My 97 non turbo 850 wagon is having total shut off/ no start trouble. Came on suddenly. Put in new filter drained tank, jumped relay. Pump runs and delivers but pressure seems erratic.
pressure regulator looks to be vac controlled from a tee in a line that goes for and aft.
whats the unit that vac line connects to to the rear? Vac line the was totally fractured. Could that be the source of trouble? Thanks for any suggestions!

 

did you measure the fuel pressure at the rail? If you jumper the FPR, you should see something like 40 PSI The vacuum line to the rear is probably the evap purge valve line that sucks the gasses from the charcoal cannister into the intake. Usually that will throw a small evap leak CEL If you have pressure at the rail and still get a no start, next thing to check is the injector relay - it should be a gray box up by the fan shroud. give that a few taps to see if that unsticks the relay to help it start up. Otherwise find a "noid" light to see if you are getting a signal to the injectors. The pressure regulator is under the intake manifold. usually when they fail, its because the diaphram tears which allows pressure to bleed off once the car is shut down causing hard cold starts Jumpering the relay should take this problem out of play. A quick test is to pull off the vacuum hose, and if gas drips out, its bad.

 

I had a fuel pressure regulators with no leak causing no start condition. Yes the fuel pressure gauge (with reduction to car schrader valve) is essential tool for these cars. Stronger vacuum sucking membrane of FPR = lower pressure at the rail. When you disconnect whole vacuum hose from FPR the pressure increases from 40psi to about 50 and idle goes up. Higher pressure is not that bad like low for injectors to spray nice fuel mist to start the engine. Lower pressure makes injectors spit large fuel drops that can´t be ignited by spark.

When you do troubleshooting you have to go from root of the problem. I mean, spark and fuel.

Are there any codes on OBD? Is the pressure on rail right? Do injectors open (ticking) Is the spark strong enough?

One relevant sign of bad FPR: Car catches for half second right after turning the key, than dies and don´t want to catch anymore. (without engine running, on the rail is pressure high enough to start the engine but after engine starts turning and making vacuum, FPR membrane sucked by vacuum cause pressure decrease and engine dies immediately)

 

Thanks for all the input! At this point, I put another fuel pump from a different 850 in and the fuel regulator from that car. Of course, it’s a junkyard car, so no idea if they’re good and I don’t have a very good fuel pressure gauge at the moment, but I’m working on that. Pulled all the plugs and it really appeared that the thing had been flooding. Cleaned them it started up and ran for quite a while up to temperature anyway then died. Now, oddly, it will start easily and run smoothly. If I pulled a fuel pump fuse, but the minute I plug it back in it, cuts out and dies . Just pulled a plug and it’s black and sooty. Only code is P0410 secondary air. Helllllppp!

 

You can randomly change all the parts that could be releated to this issues and never find the culprit. What you need is get relevant measurements in numbers. Like vacuum numbers, fuel pressure numers, compression numbers, fuel pump current numbers, Lambda factor, everything... And operate with them. And solve why the car dies by detecting real time values changes.

 

As it turns out, this was not a fuel delivery problem at all despite the fact that it acted just like one. I unplugged the MAF sensor in the thing ran fine, so I bought a new one for 40 bucks put that in and the car is off and running. the underside of the air cleaner looks like someone had put a torch to it I suspect, perhaps at some time it inhaled a burning mouse nest from the warm air intake, and that may have been what gummed up the sensor.

 

No surprise there. For future reference, the non-turbos will run great with the MAF unplugged, so you can try that for free. These cars are old, and it would be really smart to hook up a scan tool and make some baseline measurements (and write them down) when the car is actually running okay. I would not want to try to keep this stuff running without a scan tool. It's just not worth the frustration to me. I just wish they had pointed the fuel pressure test connection in a different direction.