Fuel Fluke

[moper]

I think the next step requires repeated lateral Gs in a commuter parking lot to make sure it doesnt punk out during repeated donuts. And a video would be cool too .
Glad you found it.

 

[mullinax95]

OH! Sooo, were in good shape now?

So far so good.

Good to hear you have this resolved. Moper was right about the fuel line routing as it would leave a bubble of air in the high spot which whould make the pump cavitate. Just like vapor lock, but not caused by heat. The previuos owner must have used the electric pump to try to overcome the problem.

That's what I figure.

Could it have something to do with gravity and the fuel being siphoned back to the tank working against the pump?
Andrew

I guess so... the pump couldn't pull the fuel up the hill after everything got warm.

A regulator wouldn't hurt, but an HP carb should be able to deal with 8 psi.

If you want to go electric, and want quiet. Try a Mallory pump. Way more reliable than the holley and *very* quiet too (not as quiet as a mechanical though-LOL). Vane vs. gerotor. The Aeromotive carb type pump is even louder than the holley.

Sometimes its the dumbest things. I had a fuel boiling issue when I got my car. it was because there was a small leak in the manifold by the flapper valve, which is right where the fuel line runs.

Glad you got it fixed.

Steve

The pressure today was in between 7.5 and 8.

I'm going to try and run it without a regulator.

 

[mullinax95]

I think the next step requires repeated lateral Gs in a commuter parking lot to make sure it doesnt punk out during repeated donuts. And a video would be cool too .
Glad you found it.

LOL!

The test it's got to pass for me is in stop and go traffic and not shut off. I hate that feeling cars everywhere and you are sitting the middle of the road! Like I have said before everytime the motor shut down I was lucky enough to be able to coast out of traffic

I wouldn't found it or took notice rather of that fuel line until it was brought up by you guys.

 

[jimbo]

I am having that same problem. I am running a OE system with a new Summit mechanical fuel pump. The car will sit overnight and the filter will fill with fuel, but when I try and run it it runs out of fuel. Really sucks when you are at the 1/8 mile mark at the racetrack. I just went thru the entire fuel system this past weekend, blew it out, replaced hoses and clamps, etc. Still runs, but will stall for lack of fuel, is there an air bubble in the line somewhere? Where is the air coming from? Cap is vented.

 

[mullinax95]

I am having that same problem. I am running a OE system with a new Summit mechanical fuel pump. The car will sit overnight and the filter will fill with fuel, but it runs out of fuel. Really sucks when you are at the 1/8 mile mark at the racetrack. I just went thru the entire fuel system this past weekend, blew it out, replaced hoses and clamps, etc. Still runs, but will stall for lack of fuel, is there an air bubble in the line somewhere? Where is the air coming from? Cap is vented.

That sounds just like mine would do... after the motor cooled the filter would fill back full of fuel. What fuel pressure do you have when you first crank it? What pressure do you have after the motor is hot? Mine would nose dive!

Ok... when you say "when I try and run it" does that mean that the motor is up to full running temperature? Mine would do it around 190 degrees. It took the motor awhile to get there but it would slowly heat up.

 

[jimbo]

From what I am gathering as a lifelong Plumber and Mechanic, the fuel feed is shaped like the letter P lying on its back. If the fuel line is drained it must be filled completely with fuel before it will operate properly otherwise the air bubble will remain in the curvature over the rear fenderwell. Like when you lose a siphon, I believe the fuel filter is filling with this air bubble. I will try to feed fuel from the pump end backwards, seperate the line from the sending unit to bleed the air out and hook it up again to see if this does the trick.
In theory it should work. :read2:

 

[mullinax95]

OK guys the car shut off on me in traffic again. I drove the car about ten miles but once I got caught in the red light traffic it shut off again.

I have 8 psi when I first fire the motor up. I was in stop and go traffic and it "ran out of gas". I was still rolling in the median and cranked on the starter.... it fired up then shut back off. Pulled over in a safe area... let the motor cool off... fired it back up and went home.


