Fuel Fluke

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mullinax95

mullinax95

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Ok......yesterday I had a vapor lock problem (I think). I drove the car in open air on the interstate, went to a car show, left, got in stop go traffic and my acted as if I ran out of gas. I filled the car up and my fuel gauge reads that I have gas. I smelled gas as I was opening the hood, popped the breather off and the carb butterflies was soaked in gas and gas was running down in the motor. The temperature was around 190* and never got over 200*. I have a 1"spacer under the carb and the carb didn't feel hot nor did the fuel line. I got the car fired back up and it did it again .... motor shut off pulled over same thing.

Where should I start to find the problem? The car runs fine in open air but the stop go gets to it but it is not over heating. Here is a picture of how my lines are ran. I have a electric fuel pump as well as a mechanical fuel pump. The electric fuel pump was on when the shut off occurs. The clear fuel filter would be empty when I pop the hood but after I let it cool down some fuel will come back in it and off I go down the road again.

I really don't know where to start. Is running a electric with mechanical a good idea? I do know that it is flooding out the motor because I saw excessive fuel pouring out of the carb.

Any suggestions?

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Maybe a fuel pump problem. Disconnect the mech and see if it still does it. Or maybe the electric pump is bad. Do you have a regulator? I had a problem with my 69 RR, and the pump crushed the carb float.
Nice engine compartment by the way.
Good luck!
 
NICE MOTOR!!!! Sorry I couldn't resist. I was thinking that your fuel pump is acting up. Do what bobscuda67 suggested. And I didn't see a regulator. I use them. They work good. I almost thought "vapor lock" at first but I'm almost positive that it is not. I'm sure one of these professionals on here will be forced to chime in, hopefully??
 
The electric fuel pump is not one of the big Holley type monsters. It's a small type that puts out 7 psi when I have it on along with the mechanical. It always stays in the 7 psi area with both pumps.
 
do you have a controller for your fuel pump. I know for my fuel injected engine when I put an electric pump on it they required a controller to slow the pump down at idle and allow the pump to go full speed when accelerating. Also a return regulator might be a good idea.
 
Well I just got back in from running the motor.

OK.... when I first crank the motor with it running it has (without the electric pump on)7.5psi. When the motor started to get warmer the fuel pressure started to drop slowly. It got to 190* and then the bottom feel out. The pressure dropped to 4.5psi and the fuel started to bubble in the clear plastic filter like it was being sucked out of the filter back towards the tank!!!! I didn't run it any further to see if it was going to flood because it was getting the 200* range...???

I was feeling the aluminum lines, rubber gas hose, filter, carb block, carb the whole time this was going on and non of it felt extremely hot.
 
Looks to me like your fuel line may be picking up too much extra heat at the cowl where it looks to be close to your headers. Since I don't see it, I am going to assume the electric pump is mounted near the tank. Running both pumps shouldn't cause the problem you are describing since the carb will only see the pressure that the mechanical pump can put out. One way to fix it is to install a return line from the carb to the tank. This will keep fuel flowing in the line constantly and it won't have a chance to boil. Another way to fix it is to install a smaller fuel line which will do the same thing as a return line. My personal favorite is to run the tank line into a cool can mounted under the horns, from the can to the mechanical pump, and add a 3/16" or 1/4" return line. Fuel boils at a much lower temperature than water. Also remember that steel lines do not absorb heat as fast as aluminum. Never had a problem yet with that setup, even without ice in the can. Hope this helps.
 
My Suggestions Would Be As Follows:

1st remove he fuel lines to buy-pass the mechanical pump and try running the engine with only the electric pump. If this takes care of the problem then the mechanical pump is bad and may even have a leaking diaphragm. In this event you should also make sure it did not leap gas into the crank-case. Check you oil level and smell the oil to make sure there is not gas in it. If there is drain the oil, buy a cheap oil filter and low cost oil, do the oil change and run the engine for about ten minutes and do another oil change with a higher quality filter and the oil you would normally use and you should be ok.

2nd if the mechanical pump is not leaking into the crank-case and electric pump along did not shove he problem then switch the process and remove electric pump any run it on only the mechanical pump.

3rd if neither of these fix your problem then you should check you needle seats and float levers.

Good Luck!
 
If your running a holley the floats will get sticky and flood the car out. Also all electric pumps need a regulator. Vapor lock is when vapor blocks fuel flow and you don't get any fuel. What you had is called flooded. My 73 Charger sits a lot and God only knows how maney times its happened to me. I tap the bowls with a wrench wipe up the gas start it and keep going.
 
Ok... thanks everyone.

I checked the oil by pulling the dip stick... feeling the oil... smelling the oil and it does not have gas in it.... smells like oil.

I really don't think the floats are getting sticky because it only does it when the motor hits 190* or higher. Of course I'm not ruling out completely because it could be vapor lock along with float trouble.

I took some more pictures of the fuel line showing exactly how it's ran so to shed more light on what might be going on. There is two places that are close to the headers... one at the cowl.... two at the fuel pump (rubber hose) that might be the problems.

I think I can fix the two spots... at the cowl I could wrap the line in some kind of heat protection and at the pump I install a 90* fitting and let the fuel line go toward the front of the car some more then turn and back into the 90* fitting at the pump. Getting it away from the header. There is a short piece of aluminum fuel line that is between the mechanical pump and the filter but it does not feel hot like it would be causing it. If I ran rubber hose from the pump to the filter would that be better?

For right now I'm pretending like I don't have a electric fuel pump on the car... I'm leaving it off and use it for back up. The car will run off of the mechanical pump anyways with a pressure of 7.5 I don't mind wrapping all of the aluminum line with heat protection IF is doesn't look tacky. I might too.

