Fuel system check valves

[R.O.R-2.0]

my car has been getting air bubbles in the feed line, and losing prime if its not running..

once you fire it up, theres a few bubbles in the feed line momentarily, then it goes away, and has a solid stream of fuel.

i have a primer pump, so it should show any leaks that i could have, correct?

or is it just that there are no check valves in the feed/return lines? the pump stayed primed in the rabbit with the same filter setup..

what do you guys think?

[ORCoaster]

Mark talked about putting a vacuum gauge between the filer and the IP to determine if there was a problem with the fuel filter in some threads. 

I wonder if you could put one in after and figure out if you have vac being set up from the fuel leaving the tank.  And if the vent hole or fuel cap is the problem.  Seems to me the air is coming in from a leak that is primarily driven by a vacuum after you shut down for the night.  So a longer drive more than just a start in the drive.

Have two gauges?  one on either side of the fuel filter might tell you something as well. 

This is so weird.

[8v-of-fury]

Definitive leak at a connection somewhere.

It is allowing a small amount of air (as seen by only a few air bubbles on startup) to get in to the system. I don't think you would see a leak with the elctric pump because the pump is also sucking your pressure, so the fuel line is probably at a no vacuum no pressure stand point.

I would start by checking every fuel connection.

[R.O.R-2.0]

Definitive leak at a connection somewhere.

It is allowing a small amount of air (as seen by only a few air bubbles on startup) to get in to the system. I don't think you would see a leak with the elctric pump because the pump is also sucking your pressure, so the fuel line is probably at a no vacuum no pressure stand point.

I would start by checking every fuel connection.

i just put the connections together less than a month ago.. i used good hose clamps on all connections, and made sure the ends of all my hoses were clean, and went on the hose barbs good and tight.. im thinking my return line is draining back to the tank, then letting air come back up it, and then letting the fuel in the pump flow back out the return..

[8v-of-fury]

then checking them over real quick will take no time at all lol

[R.O.R-2.0]

then checking them over real quick will take no time at all lol

still tho, that has not answered my question as to if check valves are required.. if check valves are REQUIRED to make the pump not lose prime, then im going to be PI$$ING up a rope trying to find an air leak that isnt there..

[8v-of-fury]

Well then to answer your questions, the mk1 did not use a check valve. However I do believe the mk2 might have.

If you make your fuel lines go so the fuel pump is not your highest part of yuor return line.. Then there will be no drainback.

[R.O.R-2.0]

Well then to answer your questions, the mk1 did not use a check valve. However I do believe the mk2 might have.

If you make your fuel lines go so the fuel pump is not your highest part of yuor return line.. Then there will be no drainback.

the pump is NOT the highest point. but i feel that its draining back out the INLET.. not the outlet. the pump cant drain out the outlet while installed on a car..

[8v-of-fury]

So if its not the highest point where is it draining to? Is it then draining up hill?

[burn_your_money]

Did you install a diesel gas cap? If not, leave yours loose and see if the problem goes away

[jseeley]

Well then to answer your questions, the mk1 did not use a check valve. However I do believe the mk2 might have.

I can't speak to check valves being a requirement, but they were definitely included on the Mk2's. When I deleted my rear water separator and replaced all my softlines (Mk2 1.6NA) I came across check valves back by the tank for both the send and return lines. The one on my send line was actually failed. I was unable to find an OEM replacement (for a reasonable amount of money) and I replaced it with a generic check valve from ebay that was diesel compatible.

here is a pic of the mk2 check valve->

[R.O.R-2.0]

Did you install a diesel gas cap? If not, leave yours loose and see if the problem goes away

i deleted the charcoal canister, and ran the vent hose to a suitable location.. that should do the same thing, correct?

and uh, i may have found my problem last night.. wiggled the return line from the pump.. LOOSE.

tightened it, watched my feed line the rest of the night, and never saw a bubble form.. may have fixed er..

[burn_your_money]

i deleted the charcoal canister, and ran the vent hose to a suitable location.. that should do the same thing, correct?

I'm not familiar enough with gas evap systems but probably.

and uh, i may have found my problem last night.. wiggled the return line from the pump.. LOOSE.

Funny how things like that happen to keep us humble

[R.O.R-2.0]

i deleted the charcoal canister, and ran the vent hose to a suitable location.. that should do the same thing, correct?

I'm not familiar enough with gas evap systems but probably.

and uh, i may have found my problem last night.. wiggled the return line from the pump.. LOOSE.

Funny how things like that happen to keep us humble

yup, things like this pop up from time to time just to remind me that i DO still make mistakes..

and now, i think my IGN switch is going out.. sometimes when i turn it on, the fuel pump and injection pump dont get power..

(i have the power to the stop solenoid coming from the fuel pump relay.. but i put a load reduction relay in place of the FP relay, so the low pressure pump is running the entire time the key is)

and sometimes, my pump just wont kick on unless i cycle the key a half dozen times.. i know my injection pump isnt getting power if my fuel pump doesnt come on..

safe to assume that an ign switch replacement is in my future?

[ORCoaster]

You had the problem figured out way back when you posted this:

im thinking my return line is draining back to the tank, then letting air come back up it, and then letting the fuel in the pump flow back out the return..

Hope you can report in the future that it fires up and is solid from now on.

Who was it that said check all lines?