65 bogs down and dies on highway

saffron · Jul 6, 2005

Hi all, I was hoping to get a little advice from the group as I searched and did not find...so here goes.

I have a 65 coupe with a 289 and other than the Edelbrock carb and intake dual exhaust, and electric fan it's pretty much stock. It was rebuilt somewhere around 5000 miles ago and has a rebuilt C4 bolted on the back of it.

My problem is that it will bog down and die shortly after gaining speed on the highway. It also does this after cruising at 50 or 55 for about 20 minutes or so. Once the car is put in park or neutral, the problem goes away. I've noticed a lot of gushing going through the fuel filter when it happens, but I can't tell if it's boiling or just getting pushed around because it's messing up. But let me tell you what I've done so far to try and fix it:

Brand new Edelbrock 500 cfm carburetor (had same problem with Holley 4150)
Ran new fuel lines from fuel pump
New fuel filter
New battery (unrelated)
Wired electric fan to run all the time (temp. sensor broke anyway)

And some other things I'm sure I'm forgetting. I know there isn't an internal vacuum leak and don't see how I could have an external one. Let me tell you what my next guesses are:

1) Overheating transmission
2) Vapor lock
3) Screen in fuel tank getting sucked into the line
4) Bad fuel pump
5) Bad thermostat

Any suggestions/comments/other guidance would be greatly appreciated. I'm trying to get the car (my daily driver) to work and I'm coming on the end of the semester very quickly. Thanks in advance!

Max Power · Jul 6, 2005

I think it looks like a fuel starvation problem, you will have to check the systems from there. If it doesn't happen hot or at idle, I think you can rule vapor lock out. Make sure your gas cap is vented, if it should be. Test the output of the system into a bucket. Check your float levels, etc..

65up2d8 · Jul 6, 2005

What happens if you rev the engine quickly and pretty high in the rpm range while parked? Does it bog then? Do you sometimes have to try to crank it for several minutes after it dies? If so, I'd try replacing the fuel filter. If the car sits for substantial periods between running it you might also want to drain the fuel tank. I had an old CJ5 Jeep that acted similarly to what you are describing, and it was the fuel filter. This can be caused by some water in the gas, varnishing of the fuel due to sitting too long, etc. Just my $.02.

notny41 · Jul 6, 2005

I doubt that this is it, but I had a problem where my car would just start chugging and eventually kill. It turned out to be the coil wire. It must have been arcing and heating up the wire because the insulation got real fat and pushed itself out of the coil (in effect disconnecting the wire from the coil).

Might be an easy fix if that is happening to you too - just replace the coil wire.

saffron · Jul 6, 2005

65up2d8 said:
What happens if you rev the engine quickly and pretty high in the rpm range while parked? Does it bog then? Do you sometimes have to try to crank it for several minutes after it dies?

Thanks for the replies all! That's what was making me think it was the transmission, 65up2d8. It runs great sitting still. I can keep it revved up with no problem, but when I put it in gear, it bogs and dies. It even does it when I power brake it. And it usually starts right up when it dies and stops.

What do you think about the transmission idea? What happens when a transmission overheats? Thanks a lot for the help!

latamud · Jul 6, 2005

I had a problem with my carb like that. It was a tiny metal shaving caught in between the needle and seat. I noticed right after killing the engine I could look down the carb and fuel would still be dripping in. Also, with the engine off I could start the electric fuel pump and get the same. It would cause a hard start afterwards though.
Another idea, you said you have a new fuel filter. I once bought a car that had a fuel filter installed in reverse. Idled great but in higher RPMs would bog down. Max speed on that I6 was 35mph until we figured out the filter was backwards. Check for that.