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Exactly what kind of electric pump are you running? Is it the El-Cheapo parts store type? Is your gauge liquid filled or not?
 
Exactly what kind of electric pump are you running? Is it the El-Cheapo parts store type?
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Yep it's that type. I don't even know really why it's on there except for back up purposes. It was on there when I bought the car. But for right now I'm not going to turn it on.... it's not there any longer until I figure out what's going on.


Is your gauge liquid filled or not?
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Nope... it's bouncy but it reads correctly enough when I hold my hand around it but still is not dead nuts accurate. It was wired... the longer the motor runs the less fuel pressure I have... dropped down to 4.5 then it looked like some monster was sucking the fuel back in the tank through a straw LOL!
 
This may be a dumb question, but, is the tank vented properly, is gas cap vented and working ok?
 
Just a thought here,your gas cap.The vent hole could be plugged,causeing pressure buildup,not venting?Just a long shot.Crack your gas cap loose and see if this sucking continues?
 
bobscuda67 said:
This may be a dumb question, but, is the tank vented properly, is gas cap vented and working ok?
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pettybludart said:
Just a thought here,your gas cap.The vent hole could be plugged,causeing pressure buildup,not venting?Just a long shot.Crack your gas cap loose and see if this sucking continues?
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Will do.

I have not thought of that.

I have forgot to mention that I have the crub idle set at 950 RPMS but after I run the car awhile, get nice and warmed up that it will not idle down to 950 but stays around 1100 RPM. I'll ease the clutch out and bog the motor to "kill it" so the idle will drop down to 950 RPM when at a stop light. There is some weird stuff happening here.:angry7:
 
Just my 2 cents. I would put a regulator between the pump and the pressure gauge. The Holley carbs don't like 7.5psi. That high pressure causes the seats to fail. In-turn fuel continues to enter the bowls. Lower the fuel pressure to about 6-6.5 psi. Then reset the floats. It sounds like you have a flooding problem. As I said, just my 2 cents worth.
 
Do what pettyblue suggested first. If that doesn't work, by-pass the electrical pump with a piece of hose. Those diaphram style pumps make it very difficult for the mechanical pump to pull through when they get weak and/or fail.

Since it's not a liquid filled gauge, it is most likely reading correctly. The filled ones give erroneous readings under the hood when hot.
 
OK...... I bought some heat protection made by DEI and installed it on all of the fuel line from the pump back past the header. This is what I used.

"Keep your lines cool!
Design Engineering Fire Sleeves offer ideal protection against intense underhood heat, making them perfect for protecting hoses, oil and fuel lines, and electrical wiring. The Fire Sleeves are constructed of a woven fiberglass braided sleeve heavily coated with 100 percent iron oxide silicone rubber. They are capable of withstanding temperatures of up to 500 degrees F continuous and up to 2,000 degrees F intermittent. "

I cranked the car up and fuel pressure was between 7 and 7.5 psi. Now when it got to 190* it started dropping until it got to 5 psi. The carb runs lean and the idle goes up. Same story all over again BUT this time the gas cap was open the whole time!!

The carb is not hot to touch... the fuel lines aren't hot ... The only thing I haven't done yet was by pass the electric fuel pump. So that's where I'm at folks!
 
OK ..... HELP!

I by-passed the electric fuel pump and the fuel pressure is more stable now. The needle isn't jumping wildly like it did before. It's actually on 7 psi now...??

Same problem.... HELP!
 
cudaspaz said:
http://www.recarbco.com/technical/newtrouble.html#Warm_drive

I found this in a google search, don't know how much it will help if any, but maybe may spark an idea or 2.
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I don't see "bubbles in fuel filter" or "fuel pressure drops suddenly" LOL!

I've checked bowl level while the motor is running... front and back.

Can the mechanical fuel pump get to hot and cause vapor lock? It's the warmest part of the entire fuel system from tank to carb.

The only thing I know to do is get rubber hose stick in a gas can and hook it straight to the fuel pump. That would eliminate the tank, and fuel line.
 
Hi mullinax95. I wanted to come and let you know,I think your car is awesome and that I hope you can get your fuel related problem fixed quickly.

I am curious as to why you are running both an electric and mechanical pump.Wouldnt either one alone get the job done? I would think the mechanical pump alone would be less hassle.
 
17remfan said:
Hi mullinax95. I wanted to come and let you know,I think your car is awesome and that I hope you can get your fuel related problem fixed quickly.

I am curious as to why you are running both an electric and mechanical pump.Wouldnt either one alone get the job done? I would think the mechanical pump alone would be less hassle.
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Thanks for the complements!

I am curious to know myself actually..LOL!

When I bought the car it already had a electric fuel pump hooked up with a switch. I just left it off because I had a 273 with a 500 CFM Edelbrock carb. Now I have a 360 with a 750 HP DP carb and still don't cut it on. I started having fuel trouble (like it was running out of gas) so I flip the switch and left it on... but it didn't help any. So now I'm back to square one again. I'm going to get some hose tomorrow and stick in a gas can... I don't know what else to do. The car stays running now instead of cutting off but that low fuel pressure is not going to cut it. I have seen low as 4.5psi and my (clear) fuel filter goes empty instead of stays full.
 
Were you having any of these car stalling problems with the old Edelbrock carb or did it begin when you went to the HP750? By the way, I had an hp 950 Holley on my 462 pontiac and it always worked fine once I reduced the pressure down to 6/ 6.5 lbs
 
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