Pain in the FUEL TANK

[Chuck]

I'm learning the hard way!! I have installed the kit tank with a external fuel pump (Holley blue w/regulator, 392 stroker). I'm finding out now (no indication during go-carting) that I cannot maintain pressure for extended period. After 10 to 15 minutes my pressure drops to zero. There is a slight siphing effect but not enough to keep things going. I'm thinking about putting a Boyd tank with a gravity feed to the fuel pump to correct this. Like others have said I'm not real crazy about having to remove the body from the chassie. I've just completed the relocation of the filler (no longer takes 20 minutes to put 8 gallons of gas in the car) so the roof & interior are already out of the way. Any thoughts would surely be appreciated. If need be I'm going to take the body off but sure not looking forward to it.

[65 Cobra Dude]

Chuck,

What size fuel line are you using? It sounds more to me like you have too large a supply line. I had this issue when I used -8 line. I switched to -6 and was able to hold pressure.

One more question - carb or EFI?

Henry

[1fastsedan]

Have you tried opening the cap when it runs out? could be that your vent may be too small and/or clogged and your're creating a vacuum as you remove fuel at a faster rate than air can get back in.

[Chuck]

Henry,

Not sure -6 vs. -8. All my lines are 3/8" ss braided or ss tubing. I'm running the same set-up on my Cobra (MKII, #4135) with the exception I'm pulling from the bottom of the tank instead out of the top.

[65 Cobra Dude]

Chuck,

Carb or EFI? If EFI, the return line should be smaller diameter.

Henry

[Chuck]

Good question, I thought of that and there is no difference. FFR sent me a new vent fitting that I installed. I would rather pull my finger nails out than pull this body off. Thanks for getting back with me.

[Chuck]

Understood, carb I used the larger diameter and capped the smaller.

[65 Cobra Dude]

Chuck,

Try using the smaller diameter that is capped and see if that helps out. Wish I was still in FishHawk. I'd come take a look.

Henry

[ehansen007]

Hey guys, I to am using the supplied tank and the larger line and did not have a problem with pressure until the other day. I thought maybe it was an adjustment to the carb I made but I was actually trying to lean it out. I noticed the pressure dropped from around 5-7 down to 3. think it's the same problem? I think it's weird that it just started happening. I also thought maybe something was impeding the fuel line like dirt or something fell into the tank and was stuck to the pickup line in the tank. This post has got me wondering now!

[Chuck]

What type pump are you using?? If you shut it down after the pressure has dropped and the car sits 15 minutes or so do you have difficulty re-starting the car??

[65 Cobra Dude]

I had the same problem and symptoms as you guys and it ended up being too large a fuel line. It handled volume but not pressure and carbs are sensitive to the pressure.

Henry

[Chuck]

Henry,

Another little tidbit - If I wait after shutting it off hour/over night my pressure is restored. I'm going to give Holley a call and give them my application and see what concerns or thoughts they might have. What this has me thinking is trash in the tank is accumulating on the pickup screen and plugging things up and after you shut things down it falls away. I'll let the group know what Holley has to say. FishHawk huh, we were neighbors.

[ehansen007]

What this has me thinking is trash in the tank is accumulating on the pickup screen and plugging things up and after you shut things down it falls away.

I was thinking the same thing. I'm going to peek into the tank by removing the sending unit. But what are the odds we're both having that problem?

[65 Cobra Dude]

Chuck,

Yes, please let us know what they say. You have your fuel pump in the same location as I do and remember those are pusher pumps vice pullers so they want to be as close to the tank as possible. I'm still betting on too big of fuel line though FishHawk - I was stationed at MacDill for the last 3 years or so and loved it, especially because of this weather in MA... I just moved to MA last July.

Henry

[ehansen007]

Ok, so Chuck, I think we just have a pressure problem. I went and opened the tank from the sender side and looked inside. A few flakes of this and that (mostly from trying to seal the damn sender unit --BTW, I used an extra O-ring from my pool filter rebuild kit), but nothing major and I stirred up the fuel and didn't see anymore coming my way or swirling, so I think took off the fuel filter (which may be the problem since it's in front of the fuel pump) and I blew it out and nothing there. Then I took and shot some air through the fuel line and up into the tank to see if any loose dirt would come away from the pick up and nothing. So, I think I've eliminated the pickup being clogged. As far as the line being too big, I don't think that could be the issue either. The fuel filter line has to be the right size just to get it onto the fuel filter and mine's tight on there so it has to be the right size I would think. I'm going to call Holley and just see what they have to say.

[Olli]

Have either of you considered a power supply issue? If you have fluctuating voltage your pump will not be happy. I have used the Painless fuel pump relay kit in the past.

http://www.painlessperformance.com/w...rchField=50102

Olli

[ehansen007]

I don't think so. I have minimal amounts of pull on the battery since I don't run EFI, Power Steering and I had my radio off. Still I'll look into the relay just to be sure. I'm headed down to exchange my fuel pump right now. I spoke to Holley and they said it's most likely a pressure problem and we should have a 80-100 micron filter before the bump and a 10 micron filter after it in front of the carb so the fuel filter in front of the pump is not causing the problem.

