924Board.org

[McMichem]

I have a 1980 931 I have been messing with, seems to have low fuel pressure because I can't get the injectors to open when adjusting the afr screw. They only open when I manually press down on the metering plate.

Before it's mentioned, I am going to invest in a via pressure tester at some point just don't have the money and feel like tinkering.

My external pump vibrated a lot when I originally got it and Im kinda thinking its on its way out.

-Which pump provides the most pressure in the system?

-if it's not the pump, and I would like to do this regardless... Would it hurt or help anything as far as cleaning the distributor and the injectors to fill my tank and add a modest amount of seafoam or fuel injection cleaner and run a few gallons of fuel through the injectors with them out? I wonder if over the few years it's been sitting if anything is stuck inside the dist.

I know I need to clean the tank at some point regardless, I just don't feel up to it myself in my small garage without a lift, it just feels like the kind of thing I would mess up and be out of luck.
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1980 931 ~ 67,000 miles

[Nordic_Boost]

underneath the distributor there is a large silicon hose going to the turbo, if this has cracks and tears in it its not going to open the plate in the distributor properly. which leads to no start. this happened to me

[ideola]

The external pump is the high pressure pump. The internal pump only provides a prime. There apparently is a TSB about the internal pump being superfluous, although I've never had a need to eliminate it on any of my cars.

I agree with Nordic_Boost about checking for leaky boot between AFM and turbo inlet. However, you should also check voltage at the pump itself, as the wiring is prone to building up resistance over time, and you may not be getting sufficient voltage there. It is a common fault, and one that can lead to premature pump failure.

As for the rest of the system, you really should invest in a proper CIS tester because there's no other way to tell whether the CIS components are working correctly. When you do, here is a write up on how to conduct the tests: http://www.924board.org/viewtopic.php?t=35734

In the meantime, you can definitely try running a bottle of Techron fuel system cleaner. Use the Fuel System cleaner, not just the injector cleaner, and get the bottle good for 20 gallons. This stuff is magic, and all of my cars get an annual treatment.

The other thing to check is the fuel filter. Replace it if you haven't already, and make sure you install it correctly. The direction of flow is TOWARD the windshield. Many owners install it the wrong way round, and this will impede fuel flow. If you find it installed backward, DO NOT reuse it in the correct orientation, as you will flush all sorts of nastiness toward the fuel distributor and injectors.

Good luck!
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erstwhile owner of just about every 924 variant ever made