496 Map senser/ fuel psi.
04-17-2005, 05:52 PM
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496 Map senser/ fuel psi.
I have a 496 and has bad hesitation from idle to half throttle , I disconnect the map senser and the hesitation is gone the fuel psi is 42 and disconnect the vacuum line and the psi drops to 32psi any suggestions. Thanks Jeff
04-18-2005, 09:27 PM
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Re: 496 Map senser/ fuel psi.
Jeff:
Make sure that the throttlebody you are using has a 3/16" to 1/4" hole in the throttlebody plate below the throttleshaft. Also when you set your fuel pressure. Have the engine running at idle. disconnect and plug the vacuum line to the regulator and then reset the fuel pressure to 43-44 lbs. then plug the vacuum line back on. Don't worry about what the fuel pressure reads with the vacume line connected, it will always be higher. If this does not resolve the problem, check the map sensor it could be bad and check to make sure you don't have a vacuum leak. You can use a vacuum guage and connect it to the same line that feeds the regulator. You should have about 16" of vacuum at idle. You can also use a digital ohm meter to read the throttle position sensor with the plug disconnected or you can use a volt meter to read between the ground wire and the ECM terminal on the sensor with the plug connected. You should read between 1.0 volt and 4.6 volts as the throttle is opened and closed. This should help isolate your problem. Make sure all the other sensors are hooked up and you do not have a reduced power level on the engine due to a fault code on the Merc ECM.
Good Luck,
Ray @ Raylar
Make sure that the throttlebody you are using has a 3/16" to 1/4" hole in the throttlebody plate below the throttleshaft. Also when you set your fuel pressure. Have the engine running at idle. disconnect and plug the vacuum line to the regulator and then reset the fuel pressure to 43-44 lbs. then plug the vacuum line back on. Don't worry about what the fuel pressure reads with the vacume line connected, it will always be higher. If this does not resolve the problem, check the map sensor it could be bad and check to make sure you don't have a vacuum leak. You can use a vacuum guage and connect it to the same line that feeds the regulator. You should have about 16" of vacuum at idle. You can also use a digital ohm meter to read the throttle position sensor with the plug disconnected or you can use a volt meter to read between the ground wire and the ECM terminal on the sensor with the plug connected. You should read between 1.0 volt and 4.6 volts as the throttle is opened and closed. This should help isolate your problem. Make sure all the other sensors are hooked up and you do not have a reduced power level on the engine due to a fault code on the Merc ECM.
Good Luck,
Ray @ Raylar
Last edited by Raylar; 04-18-2005 at 09:29 PM. Reason: spelling
