Dancing Boost Gauge Needle
09-04-2002, 09:30 PM
#1
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Dancing Boost Gauge Needle
The boost gauge in my '87 930 has all of sudden started to flicker back and forth. Not always, just some of the time and under different throttle positions. My mechanical VDO gauge reads steady and correctly. Think it might be the sender gone bad? Or maybe a ground? I have the Kokleln I/C, but I believe it's grounded properly.
I noticed it after driving the car one day for about a mile from home and the car just stopped running. I pulled over and after two tries the car started up and I made a beeline for home.
I couldn't determine what the problem was, but after trying several things, I grounded the overboost switch and it seems to run good now except for the dancing boost gauge. Still leary about driving it too far from home though.
TIA.
Regards, Jim
I noticed it after driving the car one day for about a mile from home and the car just stopped running. I pulled over and after two tries the car started up and I made a beeline for home.
I couldn't determine what the problem was, but after trying several things, I grounded the overboost switch and it seems to run good now except for the dancing boost gauge. Still leary about driving it too far from home though.
TIA.
Regards, Jim
09-04-2002, 11:58 PM
#2
Rennlist Member
Jim:
I had the same exact problem recently. I have an electronic boost control with digital readout of boost pressure (as a control). The boost sender went completely bad after several days of flickering, eventually reading full boost at all times, even when ignition on but engine not running. I replaced the boost switch with a new one - same problem with flickering. Finally figured that the IC was not sufficiently grounded - when I grounded the IC with a jump wire, the flickering immediately stopped. I made up a supplemental ground and... voila...works fine. I determined that the sender was bad by watching the dash gauge as the key was turned from off to on (but not starting engine), while the sender was out of the IC and resting on grounded metal. If functioning, the gauge should go from far left stop to the "0" point, and not flicker. My bad sender continued to go full to the right stop while adequately grounded, so I knew if was internally flawed. Plus the fact that it rattled when I shook it. The new version of this sender costs about $108. I have one if you're interested, as I was able to find an older version that works fine, even though used.
I had the same exact problem recently. I have an electronic boost control with digital readout of boost pressure (as a control). The boost sender went completely bad after several days of flickering, eventually reading full boost at all times, even when ignition on but engine not running. I replaced the boost switch with a new one - same problem with flickering. Finally figured that the IC was not sufficiently grounded - when I grounded the IC with a jump wire, the flickering immediately stopped. I made up a supplemental ground and... voila...works fine. I determined that the sender was bad by watching the dash gauge as the key was turned from off to on (but not starting engine), while the sender was out of the IC and resting on grounded metal. If functioning, the gauge should go from far left stop to the "0" point, and not flicker. My bad sender continued to go full to the right stop while adequately grounded, so I knew if was internally flawed. Plus the fact that it rattled when I shook it. The new version of this sender costs about $108. I have one if you're interested, as I was able to find an older version that works fine, even though used.
09-05-2002, 09:23 PM
#3
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I'm going to try and ground the I/C first, among a few other ideas and if they don't work, then I might take you up on the sender.
Thanks,
Jim
Thanks,
Jim