[ehansen007]

Fuel Pump! Of course the last thing I've checked but I knew I should have checked it first. I just couldn't believe that a pump would go bad after 500miles. Now my pressure is at 7PSI solid. I had this problem with a corroded tank in my 69 bug years ago so I was betting it was the pickup valve. Thank god it's not! Chuck, which pump are you running?

[Chuck]

The kit comes with the Ron Frances harrness with a dedicated circuit/fuse just for the pump. From this response you can probably tell I'm not electrical. If I put a volt meter on the pump and keep an eye on it would I see the fluctuation in voltage??

[Chuck]

Holley blue w/regulator for both street and strip.

[65 Cobra Dude]

Erik,

I really hope you figured it out. I also replaced my fuel pump but the problem returned after a short time. I can't believe 2 fuel pumps would have the same problem so I started looking elsewhere and that's when I stumbled upon my fuel line being too big. Like I said, I hope you got it fixed for good.

Henry

[ehansen007]

Erik,

I really hope you figured it out. I also replaced my fuel pump but the problem returned after a short time. I can't believe 2 fuel pumps would have the same problem so I started looking elsewhere and that's when I stumbled upon my fuel line being too big. Like I said, I hope you got it fixed for good.

Henry

Henry, I'm intrigued here. This is my setup. From the tank I'm running about 4 feet of 5/16 rubber line into the fuel filter. This can't get any smaller as it won't fit over the fuel filer inlet on either side. From the filter I've got 6 inch of 5/16 rubber line to the supplied steel fuel line which is also 5/16 and the larger of the two diameter I got with the kit. This line is about 6' and goes straight into the fuel pump As per the manual the 5/16" line is the main and the 1/4" was for the return line for Fuel injection which I don't need. Therefore, I have 5/16" from the tank to the fuel pump. The pump I'm running is this one. It's the airtex e8120s and was $50 from the local, educated parts store. It supplies 5.5 to 9 PSI and averages 6.5PSI on my tell tale gauge at the carb.

E8012S-1.jpg

[65 Cobra Dude]

Erik,

I initially used -8 AN which equates to 3/8". I then switched to -6 which is 5/16" so you should be OK. FFR used to ship 3/8 and 5/16 but they must have changed. Sorry if I confused the issue. Are you running a regulator and line filter as well near the carb?

Henry

[ehansen007]

No problem. I just purchased a filter for the carb which I'm going to put in . I'll install that today. The pump has a built in regulator.

[Chuck]

Henry,

I just sent Holley as good of a description explaining my problem as I could muster up. In doing so I re-measured my lines. My SS braided is 5/16" ID and the SS tubing 3/8" number I've been talking about was an OD number. After seeing you latest to Erik I think we might be on the same page. What do you think? I'll post what I hear back.

[ehansen007]

Where'd you install the pump. It has to be below the tank which I'm sure it is. I still haven't driven mine for any period of time so I can't say I've solved the problem however pressure is restored with this new pump. If it goes again, I will most likely remove the small filter in front of the pump which seems to have broken last time.

[ehansen007]

Well I spoke to the airtex people and they said I should remove the large filter after the tank as it will cause the pump to be overworked. It's got a smaller filter on it already so I'm hoping it will be okay.

[Chuck]

THE FIX a FAULTY FUEL PRESSURE GAUGE. I heard back from Holley (Ricky) who gave me the FIX to my slow loss in fuel pressure. Problem = When running the engine set at 1500 RPMs the pressure @ 3 mins dropped from 6.5 to 6 lbs, @ 6 mins from 6 to 5.5 lbs, 10 mins from 5.5 to 2.5 lbs and @ 15mins from 2.5 to 1 lb. My concern was that I was pulling fuel from the top of the tank vs. gravity feeding or trash in the tank was collecting around the stand pipe and falling away after shutting the engine off. I was very worried the fix was going to require me pulling off the body. Ricky w/Holley Tech. asked if I had a liquid filled gauge and if the engine was shutting down when the pressure got to zero. I have a liquid filled gauge and the engine never shut off when the pressure hit zero. Ricky suggested a faulty gauge and told me to apply ice to the back of the gauge and see if the pressure would restore. This morning (figures above) then applied a ice pad (used for my sore back) around the gauge and in +/- 5 minutes my pressure was reading my original set point of 6.5 lbs. I'm on my was to the auto parts store to purchase me a non-liquid filled gauge. I all most pulled the body off this thing, what a scarey thought. I'll check back in once I have installed a new gauge. Thanks for the suggestions and feedback.

[ehansen007]

Glad to hear it. No one wants to pull that body off (especially with the paint job you have!)

[KGB911]

Glad to hear it. No one wants to pull that body off (especially with the paint job you have!)

Guy's! Unless you have a Beta car with the two hoop roll bars the tank can be removed with simply taking the seats out and the waterfall off!
Dr. Ruth

[ehansen007]

Chuck and I both have the hoops (added ourselves). So we are relieved.