Hi
My 300TE always needs two starting attempts to fire up. It is very consisted in doing that.
The first start attempt sounds like it almost wants to fire up but then falls back in just cranking.
After a second start (or continue first attempt for a 3-4 seconds) it does fire up.
Every day the same.

Anybody an idea where this could come from?

 

i had the same problem but with my w140. I searched the forums and the members told me to replace the Fuel Pressure Regulator. After i did that my car will fire right up on the first crank. Its the cheapest route i went with before i did anything else and the pasts cost me around $55. Here is what the w124 should look like.

 

thanks
checked prices of this but cheapest i found (uk) is 75 pound for a used one. I will keep looking and give it a go.

 

have sourced a part. Will update when it is fitted

 

Good, because I've got that same issue with my 91 300TE. I've replaced just about everything by now as part of scheduled maintainence, and yet, still the double start move needed.

 

Same here but the mb tech already advised me I need cap/rotor and spark plugs. 90 300E. Will update when I get these 2 things done if this does the trick.

 

placed the part...same ...stil have to start twice.
Although I replaced it with a used part so there might be a chance that this part is faulty too.
Any other ideas?

 

1)use a new part.

when my rotor and cap was old it caused erratic running and occasional backfires.

2)check to see if the is any trace of green inside the cap and on the arm, if yes, then change/clean

 

One thing.. Do you ever smell gasoline outside or inside your car when you have it parked?

The rubber fuel hose from the back end of the fuelfilter has a tendency to get soft and crack up after years of transporting fuel. If you got just a tiny leak in this hose the fuelpressure accumulator can't keep up the pressure, and you will have that exact problem that you describe above..

If the hose has got a hole it will drain the hose empty of fuel when you shut your car, and the fuelpressure will be gone. The short burst of the fuelpump on ignition will not be enough to get the pressure back up to its full.. Just a thought in hope to help you resolve your problem.

 

Define "erratic running". My car backfires all the time, but for the life of me I can't figure out what's causing it!

 

I always start my car the same way; turn the key to the ON position, hold for a count of two (it turns the fuel pumps on and you can mask a faulty fuel pressure regulator problem by doing this) then start. Always starts immediately. A quicker start also builds up oil pressure faster, reducing wear on bearings and such.

 

I have had this problem on other fuel injected cars and to diagnose the problem I found it helpful to look at how the system functions.

To ensure quick starts, fuel pressure must be available immediately upon cranking. To do this, manufactures generally do two things.

First, they maintain fuel rail pressure using the pressure regulator and a reverse flow check valve (see pic). When the car is not running, the regulator does not permit fuel flow to the tank via the return line and the check valve does let fuel leak back via the feed line. Failure of either will result in a pressure loss after engine shutdown. The regulator you know about. The check valve can be a separate component along the fuel line or can be integral part of the fuel pump and/or fuel pick-up.

Second, the fuel pump is usually run as soon as you turn the key to the first position before you turn it further to start the actual cranking. This helps compensate for any bleed-down that does occur. Note that for the pump to continue to run beyond approximately 2 - 5 seconds, the pump control circuit needs to get an "engine run" signal which only occurs after the engine is running and for some cars, during cranking. This is done for safety so that fuel does not spill through ruptured lines in an accident.

It sounds like your car is not maintaining or building fuel pressure fast enough. The proper way to diagnose this is with a fuel pressure gauge. MB provides a fitting to connect one so you can observe the pressure under the above conditions.

If you don't have access to a gauge, perhaps you should check the following.

On my M104 engine the fuel test point is a schrader valve. If you have then same, you can do a rough test for pressure. With the engine COLD, start it at let if run for about 15 seconds. Stop the engine and let stand for about 10-20 minutes then remove the protective cap on the fuel test point. Use a small screwdriver wrapped in an old rag to gently press on valve stem. Wear safety glasses and be aware that gas may spray in any direction (hence the rag). No need to drain the line, just verify if you have static pressure. The presence of pressure points to an electrical issue. No pressure = regulator or check valve.

Does the car take two tries on a re-start after the engine has recently been shut down? If so, this points to a significant pressure bleed issue.

Try turning the key on, but not to "crank" for 2 seconds, then off and immediately on again (but not to "crank"). Then immediately try to start. Does it still take two tries? If so, this points to an electrical issue (pump pre-start prime not occurring).

For what it's worth,

- FD

 

weel thought i follow up one of the advices to check rotor and cap.
Finanily in front of my car, airfilter about to be taken off: "this car has electronic injection, silly me!"
Finally got back to this thread and saw a large amoutn of useful replies to my suprise. Thanks all!!
I will start with taking a look at the fuel hoose

 

Hi Floodydust,
the car does not need a second start when it has just been used. Although it does not start at the first crank but that is maybe to much to ask
i tried what you suggested, switch the key a couple of times to run the fuel pump. It still needed two starts (or a very long single start)
So, this could then be your suggested electrical problem. You can here the pump running. What is the 'pre-prime' you mentioned?
thanks

 

By pre prime my guess is he means the pressure build up by the fuelpump on ignition. When you turn your ignition on to full but not to crank, the fuelpump runs for aprox 2 sec to build up fuelpressure in the fuel line, this pressure may not build properly if you have a leak in the fuel line.

Most effective way to look for such leaks would be to turn the key to ignition for a few times first, then go under the car and look for wet hoses and smell for gasoline.. If there is no smell of gasoline present you could rule out a leak being the problem. Because the pressure by the pump would spray the fuel out of the tinyest hole, leaving a distinctive smell of fuel in the area.

And.. don't smoke while doing this!

 

Amen. Did that when my old E30 developed a leak.

 

I dont know if someone did mention it already but maybe your fuel pumps are tired and not giving enough fuel pressure? did you ever changed it or even tested it?
Fuel injectors...ever taken out and cleaned or changed?

 

been to teh garage with it.
The checked stuff and could not find anything...yet
The also suggested injectors. As a start I have now got fuel cleaning stuff in my tank. Will see how that goes.

 

the fuel cleaner seems to have done the job. It starts great now
thanks everybody!

 

keep an eye out for the injectors. You may find that the fuel cleaner to be just a temporary fix.

 

would proper cleaning be good to do? And how do you do clean injectors?

or when is repolacement required, do you know?

regards

 

finally got new injectors installed: no chance :-(
what you suggest next?

 

good news! solved it :-)

yesterday suddenly no starting at all, dead battery.
cause was a poor battery. Battery replaced and ....starting problem solved to. It fires up now immediately.
so at was just not enough amps to get it going.

case closed!

 

My case is still open. It wouldn't start at all today. Now my SA at Globe Motor Car back over the summer told me I needed 2 fuel pumps. He said 1 wasn't pushing any pressure and the other was well below spec. They were going to charge me over a grand. Whateva. It would start but it took me more than 1-2 turns in ignition. Now it is dead. I did smell gasoline when I turned the ignition. Enough to smell up my garage. I am hopeful that this is my only issue. Maybe for a car with 133k I may need cap and rotor as well. That's what I thought was my original problem in starting in the first place. Stay tuned.

 

hmmm that is bad
i think i need to look at distributor too as it makes quite a ticking noise.

...i do have a new challange :-( leaking coling fluid dripping of the fywheel house. Looks like comming from back side of block. Difficult to see as head board is very close to engine. There is one hose pipe there ..or gasket