rbohm · Jul 7, 2005

first thing to do is check you fuel pressure at speed. the easy way to do that is to take the hood off and connect up a fuel pressure gauge and tape it to the windshield. then drive as normal and watch or have someone watch the gauge and see what happens during each driving condition. if you have good fuel pressure, then you can rule out the pump and check the carb settings, mostly float level, and the condition of the needle and seat. also check the condition of the fuel filter as well. if it is clogged, or installed wrong it will cause problems. if the pressure drops suddenly, then you may have a vapor lock condition, or a partially clogged fuel line. if the pressure fluctuates, and then drops, i say bad fuel pump. also if the pressure in under say 4lbs on the gauge, then likey you also have a bad pump. the gauge should be set in a "T" fitting before any pressure regulator to get the most accurate reading.

jerry S · Jul 7, 2005

I had the same problem. It was a fuel starvation issue. I was driving my car down the highway to the dyno tuner and the car died on me about 12 times along the way. They disassembled my brand new carb and found that the needles were stuck. The previous mechanic who prepped my car for its safety inspection encountered the same thing. He thought it was a bad fuel pump so he replaced a perfectly good, brand new fuel pump with another one, which I subsequently swapped out for a holley electric blue. So anyways......anyone need a fuel pump for a 69 351W? I have two Scott Drakes with less than 50 miles on them.

saffron · Jul 7, 2005

latamud said:
Another idea, you said you have a new fuel filter. I once bought a car that had a fuel filter installed in reverse. Idled great but in higher RPMs would bog down. Max speed on that I6 was 35mph until we figured out the filter was backwards. Check for that.

Thanks a lot latamud and everyone. I'll get cracking today after work and let you know tomorrow what happened.

saffron · Jul 8, 2005

Latamud, you are my hero for the moment. I went out and looked and sure enough, the "in" side of the filter was pointed straight out toward the carb. I'll be driving it again this afternoon and will let you know what happens.

saffron · Jul 8, 2005

Well, no such luck. The car still stops dead after half a mile on the highway. But this time, when I got it home, I tried something new. I checked out the fuel filter while I kept the car at around 3000 RPM in park. The fuel filter seemed to be emptying out while the carb sucked in the gas, but never emptied out completely after about 2 minutes. Of course, the gas could easily disappear on the highway after the secondaries open right?

Second thing I found was that the water/coolant mix kept pouring and pouring out of the top of my radiator and the top hose from the manifold to the radiator was vibrating (i.e. boiling).

So what does this mean? Do I need a new fuel pump? Do I need a thermostat? Or, since I live in Florida and it's about 101 degrees outside today, should I take the thermostat out altogether?

Please help, and thank you for the comments thus far!

Loup-garou · Jul 8, 2005

saffron said:
Well, no such luck. The car still stops dead after half a mile on the highway. But this time, when I got it home, I tried something new. I checked out the fuel filter while I kept the car at around 3000 RPM in park. The fuel filter seemed to be emptying out while the carb sucked in the gas, but never emptied out completely after about 2 minutes. Of course, the gas could easily disappear on the highway after the secondaries open right?

Second thing I found was that the water/coolant mix kept pouring and pouring out of the top of my radiator and the top hose from the manifold to the radiator was vibrating (i.e. boiling).

So what does this mean? Do I need a new fuel pump? Do I need a thermostat? Or, since I live in Florida and it's about 101 degrees outside today, should I take the thermostat out altogether?

Please help, and thank you for the comments thus far!

I think you're just seeing the "heat soak" boil-off that these cars sometimes exhibit after shut-down - that's why later models have an overflow bottle. As for the thermostat, if the car is not overheating when you drive it, there's probably no problem there.

It sounds like you've got a weak fuel pump or a fuel system blockage. That pump should be keeping the filter filled as long as the engine is running. Don't forget to check the in-tank pickup screen for blockage.

saffron · Jul 8, 2005

Loup-garou said:
It sounds like you've got a weak fuel pump or a fuel system blockage. That pump should be keeping the filter filled as long as the engine is running. Don't forget to check the in-tank pickup screen for blockage.

Thanks, Loup-garou. That seems to be the consensus amongst the posts, so that'll be my next job. I suppose I'll make a new post when I know anything new, but will check this one for any more comments. Thanks again everyone.

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