Help diagnose, please
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Geaux Tigers!
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From: Louisiana
Help diagnose, please
Friend has a 87 928S4 that does not start. Car will turnover but won't start. Hotwired the fuelpump and found out it works. Replaced Jetronic Relay and Fuelpump relay and still won't do anything but turnover. Someone suggested that he do a continuity test on "schematic no. 86 which is solenoid valve for the auto trans and the kickdown." Doesn't make sense to me but then again who am I...........
Any suggestions guys or gals?
Any suggestions guys or gals?
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From: AZ
You need to round up all the usual suspects .... spark, fuel, compression ... and determine which aren't working.
Do a rennlist search of the term "ezx" and pick the article on Spark & Fuel Diagnostics. This provides a fairly extensive set of diagnostics.
Do a rennlist search of the term "ezx" and pick the article on Spark & Fuel Diagnostics. This provides a fairly extensive set of diagnostics.
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Geaux Tigers!
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From: Louisiana
Thanks Rich. Forgive me as I'm trying to help this guy over the phone.
Basically they've hotwired the fuelpump and the car will start. Their diagnosis seems to be that the ECU is keeping the pump from running once the key is turned. One caveat is that there is a Bulldog alarm on the car with starter disable. The disable is supposed to hook directly to the starter but they beleive that it goes somewhere to the ignition. It could be the alarm or it couldn't.
One of the guys on the phone says that he can't seem to make the "ECU ground the fuelpump." Does any of this make any sense to you and if so any suggestions?
Again the car runs by hotwiring the fuelpump. Something is keeping the fuelpump inactive.
Basically they've hotwired the fuelpump and the car will start. Their diagnosis seems to be that the ECU is keeping the pump from running once the key is turned. One caveat is that there is a Bulldog alarm on the car with starter disable. The disable is supposed to hook directly to the starter but they beleive that it goes somewhere to the ignition. It could be the alarm or it couldn't.
One of the guys on the phone says that he can't seem to make the "ECU ground the fuelpump." Does any of this make any sense to you and if so any suggestions?
Again the car runs by hotwiring the fuelpump. Something is keeping the fuelpump inactive.
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From: Ball Ground, GA
1. Remove Relay XX - Fuel Pump Relay.
2. Test for 12vdc on terminal 30 of relay socket. If there is no voltage, check connection of smaller red wires on positive battery post, wiring from battery to Central Power Panel, and make sure that Plug U (4th from right end) is securely plugged in.
3. If there is 12 vdc on terminal 30 of the relay socket, jumper from terminal 30 to terminal 87. The fuel pumps should run. If not, check fuse #42, wiring to pumps.
4. If the pumps run with the relay jumpered, turn the ignition switch on and check for 12 vdc on terminal 86 in the relay socket. If there is no power on terminal 86, there is a problem with the ignition switch or the wiring in the Central Power Panel.
5. If there is power on terminal 86, make sure that Plug W (2nd from right) is securely plugged in. If the pumps do not run with the relay plugged in, either the relay is bad or terminal 85 in the relay socket is not being grounded thru terminal 20 on the LH ECU. This may be caused by:
- Bad EZK (Ignition) relay (Relay XVI). Relay XVI will look different from the other relays, as it includes a fuse tester. Despite the appearance, the relay is electrically identical to the other "53" relays, so the starter relay (XIV) or the backup lamp relay (XXII - only if automatic transmission) may be swapped for testing.
An aftermarket alarm can cause any number of problems, and would require on-car testing, since there is no way to know how it is installed.
Good luck!
2. Test for 12vdc on terminal 30 of relay socket. If there is no voltage, check connection of smaller red wires on positive battery post, wiring from battery to Central Power Panel, and make sure that Plug U (4th from right end) is securely plugged in.
3. If there is 12 vdc on terminal 30 of the relay socket, jumper from terminal 30 to terminal 87. The fuel pumps should run. If not, check fuse #42, wiring to pumps.
4. If the pumps run with the relay jumpered, turn the ignition switch on and check for 12 vdc on terminal 86 in the relay socket. If there is no power on terminal 86, there is a problem with the ignition switch or the wiring in the Central Power Panel.
5. If there is power on terminal 86, make sure that Plug W (2nd from right) is securely plugged in. If the pumps do not run with the relay plugged in, either the relay is bad or terminal 85 in the relay socket is not being grounded thru terminal 20 on the LH ECU. This may be caused by:
- Bad EZK (Ignition) relay (Relay XVI). Relay XVI will look different from the other relays, as it includes a fuse tester. Despite the appearance, the relay is electrically identical to the other "53" relays, so the starter relay (XIV) or the backup lamp relay (XXII - only if automatic transmission) may be swapped for testing.
An aftermarket alarm can cause any number of problems, and would require on-car testing, since there is no way to know how it is installed.
Good luck!
