CIS Problem?--AGAIN!!!--SOLVED!!!

[E. Roy Wendell IV]

On Dec 26, 2006, at 9:27 PM, Ben Swann wrote:

> I suspect the pump may have failed in part to ingesting some debris  
> in the
> tank, but may have indeed been a dud.
>
> I relay mine with 30Amp fuse.  Connection is under the seat as I  
> recall.  The
> fusebox wiring should not be passing the kind of current that a  
> fuel pump will
> draw.
>
> Ben


I'm with Ben on this one. Every type 44 I've acquired so far has  
spent significant amounts of time sitting around in a non-running  
condition and therefore has a rusted up fuel tank. The usual result  
is a clogged up screen on the bottom of the fuel pump. The really  
fine rust bits get right through the nylon screens in the sump but  
not the really fine stainless mesh in the bottom of the pump. Because  
this screen has a small surface area it clogs almost immediately  
after startup resulting in a car that won't do much more than idle  
and a pump that howls loud enough to wake the dead due to cavitation.  
The usual fix is to take out the pump and cut out the  stainless  
screen thus allowing the fine particles to pass right through and be  
caught by the filter. This usually works just fine as the nylon  
screens in the sump still catch anything large enough to jam up the  
roller cell pump.

The problem that can occur though is that the rubber seal where the  
pump sits in the mount is usually stretched out and brittle. It no  
longer prevents fuel from flowing over the top of the mount and  
through the gap between the side of the pump and the mounting ring.  
This allows large bits of crud to get right into the pump element and  
jam it up. The solution is to go to the stealer and order a new seal.  
Take the three bolts out that hold the plastic flange with the three  
pump mounting pins to the sump, lift it off, swap out the seal, and  
reassemble.

The Bosch pump has gotten a reputation for being noisy right out of  
the box but it has been my experience that they are perfectly silent  
is the intake isn't restricted in some way. The instant that there is  
any negative pressure on the pump intake then cavitation occurs and  
noise is the result. If you install a new Bosch pump and it's noisy  
right away then either or both of the intake screens are clogged.  
When I was having problems with my current daily driver 200, I could  
predict when the engine was about to quit due to fuel starvation  
purely by the pitch of the fuel pump. It got to the point where it  
would run for five minutes at a time due to rust clogging the  
stainless screen in the bottom of the pump. I actually got it home by  
starting it up, accelerating to the highest speed I could get away  
with, and then turning off the engine and coasting so that the rust  
would fall away from the screen and I could start the cycle over  
again. Even after all this abuse the pump has been silent now that  
I've cut out the screen and vacuumed the rust out of the tank.

A pox on the Audi engineer who decided to install the pump mount/sump  
and weld the top half of the tank around it thus making it virtually  
impossible to use any of the standard tank coatings that would  
eliminate the rust problem once and for all. The sump can be unbolted  
from the bottom of the tank and moved around but not removed as it's  
about four times bigger than the access hole in the top of the tank.  
I can't see any way of lining the tank without clogging up the nylon  
screens in the sump.

Roy Wendell
erwendell at mac.com
Too many type 44 tq
A pair of MR2s