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Fuel Pressure Problem, Dual Kadron Carbs (Problem Found VID)
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A-Wall
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PostPosted: Sun Jul 04, 2010 12:36 am    Post subject: Fuel Pressure Problem, Dual Kadron Carbs (Problem Found VID) Reply with quote

I just got my dual Kads on my 1600 and it's my first time i've had a fuel pressure gauge on the car. When the car starts up cold, i have just slightly under 3psi with no shimming of the pump. As the car warms up the fuel pressure starts to drop to where it reads slightly above 0psi but the car still runs with little higher idle. I have not driven the car yet, kinda sacred to run it lean.

what do you think the problem is? is something thermally growing with engine heat. is the pump diaphragm getting weak a stretchy with heat?

i have no leaks, if i shut the car off before it reads 0 the system stays pressurized for quite a while.

I thought about the tank being under a vacuum, but it does it with the gas cap off also.

the pump is a new but possibly crap Brosal. the pushrod length is within .003" stock length for an alternator style pump. the pushrod stroke is .160".

thanks!


Last edited by A-Wall on Mon Jul 19, 2010 11:42 pm; edited 2 times in total
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runamoc Premium Member
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PostPosted: Sun Jul 04, 2010 5:54 am    Post subject: Reply with quote

You will only have pressure when both float valves close. The flow might be so low that the pump is doing all it can and not filling the bowls fast enough to close the float valves.
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A-Wall
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PostPosted: Sun Jul 04, 2010 9:44 am    Post subject: Reply with quote

so a weak pump then?
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PostPosted: Sun Jul 04, 2010 10:07 am    Post subject: Reply with quote

is your float(s) set correctly?
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A-Wall
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PostPosted: Sun Jul 04, 2010 11:14 am    Post subject: Reply with quote

I bought them from the Kaddie Shack "57Baja", they are supposed to be setup for a stockish 1600 single port. From what i've read the only way to adjust the float level is buy shimming the needle and seat.
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PostPosted: Sun Jul 04, 2010 5:51 pm    Post subject: Reply with quote

OK - back up a sec - how is the flow from the tank? Is your filter clogged? Is a fuel line clogged? Try the gas can test - run a fuel line into a gas can to your fuel pump inlet line - see what happens......
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A-Wall
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PostPosted: Sun Jul 04, 2010 7:48 pm    Post subject: Reply with quote

initially i thought it was a flow problem. so i changed my filter and let the line at the engine gravity feed into a gas can and the flow seemed great. i'll try the gas can feed to see if it makes a difference. it's just weird that it only happen after the engine warms up and everything heat soaks.
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Hotrodvw
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PostPosted: Sun Jul 04, 2010 11:34 pm    Post subject: Reply with quote

Correct pushod for the pump?
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A-Wall
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PostPosted: Sun Jul 04, 2010 11:36 pm    Post subject: Reply with quote

yes im using the 100mm one for this alternator style pump.
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PostPosted: Mon Jul 05, 2010 3:46 am    Post subject: Reply with quote

Never had this happen myself, but possible problem with pump itself due to heat? check this thread - see the secon post in particular....http://www.thesamba.com/vw/forum/viewtopic.php?t=4...mp;start=0
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spanky324
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PostPosted: Mon Jul 05, 2010 4:36 am    Post subject: Reply with quote

A-Wall wrote:
I bought them from the Kaddie Shack "57Baja", they are supposed to be setup for a stockish 1600 single port. From what i've read the only way to adjust the float level is buy shimming the needle and seat.
Have you talked to 57baja?
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A-Wall
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PostPosted: Mon Jul 19, 2010 11:40 pm    Post subject: Reply with quote

well i found the problem!

turns out my gauge doesn't like being warm....

http://www.youtube.com/watch?v=ZdkWbRV5JyU&feature=channel



as the beetle warmed up the fuel pressure would drop, but it still ran. so i changed my pump anyway in fear that it was dieing, it sure wasn't, it's the MADE IN USA gauge i got instead of the china one.
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74 Thing
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PostPosted: Tue Jul 20, 2010 8:06 am    Post subject: Reply with quote

