I need to know what might be wrong with my husband's 1989 420SEL Mercedes Benz


Asked by Apr 25, 2012 at 09:49 AM about the 1990 Mercedes-Benz 420-Class 4 Dr 420SEL Sedan

Question type: Maintenance & Repair

My husband's 1989 420SEL, keeps shutting of even
when you are Driving,  what could it be.

6 Answers


Does it start right back up or do you have to crank a while? Fuel pump relays are a big culprit on those 126 models.

1 out of 1 people think this is helpful.

Abou how much will a fuel pump relay cost for this car ?

1 out of 1 people think this is helpful.

Fuel pump relay will be around 75.00 depending on geographic area. What I usually do is open up the one I have and see if solders are burned. If they are then replace the relay. But I'm handy like that. You may have to spend time and money with someone who can do this, but for a 75.00 dollar part it may not be economically feasable. The best advice is not to throw parts at it but have it diagnosed properly. I realize it can be costly but would you rather spend it on diagnosing and replacing what is needed or on parts and labor you do not need? Shops will not stand behind a customers" self diagnosis" which means if you tell them to do something and it does not fix it, you do not get your money back. Hope this helps.

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Best Answer

Thank you so much


If it is not the relay the more likely fault is the fuel pump, bearing in mind the age of your car thats 23 years worth of fuel that may have been poor quality or water contaminated. I had an old Volkswagen with the same problem this was due to a corroded fuel filler neck allowing rain water into the tank. Also another fault i have come across is a partially blocked fuel filter. Mercedes recommend replacing the fuel filter every 36.000 miles on these models.

1 out of 1 people think this is helpful.

I agree with the above posts - first replace the fuel pump. Then I would check the fuel line and filter for clogs or pinches; Next: check the relays.

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