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Old 02-25-2012, 11:53 AM
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Strange Starting Problem 72 280SE 4.5

I have a rather strange starting problem. My car is a 72/73 280SE 4.5.

After sitting for awhile (this could be a few hours or a couple months) I will turn the key to run wait for the fuel pump to prime for a few seconds, it then clicks off and when I turn the key to the start position I will hear a relay click but the starter does not crank. I can repeat this many times, what solves the problem is turning the key back to off and then swiftly/without stopping at the run position turn the key all the way to the start position. It will then crank and start just like it should. Any ideas?

+I have tried moving the gear lever through its positions, trying to start in neutral, etc. and no change in behavior.

+Also if I am using the car regularly (short trips) etc. I can turn the key to run, wait a few seconds for the pump to prime and stop and then turn the key to the start position and it works fine…but if the car sits between trips for more than a few hours generally you again will have to turn the key more rapidly to start to have the starter engage and crank.

Thanks
Jason

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  #2  
Old 02-25-2012, 02:50 PM
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I had something similar a while ago, but not exactly. Search for a thread on "wiring or starter problems" that I started and see whether that matches your symptoms.

Clean the master relay cable that connects to the battery. Also clean the large terminal on the engin block behind the alternator. Check voltages when it works and doesnot. I had a voltage drop that sometimes was there, and sometimes wasn't. I think I cured it with the master relay cable cleaning.

Bert
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Old 02-26-2012, 04:50 PM
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My 4.5 did this when the starter was on its way out. I'd have to whack it with a hammer every now and then. The solenoid is on the starter itself, it could be either one; I found a rebuilt starter in the junkyard literally hanging on a w126 that someone pulled the trans and engine from. It was rebuilt within 2 years of me pulling it so I knew it had to be worthwhile. It was!
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Old 02-29-2012, 06:23 PM
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Thanks for all the suggestions, I'll update on how the problem is coming along as I try the different ideas.
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Old 03-18-2012, 09:15 PM
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The germans have the electrical ignition switch wired in such a way that if you pause in run, then go to start it will not crank. Or if the car fails to start, you must return the key to the off position before attempting to re crank the engine over. The idea behind it is that no power will go to the starter if the engine is already running, possibly damaging the starter or ring gear. Pausing to prime the system is not a normal starting procedure. If you insist on priming, just turn the key back to off then quickly turn it to start. On short trips, the system holds "rest pressure" normally and should not need to be primed.

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