On-road fuel pressure test
Discussion
Has anyone attempted an on-road fuel pressure test by tapping into the schrader valve on the fuel manifold? I have a rough running problem (see separate thread) and want to rule fuel supply out as an issue. I've connected one of the pressure testers (available off amazon/ebay for about £15) and the fuel pressure read fine when sat at idle and accelerating when the engine is cold and the problem isn't evident, but I'm curious as to what the fuel pressure reads on the road when it starts jumping and coughing.
My logic tells me that trying an on-road test with hot exhaust manifolds is retarded, as if there are any issues with the connection to the schrader valve then I'll have fuel squirting out under high pressure across a hot engine = raging fire and destroyed plastic car!! So, anyone on here ever been brave enough to try it (seen some youtube videos of it)? Is there likely to be any merit to it at all if the pump provides adequate fuel pressure static, at idle and accelerating but whilst cold and not under load?
My logic tells me that trying an on-road test with hot exhaust manifolds is retarded, as if there are any issues with the connection to the schrader valve then I'll have fuel squirting out under high pressure across a hot engine = raging fire and destroyed plastic car!! So, anyone on here ever been brave enough to try it (seen some youtube videos of it)? Is there likely to be any merit to it at all if the pump provides adequate fuel pressure static, at idle and accelerating but whilst cold and not under load?
When I first got my S1, I had all sorts of problems with the car missing when it was hot. I plumbed in a pressure gauge to the fuel system using proper pipe fittings and monitored the fuel pressure. This showed that I had a fuel pump pressure problem once everything was warm, with the gauge indicating that the pump was unable to pump the warm petrol. I suspect petrol gets thinner as it warms up (like oil) and the pump was unable to pump the thinner petrol at the pressure required by the mechanical injection on the S1 (which is higher than that required for the electronic injection). A new pump fixed the problem.
Dave
Dave
I have plumbed in a pressure gauge into the flexi hose in the engine compartment just prior to the fuel rail. My car had suffered several fuel starvation stops and I wanted to know exactly where the problem had been occurring - pump / relay / filter.
The gauge electrics were taken from the 12v supply to thepump - so if gauge did not light up then it was the relay
The gauge reading would show the pressure so confirming the pump pressure supply at both idle and full load which also showed any pressure drop on full load so confirming the filter
The installation both cheap and simple
did turn out to be a faulty new pump.
The gauge electrics were taken from the 12v supply to thepump - so if gauge did not light up then it was the relay
The gauge reading would show the pressure so confirming the pump pressure supply at both idle and full load which also showed any pressure drop on full load so confirming the filter
The installation both cheap and simple
did turn out to be a faulty new pump.
There's a handy opening at the back of the bonnet so you can mount a mechanical gauge on the outside of the windscreen where you can see it. You would need to make sure the plumbing was secure but I don't see that as hugely dangerous to do. Petrol is arguably less dangerous than oil - you need a spark to ignite petrol because it boils below its flash point, but oil will happily catch fire on a hot manifold.
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