Gas cap vent question

[bravekozak]

quick start

A couple of squirts of quick start in the carb should prime the line very "quickly".

[drddan]

I used starting fluid. Then started using gasoline, as starting fluid is not good for engine. Can run with gas, as long as I am squirting in carb. No fuel is reaching the fuel pump. Actually had it running for almost a minute, squirting gas into carb, still no fuel coming out of the fuel line at carb, still not reaching pump.
Please READ my posts before commenting, as all is explained in posts.
I had to PRIME this NEW fuel pump when I installed it, 3 weeks ago.
This is not like the EFI, where pump is in tank, and has more pressure.
Carbs have the pump in engine bay, with just a fuel line going to tank, and I believe has less pressure than an EFI system. I also thought it should prime itself with a few cranks, but that is not the case here.
See MTec007's post and he had same problem with his new pump.
I AM wondering if the extreme reverse pressure this system has experienced, has messed up the fuel pump. (again, please read my posts)
I kinda doubt it, but..... there is a rubber diaphram inside the pump, and the reverse pressure was way greater than the pump pressure.

The pump is new and I can return it for another. I still have the receipt!

[Ogrekhan]

Hey,

I did read through before I posted hehe, well perhaps skimmed is a better description. Both my festys are carbed , and I didn't have that issue when I replaced the pump on my 88. My suggestion with the fuel cell/gas can was to make testing/priming the fuel pump easy while isolating the fuel pump from the rest of the fuel system. Sorry if I ruffled your feathers, was only trying to be of help . Hope you get it figured and back on the road

[drddan]

Thanks> No ruffled feathers here! Just sometimes peeps read last post and try to give answers, to things I have already done and posted about, then I try to re-explain all I have already explained in previous posts.
I still appreciate all attempts from anyone with answers! They are trying to help!
I've never had this kinda problem with a simple fuel pump, as I have with the ones for this car. The new one did need "primed", and I just never had to do that with fuel pumps before. I had blown out the long fuel line from the tank to the engine bay pump with an air compressor and air nozzle. There was no blockage, and blew out clean gas. So...WTF?
I will try the gas can method, but i'm still wondering about the effect the reverse pressure had on the pump. Could it have destroyed the diaphram inside the pump? From the extreme suction I heard/experienced, when unscrewing the cap, it had to be like 40-50 lbs of air pressure. Maybe more.
It was a LOT!

[Pu241]

............... From the extreme suction I heard/experienced, when unscrewing the cap, it had to be like 40-50 lbs of air pressure. Maybe more.
It was a LOT!

Not possible!
Experience needs to be revised!

14.7 psi max!

And that isn't possible, or your tank would have imploded in on itself.
Likely only 2-3 psi negative pressure, but 5 gals in volume (1/2 a 10 gal tank).
Big difference.

[MTec007]

i would first simply try a new/another gas cap, i meant to put that in my last reply, i appologize

[drddan]

14.7 psi max!

That is atmospheric pressure, is it not, John? The purpose of a vented cap is so the atmospheric pressure is equal inside and outside the tank. For the amount of suction and the velocity of the suction, it was a heck of a lot more than 14.7 psi! I couldnt measure it, but I have been around air systems and air devices my whole life, and this tank had quite a bit of pressure on it. The vacuum suction it had, was like an air nozzle on an air compressor! If it had been blowing, instead of suction, it would have blown my hat off!
Maybe it WAS about to IMPLODE!

[drddan]

I am about to go shove the short end of the inlet fuel line of the pump in a full gas can and see if the pump is working properly. Still dont know if that pressure has affected the pump. IDK if it could, but I believe there is a rubber diaphram inside the pump (which makes it work) and IDK if the reverse pressure could have messed it up or not. No one has said anything about that yet, and I just dont know. The line is clear. The pump is new and was working. Maybe I got a bad new pump. Will see in about 5 minutes from now.

