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  #1  
Old 12-22-2018, 04:57 PM
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Join Date: Nov 2000
Location: Vernon, CT
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‘99 SL500, cranks, won’t fire over

It’s been a very long time since I have had to ask a question.

My wife’s car cranks very strong, but won’t fire. Pulled a spark plug out and it was bone dry which indicates to me that the engine isn’t getting any fuel. With the key turned, I can feel/hear the fuel pump relay click. So the relay is good.

So if as I suspect it is a fuel pump issue, these cars have 2 pumps, how do they both go bad at the same time?. Though now that I say that, is it possible that one has been bad and the functioning one was the only one providing fuel and it too has now crapped out?

I haven’t gotten under the car here to see/feel if the pumps actually are pressurizing.

Any thoughts/ideas would be greatly appreciated. Oh and I checked the fuse for the ignition coils and it is good.
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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
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  #2  
Old 12-22-2018, 05:22 PM
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Join Date: Jan 2012
Posts: 7,149
The two pump system went away in the early 90's when CIS / K jet was replaced with electronic FI.

The fuel pump is under a fiberglass cover so you need to remove it for access.

Under the hood, locate the fuel pressure regulator at the end of the fuel rail. Listen for this to buzz / squeak for 3 seconds when key is turned on. Since the pump only runs for 3 seconds, have a helper. Also, the throttle body will make buzzing sounds so don't confuse this with the regulator.

I'd give the engine a puff of starting fluid / carb cleaner and see if it kicks. ( Do this after the air flow sensor )

Next step is to look at scan tool data while cranking and see if there is any RPM. If you lose the crankshaft sensor signal, you will lose fuel injector pulse and ignition.
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Old 12-22-2018, 05:32 PM
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Join Date: Nov 2000
Location: Vernon, CT
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Thanks for the additional tips. I only remarked about the two fuel pumps because per the DIY article on this site, on how to remove the fuel pump, it cited 2 pumps for this car’s up to 2002....
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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member
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  #4  
Old 12-23-2018, 11:19 AM
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Join Date: Feb 2007
Location: los angeles
Posts: 590
Replace the crank sensor,or remove it and test it with hairdryer, get it to 200or less degeess, with an ohm meter it should show continuety, or Replace !
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  #5  
Old 02-13-2019, 02:24 AM
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Join Date: Feb 2019
Location: Beverly Hills, CA
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Had this exact issue with my girlfriend's 99 SL500, replacing the crankshaft position sensor did the trick.

It's an incredibly easy job that took me all of five minutes and about $30 off Pelican.
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