Hard start, no start, car shuts down traveling down hwy

Tiny
GOOMBAH8747
  • MEMBER
  • 1998 MERCEDES BENZ 500SL
  • 114,000 MILES
The car sometimes will not start after driving for a while, turns over and acts like it wants to but won't start. Sometimes it will start and then immediately shut off. I'm thinking it's a security key recognition think as I have been able to get it going by locking and in locking several times by the key fob, I try all kinds of combinations of locking trunk and unlocking by key, opening and closing doors, very frustrating. Yesterday it actually shut off going down the hwy, had to do emergency move to get over off the road. I eventually got it started but don't know what worked other than locking and unlocking. Possibly an egnition prob that overheats and needs time to cool down like magnetic pickup in distributor? Maybe I was vying time by locking and unlocking thinking it was a security recognition issue when it is an electrical prob? I do smell an electrical burnt smell but cannot locate a problem under hood which no one with out proper equip could. Can you relate any previous issues with other cars that may direct me in the correct direction? Any recalls with this type of problem? Key fob works so battery is good
Wednesday, October 9th, 2013 AT 12:59 PM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
If it was the anti-theft system, I would think the light would come on to identify it. Also, there are no related recalls. Let me ask you this. When the engine dies and doesn't restart, have you checked to see if there is proper fuel pressure to the engine as well as a good spark to the plugs?
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Wednesday, October 9th, 2013 AT 6:05 PM
Tiny
GOOMBAH8747
  • MEMBER
  • 4 POSTS
No I have not checked for fuel pressure or spark yet, the car will start after it's been sitting for a while. What light are you referring to as to anti theft?Wfat about the burnt elect smell I'm getting?This problem occurs intermittently and not when I have equip available to diagnose. An example is when I left a mcdonalds drive through and made a let turn into the turning lane, the car died on me and there I was stuck in the turning lane. After unlocking and locking using the key fob and opening and closing the trunk lid and doors, dancing a gig around the car and cussing profusely and almost running the battery down cranking over and just after I had called aaa to flatbed it home did it start. It got me down the freeway approximately 20 mikes then died while driving about 70 in the #3 lane and I got off the road. After about 10 mins of sitting and doing the aforementioned procedures, it started for me and I was able to get it home, approx another 40 miles. After I got home I shut it off and it restarted. Go figure--- I am frustrated as to where to start and it seems I will have to carry a plethora of tools with me if and when it happens again. My other half refuses to drive the car and I do not blame her. Thus the inquisition to you folks, hoping that this problem has occurred with someone else I'm the past and someone in your scope of brotherhood of mechanics can shed some light---I've been thinking that it is a security problem with the unit that reads the key fob, now I'm thinking that maybe an elect part nay be heating up and breaking down then when it cools, performs as should? Your thoughts?
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Thursday, October 10th, 2013 AT 5:44 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
There are so many ignition components that can cause issues. What makes it tough is you smell something. That makes it a guessing game for me. Have you ever had the computer scanned for trouble codes?

As far as the security system, there is a light on the dash that should turn on if there is a problem with the anti-theft.

As far as the other half, I can understand not wanting to drive it. There has to be a lot of apprehension.
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Thursday, October 10th, 2013 AT 9:21 AM
Tiny
GOOMBAH8747
  • MEMBER
  • 4 POSTS
I'll check the owners manual for which light to look for, all the lights go on before starting so nothing is glaring at me to figure out, thanks, I just don't want to invest money I do not have on parts that I might not need, I'm sure you understand, I just wish I knew what I was looking for ----if a part is broken than I can find it these intermittent problems are crazy, you almost need a Chrystal ball/--
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Thursday, October 10th, 2013 AT 10:24 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
I couldn't agree with you more. Today's cars have become nightmares to work on. Let me know what you find.
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Thursday, October 10th, 2013 AT 5:03 PM
Tiny
GOOMBAH8747
  • MEMBER
  • 4 POSTS
Thanks for your time, your thoughts on engine elec, is there a unit that drives the dustributor, besides the computer? I'll take the car to Mercedes and ask if they can upgrade computer or check various components, any suggestions! On what to check !
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Thursday, October 10th, 2013 AT 7:25 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
I wish I could be more help. As far as taking it to the dealer, have them check the fuel pump pressure to see if it is within spec.
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Friday, October 11th, 2013 AT 6:56 PM

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