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1967 Mercury Cougar with 351 clevland

So I recently picked this car up. It’s a great ride But every morning I drive it to work (18 min) stopping at the jeffy shutting it off n starting it then to work with NO problems samething on the way home (without the jeffy stop) But when I go to lunch in the middle of a hot florida day she starts at work no problem then I drive 7 miles to the same resteruant eat 30 min later go to head back n she doesn’t like to start. Then she wants to stall at every light well that tourney in to not starting today without a jump and stalling at almost every light. I thought it was vapor lock so I removed 2 of the three fuel filters and rerouted the fuel lines. Now the tank and fuel lines are brand new and the fuel,pump looks just as Newburgh not 100% on the pump. So basicly when she gets hot it doesn’t want to run. I popped the hood today while having these problems and noticed the fuel filter was empty and gas only squirting into it when trying to start or finally running but after 30 seconds or so it being empty again. The fuel line is now shorten n not running along anything hot but when I took the fuel cap off tonight it still gasped for air like a beast. Maybe fuel pump? No leaks I put it on the lift today not one leak that I can see. I did notice the fuel tank doesn’t have vent if that matters. Any info would help at this point. It’s a 351 clevland 70 or 71 in a 67 Merc cougar. Thanks everyone

It sounds like you may need to replace the fuel pump. Also make sure there are no restrictions in the line back to the tank.

If the gasoline you’re using contains ethanol, that’s a classic symptom of vapor lock.

The first thing I would suggest is try to find a gas station that sells non-ethanol gas.

Other than that, don’t drive it on hot days.

You should also know, if the fuel system hasn’t been updated to handle ethanol gasoline, damage to fuel system components can occur.


I would look a spacing the fuel supply lines farther away from the manifold.

The fuel pump can leak down the pump shaft so you won’t see it. Also, this engine gets hottest about a half hour after shut down.

One filter is all that is needed. Filters are expansion chambers and they can worsen vapor lock problems you were wise to remove the extras. And unless the filters are mounted with the output directly on top there will be an air bubble in them commensurate to the system pressure.

But otherwise I agree with the good advise given here except to add that the fuel lines back to the tank may be old and deteriorated to the point of being porous and allowing air to be drawn in which would worsen the appearence of air travelling through the filters and the accumulation of vacuum in the tank which would in turn increase the amount of air being drawn in. Of course the accumulation of pressure or vacuum in the fuel tank indicates that the vent is plugged.

BTW, which carburetor is on the engine and is the fuel line properly routed?

Years ago I had a 67 cougar & put a 351 Cleveland out of a 71 Torino in it . The cougar came with a 289 & the 351 bolted right up . The Cleveland had 14 mm spark plugs & other 351’s had 18 mm plugs . Don’t know what your problem is but sure brought back memories .

Somehow you got to narrow it down to either fuel or spark first. I think what I’d do if I had this problem with my early 70’s Ford truck, when it wouldn’t start I’d pop the top off the carb and see if there was fuel in the carb’s fuel bowl. I’ve had that fuel inlet valve inside the carb stick shut sometimes.

Edit: BTW, great purchase! Sort of reminds me of that episode on Mythbusters where they put a jet engine on a 1967 Impala. A must see episode for car enthusiasts.

Offhand, sounds like vapor lock and that’s very common on older carbureted cars using unleaded and/or Ethanol gaosline.

If there is nothing between the intake manifold and carburetor but a plain, thin gasket you might consider the addition of a fiber or phenolic block. Depending upon the type these blocks are anywhere from 1/4" to 1" thick and can greatly help prevent engine heat soak into the carburetor which is what cause vapor lock to begin with.

If the fuel line is touching the engine or is too close to it, bend it or insulate it. Also check the heat riser valve to make sure it isn’t stuck closed.

Rod Knox, ity is a Edlebrock an older one i guessing 4 barrel but thats all i know about it n last nite i rerouted the lines for the 3rd time this time instead of going from the front of the engine bay to the back then over to the passager side behind the engine i went up and over directly to the carb inlet. Its the shortest route im hoping that changes something.

ok4450 there are what looks like a few 1/8" plates that add up to about 3/8’ between the engine n the carb. Think i should get a 1"spacer?

Pleasedodgevan, thats what i was thinking i would do today if last nites rerouting didnt do anything. Insulate the fuel line

Do you guys think putting an electric pump on her would do anything?

Tester im definutly looking for a gas station that sell gas without ethanol but its been hard than i thought…argh

ok the tank is brand new in December by PO and the fuel line from tank to pump looks brand new too(he said they both were done in december) Now the pump “looks” brand new but i found what looks like another new one in the trunk last nite. it had been installed too. So maybe he had the same problem and thought it was the pump? Either way i bought a brand new one last weekend should i just install it to see what happens? Im thinking its vapor lock though and i dont think a new pump will help that rite? Man Insulating the fuel line in the engine bay isnt hard and might do something rite? Hey Thank you Everyone!!! ive been racking my nugget for a week over this its nice to have people to discuss it with!

I’m wondering what would happen { if anything } if you tried leaving the gas cap loose .

If your gas tank is “gasping” when you open the filler cap, you have a plugged vent. To test this drive with the cap loose and see if it then fills the filter.

When the pump runs with the vent is plugger and an increasing vacuum is formed in the tank and when it gets as strong as the fuel pump-no more fuel.

I tried to delete the above post because my answer is not heat dependent but I couldn’t figure out how to delete it,

oldtimer and sloepoke, you guys think like me. Yesterday when it happened to me i removed the cap, Boy did it Gasp for air then i left it off and it stalled 5-6 more times getting home. the first time it happened i got under the car and looked for the vent but i can not find one. Then i looked up a 67 merc cougar gas tank and i dont see where there is a vent. you know i thought All gas tanks have vents but i just dont see one and filling er up with gas is a half hour ordeal.
The pump keeps clicking off.