[T3] Why is it that when I got my 73 SB I never had to turnthekey several times to prime the system .

[William J]

----- Original Message ----- 
From: "William J" <catnine09 at dslextreme.com>
To: <type3 at vwtype3.org>
Sent: Friday, August 04, 2017 11:26 AM
Subject: Re: [T3] Why is it that when I got my 73 SB I never had to 
turnthekey several times to prime the system .


> Jim: wanted to add . yes my rubber hose from the fuel filler to the tank 
> is cracked . I can't even begin the describe all the hoses on the tank 
> then to the expansion tank and charcoal canister for the venting . I know 
> the tubes are all there and hoses yet I never checked to see if they are 
> all clear it still has the metal tube running on the left side from the 
> expansion tank to the charcoal deal and it seems to be open yet I never 
> tried to blow air through it. There are more tubes on the left side of the 
> tank from plastic tubing to metal tubing out to the expansion tank it's a 
> Calif car built 11/12/73 so it's a very late model 73 so I can't say what 
> they added and it had the EGR which I removed along with it's relay . If 
> you can let me know the price of your kit I will do this. It just does 
> seems to have many more hoses than any T-3 venting system I have seen in 
> posts.
> I think I understand the fuel pump now . Let me know if I have this right.
>
> The so called check valve if it fails one way no fuel output and the other 
> way it won't hold pressure in the system after shut down . In the later 
> this means to me if it won't hold pressure after shut down this would be 
> every time the car is started and shut down one would need to cycle the 
> key even if it were a short trip IE the pressure would just drop to zero 
> right after shut down or slowly bleed down so the car may start right up 
> depending over all on how fast the pressure drops to zero.
>
> There was some spec on how long the pressure would hold if all if working 
> well wasn't there? And a certain amount of pressure needed to just turn 
> the key and it would start . The 1.5 seconds the pump relay runs the pump 
> if everything is well should bring the pressure back up for one turn of 
> the key start up as long as there is a certain amount of pressure still in 
> the lines . Also after shut down when the starting is engaged at the same 
> time the fuel pump relay is so no need for the 1.5 second time out .
>
>
>
> This hot soak fuel boil is what forces the liquid fuel back through the 
> pump leaving just vapor because of the pressure difference 30 PSI line 
> pressure  and 20 PSI is what it takes to force the fuel back through the 
> pump leaving vapor only due to the so called check valve thus the key 
> cycle deal  or added switch.
>
> what I still can't get past is why I never had this hot fuel soak and 
> vapor and never needed to cycle the key before.
>
> As it is now the car can sit after hot shut down over night and will start 
> in the morning yet I don't drive everyday . I can drive it and shut it 
> down and it will fire right up even after a 10 mile trip in hot weather 
> after sitting over an hour. I can drive a mile or more and it always 
> starts . I've driven it 4 miles 4 starts park in a hot garage and then get 
> in and it fires right up.
>
> I have a momentary contact toggle switch rated at 25 amp figured I'd just 
> wire it fused  side of  a hot all the time fuse tied to the fuel pump hot 
> lead where it connects to the pump relay. Pump has it's own ground not 
> dependant of relay.
>
> ----- Original Message ----- 
> From: "Jim Adney" <jadney at vwtype3.org>
> To: <type3 at vwtype3.org>
> Sent: Friday, August 04, 2017 6:25 AM
> Subject: Re: [T3] Why is it that when I got my 73 SB I never had to turn 
> thekey several times to prime the system .
>
>
>> On 3 Aug 2017 at 15:12, William J wrote:
>>
>>> If the check valve goes completely then the
>>> pump will not put out pressure is this true?
>>
>> There are at least 2 ways in which the check valve can fail. If it fails 
>> one of
>> those ways it can block the pump outlet, preventing any gas from getting 
>> out
>> of the pump. If it fails the other way, the pump will still put out gas 
>> at
>> pressure, but it won't hold pressure in the line after shutdown.
>>
>> Our pumps are now old enough that they are all starting to fail one way 
>> or
>> another. I can usually rebuild them, giving them another few decades of 
>> life.
>>
>> It's very important that the "overflow" hose under the RF fender be 
>> intact,
>> because leaks there let water and dirt into the gas system. Since the OE
>> hoses are always cracked by now, and the OE hose is NLA from VW, I've
>> developed a kit to repair it. So far, I've not seen or heard of any of my 
>> kits
>> failing, and they've been out there for about 10 years, which is about 
>> 3x - 4x
>> longer than the OE hoses tended to last for me. These were always a weak
>> spot in the '68-73 Type 3 design.
>>
>> -- 
>> *******************************
>> Jim Adney, jadney at vwtype3.org
>> Madison, Wisconsin, USA
>> *******************************
>>
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>
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