What do you recommend I try to do next?

The fuel line has been re-routed to the frame with heat shield on it going straight to the Carter fuel pump. I've done various tests with the gas tank cap open and it did it shut or closed. Something is getting hot somewhere because it will only do it in traffic. I just can't pin point where it is happening. I have both the electric pump and the mechanical pump working together.

HELP!

 

[Badart]

How old is the tank? If it is old it could have rust and sediment in the tank. Do you think the fuel pickup could be partially blocked and when you are sitting still it is settling in the screen? I had a jeep that did the same thing and drove me nuts. The screen was full of crap from the tank. Just a thought.

 

[mullinax95]

How old is the tank? If it is old it could have rust and sediment in the tank. Do you think the fuel pickup could be partially blocked and when you are sitting still it is settling in the screen? I had a jeep that did the same thing and drove me nuts. The screen was full of crap from the tank. Just a thought.

At this point I really don't know what to thank! LOL!

I have eliminated the tank being the problem because I stuck a hose in a gas can and ran it straight to the mechanical fuel pump and it still shut off.

I'm pretty sure it's the stock tank that came in the car. I've had it completely out of the car, cleaned, new sock on the sending unit and reinstalled. The tank had no crude built up in it and was in good shape so I reused it.

What I don't understand is I get on the car hard and bark 2nd .. then bark 3rd...and keep it to the floor through 4th... winding the motor up to 5500 RPM each shift with no problems. But when I sit idling for a small amount of time I'm doomed.

 

[mopar head]

Hey Mulli, sorry to hear this is still kicking your butt. I`ve been following this thread from the begining. A lot of good tips thus far and the inverted trap was definetly a nono. If it were mine, I`d do away with the electric pump/or bypass. Pull the carter and replace with a factory style. Also as recommended, check the sender sock, r/r if nessary. I have one of those carter pumps too, It was delegated to a conversation piece very early of its life. You should be able to see the sock, with flashlight, straight down in filler neck. Keep us informed of solution, good luck

 

[bama-a-body]

just curious here but just how close is that plastic fuel filter to your radiator hose??? and do it feel hot when motor is at 190

 

[mullinax95]

Hey Mulli, sorry to hear this is still kicking your butt. I`ve been following this thread from the begining. A lot of good tips thus far and the inverted trap was definetly a nono. If it were mine, I`d do away with the electric pump/or bypass. Pull the carter and replace with a factory style. Also as recommended, check the sender sock, r/r if nessary. I have one of those carter pumps too, It was delegated to a conversation piece very early of its life. You should be able to see the sock, with flashlight, straight down in filler neck. Keep us informed of solution, good luck

What kind of problems was you having with the Carter pump?

I bypassed the electric pump altogether and the fuel pressure dropped to 4 psi. I guess I need to buy a stock pump and put it on.... I really don't know what else to do. The tank might have debris floating around in it but gosh I made sure everything was spotless before re-installing the tank.

just curious here but just how close is that plastic fuel filter to your radiator hose??? and do it feel hot when motor is at 190

I have changed it to a metal fuel filter since then. I have felt the filter numerous times and it does not fill warm. The warmest part I have found by feeling with my hand is the Summit line block there at carb... where the fuel pressure gauge is located. But I don't know how hot is to hot but that is the warmest part.

 

[mullinax95]

Well I tried looking down the filler tube and all I can see is the curve of the tube.

 

[barracuda man]

Take the fuel line off the mechanical pump.Get air hose with 120psi and blow threw the line. if the sock in the tank is stopped up you'll hear it when it comes off.make sure the gas cap is open.if this dosn't fix it your machanical pump is bad.

 

[mullinax95]

UPDATE

I finally got around to try to fix my fuel problem. I took the line loose from the rear full filter and blew into the tank using my mouth. I heard debris shooting across the bottom of the tank. Then fuel started shooting out of the hose like crazy. I don't know if I dislodged the trash and it started flowing or by blowing in it I made a siphon. I had the gas cap popped open when I did this. But one thing is for sure is that I did hear something other than air in the tank. I swore I had that tank clean before reinstalling it. It was much cleaner than it was when I dropped the tank!

