Hi,
25 years without making mechanics and rude comeback with an old V8 full of electronics...
Old engine, don't know the history. I changed all this:
- water radiator, oil pump, steering pump, front airsprings, all filters, all fluids, the plugs, the ignition coils, ...
It ran good up to suddenly it started needing two to three cranks to starts (except some mornings where it started good).

As I had the engine light, I bought a code reader (ANDROID Torque, which is quite amazing) and found a weak EGR flow feedback error. Then I changed the EGR valve (a great pleasure with a toys toolbox!), the solenoid control valve and the feedback differential pressure sensor. The idle is now worse than before, but the engine error is gone and I have recovered a bit of gas mileage. I'm certainly on the good way...

I read your exciting forum and understood it might be a problem of R303. I took days and two attempts to find a corresponding relay and changed it on the fusebox plate (which was brown at this relay location). No change on the starting. I ear the fuel pump for 1 second from the gas cap open.

I rented a fuel pressure gauge and put it onto the rail.

When running, the pressure is 31PSI, going to 40 if I accelerate or if I create a vacuum leak. I understood the fuel pressure regulator works fine.
If I ask for load (speed engaged and accelerating while keeping foot on the brake) it goes to 40 PSI and keeps the pressure constantly. I deduce the fuel pump is strong enough and the fuel filter is not clogged.

Thus I don't know. Everything looks like OK.

The only thing I noticed is the following:

When I shut off the engine the fuel pressure goes down to 0 straight. When I cycle on, it goes to 31PSI straight and straight to 0 after one second (like tic-tac, the pressure moves very fast from 0 to 31 and 31 to 0).
When I wait some minutes and cycle on, the pressure stays to 0 first, and tries to increase at each cycle on but the fuel pressure gauge needle is moving against a sponge, rising and going back slowly, every time at a higher pressure but "in the butter".
Thus I noted the fuel pressure gauge is full of air and even difficult to purge. Tu porge it I have to run the engine for a while.

In summary, I have a rail fuel pressure loss quite fast after stop, and I have air into the rail that makes difficult the pressure to reach the right 31PSI.

Could all this be caused only by a worn out fuel pump or could it be caused by any other component ?

Thanks for further support,
& thanks for your super forum !!

 

The anti-drainback valve in the fuel pump is worn out.

 

If you were able to diagnose that and are right, you are a god to me my friend.

 

another option ?
thanks a lot, KR

 

Thanks a lot for your assistance.
Just for info, it arrived quite suddelny after I put a huge amount of fuel system cleaner in my tank. Maybe dirt was helping my worn out pump check valve...
I'll change the pump asap.,
KR, fmw