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  #1  
Old 05-05-2003, 03:45 PM
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Join Date: Oct 2002
Location: Alaska
Posts: 33
420 SEL Starting Problems + Low idle etc :(

Alright, a few months back I was having a problem with hard starting and the idle was always high after the car had warmed up (>1K). So now after having changed the fuel pump check valves, fuel pump relay replaced, OVP replaced, Bosch fuel pumps bench tested, Fuel filter replaced, techron ran twice; there seems to be no imporevement on the hard start issue and a wierd problem arose yesterday (which took care of the high idle), all of a sudden the car has started having a really low idle. Less than 1K, and it stalls every once in a while (and sometimes this is very dangerous situation), usually when I am braking (i.e. don't have the gas pressed) and comming to a stop at an intersection, the car's idle starts to drop and then it stalls (however it restarts without any problems).
Now the starting issue is that if after running the car, I park and and return after any time greater than 30 minutes it takes about 3-4 long cranks before it starts.
I think it can be anything from clogged catalytic converters to either leaky injectors or clogged injectors or a bad fuel distributor or a bad distributor and rotor.
Any suggestions would be greatly appreciated
Oh and also how many fuel filters do 420 SEL's have and where (I know of only one, which is next to the fuel pumps).
Also the car has 179,000 miles and it is a 1989

Thanks
Sohaib

Last edited by xsohaib; 05-05-2003 at 04:06 PM.
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  #2  
Old 05-05-2003, 06:54 PM
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Join Date: Sep 2001
Location: Austin, TX
Posts: 563
Is it hard to start after leaving it overnight? If not, then you may be experiencing a vapor lock problem. Most likely the fuel accumulator is bad. That shouldn't be causing your stalling problem though.

When was the last time you replaced the plugs? What plugs did you use? Have you looked at the distributor cap lately? How about the rotor? Have you ever replaced the plug wires?

How much history of the car do you have?

Personally, for the starting problem, I'd check the ignition components first since they're easy to test and relatively cheap to replace. Then look at the fuel system.

I'd also check the breather hoses and clean out the idle control valve. This could be one of several possibilities for the stalling problem. You seem to have covered several of the more common causes of this. This thread talks about some of the not-so-common problems:
'87 300E Stalling

Do a search and don't ignore the threads on the 300E. There's a lot of good information in the 300E/M103 threads that apply to your engine also.
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Mike Heath
1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino
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  #3  
Old 05-07-2003, 04:35 PM
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Join Date: Oct 2002
Location: Alaska
Posts: 33
Sorry for not being able to reply but yes, it is exactly THAT, the car is not hard to start after being left over night. It is a hot start issue. About 2k miles ago I had the timing chain replaced and at that time the mechanic told me that my plugs were like new. But I haven't checked the distributor cap or the rotor. Also when my mechanic told me that the plugs were good the car still had the hard start issue. The whole thing started when I gave my mom the car and she put in it some type of gas (I think 89 octane), and it was a generic type of gas. Personally I use only Chevron 92 octane. But do you think something of THAT sort could have caused the problem.

Thanks
Sohaib
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  #4  
Old 05-07-2003, 05:03 PM
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Join Date: Sep 2001
Location: Austin, TX
Posts: 563
I suspect that it's two different problems. The fuel accumulator is still the most likely cause of the hot starting issue, but I'd still check the distributor cap and rotor first.

You've already covered two likely causes of the stalling issue. The fuel pump relay and the OVP. I'd clean out the idle valve with carb cleaner and check the condition of the breather hoses. Those hoses are pretty inexpensive, so if you see anything wrong with one, just replace it. Shouldn't take very long either. Check vacuum lines for obvious problems.

Do a search on stalling and see what else comes up.
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Mike Heath
1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino
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  #5  
Old 05-08-2003, 04:16 PM
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Join Date: Oct 2002
Location: Alaska
Posts: 33
Thanks, I shall be getting to it on sunday. Hopefully I will have it uncovered.
Thanks Again, I really appreciate the help

Sohaib
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  #6  
Old 05-08-2003, 04:44 PM
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Join Date: Apr 2003
Posts: 24
fuel accumulator

Where exactly would the fuel accumulator be located? And also where is the Idle air control valve located on the 420 SEL?
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  #7  
Old 05-08-2003, 05:38 PM
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Join Date: Sep 2001
Location: Austin, TX
Posts: 563
The fuel accumulator is part of the fuel pump assembly and is located near the right rear wheel underneath the vehicle. It looks like this:


It's been awhile since I looked at the 420 engine, but I seem to remember that it's quite similar to my 560. In that case, it's on top of the engine, between the valve covers, towards the front. You might be able to see it with the air cleaner on, but you'll want to remove the air cleaner to work on it. It looks like this:

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1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino
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