When the pump is not running the pump will allow the pressure to bleed off back into the tank up to a point at least.
That is where I fell the problems is. Fuel should not run backwards down the feed pipe. If it does, you get the situation at hand. Whatever is supposed to stop that is not doing its duty,
assuming there is no injector leakdown.
If the simple valve and spring in the filter...
You are suggesting there is an one-way (aka check) valve in the fuel filter.
https://board.moparts.org/ubbthread...line-fuel-filter-with-a-check-valve.htmlIf there is crud in the tank that gets past the pump strainer then it will travel right round the system to the filter where it will be removed just before returning into the tank.
Yes. A strainer is the primary filter. It is there to protect the pump. The second filter, a finer one, is there to protect the injectors et al engine from minute debris.
Was the strainer checked (PUN!) It is more than possible to re-plumb the fuel system to allow thew fuel to be filtered before the injectors and to use a better, dedicated, pressure regulator that controls the fuel pressure much more accurately and consistently than the standard arrangement (no pressure drop at full throttle and high revs which does happen even with a brand new standard filter/regulator and new pump) plus you can even fit one or more check valves to maintain the pressure in the system if you wish, but the benefits are mainly confirmation bias related...guess how I know!
Regulators do not normally (AFAIK), act as check valves. Thoough an improperly seated fuel pressure regulator diaphragm WILL allow back flow more readily. Guess how I know?
Good thinking Red. In any event, both your theories and mine are easily tested if back flow is stopped. Depending on the hose type, which I asked about, that can easily be done by clamping the feed line
with a small needle nose vice grip after closing the engine off. Then see if there is the same problem when starting up 15 minutes later as there is now. If it starts right up (before stalling for lack of fuel from
a clamped line). we have absolutely confirmed that the leakdown is happening backwards (pump, filter etc) rather then forwards (injectors and regulator) . Easy, cheap, more reliable fix.
gmg
P.S. BTW Red, I found I halved my EFI engines on road diagnosis time by adding in, permanently, pretty fuel pressure gauges per car. If the fuel pressure is fine at a glance, then it has to be electrics/electronics.
One of the major UK suppliers, in the day, adopted the idea wholesale for V8s. Cost is 15$.
