4000 Quattro fuel circuit overheats

[Cody Forbes]

I'd just think the pump is going bad and drawing too much current. It may have an internal short in the windings or worn brushes.

How could the inlet pressure ever be higher than outlet? The pump is generating well in excess of 75psi. If the inlet of the pump (the gas tank) was at 75psi the tank would blow up like a balloon to a size bigger than the car (likely it would split at the seams long long before that). A bowling ball air cannon that can launch a bowling ball a quart mile requires about the same psi and has WAY less surface area than a gas tank.

 Beyond that, fuel pump INLET pressure being even slightly higher than normal would DECREASE load on the pump, not increase.

The fuel pressure regulator in stock trim cannot be adjusted, nor should it ever need to be. If the pressure is wrong than the regulator is bad and needs to be replaced. The only way this could increase load on the pump is if the pressure was too high, but these systems are designed for pretty extreme pressures so it would have to be a lot to be overloading the pump. The car would not run well with this much excess fuel pressure.

A clogged fuel filter, or anything between the pump and the CIS metering head/regulator assembly, could potentially cause a high pressure at the pump, but that restriction would also cause a low pressure at the CIS metering head which would cause the car to run poorly.

-Cody Forbes (mobile)

> On Dec 23, 2015, at 10:26 AM, David Vanden <vandendavid18 at yahoo.com> wrote:
> 
> This is probably out of my league, but the fuel circuit overheats or seems to on my 4000 Audi Quattro.  It has been suggested that the fuel pump is getting clogged and that the pressure  regulator needs to be adjusted; or that the inlet pressure is more than the outlet pressure.  Any other hypothesis.  I ran the inlet outlet pressure theory  by the mechanic and he didn't think that was it.  I will probably end up taking it to him anyway, but I wondered if anyone had any other ideas?
> David
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