400E hard start issue
06-24-2010, 09:40 AM
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400E hard start issue
Symptom: More and more over the last month my 1992 400E has had a hard time starting regardless of temperature. It turns over but to get the car started I have to pump on the gas a number of times to get the car started. It's scared me a couple times thinking I was going to get stuck somewhere. One other interesting thing I found out yesterday though was that if I turn the car to the on position for 10 seconds (which of course allows the fuel pump to run for a bit) I can then go to start it and it starts without me pumping it.
My tests: I did a tuneup first.
1) I looked for the OVP relay. Apparently after reading posts there is NO OVP relay for my 400e and even I called the MB dealer and they could not find one on their parts look-up. But, after reading posts, under the hood in the black box on the passenger side there are some fuses to check and I checked all three. All good.
2) My other suspect is a fuel pump relay. I read to check on my drivers side engine bay right behind my fuse box. I found the green relay which I suspect is my fuel pump relay. Interesting though it does not have the fuse in it though like ones I have seen.
If anyone can chime in with ideas that would help me. I think I am getting closer to figuring this out and am about to go buy at least a fuel pump relay today for $22. The only I am doubting this relay is bad is because the car does start and runs fine afterwords.
My tests: I did a tuneup first.
1) I looked for the OVP relay. Apparently after reading posts there is NO OVP relay for my 400e and even I called the MB dealer and they could not find one on their parts look-up. But, after reading posts, under the hood in the black box on the passenger side there are some fuses to check and I checked all three. All good.
2) My other suspect is a fuel pump relay. I read to check on my drivers side engine bay right behind my fuse box. I found the green relay which I suspect is my fuel pump relay. Interesting though it does not have the fuse in it though like ones I have seen.
If anyone can chime in with ideas that would help me. I think I am getting closer to figuring this out and am about to go buy at least a fuel pump relay today for $22. The only I am doubting this relay is bad is because the car does start and runs fine afterwords.
09-13-2010, 12:54 PM
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final outcome
I just wanted to follow up on this for others to benefit from my experience. I ended up replacing the fuel pressure regulator and after that the car started up just fine after that. I have started the car about 30 times since without any problems. Thanks guys.
On another note....I left the regulator hole open for a day while getting the part and I think the fumes or gas had gone into my air flow meter and toasted it. I idles rough. I tried to clean it first using air flow meter cleaner. Of course I did check all vacuum lines but all are fine. I then unplugged the AFM and the car idled fine after that. Now it's time to look for a good air flow meter.
On another note....I left the regulator hole open for a day while getting the part and I think the fumes or gas had gone into my air flow meter and toasted it. I idles rough. I tried to clean it first using air flow meter cleaner. Of course I did check all vacuum lines but all are fine. I then unplugged the AFM and the car idled fine after that. Now it's time to look for a good air flow meter.
