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Old 04-27-2009, 02:23 PM
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Is this considered vapor lock?

I rebuilt a '68 Ford 302 (in a Cougar), with new Edelbrock topside - intake, carb, heads, fuel pump - and added an HEI Pertronix distro. But when the engine is hot, especially after parking for a bit, it immediately stalls when put into gear (auto C4 trans). I would guess vapor lock, but it starts immediately every time, seems to idle OK, and only stalls when shifting from park or neutral into gear. Or, if I keep the revs up when shifting, I can keep it lit, but it will stall coming up to a stop. So, when hot - stalls under load. If I let it cool, everything is fine again.

A couple of other notes; the idle vacuum is around 15"; I had to replace the hard fuel line from the pump to the carb with a hose that I admit is run too close to the engine and heater hoses, but I have a see-through filter so I can see some gas coming in though the filter never seems to fill up.

I'd appreciate any ideas - if vapor lock shoudl I rerroute the fuel line from the pump? Go to electric pump? Could it be other than fuel, like could the coil over the distro be causing a problem? thanks.
David

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Old 04-27-2009, 03:20 PM
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Doesn't sound like vapor lock to me. I'd look at adjusting the choke so it has a little more choke when idling. If that doesn't work then thr a little more timing.
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Old 04-27-2009, 03:49 PM
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Sounds like maybe a defective fuel pump not delivering enough fuel to keep the bowls full. Since you say the fuel filter never "fills" up, I would look at checking the fuel pressure first. It may also be that the carb floats are not set correctly. Vapor lock is pretty much a thing of the past these days with the fuel quality. You may want to drain a little fuel and check for water in the gas also.
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Old 04-27-2009, 04:19 PM
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All the inline filters that I have seen always look about half full. There is plenty of air in them.
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Old 04-27-2009, 04:33 PM
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Yes it does sound like you may have got a faulty fuel pump. But also sounds like it could also be the timing and possibly the carb may need alittle tuning. make sure the floats are set right also . Cole
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Old 04-27-2009, 04:47 PM
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if I was a betting man Id say fuel percolation is your issue.
you need an insulating spacer between carb and intake.
heat transfers from hot intake to the carb which makes fuel boil in the bowls.
vapor lock is car wont start at all until you open gas cap and vacum releives then car will start.
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Old 04-27-2009, 05:21 PM
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just my $.02 but anytime ive come across stalling when put into gear it was always ignition timing and/or intake vacuum leak somewhere such as bad base gasket, or intake gasket,


welcome to HR forums



good luck

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Old 04-29-2009, 12:26 PM
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More info on vapor lock question

I put a little fuel pressure guage inline just before the carb. When cold, the needle jumps from about 3 to 7 PSI very rapidly - no doubt in time with the cam driving the Edelbrock fuel pump. However, after idling for 15 minutes, the needle stops moving, or actually hovers at just under 5, sometimes slowly drifting down to 3.

I am sure this means something?
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Old 04-29-2009, 09:17 PM
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Quote:
Originally Posted by S10 Racer
Vapor lock is pretty much a thing of the past these days with the fuel quality.
Actually for older cars it's the exact opposite, vapor lock has become a big issue. The new fuels are blended for high pressure fuel injection systems and the high pressure pumps are why vapor lock isn't an issue... on newer cars. The additives they used to put in the fuel to prevent vapor lock aren't there any more because for modern systems they aren't needed.

Go to the HAMB or one of the antique car websites and you'll find plenty of posts about vapor lock on older cars with low pressure fuel delivery systems. I know ALL about it all too well! As soon as the rear end swap is done on my Stude I am revamping my fuel system because my car vapor locks when it gets above 80 degrees out. I'm installing an electric fuel pump because the brand new mechanical pump can't keep the sytem under enough pressure to keep the fuel from vaporizing.
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Old 04-30-2009, 07:53 AM
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I think this is vapour lock:

One hour run to offshore fishing spot with mercruiser (basically a 260 hp chev 350) running about 3000 rpm. Immediatly shut down on arrival (vs letting engine cool at idle). Engine under hatch cover. Two hours later go to restart. Cranks but no firing. Battery gets low. Switch to back-up battery. Back-up battery dead (Day before I had replaced the one I thought was dead.....oops......got the wrong one). Opened hatch to let carb/engine cool. Waited for battery to come back the little bit they do after you crank them to death. Put both batteries in parallel. Looked at the far-away shoreline.......looked at the worried faces of my buddies......thought briefly about wether the lifejackets should come out as we can't paddle a 26 ft boat in open ocean and that rocky shoreline looked perfect for a shipwreck......thought a bit longer about a strong rum and coke.....and then cranked the engine....and it caught! Hooray!.....you can be sure I didn't shut it off again until back to the dock.

Now in my mind....that's vapour lock.....a hot engine that turns gasoline into "gas" in the carb and fueline and it just won't start.
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Old 04-30-2009, 08:30 AM
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put a 1 inch heat insulator under the carb.

if you don't have the room for the spacer then get a 600cfm holley. Edelbrock carbs are extra bad for vapor lock. I threw two of those carbs in the trash for that very reason, for that and for sticky accelerator pumps.
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