Is that gauge liquid filled-if so you may need to pull the plug on the back to "burp" the extra air from inside.
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61ghia
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PostPosted: Mon Jan 07, 2013 6:32 pm    Post subject: T connecter is to blame Reply with quote

having the same issue myself and thought it was the fuel pump or clogged fuel line from the gas tank. Turns out I have a T just past the fuel pressure gauge and when I disconnected the hoses running to each carb, put them in a container and turned on the fuel pump, only one side was getting fuel. Then I put my finger to plug it up and then the other side would flow. It would actually alternate between the two. I am going to try a smaller T (1/4") this time to match the fuel hose diameter as the one I used was slightly larger. I think the better solution would be a Y instead of a T. I have a Y in my 75 Carrera and never had this problem.
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PostPosted: Mon Jan 07, 2013 6:43 pm    Post subject: Re: T connecter is to blame Reply with quote

61ghia wrote:
having the same issue myself and thought it was the fuel pump or clogged fuel line from the gas tank. Turns out I have a T just past the fuel pressure gauge and when I disconnected the hoses running to each carb, put them in a container and turned on the fuel pump, only one side was getting fuel. Then I put my finger to plug it up and then the other side would flow. It would actually alternate between the two. I am going to try a smaller T (1/4") this time to match the fuel hose diameter as the one I used was slightly larger. I think the better solution would be a Y instead of a T. I have a Y in my 75 Carrera and never had this problem.


interesting.. Are you using the stock mechanical pump?

I'm having problems with dual webers where it feels like (feels, sounds, whatever..) I'm not getting enough gas.. it won't even start unless I manually pump the linkage like 20 times before turning the key, and then it runs for about 3 seconds before dying..

I wonder if maybe I should open my regulator up some.. I know webers want 3.5, but maybe that's too low to make up for the t-fitting? (I have -6AN from tank to carbs with a Holley Red pump..
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61ghia
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PostPosted: Tue Jan 08, 2013 7:47 am    Post subject: Reply with quote

I am using an electric fuel pump. The car will idle fine, but when I go for a drive above 30mph, it seems to run out of fuel. I let off the gas for a few seconds and then its ok. Changing to a smaller T later today and see if that will work.
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tattooed_pariah
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PostPosted: Tue Jan 15, 2013 3:13 pm    Post subject: Reply with quote

how'd the smaller T or Y fitting work out?
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61ghia
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PostPosted: Wed Jan 16, 2013 7:30 am    Post subject: Reply with quote

Still same issue, but it took longer to occur. I ran into a bit of an issue, cant find 3 or 4th gear so I couldnt test on the highway. Will do more testing this weekend if the weather is good.
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Dale M.
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PostPosted: Wed Jan 16, 2013 9:57 am    Post subject: Reply with quote

I think you guys are playing with your selves with size of tee.... Fuel or water or air takes the path of least resistance... If one carb float bowl fills up then shuts off needle valve, the fuel will flow to other carb .....

What you are experience as a fuel problem is a volume problem... Pump its self may not be producing enough fuel (volume) to keep up with engine demand....

On my race car and my street car ( both 2000cc + with dual Weber 44IDF) I ran stock fuel pumps and 5/16 diameter fuel lines and tee fittings and never ran out of fuel in either carbs, even with long sustained high rpm runs....

Only fuel "volume" problem I had was when there was a "hairball" of aluminum filings and some other fibrous "stuff" partially blocking fuel line in pan....

Blow out all you fuel lines, replace filter screen in tank if you still have one, replace all rubber lines and inline filters, and do fuel pump pressure test.... This is not rocket science its simply hydraulics....

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PostPosted: Thu Jan 17, 2013 12:03 am    Post subject: Reply with quote

I'm running a holly red pump with the petrol king regulator, guage says between 3.5 and 4 psi.. All the AN lines were brand new and I blew them out with compressed air after making cuts and putting the fittings on. I cleaned my tank out using about 3 gallons of white vinegar and a chain (the shake method), followed by a water rinse, blow out and sit in the sun for a day to dry..

I'm relatively certain there is nothing blocking the flow of fuel for me.

Unfortunately, I can't do any more testing yet because an unrelated issue led to me frying my battery, so until I can afford to replace it, my red top optima only has about 6.7 volts in it Sad
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