuel line runs along the firewall shelf to the cowling near the vent then to the carb.last year I put some fuel line silver wrap on the line and don't know if that fixed it. I have replaced all the fuel system rubber hoses with EFI hose ,replaced the fuel pump.the Ign system ,,coil, petronix ,wires ,cap rotor .The engine never overheats, when it dies the car will start up after 20 min like nothing was ever wrong ,after it dies I have put another dist ,coil ,and it makes no difference. I never had this problem until the new fuel was put on the market.last year I went to an airport and purchased some aviation fuel which seems like the car really likes. When it dies I cannot look in the carb to check the fuel level.

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copernicus Avatar
copernicus Nick Kopernik
Finally Snowing in, CT, USA   USA
Vapor lock in NJ, mid winter, is an unusual event; this may be an electrical issue. Some Petronix failures have been commented on, as well as coil failures, even when new. Is timing set properly; carb mixture OK? What do you mean by "new fuel on the market"? Is it E15?

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RoyS Avatar
RoyS Roy Sperbeck
deptford, NJ, USA   USA
this happens in summer over 85 deg. fuel is 10%

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bikermga Avatar
bikermga Peter Tilbury
Surrey, BC, Canada   CAN
Roy,

Most vapour lock issues come from running a too lean mixture. have no idea about Mikuni carbs, but try richening the mixture a bit.

Peter.

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JRSCA Avatar
JRSCA Silver Member John Smith
Woodstock, ON, Canada   CAN
The best thing I've done in this area was to install the 4" tubing in front of the radiator and vents fresh air on the carbs.

Also, make sure you have the felt pad installed that sits between the bonnet and the top of the radiator.

John

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Rob Z Avatar
Rob Z Silver Member Rob Zucca
Camarillo, CA, USA   USA
1960 MG MGA
Roy,
Sounds like fuel vaporization in the float bowl(s). Not familiar with the Mikuni at all, but the standard SU set up can give headaches in hot weather from heat soak under the bonnet. You might try the bilge blower approach if reasonably certain it’s “vapor lock” or boiling fuel. The ethanol doesn’t help. See Barney’s page on the blower. People have had good luck with it. See here.......

http://mgaguru.com/mgtech/carbs/cb208b.htm



"Time flies like an arrow......Fruit flies like a banana"

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JRSCA Avatar
JRSCA Silver Member John Smith
Woodstock, ON, Canada   CAN
I added a bilge blower as well - a bit of belt and suspenders approach. I wired it in using the "F" switch. I tend to switch it on when I'm in stop and go traffic on a hot day. I had experienced 3 events that seemed to be vapour lock issues prior to adding the 4" piping and the blower. None since the changes - touch wood.

John

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Breisap Pete D
Mansfield, UK   GBR
1960 MG MGA 1600
1997 MG MGF "Audrey"
2004 MG ZT 260 "Nemesis"
I've fitted a bilge fan and flexible fireproof strip to reduce air bypass under radiator (see photo).


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