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1985 740 N.A. Last weekend I posted a message about intermittent stalling and realized that the in tank pump was not working. Heres where it led: After trying a known good AMM, fuel pressure regulator and Impulse Sender the car would still quit at random. I realized that I needed to know the fuel pressure, so I cut apart the appropriate section off an old fuel rail and with a 1/2" tee and some hose clamps I made a fuel pressure tester. I had 28-30 lbs. at the rail and the pressure would fall when I accelerated. Put on a new main fuel pump and pressure went to about 35 lbs but the car would still quit. The tach needle would not instanlty go to zero and I could not confirm fuel pressure because it would only "stall" after the car was warmed up and at speed.By the time I opened the hood and looked at the pressure guage it would read 40-42 lbs. I had to lower the tank to get to the very rusted plate for the sending unit and re-wired pump and sending unit (gas guage now works) the symptoms still continued. Finally the car started quitting when it was cold and what was happening was the fuel pressure would slowly approach zero and when the engine stalled the pressure would shoot up to 40 lbs-car would instantly restart and then the cycle would repeat itself. I was able to convince a friend to "lend" me his fuel pump relay out of his '87 and now the car is fine. I just found it very confusing that the FP relay would act in such a strange manner. I switched between two relays I had around and both would act the same way. Upon examining themn a little closer(w/ a 4X magnifier) I realized one had a couple cracked connections-Moral of the story is to work from simplest to hardest and look real close at all the components in the equation. I now have a new fuel pump, a working gas guage and pre-pump but a lot of time and frustration went into figuring it all out-Thanks for everones suggestions last weekend-now I can return the car to my daughter and get my Saab back-Dave F.
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