Injector pump "loses it's prime"

[Wayland]

Car is an 85 Jetta, NA. If I leave it for 2 days or more, I have to crank it for several minutes before it will start, like there's no fuel in the pump. The same thing happened a few months ago, and at that time I found a loose hoseclamp on one of the fuel filter connections. After I tightened it it seemed fine, now the problem is back. I checked all the obvious connections on the fuel line and they all look tight.

[Rabbit TD]

If you tightened a line a while back and it fixed the problem then it's obviously not pump related but more air getting in again from a line or connection either at the same place or a new one.  It happens to all of these eventualy it seems and don't assume a line itself is good just because you don't see fuel leaking from it, the feed line is under vacum and not pressure.  The lines themselves will leak also and not just at the connections.  You sound like you definately have deteriated lines allowing air in and that's why it's so important to have a good clear line from the filter to the pump to check for it.  I just went through this myself getting ready to blame the pump instead until I saw all the air getting in it with a new clear line.  It seems we all at some point replace a fuel lne on these wiith something we have available and figure if I just tighten the clamp enough it ill be OK and figure if we don't see a leak it's allright but it won't visably leak but let air in instead and that's why VW put the clear line on to check for this.

[smutts]

What is not so obvious is that if perished, the rubber leak-off lines between the injectors will also allow air in, and bugger up the prime. Cost pennies though.

[Wayland]

What is not so obvious is that if perished, the rubber leak-off lines between the injectors will also allow air in, and bugger up the prime. Cost pennies though.

Aha! I was wondering if this could be the case, because I definitely have a bad leak-off line. I happen to have a roll of new line sitting on the table in front of me, which I was going to install. I didn't realise this could cause a problem with air getting in. Thanks.

[fatmobile]

The '85 should have a check valve in the fuel line to keep it from syphening back.
 They clog up and restrict the fuel line and I usually remove them, along with the water seperator,..
 so you might not have one.

[Wayland]

I replaced all the leak off lines today (they were all pretty rotten) and the problem seems to have gone away. My car actually still has it's water separator, I've never got around to removing it. Where abouts is the check valve you're talking about?

[fatmobile]

It's just after the water seperator,.. in the fuel line going to the engine bay.
 Keep that in mind when you get a fuel line restriction 
 Doesn't sound like it is working.
 I can't imagine fuel syphening back to the tank through the return line, especially with air leaks in the lines between the injectors.
 It had to be going back out the front of the pump and back through the filter, that can't happen with a good check valve.

[smutts]

Where is the check valve to? As it has been a while since I had a grand tour of the fuel lines.

[Fisher]

The Shaft Seal can allow the Pump to lose it's prime also.