Starter yes or no

[glennspiegler]

Battery 12.6volts, yellow wire at the starter 12v with key on and in start mode and hear what I think is the fuel pump run. Connect the yellow wire to the starter and no voltage with ign switch on and in start position and when connected the fuel pump stops running. Disconnect yellow ign switch wire and the fuel pump comes on and the 12v return. Think it is the starter, but when I jump the starter red power wire to the yellow ign switch wire it turns over fine. Is there a short somewhere? Once a day it works normally again.
Also don't understand why the ign switch in the on position in addition to the start position makes the yellow starter wire hot. Did replace the elect portion of the ign switch a few months ago (it was bad). Have done a recent H4 with relay addition which works fine.
Any help would be great before work tomorrow. Glenn

[glennspiegler]

Please

[80-911SC]

i thought the yellow wire was constant hot and the red with the switch ??

[glennspiegler]

Bentley shows the red wire post 30 to the battery, yellow post 50 a small wire to the switch. Since 50 has power with switch on and in start position is that a problem? Would think power should only be with ign in start position. If it is normal could a bad solenoid drain the power from the fuel pump when yellow wire connected and key on. When I disconnect yellow wire I then hear fuel pump rev on. Then when I connect 30 to 50 and it turns over. Do I have a voltage drop in the solenoid that is overcome by a direct power from 50. Thanks, Glenn

[T77911S]

i dont know much about your year, but, based on most fuel injection systems, the fuel pump should not run if the engine is not running. with newer cars, the FP will come on for about 5 seconds when you first turn the key to on, then stop.
go back and check your modification, perhaps you wired something wrong.

do you hear a clicking sound when you try to start the car?

are all main power connections clean? grounds, body to tranny, battery to body.

measure battery voltage with key to start position


the solenoid can go bad. the most common thing is the contacts inside get corroded or burned from the current. you can remove the end of the solenoid, clean the contacts, rotate them 180 deg to expose new metal. soldering is required though.

[Quicksilver]

As T77911S said: On the Motronic Carreras the fuel pump doesn't run unless the DME detects that the engine is spinning enough for it to be running. The injector system has a check valve system that retains 20psi at the injectors when the car is off.

[glennspiegler]

Ground wire cleaned, 12.6 volts at the battery with key off, will try with key on. The fuel pump runs with key on and yellow 50 wire disconnected from solenoid. When I reconnect it the pump goes off. Since I can jump solenoid by connecting terminal 30 to 50 and it turns over am I correct in feeling solenoid is ok? It has been suggested that I tap into the yellow wire behind the ign switch and run to batt pos to see if it turns over. If it doesnt bad yellow wire, if it does bad switch. Thanks, I will post result of this tonight. Bit of a sore back from pushing it down the driveway, good hills at work. Glenn

[rick-l]

lets try these one at a time.

Originally Posted by glennspiegler

Battery 12.6volts, yellow wire at the starter 12v with key on and in start mode and hear what I think is the fuel pump run.
This was with the yellow wire disconnected right? Start (the yellow wire) goes to the DME and turns on the DME relay that runs the pump

Connect the yellow wire to the starter and no voltage with ign switch on and in start position and when connected the fuel pump stops running.
This kind of says the switch contacts in the ignition have a higher resistance than they are supposed to
Disconnect yellow gin switch wire and the fuel pump comes on and the 12v return.

Think it is the starter, but when I jump the starter red power wire to the yellow ign switch wire it turns over fine.
I'd say this exonerates the starter



Also don't understand why the ign switch in the on position in addition to the start position makes the yellow starter wire hot.
This is with the yellow wire disconnected at the starter right? To turn things off while starting a lot of circuits rely on ground through the starter solenoid.

[glennspiegler]

Rick:
Don't know how to draft the answers to the questions like you did. So these are in response to your comments in order.

Yes it was with the yellow terminal 50 wire disconnected. Didn't know it went to the DME also. Thought it went to the ign switch and was energized when the ign switch was turned on.
Agree I could have a problem with the new switch.
Glad I don't have to swap out that starter again. Did it 3 yrs ago.
Yes the ign on position causing 12.6v at yellow term 50 wire was with it disconnected.
Tonight I will tap into the yellow wire behind ign switch with a posi-tap and run to positive battery, if it starts it is the switch, if not the yellow wire from ign switch to solenoid is bad. Sound right? Thanks for helping me to understand this. Glenn

[rick-l]

I'm betting on the switch also but since you just replaced it a couple of months ago this gets deeper and deeper.

[3.2 CAB]

I had a no start condition with my 3.2, you could try to start it, but the yellow wire would show 12+volts prior to cranking it, but just as soon as it was tried to start, the yellow wire, had deteriorated so much over the years, that it would not deliver the current to make the solenoid engage and allow the starter to actually crank. I replaced the yellow wire from the ignition switch all the way to the solenoid. I have not had that type of a no start problem since. This was done 2000 or 2001 I think. I posted a thread about the entire testing and the repairs at the time. Good luck, Tony.

[glennspiegler]

OK, think it is solved. Tapped into the yellow wire behind the ignition switch and ran it to batt pos. It turned over fine. Therefore my new switch was defective. What I don't understand is, I had 12.6v at the yellow wire by the solenoid with this switch on start. Why was the voltage from the battery more successful than the 12.6 delivered from the switch running down the same wire. Really appreciate all the help. Glenn