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Re: [T3] Running hot


Mark Healey wrote:
> I've had problems with my car running hot for some time now.  I've
> tried several pressure sensors.  The one I have in now is still
> sealed.  I've checked the fuel pressure, OK.  I did the resistance
> checks on the temp sensors, OK.
>
By "running hot" do you mean the engine is running hot, or that it runs
badly when the engine is hot?
> One weird thing.  Somehow air seems to get into the fuel lines.  If I
> just get in after the car has set for a day or so it takes about 10
> seconds to start.  If I run the fuel pump without starting the car for
> that 10 seconds it fires right up.
>
This is normal in most Type 3s that are old enough. The theory is that
the pressure relief valve in the pump gets leaky as the rubber
deteriorates and allows for the system to lose pressure (and possibly
take in air from the tiniest imperfections in the hoses, fittings,
injector tips that would leak a small molecule like air, but not a large
one like gasoline). This problem is usually worse in a hot car, but also
manifests itself after sitting around a few hours.

The pressure, with the engine running, should be around 28psi, and when
new, the line pressure should not drop below 19lbs. This was the spec
when new. On mine, it drops immediately to 19 like it should, and then
slowly crawls down to zero within a couple of hours.

It's not an indication that the pump is failing, per se. It's a fairly
normal part of a Type 3 getting old. Jim Adney had some success
rebuilding the offending part of the pump and getting it working like
new. As an alternative, you could also rig a switch to trigger the pump
relay and prime the system in this manner. It's what I've done, and is a
pretty reasonable workaround.
> Could enough air be getting into the fuel lines to cause it to run lean?
>
Unlikely, I would think. If you have a leak in the system, I wouldn't
think it likely to suction in air and fuel during normal pump operation.
A pressurized line is running a bit above atmospheric pressure. A leaky
line will leak out, not in, when pressurized.

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