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Old 02-19-2003, 11:58 PM
Posts: n/a
1989 420 Sel Mystery

I'M posting this just to see what you guys think about it. I was talking to my sister who owns a very nice looking 89' 420 SEL and asked her about her car since she was not driving it and told me that is tired of it, here is the problem: driving around the city on the streets, runs fine but any time she gets on the freeway and keeps speeds over 55 mph, after maybe 20 or 30 minutes the car dies and She has to coast for the nearest shoulder in the freeway then let it rest for about 30 minutes, then it'll start again and the story repeats again, so now she drives only on the streets only, and then told me that already took it to a couple of german car specialists? and after about 1,800 dlls. still does the same thing, any ideas? or a good mechanic in the Anaheim Ca. area where to take it? thanks!!. I say; is this a mystery?.

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Old 02-20-2003, 03:23 AM
goldstone's Avatar
W126 Lover
Join Date: Oct 2002
Location: Dutchess County, New York
Posts: 156
What a nightmare!

Be more specific about how it dies, please. Does the engine kick out but the electrical system continue to function? (Does the starter still crank?) How old is the alternator?

Has any fuel line related work/maintenance been done prior to the first incidence of the problem (fuel pumps, fuel filter, etc.)?

Are there other symptoms/factors your sister can relate? (And what did the German car so-called experts check-out for that $1,800 she dropped?)

I have the same car and have never experienced anything remotely like your sister's recurring nightmare.

Please, keep us apprised!

1991 560SEL-Euro (185,000 miles)
1989 420SEL (Retired from daily use at 325,000 miles; Use as donor vehicle)
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Old 02-20-2003, 04:24 AM
Registered User
Join Date: May 1999
Location: New Location: VA Palo Alto HEALTH CARE SERVICES
Posts: 109
check or replace fuel pump relay...
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Old 02-20-2003, 12:57 PM
AWS AWS is offline
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Join Date: Feb 2003
Location: Bloomington, IN
Posts: 20
I seem to think similarly to the others in that this is fuel related. Fuel pump relay is a good place to start.

It would definitely help to know what work has been done so far.

1992 190E 2.6L
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Old 02-20-2003, 02:08 PM
cam69ss's Avatar
Turbo Member
Join Date: Sep 2002
Location: Worcester MA
Posts: 291
ignition or gas problem. Maybe a week coil??
1969 RS/SS Camaro Conv. L-89 Alum. Head 396 375HP 4-spd

1987 GNX #419, 2002 RX300

FS: 1934 Ford Street Rod, Blown 383 $48,500 Firm
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Old 02-20-2003, 08:40 PM
Registered User
Join Date: Jan 2003
Posts: 140
I had a great mechanic in Santa Monica if you can make it there. His name is Rick and the service is called Pacific Motors (only Mercedes cars). Call him at 310-450-8129.

Also, how do you guys add the termometer to your signature at the post? I'd love to add one to mine.
1984 MB 300D Turbo Diesel W123 Sedan 132K
1987 MB 300D Turbo W124 Sedan 295K
1983 Porsche 944 104K
1989 Audi 80 Quattro 180K
2002 Audi A6 3.0 Quattro Avant 49K (Wife's car with warranty )
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Old 02-21-2003, 02:38 AM
Posts: n/a
add to the mystery

OK, guys I didn't want to put you to sleep with the whole story on the 420 SEL, but here it goes: My sister bought this car about a year ago from an ad in the paper for 8,900 dlls and it looked so nice(black on black leather and chrome rims) that she didn't even take it to a mechanic, (love at first sight) it has about 120K miles then after about 11 months the problem started and she never told me about it , she drives about 80 miles every day to work both ways, and every time the engine dies, it cranks strong, electricity is there and everything else, but it won't start, then she waits about 20 to 30 minutes and the car starts again. Then, about the 1800 Dlls she got charged, I asked her to read to me what it says on the bills, and what they replaced is mostly smog related items(catalytic converter, belts, some gaskets, those little valves for smog, etc.) then, when I told her that all that had nothing to do with the original problem she came out with another story about not passing the smog test (you know this is Calofornia) and still wont pass it, after all those replacements. So there it is, the whole story on the 89' SEL, and I too, think, that the problem(engine dying) is related to the gas pump, filter,or coil,but last she told me is that she found a super mechanic close to her house.......... I'll keep you posted ..........
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Old 02-21-2003, 12:45 PM
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Join Date: Aug 2002
Location: La Quinta, CA
Posts: 271

any time she gets on the freeway and keeps speeds over 55 mph, after maybe 20 or 30 minutes the car dies and She has to coast for the nearest shoulder in the freeway then let it rest for about 30 minutes, then it'll start again
I had this same problem years ago with a 1968 Dodge Charger. The problem was water in the gas tank. Seems the water had gotten in the tank with a bad load of gasoline. After the water sat on the botton of the tank for who knows how long it it started to clog up the in-tank fuel line access opening. When the car was on the freeway the suction from the fuel pump pulled hard enough on the bottom of the tank that it would pull the glob of water over the intake and cut off the fuel supply. The car would die....after sitting for 20 to 30 minutes the glob of water would recede from the intake, gas would go to the engine, and the car would start again. We found the water in the tank by using that grease-like stuff that turns red when it is in water. The solution was to remove the gas tank, completely clean it and remove some light rust that had formed. We re-installed the gas tank, filled it up with fresh gas.....and no more problems. I might add that when water sits in the bottom of a gas tank it becomes almost "jelly like"...that was what was restricting the gas from going into the fuel system to the engine.
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Old 02-21-2003, 05:47 PM
Thomaspin's Avatar
Join Date: Jun 2001
Location: CA
Posts: 531
You can check if it's the fuel pump relay for no cost

Go this this thread and look at the email from Reinhard Kreutzer with the photo - that will help you identify the FPR.

Pull the FPR and short teminals 7 & 8 on the socket with a piece of insulated wire. The fuel pump should start to run - you will hear it. Drive the car for the Time to Failure and see if the problem recurs. If it does, replace the FPR with a new one.

Pull your shorting wire if you park the car - it will continue running the pump and drain the battery.

As for smog, have you tried adjusting (or having your mechanic adjust) the fuel mixture to the lean end of the range before the test?
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Old 03-06-2006, 03:28 PM
Registered User
Join Date: Jan 2001
Location: Cedar Rapids, Iowa
Posts: 63
My '89 420 SEL had the same problem and it was the coil. Drive for a while and it would quit and not restart until it cooled. It took two tries to get the correct coil, too, as the parts books seem to be confused.

'89 420 SEL "Moby Dick"
'30 Ford Coupe
'31 Ford Slant Windshield Town Sedan
'33 Ford Pickup
'34 Ford Pickup
'01 Honda Passport
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