[drddan]

Okay! The fuel pump is fine. Just started and ran great. Since I just cleaned the ALL fuel lines, installed a working send unit, and checked the tank in this car 3 weeks ago, and all was clean, clear, or practically new looking, it has to be that it is having issues with pulling gas through approx 9 foot of fuel line, a filter, and the pump itself. I needed to prime it on install when I bought it, so it must be that it needs primed now. I'm working on the theory that it being just air in the line now, it is having trouble pulling that distance. I may remove the pump and get a new one just for kicks, as this one may not be as strong as should be. Think i'll call O'Reilly's right now. Its still under warranty.

[Pu241]

That is atmospheric pressure, is it not, John? The purpose of a vented cap is so the atmospheric pressure is equal inside and outside the tank. For the amount of suction and the velocity of the suction, it was a heck of a lot more than 14.7 psi! I couldnt measure it, but I have been around air systems and air devices my whole life, and this tank had quite a bit of pressure on it. The vacuum suction it had, was like an air nozzle on an air compressor! If it had been blowing, instead of suction, it would have blown my hat off!
Maybe it WAS about to IMPLODE!

Yes, 14.7 psi is atmospheric pressure, it is not possible for you to have pumped your gas tank down to a vacuum. 1) your tank would have imploded form the force of 14.7 psi on each and every square inch of surface area of the gas tank, of which it has many. 2) Much of the gasoline itself would have started to boil in a near vacuum, thus countering some of the loss in pressure.

Have you ever worked around bulk material rail cars?
Plastic pellets are transported in these, the walls are up-wards of 1/4" of steel in four sub-compartments.
A 5 HP motor is used to vacuum out the pellets and transport them into a silo a few pounds at a time.
This works well, unless someone doesn't open the hatch on top of the rail car.
When that happens the pump pulls all the air out of the compartments and 1/4" of steel plate or not, 14.7 psi air pressure crushes the rail car.
BTW, it makes a hideous sound when large amounts of metal are crushed like an aluminum can!
That's why I think your problem has to do with tank venting else where, not necessarily at the cap.

What happened to the OEM cap?

Have you tried filling the tank and driving down a few gallons then opening the gas cap, before you reach 1/2 a tank, and then drive some more to see if venting it delays the start of it acting up?

[91_festy_Gl]

I know when my car gets 1/2 to 1/4 of tank of gas, its sucks air in when the gas cap is removed. You can hear the tank make a thump noise once it has inhaled.

[drddan]

My cap is OEM, it is not venting. New pump will be at O'Reilly's tomorrow 10:00 AM. I will be getting a new cap then also.
Where else would this car have a venting problem? Dont forget, all emission stuff went bye-bye, and have a Weber 32/36 on there. Had this problem with old stock carb too. All non-used vacuum ports are plugged. (triple checked)
There is only a send unit, lines, filter, pump, and carb to this system. It is no longer a feedback system.

[Pu241]

Did you start having this issue when you "altered" the spaghetti?
Is there a return line from the carb to the tank?

[drddan]

Yes, there is a return line, as the pump has it on there.
As far as this issue, I believe this was my problem all along, from when I was having problems a month ago. It stopped running, then ran again, then stopped again. I looked at electrical, then fuel. (See post #7 links)
Someone suggested carb and I went after that, wound up loosing a part from the carb and that led to a Weber carb (which I wanted one anyway) So, yeah, this problem has been around awhile. I had filled it up, and got to 1/2 tank when this happened with the old carb, and the spagetti was still there. Actually did it twice with the old carb.
This car ran great for 2 weeks, until I filled it up with gas, and then got to 1/2 tank and quit again. I just noticed the "pattern" of, fill, and reaching 1/2 tank and it quitting running. Every time it quit, it had a lot of pressure build up in tank.

[drddan]

Yeah, my car is running!!!! I went out, took fuel line off the send unit in the cargo area, primed the line that runs from tank to engine bay, and it ran!!!!
Still going with another fuel pump tomorrow. I can take it back and exchange it for another. I just dont have faith in this one.