I hooked the hose up bypassing the electric pump altogether.... so it's only running on the mechanical pump which gives me 6 psi at the carb with the motor hot. I guess I will just go ahead and get a new tank and be done with it. Not really 100% sure if it causing the problem actually. What do you guys think?

 

[sixpakmopar]

i had a mach 1 that had sat for years/ stranded me on the way to show it off to my friends the tank was full of scale and varnish i took the tank out of the car and threw some lug nuts over in it and shook the hell out of it to break all the crap loose i then kept washing it in a parts cleaner till nothing else came out /poured a gallon of lacquer thinner in it to cut the varnish reinstalled and all was good!

 

[mullinax95]

i had a mach 1 that had sat for years/ stranded me on the way to show it off to my friends the tank was full of scale and varnish i took the tank out of the car and threw some lug nuts over in it and shook the hell out of it to break all the crap loose i then kept washing it in a parts cleaner till nothing else came out /poured a gallon of lacquer thinner in it to cut the varnish reinstalled and all was good!

I washed the tank out with water and let it dry.... tried to shake the tank and see if anything fell out which it didn't. I examined it with a flash light and didn't see anything that would be of concern. Maybe I over looked something that I thought was ok. After today I know I did. I'm going to order a new tank just to make sure. That would be my best bet and rule out one thing that might be the problem. Here goes more $$$$$. If I didn't have a Fastback with the let down door in the rear I would buy a fuel cell.

Do they have fuel cells that mount under the car? The reason I'm asking is I had to enlarge the sending unit hole in order to get my Autometer sensor in the tank. So if I get a new tank I'm going to have to cut the new tank.... don't really want to do that.

 

[mopar head]

Hey mulli, what is this autometer sensor? I`d highly advise against a fuel filter on the suction side of the pump. I would try what 6pak suggested. I`ve heard alot of people doing this with good results, even without the parts cleaner part of it. If your tank is clean, and your using a factory sending unit,with clean sock, no filter on suction side, a factory pump, and unobstructed lines and vent, there should be no reason for fuel problems. keep us updated8)

 

[1qwikScamp]

why do you have two fuel pumps

 

[demon seed]

My turn Mulli, if you can't see or hear anything rattling around in the old tank it should be good. Make sure the sock on the end of the pickup is good and hook everything up running the fuel line along the frame rail then up into the mechanical pump (electric pump bypassed). Remove the rubber line that goes into the mech. pump and connect about 4 feet of clear plastic hose to it and bring the open end out to beside the front wheel. Then with the fuel tank 1/2 full of gas get a syphoning action going into a pan close to the floor. This practice will ensure the fuel line is clear and watch for bubbles in the plastic line, if there are any indicates a pinhole in the sender tubing or the rubber hoses you're using. Next another fuel pressure guage cuss we're going to make sure the original ain't lying to ya. Next plum in a pressure regulator as close to the carb as possible like the one linked and set for 6-6.5 psi. I've had Holleys float levels bounce around at pressures over 7 especially with a hot engine.


http://store.summitracing.com/partd...4294839053+4294880914+400178+115&autoview=sku
Terry

 

[1970BBDart]

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.

I have had the same issue in the past, same problem, same solution:-D

 

[mullinax95]

Hey mulli, what is this autometer sensor? I`d highly advise against a fuel filter on the suction side of the pump. I would try what 6pak suggested. I`ve heard alot of people doing this with good results, even without the parts cleaner part of it. If your tank is clean, and your using a factory sending unit,with clean sock, no filter on suction side, a factory pump, and unobstructed lines and vent, there should be no reason for fuel problems. keep us updated8)

The sensor came with the AutoMeter gauges.... in which was designed to slip down into to a racing fuel cell. The original Mopar sending unit does not put the proper ohms so I had to fab the AM sensor to the factory sending unit in which it reads correctly now.

