Why does it buck and die?

[Dan H.]

Re: It is not the coil.

David, looking at your pictures the fuel line looks very close to the head which will really heat it up and cause vapor lock. Like others suggested, insulate the fuel line and retest. Might want to bend it out from the engine also. Also, get infrared heat indictor gun and see if you have some hot spots. Although not ideal, the pump gas should run in your car if vapor lock sources are dealt with.
Dan

[David P.]

Re: It is not the coil.

Have you checked the fuel filter? I had one that was almost totally plugged, would let me drive about 6 miles then start starving for gas and die. It would start right up and idle but as soon as you put a load on it, same result. Just a thought.

[David K.]

Fuel line 1.jpgFuel line 5.jpg

[Patrick B.]

Re: It is not the coil.

A quick check for vapor look: take a garden spayer filled with water and when the bucking starts pull over and cool the lines with the water spray. If it starts to run well immediately you have found the problem.

[David K.]

Re: It is not the coil.

I bet the water spray would work. But, it is running better now, as soon as you get your foot off of the gas. It will idle as it should as it always has. Drive it and get a brisk run up through the gears now and by the time you are 1/2 way through 3rd gear. It will buck until you get your foot out of it. I think we are getting closer. The temperatures I posted were when it started bucking, I immediately pulled over with the infrared temp gun in my hand.

[Edward J.]

Re: It is not the coil.

Dave, Have you tried a moderate throttle take off to see if it is in deed a fuel related issue? most of the time when accelerating from a stop the engine will require much more fuel and if the pump is not keeping up with demand the engine will lay flat once the carb. runs out of gas. Could this be the issue your having?

[Monte M.]

Re: It is not the coil.

Dave,
When we started this and I initially brought up a possible vapor lock, I suggested getting a piece of heater hose, run a slice through it and wrap it around the fuel line. Slap a couple of zip ties on it and see if it solves the issue.
So, go ahead and give that a try. If it solves the issue, I will then tell you how to fix the problem for good.

The bottom line is rebending your fuel line. There is plenty of line there to work with. I will tell you how exactly how to do it, but let's make sure this is indeed the whole issue as we guessed early on.

Monte

[David K.]

Re: It is not the coil.

Edward, there is no power problems until I get about 1/2 way through 3rd gear under pretty hard acceleration now. 4th gear will be the same if you start at around 1500 rpm and let the engine pull hard to 3500 rpm it will buck. If I back off the throttle a little, it will smooth out. Much better than before.

Monte, sorry have not tried the heater hose around the fuel line yet. I did bend the fuel line as far as is possible, away from the engine. It is near tight to the engine mounting plate. If you look at the pictures I have attached in a previous post, you can see how much it was, what I bent it to and now I bent it again, at the very lowest part of the line close to the fuel pump. There is no doubt in my mind now, that it is vapor lock. I will need to look at my inventory of "stuff" to see if I have any heater hose here or head to the store. I do know now, that it is vapor lock. Did you see the temperatures I posted on the various areas?

Thanks for the thoughts and help!
Dave

[Monte M.]

Re: It is not the coil.

Dave,
I am glad it seems we are making progress.
You can use anything to protect the fuel line from the heat of the head.

The temperatures do not seem way out of line. You also want to look and make sure you are getting good air flow through the engine compartment.
Also, check the fuel line a little further back. Just to make sure there is nothing else possibly heating it.

You are doing great. Just continue to keep taking it one step at a time. If you do get to the point of bending the fuel line, you will want to disconnect it at the carburetor, bend it out a bit at the very bottom. You are shooting for 1" away from the heat source. Continue to bend the pipe to get it where you want it. You may need to take some of the "hoop" out or it to reconnect. A straight shot in the last 6"or 8" just might be what it needs.

What exactly is in it for fuel right now. When you try fuels in the future only fill the car about 1/4 full. That way if it does not work out, you only have a 1/4 tank of the gas.
Today's fuel have a much lower boiling point than the older fuel. Try a few different 91 or 93 octanes. When you find one the works try to stat with it.

If by chance the heater hose jacket works for insolation, do NOT throw it away. It is something you should tuck away in the car somewhere. Just in case you are out on a really hot day and it happens again, your heater hose wrap will at least get you home.

Let me know how it goes.

Monte

[Dan B.]

Re: It is not the coil.

I think its time to take a serious look at the carb float level. If it were me, I'd give that a first look at this point. Can you try (borrow) another known good carb to test and eliminate this part off the problem?? Dan

[David K.]

Re: It is not the coil.

Monte, Currently I am running 93 octane Marathon. Not saying it is the best or the worst gas. It is just the only gas, in my little town. With that thought, it is fresh gas, as we get allot of traffic through this little town and the gas trucks come 3 times a week.

I wouldn't know how to do anything different to increase air flow through the engine compartment. It is bone stock. Nothing extra and there is a new fan clutch on the water pump, water pump was also restored by Bill Mock.

The fuel line further back is in the stock configuration on the outside of the right frame rail. Real close to the fuel pump, it passes under the frame with the factory rubber hose and fittings. From there it goes up to the carb. This is the only fuel line area that has any chance of getting heat from engine or exhaust system.

I can honestly say, I just don't know how to get the fuel line further away from the heat sources. There just is no room I can see to do so. The fuel line is pretty tight to, but not touching the front motor mount now. I will need to study the fuel line further, from pump to carb., to see where I can gain some more clearance.


Thanks
Dave

[David K.]

Re: It is not the coil.

Dan, I certainly wouldn't know where to find one to borrow. Like in an earlier post, the carb. was professionally restored. Not that it always means anything. I have bought new parts, that weren't good parts before too.

[Monte M.]

Re: It is not the coil.

Dan,

It seems we are making progress. If it does not turn out to be a vapor lock problem, I am leaning toward what you are saying.

As I mentioned in earlier, a fuel pressure problem which very easily be a float sticking or something similar.

We have solved the majority of the problem. We just need to see if we are right before heading off in a new direction.

After Dave wraps the fuel line we will know more.

Dave, just in case you cannot get the line further away from the engine, a line like that is simple to make and I am sure you will be able to find someone to make you one at a fair price, or order one from a different vender than you got this one from. Do not worry about that yet.

Monte

[Kenneth F.]

Re: It is not the coil.

Have you tried a fuel pump check to see if it will fill a pint in 15 seconds, cranking the engine with the ignition disabled?

[John F.]

Re: It is not the coil.

If it is a vapor lock problem as above. Who rebuilt the fuel pump? Did they orient the fittings properly? You could be a notch off, therefore causing your fuel line to be too close to the front of the motor. Just a thought.