End Of Rope /please Help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

slugish · 05-03-2008, 07:18 PM

HAVE ANY OF YOU HAD VAPOR LOCK PROBLEMS & IF YOU HAVE , WHAT ARE THE SYMPTOMS & WHAT DID YOU DO ABOUT IT. SOME TIMES MY 400 WONT CRANK AFTER ITS HOT & EVEN HAS A HARD TIME CRANKING AFTER ITS COOLED OFF FOR A WHILE, BUT IT WILL EVENTUALLY CRANK & RUN FINE TILL NEXT TIME & WHEN I GET IT BACK CRANKED IT WILL SOMETIMES BACKFIRE AT CRUISING SPEED.
FOWLED PLUGS ( DO GET GAS & OIL ON THEM ) CHANGE OFTEN BUT LAST TIME WERE NEW PLUGS IN WHEN IT WOULDNT CRANK .

HAVE ALSO REPLACED MSD BOX, COIL &DIST CAP & ROTOR.

LAST GARAGE I HAD IT TOWED TO , THEY COULDNT GET IT TO ACT UP
BASICALLY COULDNT FIGURE OUT WHAT WAS GOING ON .
ANY SUGGESTIONS OUT THERE?

Thumpin455 · 05-03-2008, 07:30 PM

If you have an MSD ignition and you are fouling plugs, you should check the resistance of your plug wires. They should have less than 18ohms resistance, if they are higher replace them.

Also it sounds like your carb is dumping fuel, and your valve seals are shot. Hence the abundance of oil and fuel on the plugs. Could be time for a rebuild on the 400.

Last thing to check, make sure the power wire going to the MSD is a full 12v, if it doesnt have 12v you need to run a wire to the ignition that does.

454HO · 05-03-2008, 08:41 PM

Vapor lock is caused when the fuel inside the lines boils. This can happen on either side of the fuel pump. The fix is to re-route or insulate the fuel lines from engine/exhaust heat.

AceX · 05-03-2008, 10:10 PM

Check the fuel pump's proximity to the headers as well. My uncle had a buddy who had some trick headers amde for his hot rod but they were way too close to the fuel pump and he vapor locked while going up a hill...

slugish · 05-04-2008, 06:21 AM

thanks to all for the responses. Found out after I POSTED that my fuel line runs along the frame rail approx. 1 in from the hedman long tube headers & the header pipes closest to the fuel line are splotchy white (getting hotter than the other cylinders. 1st thing I will try is rerouting fuel lines or just heat wrap them .

05-03-2008, 07:18 PM	#1
slugish Slugish Join Date: Jan 2005 Location: Earlysville, Va. Posts: 1,024	End Of Rope /please Help HAVE ANY OF YOU HAD VAPOR LOCK PROBLEMS & IF YOU HAVE , WHAT ARE THE SYMPTOMS & WHAT DID YOU DO ABOUT IT. SOME TIMES MY 400 WONT CRANK AFTER ITS HOT & EVEN HAS A HARD TIME CRANKING AFTER ITS COOLED OFF FOR A WHILE, BUT IT WILL EVENTUALLY CRANK & RUN FINE TILL NEXT TIME & WHEN I GET IT BACK CRANKED IT WILL SOMETIMES BACKFIRE AT CRUISING SPEED. FOWLED PLUGS ( DO GET GAS & OIL ON THEM ) CHANGE OFTEN BUT LAST TIME WERE NEW PLUGS IN WHEN IT WOULDNT CRANK . HAVE ALSO REPLACED MSD BOX, COIL &DIST CAP & ROTOR. LAST GARAGE I HAD IT TOWED TO , THEY COULDNT GET IT TO ACT UP BASICALLY COULDNT FIGURE OUT WHAT WAS GOING ON . ANY SUGGESTIONS OUT THERE?

05-03-2008, 07:30 PM	#2
Thumpin455 My truck is an alcoholic Join Date: Nov 2007 Location: Marquette Mi Posts: 303	Re: End Of Rope /please Help If you have an MSD ignition and you are fouling plugs, you should check the resistance of your plug wires. They should have less than 18ohms resistance, if they are higher replace them. Also it sounds like your carb is dumping fuel, and your valve seals are shot. Hence the abundance of oil and fuel on the plugs. Could be time for a rebuild on the 400. Last thing to check, make sure the power wire going to the MSD is a full 12v, if it doesnt have 12v you need to run a wire to the ignition that does. __________________ Too much stuff, too many projects to list everything. my 454 urged 76 swb beater

05-03-2008, 08:41 PM	#3
454HO Registered User Join Date: Apr 2005 Location: Austin, TX Posts: 1,223	Re: End Of Rope /please Help Vapor lock is caused when the fuel inside the lines boils. This can happen on either side of the fuel pump. The fix is to re-route or insulate the fuel lines from engine/exhaust heat. __________________ - Greg

05-03-2008, 10:10 PM	#4
AceX >130dB Moderator Join Date: Aug 2006 Location: Sacramento, CA Posts: 2,130	Re: End Of Rope /please Help Check the fuel pump's proximity to the headers as well. My uncle had a buddy who had some trick headers amde for his hot rod but they were way too close to the fuel pump and he vapor locked while going up a hill... __________________ Living Life @ 130dB LED Tail Light Conversion; How-to Friend. Father. Brother. RIP El Jay ------------------------------------------------------------------------------------------------------------------------- CLICK HERE and for less than $0.07 a day, you too can help support and build a better forum.

05-04-2008, 06:21 AM	#5
slugish Slugish Join Date: Jan 2005 Location: Earlysville, Va. Posts: 1,024	Re: End Of Rope /please Help thanks to all for the responses. Found out after I POSTED that my fuel line runs along the frame rail approx. 1 in from the hedman long tube headers & the header pipes closest to the fuel line are splotchy white (getting hotter than the other cylinders. 1st thing I will try is rerouting fuel lines or just heat wrap them .



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