CVO2FIXUP

Have a 71 LS5 great running car until it gets warm. Just got the car a few months ago. Great on the free way but as soon as you get off and hit some stop and go traffic the car wont idle, very hard to start with lots of sputtering and pumping of the throttle to get it going. Does feel like its out of fuel.

I was talking to the previous owner and he told me he had the same issues and what he used to do is carry a gallon jug of cool water. As soon as the car would dye he would pour cool water on the fuel pump to cool it down ( original fuel pump in the car ) and the car would start running normal again.

So, could the fuel pump stop working when the engine warms up to a certain point? Could it be something with the return line? PO told me to solve the problem to go with the electric fuel pump. What do you guy's think?

Duane4238

When he poured cold water on the fuel pump, it also cooled the rubber S hose that goes from the hard supply line coming from the tank to the fuel pump. As you drive and the engine bay heats up, that hose when old will collapse and cut off the fuel supply to the pump. Spend $10.00 and get a new S hose from a vendor on this forum and see if that solves your problem. Ask me how I know all this!
Duane

CVO2FIXUP

Thanx for the response. So the S hose is the one at the bottom of this diagram. Will do that as soon as the snow melts. Hope that fixes the problem. The car is pretty much undrivable with this problem.

Jud Chapin

If that doesn't fix the problem, check your fuel pressure when the problem presents itself. If it is low, you know the problem is fuel related.

Duane4238

And when you replace the hose, make sure you buy a direct replacement, because they are a molded hose. Don't just buy a piece of fuel hose and bend it to fit. Good luck.
Duane

74modified

The "sock" filter in the tank could also contribute to the problem. If it is mostly plugged, the pump can create lower pressure in the line, further lowering the boiling point of the fuel. I have also seen the interior of the rubber fuel lines deteriorate and plug the flow - check the 5/16" return line for plugging. And take a look at Lar's post on regulators and return lines.

Mike Ward

Is the return line from the pump to the tank in place? It's purpose is to prevent vapour lock which is probably what's happening.

CVO2FIXUP

I am writing all this down and as soon as the snow is gone will check all these points out. Already ordered the S hose. Will just change it out. Thanx for all the advice, I have to solve this issue as soon as spring kicks in.

Mike Ward

There's two of them.

CVO2FIXUP

Oh, I see. So one for fuel in, and the second for the return? ( I am assuming ) Both are S shaped? And if one or the other "kink's" it will cause this stalling and not idling problem?

Wish I was a car guy from a young age instead of motorcycles. Would know what the hell is going on right now. Hate being a nube.

Mike Ward

Yup, the second hose is a bypass/return. It allows the pump the constantly recirculate fuel keeping vapour lock away.

Bubba frequently removes/blocks the line not knowing what it's for.

cobrachuck

Mike is on to something here. I was going to suggest that it could be vapor lock. Fuel boiling the gas lines. I have been around several boats do this summertime hot conditions and just when you need it to the boat won't start .

diehrd

A hot fuel pump ? pour water on it ? Yep , that would be my first idea after I had downed a 30 pack of Bud..


Any one care to ignore the previous bubba owner and think it could be the ignition coil or an ignition issue . Which would cause his issues for sure and not require pouring water on any engine component

Mike Ward

Explain how pouring cold water on a hot fuel pump solves an ignition problem. The previous owner didn't invent this trick BTW- been around since the 40's or earlier.

74modified

At least Bubba could understand vapor lock.
I have even wrapped rags around fuel lines and doused them with water to make it home - in years past. Todays fuels, especially winter blends, are more likely to have low boiling points. Sure an ignition module can get hot and shut off, but how will cooling the fuel pump fix things? And, ignition problems like that usually happen a few times before not working at all. This seems to be a habitual problem.
And - you had to go and force me to agree with Mike

SH-60B

LOL at the 30 pack remark!

My first thought wasn't "vapor lock" either, it was "let's see everyone respond with vapor lock", lol! Something I have never experienced in 40 years of driving carbureted cars, but what can you say? One possible explanation is 'ol Bubba had the hood open long enough to cool the coil down enough to be drivable again, it's just possible the water on the pump trick is a red herring. Oh, BTW, my Vette doesn't have a fuel return, just a line deadhead to the carb, just like every carbureted vehicle I ever had, no vapor lock in 15 years I've owned it, guess I'm just one lucky Bubba, lol!

diehrd

Some testy people in this topic.. Guy sells a car buyer has an issue and seller saysits vapor lock.

Mike and 74 lets go with vapor lock . I am sure the previous owner would never lie about How he Supposedly fixed the issue , SUPPOSEDLY as the OP has not tried pouring water on his fuel pump to prove or dis-prove vapor lock

Last time I actually saw a diagnosed vapor lock issue it was a ignition coil LMAO .. But hey lets go with what a previous owner said , that should help this owner chase his tail oops I mean the issue ..

Jud Chapin

In adding my 2 cents, I've been driving since 1959 (yikes) and have never had a vapor lock issue. This translates into the area of 1 million miles of driving, the vast majority of which has been in carbed cars.

my 76 ray

I had a problem with vapor lock on my '76 and pouring water on the fuel pump would allow it to start. I even tested that theory in my driveway by letting the car idle until it got hot (not overheated) and stalled. I changed the fuel pump and "S" hoses and it cured the problem.

74modified

For those who think "vapor lock" is similar to the loch ness monster.
Here is a link
http://www.google.com/url?sa=t&rct=j...N32--pwY-AutXQ
Could the OP not have this problem? Sure
I go by what the OP stated, - fuel starvation