1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Thanks for the suggestions and comments. With the fuel pressure gauge hooked up I think I have finally narrowed it down to a fuel pressure problem and not the ignition electric and other controlling systems. I always seem to have good strong spark and switching most components made no improvement. The Saabina post that the injectors will not work correctly without proper fuel pressure has answered the question for me as to why when I removed the injector connectors on 3 and 4 cylinders it made no difference. I wish I would have had a fuel pressure testing set up several weeks ago. It would have saved a lot of unnecessary testing of the ignition system. Regarding the Goblin suggestion that the fuel pump was leaking inside of the tank, I am not sure how that can be on my 1988. The fuel pump is pressed into the top of the fuel reservoir / canister which is feed by the pre- pump. The output of the main fuel pump is on the top of the tank and feeds directly through the banjo connector to the fuel line which goes directly to the fuel rail. If there is a leak in that fuel line under pressure I think I would see or smell gas spraying. I know there is a return line from the fuel rail from Fuel Pressure Regulator that returns to the tank. I think there may be a check valve on that line near or in the tank on some model Saabs. I am not sure if it is on mine or where it is. I cannot see it from under the car near the tank.
To answer Phoebe Altman question about the Hall Sensor. I have owned Saabs since 1989. Currently I have an 87 and my 88 convertible which is how I am able to switch parts and trouble-shoot. They are both 16 valve Turbos, basically the same engine components with slight differences. Several years ago I had the common problem of the connector going bad on the distributor of the 87. At that time I ordered a new Hall Sensor from SobStory who I do not think is still in business. At one time he was a great supplier of Saab parts. I was able to clean up the corroded connectors and use a zip tie to keep the part on the distributor in place. So I never used this brand new Bosch sensor until a couple of weeks ago. Unfortunately I think I removed a perfectly good Hall sensor and damaged it in the process for nothing, because the sensor was not the problem.
Since I last posted I did some more testing. I replaced the 3 ft fuel gauge test line with a 3 inch one. Several tests in last few days revealed that there was no residual pressure at the fuel rail. It would take about 5 times cranking for the pressure to build to about 12 PSI at the fuel rail and for the car to start. Then the pressure would rise to about 28 PSI and then after 4 or 5 minutes of running rise to about 28 PSI and then begin to fall to between 12 – 14 PSI and hover there running poorly. The # 3 and # 4 injector connectors when removed would have no affect on engine speed. I would let it run for about 10 minutes. The car did not stall at the low 12 PSI. After I turned off the engine the fuel pressure would gradually bled down to 0. Of course the next time the same scenario would repeat, long cranking, build up pressure to about 28 PSI then fall to 12 – 14 PSI. After the shut down the pressure would bleed down to 0, the same thing repeated several times. During these further trials I decided to check voltage at the fuel pump. To be sure it was adequate. It tested at about 13.5 volts and was constant during the gradual lowering of the PSI to 12 -14. I always had the proper voltage at the fuel pump.
Today when I started the car with no alteration to the fuel pressure gauge or fuel line system, the pressure started at 0 then after the typical 4-5 cranks built up pressure and the car struggled to life. The pressure rose to about 28 PSI however the needle was vibrating strangely at 28 and then rose into the 30s and was running very good. This vibrating needle on the gauge had never happened before but was a good sign. When I checked the car was running smoothly and it was firing all injectors. I think it may have even got to 35 PSI. Thus showing when it has proper fuel pressure the injectors work correctly.
I then did a FPR (fuel pressure regulator) test. I removed the manifold vacuum hose and plugged it and applied pressure to the FPR with my vacuum / pressure tester. As I increased the pressure the fuel pressure rose into the 40 PSI range. When I replaced the vacuum hose, the fuel pressure went back to the 32 – 35 PSI range. I ran for a while and then shut the car down. This time the pressure stayed about 32 PSI. I then had breakfast and came back to the car in about an hour and a half. It had maintained the 32 PSI pressure. With good fuel pressure it started immediately however it now has reverted back to its recent habit of only showing max 28 PSI, loosing fuel pressure, and completely bleeding to 0 PSI after shutdown.
So I think my tests showed the FPR to be operating correctly when pressure was applied and there is adequate constant voltage to the fuel pump while running. Also when the fuel pressure is operating in the 30 PSI range all of the injectors seem to be firing correctly. Now I need to determine why the fuel pressure is back to bleeding off regularly to 0. Any thoughts?
posted by 76.181.107...
, Mon, 18 Oct 2021 19:40:57, Wed, 13 Oct 2021 16:32:55
, Wed, 13 Oct 2021 09:14:18, Wed, 13 Oct 2021 14:02:08
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