08-21-2014, 02:35 AM #1
- Join Date
- Aug 2014
951 DI Pressure Regulator questions
Hi all, first post so hello :thumbsup:
I apologise for the long post but I'm trying to get all my thoughts down to avoid any grey areas, for those of low attention span, the important part is the last paragraph!
I've bought a 2001 RXDI which came in a box of bits, it's all been nailed together and I'm not at the stage where I'm trying to get it running but it doesn't want to play ball. After a lot of reading, digesting the manual, testing pressures, injector pulses, sparks etc I'm at the following point;
The ski will not start without intervention. Pouring a little fuel into the bores will allow it to start and run until the fuel is used, then it stalls. The Air and Fuel injectors spray when disconnected from the head and the engine is cranked, but when fitted, engine is cranked, then fuel rail is removed, the bores seem to be completely dry.
Regulated air pressure at the fuel rail is ~76-80 PSI (as per the manual) although the gauge I'm using has a sketchy scale but seems reliable in measurement. When the return pipe from the regulator is pinched, the pressure rises well over 100 PSI before I release it, then returns to a consistent 76-80 PSI which tells me that the compressor and regulator are working as intended, washing up liquid and water poured over all joints and pipes shows no leaks.
Regulated fuel pressure fluctuates wildly, I think this may be where the problem lies. When the DESS key is connected, the fuel pressure rises to anywhere between 27 and 60 PSI without the engine cranking, when the engine is cranked, air pressure goes up to the regulated ~76 PSI but the fuel pressure (which should be, in this case 27+76=103PSI) never goes above 80 PSI and the engine will never catch.
Now the caveman testing starts, pinching the air return hose to the point where the air pressure goes over 100 PSI will cause the fuel pressure to rise to slightly over 100 PSI when cranking, if the air return is then released, the engine fires and runs for about 5 seconds and then the fuel pressure drops below 80 PSI and the engine dies.
Other than checking for leaks between the air regulator and the fuel reg, I'm pretty stuck on where to go next unless I can use a fixed fuel pressure regulator to set the fuel pressure at ~107 PSI to prove the fuel regulator or something associated with it is faulty. What is the reason for the rising rate regulator in the fuel rail and will it cause any problems if the 27 PSI priming phase is skipped in favour of a straight regulation at ~107 PSI?
Thanks for reading, look forward to your replies.
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