No gas?? Wont keep running! HELP!
 

Hello,

Here's the story 1990 300CE M104 engine 180K miles.

Car was running great then while driving started running really rough then died. Had it towed home. I will run for a little while 10-15min then stall out, with out being able to restart. I have spark, I can hear the fuel pump buzz before it starts. If I pour gas into the intake it will start again and run for a while. I cracked open the fuel line at the fuel distributor and its under pressure and apears ok, fuel present. It definately appears to be fuel related. I put in some dry gas and fuel injector cleaner.

I am at a total stump. Any input is greatly appreciated. Thanks in advance!

Fuel pouring from the feed line is not enough. System pressure should be around 70psi and if its not about 48 it will not open the injector even if it makes its way through the distributor.

Check your system fuel pressure.

1989 300SE Starts and Stalls
 

My problem sounds similar to the 300CE, except that this MB starts and runs for 5 seconds and then dies. It starts again, and dies again, etc.

I do not have a fuel pressure gauge, but there is strong pressure on the inlet side to the fuel distributor. Curiously, if I loosen the return line and let it leak fuel, the engine runs, but will not idle.

Does this sound like a low fuel pressure problem, a clogged injector allowing the pressure to leak down, or "something" causing the fuel to shut off???

All comments greatly appreciated.

GB

"Strong" is not a proper fuel pressure reading. Fuel pressure readings are in "BAR" or psi. Either buy, borrow or steal (not an approved acquisition method) a fuel gauge and see what the fuel pressure is. 10, 20, 30 psi may be described as "strong", depending on a persons opinion of what feels "strong", but none of these pressures will allow the engine to run. You have to know the number.
Stop pouring gas down the throttle body, you can ruin the engine that way.
My guess would be a bad fuel pump or a bad MAS relay, which takes the place of the fuel pump relay on this car. Best get it checked out properly before buying any unneccesary parts.
Gilly

Thanks for all your replys.

Do you think it could be something as simple as the fuel filter. I have had the car about 5 years and have never changed it. The car seems to be running now but will stall out eventually (20 minutes or so). I was under the impression when a fuel pump went, it was dead with no return.

Any thoughts is appreciated

Definitly could be the filter. Since you are overdue, and its cheaper than a fuel pressure gauge, I would start there.

OK I changed the fuel filter and it certainly improved.

Now the car will idle and drive under light to normal conditions. If you attempt a moderate to hard acceleration or encounter a hill on the highway, the car bogs out. If you let it rest for a minute at an idle you can complete your journey till the next hill.

Do you still think its the fuel pump or maybe I got a bad tank of gas? I was told fuel pumps are not intermitten problems they either work or die. Is this true?

I will call the mechanic today to make an appt to bring it in. I just hate to pay him for something stupid I could do myself.

Any input is greatly appreciated. Thanks again for all your advice.

Fuel pumps that don't run when powered are obviously bad! BUT! Like al mechanical things failure comes in many ways.

The fuel pump does not control the pressure but is designed to work at a pressure range. If the fuel delivery were to become pluged the pump would hurt itself if the pressures possible were allowed to happen (fuel is not compressable).

There is an internal check valve that by-passes when (or if) this ever happened. Its pressure is relatively close to the working pressure (higher by maybe 25%). If this valve leaks, sticks or is broken the fuel just gets pumped in circles.

There are many ways that the fuel pump can become the fuel pressure regulator. When this happens fuel control becomes impossible. All K type systems require precise, constant fuel pressure to funtion properly (or at all).

My 190E had similar problems to yours. Rough running, lack of power but only intermittently. The advice I was given was to change the filter then the pump. The filter did nothing but changing the pump cured all the problems immediately.

Thanks for all your input.

I made an appt to bring it in to the mechanic for a check. He has a fuel pressure gauge he can verify the output of the pumps with. Then I will know for sure. There are 2 pumps at over $200 each and I have been told to replace them both. I would feel better verifying thats the problem before I spend the money and its not.

Thanks again for all your help!

Hi,

It has been brought to my attention that the folowing statement me be taken offensive.

"I will call the mechanic today to make an appt to bring it in. I just hate to pay him for something stupid I could do myself. "

I want to apologize to anyone that may have taken offense to it. The statement refers to my belief that a mechanic or someone of higher knowledge has a higher value to thier time than that of myself. No disrespect was ever meant and I hope non was taken. In any future posts I will be more conscious of my wording.

Thanks again for all your help.

Well thought I would give you an update. The mechanic confirmed the fuel pumps have died. He stated one is completely failed and the other is weak.

The only fustrating part is the cost of $700 bucks to fix it. Partsshop has the pumps listed for $202, he insists they will not fit my car and the pump required for my car retails for $315 and he is selling them to me for $260 each, plus 2hr labor to instal. It kills me to pay so much for something I should have been able to do myself.

Sorry for wimpering, I just had to vent. Thanks again for all your help.

I usually don't like to speak about others business style. But, there would be no reason for a part from fastlane not fitting. What kinda cra* is that. I purchase from the same source as fastlane and the pumps will be Bosch pumps just like MB would sell.

AND the current MB list is $264. He is really giving you a deal.

I have no problem with a business selling at any price they choose, but lieing about it, I have a problem with.

If $$ are an issue, you can always try salvage. They have a huge network set up. I once bought a starter for my '75 300D. I went to a salvage yard between work and home (10 years ago). He found the part on the computer from a yard in Texas. I got the starter a couple of days later. It came off an early '80s 300D and worked just great.

I had no idea the car was supposed to crank that fast. I was used to the sloooowwww crank my car always had since I bought it. After the new starter, I could start it in sub-zero temp without the block heater.

Sorry, I got a bit off-topic.

Dean:
You shouldn't be held over a barrel to get it fixed. If you feel qualified to do the repair, then just pay the shop for the diagnosis and take it home and replace them!
Gilly