1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Members do not see ads below this line. - Help Keep This Site Online - Signup
Yesterday I was trying to diagnose the cause of base boost (5.5 psi max) on my 1988 SPG. Following the advise on the townsend website, I replaced all vacuum lines and checked all the piping and clamps along the intake track. Still 5.5 lbs max boost. Next step was to check for power and ground at the APC solenoid on top of the radiator. Solenoid did not click. No ground present. I attached a jumper wire to ground the solenoid, and it clicked. Now it boosts up to 17.5 psi before the overpressure switch cuts in. This did not seem right, so I followed the next steps in townsend's procedure. The knock sensor seems functional (I got AC voltage at the APC box when tapping on the bolt holding the knock sensor to the block). The pressure transducer (under the dash on the left side of the car) read 0.5 ohms at atmospheric pressure. The Bentley manual said it should be between 5 and 13 ohms. The reading did not change when pressure or vacuum was applied. So it appears to be bad, according to the townsend and bentley diagnostic procedure. Meanwhile I am still boosting up to 17.5 psi, which I know is not good for my unmodified engine.
Now for my questions:
1) Was it a mistake to use a jumper wire to ground the APC solenoid? Does the APC control box use that ground to activate/deactivate the solenoid? The schematic looks like it uses the 12 volt positive to control the solenoid, and the ground looks to be constant. Was I misktaken here?
2) Could a faulty pressure transducer (under dash on left side) cause my overboost problem?
Thanks in advance for any advice on this. The townsend and bentley instructions are great, but neither of them answers my current questions clearly.
SKB
88 900 SPG - with uncontrolled boost :-(
posted by 12.246....
, Mon, 17 Dec 2001 16:11:02
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
