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  #1  
Old 07-01-2011, 05:03 PM
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Starts when cold but not after that!

I have a 90 300SEL that has something wrong and I need to know where to start. So if someone out there has an idea please let me know. I have had trouble for two years now with my 300. It ran perfect until a couple years ago when I got it out of storage. It started right up and idled perfect. I jumped in to go for a burn and when I stepped on the accelerator she stalled and that was that. I did manage to get it going after awhile. I didn't run it last year because of this and ended up putting it away for the winter. (it did run after getting it going) This year when I got it out again it started up and I drove it not very far to home. Shut her off and no start. The car only has 144k klm (80k mi) It has good plugs wires all that. It is definitely fuel related I think. I think the inj seals are leaking a bit but not sure that would effect the startint that much. How can I see if it is getting fuel? I removed a line from the injector and rolled it over and no fuel came out. Can I test the pump somehow? Or just check if it is getting fuel? It has a MAS sensor, I have read that sometimes that will give these symptoms. I dunno, there must be 25 fuel lines under there. Does the injector pump need a minimum voltage to run? I seem to have only 12.5V at the battery at this point so maybe it is not charging. Would that do this?

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Old 07-01-2011, 05:23 PM
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Have you checked the coil ?
It can idle but give out when the engine is put under load.. not have enough spark to spark the spark plugs...
Just something to make sure it is ok from that side of the equation...
and be sure the grounds and all battery connections are clean and tight..
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Old 07-01-2011, 05:25 PM
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Take the air cleaner off (3 nuts, 2 are obvious, the 3rd is on the drivers side facing sideways, only need to loosen that one up, then take the whole aircleaner off).
You will see the fuel supply line, part metal, part rubber, it has a little metal bracket on it that "leans" againt the air intake housing. Loosen that line up and see if there is any fuel pressure, don't let it squirt you in the face.
Most common cause is a bad fuel pump relay, that is more towards the passenger side, between the double firewall. Black relay, medium size. You will see 2 similar relays, it's NOT the one that says "Klima", it is the other one, will say "6 ZYL" and also list an RPM, the rpm listed is the safety cut-out rpm.
See if you have pressure and report back. Oh if you want to double check fuel delivery it would be ok to turn the key to run with the hose disconnected.
If no pressure we/I can instruct on how to "jump" the relay and see if you can get the car running, that way you can be relatively sure the relay is the actual problem.
Gilly
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Old 07-01-2011, 09:35 PM
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I will do that, It may be the coil I guess, I can test that though. Usually a coil will run for a little while longer, I can put a spark tester between the plug and the coil and see if there is spark but I really feel it is fuel related. Also no one mentioned if they thought the low voltage might effect things. I can't see it myself but anything is possible I guess. I replaced the voltage regulator in the alternator last year but still not charging I don't think.
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Old 07-01-2011, 09:45 PM
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Well it's easy enough to see if you have spark.
You really think it's fuel related but now are off on this "spark" tangent. You can also pull a plug to see if there is fuel accumulating on the plug, which would both verify you are getting fuel (if the plug is wet) and that there is no spark (because the plug is wet). If the plug is dry and no smell of fuel you can then assume no fuel.
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Old 07-01-2011, 10:54 PM
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Open your hood at night in the dark and rev it up... see if you have any shorts...it should NOT look like the Northern Lights dancing around..
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Old 07-02-2011, 07:48 AM
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I would have to get it going to rev it up, There lye's the problem
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Old 07-02-2011, 09:58 AM
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As the OP stated, the car has an MAS, no fuel pump relay, but a failing MAS could be producing the same symptoms that Gilly described for a fuel pump relay. Incidentally, if you know that the voltage reg is not charging properly, why not just replace it and remove that from the equation? A regulator is inexpensive and easy to install.
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Old 07-02-2011, 11:45 AM
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I did that but still not charging, So I have to take it off and get it checked out. But I really can't see what one has to do with the other.
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Old 07-02-2011, 01:04 PM
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Is there anyway to test the MAS sensor? I removed and put it back in to make sure contact was made.
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Old 07-02-2011, 08:44 PM
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The MAS is not a sensor, it is a relay that took the place of the fuel pump relay, my bad.
This car has no MAS (or MAF, mass airflow sensor), it has the flow meter.

You can simply try jumping power and ground to the fuel pump, see if the pump seems to operate and then if the engine starts. You might have 2 pumps, jumping one should affect both.
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Old 07-15-2011, 09:12 PM
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Well, new alternator and also new OVP relay, F pump is working as I can hear it. If it is cold it starts up and will run for 5 minutes or so then stop. Then it will not start again untill it sits for awhile
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Old 07-16-2011, 04:49 PM
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Change the ignition coil !!!!! This won't be the first one to give out.
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Old 07-16-2011, 05:57 PM
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well I thought of a coil but I tested it with an ohm meter, 3.5 between the studs and 9500 from stud to high tension wire, butttt that is not under load
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Old 07-19-2011, 09:11 AM
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Can I use any coil? I have a round Bosch coil already and would like to know if I can test with that one instead of buying a new one. If that is the problem then I will buy the correct coil for her. Anyone know the answer to that?

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