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Registered
Join Date: Oct 2002
Location: Tucson, AZ
Posts: 1,599
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Opinions wanted ... vapor lock?
I've noticed when driving my V8 car around town on hot days (like this past Sat., 103F) that with slow speeds or idling at a traffic light the engine gets a 'hiccup'. A couple times I thought it might stall but it never did. Then if I shut it off for a few minutes and try to start it, it can be hard to start. It'll crank a lot and I need to pump the gas pedal a few times but being careful not to flood it. When cold it starts perfect. Cruising highway it runs great.
I've got a stock Chevy fuel pump and an inline fuel filter (metal can) an inch or two above the intake manifold, next to my thermostat/exp. tank. The fuel line all steel but nothing touching the engine between carb and pump. My theory is at low speed or idle the filter is getting 'heat soaked' and gas is vaporizing inside it since there not enough air circulating through the engine compartment. So does this sound like my problem? I think I'll mount the filter down on the bottom on the engine bar, then run rubber fuel line up to the carburetor, maybe wrap it with some insulation. Like to hear anyone's experiences with this. |
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09-13-2004, 12:15 PM
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Join Date: Jul 2003
Location: Silicon Valley, California, USA
Posts: 97
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Your theory sounds likely. When the engine is hot and not starting, how warm/hot is the fuel filter? If you can hold your hand on it, then that's not the problem.
If the filter is hot, have you considered insulating the fuel lines & filter? That might be a good start.
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Rob ------ '90 964 Cabrio - daily driver 220K miles |
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09-13-2004, 01:42 PM
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Location: Tucson, AZ
Posts: 1,599
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To be honest I haven't put my hand on it but I'm sure it's pretty toasty. You can see the thermals coming off the engine with the lid up. When I'm going down the highway my deflector is pulling air down through the lid. But once I stop the convection takes over, and that filter is getting a good dose of heat. I thought of wrapping the filter with some pipe insulation, might help, probably look like crap though.
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09-13-2004, 02:12 PM
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Join Date: Sep 2001
Location: Foothills, Ca
Posts: 699
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A couple of times it has just died. When it is hot and I try to restart within about a 15 minute span it does not want to start. I smell fuel and it sputters. Temporary remedy, I have removed the cover of one of the relays(fuel pump) and I manually activate the relay and pump until I hear the fuel regulator pump up. It fires up every time. Some day when I have some ambition I will relocate the fuel pump.
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1973 green 1.7 1973 Orange 2.0 1989 Ford F-150 |
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09-13-2004, 04:44 PM
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Registered
Join Date: Sep 2001
Location: Foothills, Ca
Posts: 699
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Oops! You have a V-8! When I learn to read, I'm going to get a
V-8. 
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1973 green 1.7 1973 Orange 2.0 1989 Ford F-150 |
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09-13-2004, 04:50 PM
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Registered
Join Date: Oct 2002
Location: Tucson, AZ
Posts: 1,599
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Hey, that's all right. I know some stock 914s have been plagued by vapor lock problems so I'm not surprised if conversions wouldn't either. I'm used to 'conventional' engine compartments that have a big fan moving air over the engine and also get more outside air coming through. So fuel line layouts that work with regular cars don't necessarily work in a 914. This evening I moved my filter away from the engine and closer to the battery and firewall. I have 3/8" hose connecting up to the carb. I'll see if this makes any difference.
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09-13-2004, 05:44 PM
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