How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Eric Your Own Question
Eric
Eric, Automotive Repair Shop Manager
Category: Mercedes
Satisfied Customers: 29954
Experience:  20+ yrs. experience as repair shop manager and technician.
3195632
Type Your Mercedes Question Here...
Eric is online now
A new question is answered every 9 seconds

I have a 1989 Mercedes 420 sel that is extremely hard to

Customer Question

I have a 1989 Mercedes 420 sel that is extremely hard to start when cold. I replaced the cold start injector but it made no difference. Once it's started the first time it will start easily and runs great. It takes up to a minute to get it started. it
chugs and runs a little then dies. Go though that a couple of times and it's ready to go.
Submitted: 1 year ago.
Category: Mercedes
Expert:  Eric replied 1 year ago.

HI,

I am sorry that you have not been helped yet. I just came online and saw your question.

Ok, first you need to check the fuel pressure after it has sat overnight for both pressure and for holding pressure. The pump could be allowing it leak down or the regulator could as well. And the ect sensor needs to be tested. An ect sensor with incorrect cold reading will cause hard cold start as well

Customer: replied 1 year ago.
OK, I'll have to get a pressure tester. How do I test the ect sensor and where is it?
Thanks
Expert:  Eric replied 1 year ago.

HI,

Ok, I have attached photo of location as well as the specs for the sensor - you test the sensor resistance at different temperatures. I usually stick in a pot of cold water and slowly heat the pot as I measure resistance and compare to the chart to see if it is within specs

Expert:  Eric replied 1 year ago.

HI,

hmm attachments didnt upload, try this again

Customer: replied 1 year ago.
Thanks very much. I'll work on this over the weekend and get back to you. For testing fuel pressure do u try to start the car or just turn the key on? Thanks much for the pictures
Expert:  Eric replied 1 year ago.

HI,

You want to do both. key on, engine off first, and then engine idling to watch for any unusual fluctuations in the pressure

Customer: replied 1 year ago.
Got the pressure tester but can't figure how to hook it up. It has about 25 different attachments but nothing that looks like it works on this old car. The instructions talk about putting the fitting between banjo fittings but there are none on this car. When you disconnect the fuel line it's a flared fitting held in place with a nut. The instructions say to hook it up at the cold start injector. Any ideas?
Expert:  Eric replied 1 year ago.

HI,

To be honest it has been ages since I have hooked one up to this year 420sel. Let me see if I got directions and diagram for this

Expert:  Eric replied 1 year ago.

HI,

Directions are attached

Customer: replied 1 year ago.
Got it. I'll try this tomorrow afternoon.
Thanks
Expert:  Eric replied 1 year ago.

HI,

Ok, sounds good

Customer: replied 1 year ago.
Hi Eric, sorry I haven't gotten back to you. Haven't been able to work on the car since I emailed you last. Before I got your instructions I pulled all of the injectors and cleaned them. They were pretty dirty. THe only difference it made was it does start quickly now but dies immediately. Takes 4 or 5 times before it starts up. I checked the plugs and they are like new.
Expert:  Eric replied 1 year ago.

HI,

Ok, let me know when you are able to check the fuel pressure and what it is