Fuel Pump Losing Prime?

[BADAZZGSX]

I recently replace the fuel level sending unit on my 92' TSi AWD. Ever since then my car has been hard to start. Like if I let it sit for a few days and then try to start it, it takes a long time to finally crank. Like the fuel lines are empty or something. I was thinking that maybe the pump is losing its prime somehow. Any help pinpointing the problem or helping repair it would be greatly appreciated. Don't like not being able to drive W I D E O P E N !!!!!!!

 

[markmakeitso]

i'm not sure how easy a fuel pump can lose its prime, but a fuel injector sticking open will allow fuel pressure to drain out of the rail and lines. that will also cause long crank times. might be worth checking out the business end first

 

[2-0turbo]

I can't recall--did you have to pull the fuel pump out of its "bracket/framework" to change that sending unit? If so, I'd guess that O'ring is torn/ripped/rolled. You are supposed to lubricate it when you put the thing back together so this is less likely to happen. I can't remember if you have to pull the pump or not, so you might not have messed with it.

 

[696]

My 2G did it once. I let it sit for a week and I had to "pump" the gas a few times and it fired up. Ran a little rich for a sec then it was fine. Others said it just drained back into the fuel tank. It only happened once and since then it has been started more often.
696

 

[BADAZZGSX]

I had to completely remove the fuel pump from the tank to change the sending unit. Also the car never did it before I changed the s.u. , that is why I don't suspect it to be a leaky fuel injector. It does this every time it sits for a few days. If I drive it daily it doesn't seem to be affected. Your guesses are as good as mine. I'll try the o-ring; you are talking about the one on the fuel line conected to the pump aren't you? If that isn't it then maybe some other dsm'ers will know a solution.

 

[2-0turbo]

Yeah, the one that sticks on that "tit" that is on the top of the FP. If that tears, rolls or pinches, you'll lose pressure over time. To be perfectly honest, I think mine is a little funky after doing my FP. After letting it set a week or so, it tends to turn over more than it used to.

 

[thump]

Mine starts real rough as well. Like after I dont drive it for a few hours.. Id estimate.. 5hrs or more it takes a few seconds of cranking then it finally fires up. CLogged fuel filter maybe? is it most likely something in the fuel delivery end of things up front?

 

[2-0turbo]

Originally posted by thump
Mine starts real rough as well. Like after I dont drive it for a few hours.. Id estimate.. 5hrs or more it takes a few seconds of cranking then it finally fires up. CLogged fuel filter maybe? is it most likely something in the fuel delivery end of things up front?

You might have a clogged fuel filter, but that usually pops its head at high RPM, high load conditions. I'd say you have a leak in your fuel system somewhere causing the pressure to bleed down. When you turn you car off, the fuel system is supposed to be sealed and it should stay at approximately 35 psi. If an O'ring is torn somewhere or you have a leak, it will drop to zero. When you go to crank the car, your pump will have to completely re-pressurize your entire fuel system. In the grand scheme of things, fuel pumps don't put out much flow and this can take several seconds.

 

[BADAZZGSX]

You all talk like it takes just a few seconds to re-prime the lines. Well my system must drain COMPLETELY because it takes a few minutes of cranking for the gas to reach the fuel rail. After it gets there it runs fine.