Fuel Pump Check Valve

[mopar head]

If you went through the whole thread? you would have noticed Kit and I had these pumps and they crapped out in short order. I replaced mine with a cheap oem style from autozone, and have had no problems with it for well over a decade.

 

[straightlinespeed]

So with that all being said, I pulled the pump off the engine to compare it to the other pump I have. Yes I have 2 of the 6270's.

Alright, with both of the pumps, still in one piece. I blew into the lower inlet and of course air came out of the outlet. I then sucked on the lower port and had my finger over the outlet. I could feel it pulling a suction. I then moved to the outlet and sucked on that one, of course air came thru. I blew into the outlet port with my thumb over the inlet port, I pulled my thumb off and heard air "poof" out of the inlet. This was pretty much identical for both pumps.

Since I have a rebuild kit coming for one of the pumps I decided to open up both pumps, to compare them. There are 3 checks, 2 for the lower bowl allowing fuel into the upper bowl. Then 1 in the upper bowl allowing fuel out to the carb. I noticed that the one check for the upper bowl had a small pin hole in the stud. There was also one check in the lower that was the same (marked by the arrow, but not visible). Same spot in both pumps. This is allowing me to pull thru in both directions, and I assume they are there for a reason so I dont want to plug them.

Greg (Trailbeast), since it looks like you have one of these pumps, could you please try blowing and sucking in the ports to see if you get the same results? I know that is a lot to ask from another guy. LOL,

The one other thing, I experimented with. My fuel pressure gauge has a equalizing stem on it. Its used to equalize the gauge when its warm since the liquid inside changes the actual reading. I just pull up on the stem and it relieves the pressure inside the gauge. I pulled up on the stem prior to even starting the car just to make sure the gauge is zeroed out. I started the car had 6.5psi on the gauge. With all the starting, and shutting off to check the gauge I noticed it was starting to not read 6.5 actually more around 6. I just left it, until I was done. Once all said and done the gauge went slightly negative. I pulled the pin and it zeroed out.

So far with everything I have done, it doesnt seem like its actually pulling a vacuum. It just looks like the fuel drains back, and with the regulator and pump lower than the carb it pulls on the gauge. Now I could be way wrong but Im not seeing the actual suction on the system.

 

[straightlinespeed]

If you went through the whole thread? you would have noticed Kit and I had these pumps and they crapped out in short order. I replaced mine with a cheap oem style from autozone, and have had no problems with it for well over a decade.

Yes I did read that. That is what I had on my car to start with, but I had a pump test done when my engine was on the dyno. The stock pump could not feed my engine the proper amount of fuel and started dropping off about 3400rpm. I wish I could run a stock pump, but I dont want to starve my engine when I go WOT.

 

[rmchrgr]

I gave this a try, it was just shy of about 8psi, but as soon as I shut it off the pressure dropped right away.

Was the car running? Fuel bowls staying full? Sounds like the fuel pump is OK now no? Was it still spitting fuel out? If it is reading 8 psi then it drops to zero then it could be the gauge or a restriction somewhere.
I don't use liquid filled gauges, they're not real accurate. Sometimes you have to pull the little plug on the back to vent it so it will read right. None of those little gauges are too accurate but I have found the the liquid filled ones are less so. They are supposed to help with vibration etc. but they tend to be more of a hassle than they are worth.

Do you have compressed air on hand? Take the inlet line off and blow some quick blasts of air into the fuel line going back to the tank. Don't hold it there, just a few quick hits. Try it with the cap on and off. Maybe get down near the tank and listen while someone mans the air. I don't know what that test will do exactly but maybe it will illuminate something.

How about this - ditch the regulator, ditch the fuel gauge and drive the car, see how it goes. If it is rich from too much pressure you can always go back and deal with it but maybe at this point you need to know for sure that the pump is bad or not. Again, unless I missed something, the car started and is presumably running, right? As long as the floats are set correctly then the carb should regulate itself based on rpm/load.

And, if the car is starting and running, I'm thinking the fuel pump is OK. Yes, the pressure dropping to 0 at shut off is odd but if there are no symptoms associated with that in particular then don't worry about it.

 

[straightlinespeed]

Was the car running? Fuel bowls staying full? Sounds like the fuel pump is OK now no? Was it still spitting fuel out? If it is reading 8 psi then it drops to zero then it could be the gauge or a restriction somewhere.
I don't use liquid filled gauges, they're not real accurate. Sometimes you have to pull the little plug on the back to vent it so it will read right. None of those little gauges are too accurate but I have found the the liquid filled ones are less so. They are supposed to help with vibration etc. but they tend to be more of a hassle than they are worth.

Do you have compressed air on hand? Take the inlet line off and blow some quick blasts of air into the fuel line going back to the tank. Don't hold it there, just a few quick hits. Try it with the cap on and off. Maybe get down near the tank and listen while someone mans the air. I don't know what that test will do exactly but maybe it will illuminate something.

How about this - ditch the regulator, ditch the fuel gauge and drive the car, see how it goes. If it is rich from too much pressure you can always go back and deal with it but maybe at this point you need to know for sure that the pump is bad or not. Again, unless I missed something, the car started and is presumably running, right? As long as the floats are set correctly then the carb should regulate itself based on rpm/load.

And, if the car is starting and running, I'm thinking the fuel pump is OK. Yes, the pressure dropping to 0 at shut off is odd but if there are no symptoms associated with that in particular then don't worry about it.

Im using my second pump, not the one that spits out fuel. Bowls stay at normal level, even after I shut the car off. I do have another non liquid filled gauge. I could try that one and see if I get the same results.

I've only taken the car for a short drive (less than 10miles) to the gas station and home and it ran great, but its not normal upon shut down and that is what I would like to figure out.

 

[straightlinespeed]

Alright, Im considering this to be a normal situation for the carter pumps.

I called the company and spoke with them. They informed me that the pumps do in fact drain back and is perfectly normal for them. Carter was never concerned about a positive seal on the checks, because of the fast pumping rate to get gas back into the lines. Plus the lower section of the bowl holds some fuel in it so that it stays primed.

I think what I was seeing on the fuel gauge was the fact that the liquid was hot and it needed to be relieved by pulling that pin. Once the fuel drained back and the car cooled down that pulled the gauge negative.

To sum this up, nothing was in fact wrong with the system, it was simply a combination of things that I didnt consider normal. I appreciate everyone input and help trying to diagnose this.

 

[RustyRatRod]

So after two whole pages and 31 posts the problem was that there wasn't a problem.

 

[straightlinespeed]

Yep, that was the problem

 

[nm9stheham]

Always good to learn new things...

 

[AJ/FormS]

I have been running one of those since 1999. No regulator. No gauge . No problems. No worries. I just drive.

 

[straightlinespeed]

Took the car for a 50 mile drive on Sunday, no issues at all.