Quote:
Originally Posted by Treozen
Yes - It looks like the check valve is where the banjo bolt / barbed line fitting connects - at least on the Bosch replacement pumps. I ordered a new one - not idea how old the one on the car is anyway. We'll see if that fixes it. Given how fast the pressure bleeds off, it doesn't seem like its leaky injectors.
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The FSM explains how to test the fuel system. You are doing most of it.
https://www.tonk.ca/Index/117.4/07.4MechElec.htm
Easy first step is to clamp the return hose closed after it leaves the damper which is downstream of the regulator. Turn the key on and off a couple of times and see if the pressure gets to 30psig and holds or still leaks down.
- If not, then the regulator is leaking.
- If it still leaks, it is either leaking back through the pump check valve. Or it is leaking through the cold start valve or injectors.
- You can clamp the hose to the cold start valve closed and see if the leak is there.
- If not, then with engine running and pressure at 30 psig, clamp the supply hose closed and turn engine off. If pressure does not drop, then you know it is the pump check valve.
You said you had a new Bosch pump? Is it a new style Djet pump like the one sold here? If so, the check valve is in the outlet nozzle. No reason not to add a second one (if you can find room) or to replace the existing one (if they are available) Hard to see a newish check valve failing though.
https://www.pelicanparts.com/catalog/SuperCat/12140/MBZ_12140_FULFUL_pg2_fuel-pumps.htm
Good luck with it.