I have always ran a filter coming out of the tank with no problems on another car I had but I will do away with it. I'm up for anything right now.

I really believe the tank has trash in it... I don't know why cause it looked clean when reinstalled.

With that being said I ran a hose straight off of the mechanical fuel pump into a gas can of fresh fuel... the pressure still dropped to 4.5!

why do you have two fuel pumps

I have no idea. It was that way when I bought the car.

My turn Mulli, if you can't see or hear anything rattling around in the old tank it should be good. Make sure the sock on the end of the pickup is good and hook everything up running the fuel line along the frame rail then up into the mechanical pump (electric pump bypassed). Remove the rubber line that goes into the mech. pump and connect about 4 feet of clear plastic hose to it and bring the open end out to beside the front wheel. Then with the fuel tank 1/2 full of gas get a syphoning action going into a pan close to the floor. This practice will ensure the fuel line is clear and watch for bubbles in the plastic line, if there are any indicates a pinhole in the sender tubing or the rubber hoses you're using. Next another fuel pressure guage cuss we're going to make sure the original ain't lying to ya. Next plum in a pressure regulator as close to the carb as possible like the one linked and set for 6-6.5 psi. I've had Holleys float levels bounce around at pressures over 7 especially with a hot engine.



Terry

I took the line loose from the rear full filter and blew into the tank using my mouth. I heard debris shooting across the bottom of the tank. Then fuel started shooting out of the hose like crazy. I don't know if I dislodged the trash and it started flowing or by blowing in it I made a siphon. I had the gas cap popped open when I did this. But one thing is for sure is that I did hear something other than air in the tank. I swore I had that tank clean before reinstalling it. It was much cleaner than it was when I dropped the tank!

The sending unit has a new sock on it that bought when I dropped the tank. I replaced all the rubber hose connections when I installed the new aluminum line.

I'll try the plastic hose when I get the new tank in and plumbed up. I'm going to get a new sending unit with two outlets instead of one so I can run a return line later.... that would work wouldn't it?

I have had the same issue in the past, same problem, same solution:-D

What the return line specifically or something else he mentioned?

 

[mopar head]

With that being said I ran a hose straight off of the mechanical fuel pump into a gas can of fresh fuel... the pressure still dropped to 4.5. Whats that tell you? fuel pump.:clock:

 

[mullinax95]

With that being said I ran a hose straight off of the mechanical fuel pump into a gas can of fresh fuel... the pressure still dropped to 4.5. Whats that tell you? fuel pump.:clock:

OK.... I just came back in from the garage. I ran the test with just mechanical pump with hose stuck down in a gas can. The motor got up 205* and the pressure didn't drop below 5.5 the whole time. It stayed between 5.5 and 6.5

I ran the test again just to make sure I wasn't loosing my mind because I have already tried so many different things but the findings above is what is going on right now with the mechanical pump.

I'm going to a car show today and I have a straight shot to it down the interstate so I shouldn't get into stop and go traffic. I have already drove it around the out skirts of the town to check see how it is doing totally by passing the electric fuel pump.

Thanks for the help! Wish me luck.

 

[mullinax95]

OK.... My problem is 80% heat related. I drove to the cruise in staying on the interstate most of the time and the temperature got up to 210*... it started vapor locking when I got into the parking lot of McDonald's. I don't have big enough radiator.. all I have is a stock mopar 2 core radiator. I was talking to a mopar guy and he said that he has a small block 4 core aluminum radiator that he said should take care of the problem. He said if it doesn't work that I could bring it back to him and get my money back. My motor is just getting to hot and causing vapor lock I honestly think. I will install the electric fan in front of the radiator and if room allows install the mechanical fan back on. I really don't what to do with the fans yet because I don't know the actual thickness of the radiator.

I think today summed up what I have been battling and that is heat. I'm still going to install a new tank and make sure everything is 100% back there.

So.... what you guys think about the plan?