1990 300CE won't stay running - Page 2 - PeachParts Mercedes-Benz Forum

Frank Reiner · #16 08-11-2015, 12:15 PM

Quote:

Originally Posted by ROLLGUY

Cool! that is exactly what I need to know, thanks. If one of the pumps is not working, would that cause it not to run?

See posts #10 & 11.

ROLLGUY · #17 08-12-2015, 03:20 PM

I did exactly as you said (after reading #10 again, I missed it the first time= duh Richard!), and I found a bad primary pump. The secondary runs fine, and the primary just binds inside when power is applied (at least that is what it sounds like). Now, the question is: How do I replace the pump when the tank is full of fuel? I thought about siphoning as much of the fuel as I can, but that will take a long time. Can I just crimp the feed hose with hose covered long nose vise grips? I have a wrecked 280E, and it looks like they have the same pumps. If not, I have seen plenty of gas 124's in my local yards. Thanks again for the guidance, Rich

lsmalley · #18 08-12-2015, 03:28 PM

Careful on clamping the hoses, especially if they are 20+ years old. If you clamp the hose and it deteriorates you are stuck and will need to siphon anyways. Best to get about 4 of those 5 gallon water bottles and siphon as much as possible, then get under the car and undo the main hose from the tank and get the rest out. Now you can change out the pump and also check the integrity of other components like the hoses in that area and replace accordingly without such an urgency. Might as well do the fuel filter with new copper washers while you're at it if it hasn't been done in a while.

Frank Reiner · #19 08-12-2015, 04:21 PM

Roller:

"Can I just crimp the feed hose with hose covered long nose vise grips?"

The short answer is, yes. The caution mentioned above is worthwhile; I have pinched off older hose than yours without ill effects. The feed hose is quite soft, and seems resistant to cracking; pinching with your fingers and a bit of judgement should stand you in good stead in making a decision. The pinch-off method is the service manual method for pump and filter changes.

Benz Mondi · #20 08-13-2015, 10:38 AM

Unless you are so confident that you've fixed the issues with the MAS, that you are willing to go through all the trouble with draining the fuel and fiddling around with the fuel pump system, I would first get another matching MAS and see what happens. They are not expensive as a good, used, with warranty part. It's also good to have another one for the in-car emergency fix kit anyway, since a bad one will strand you. Remember these parts are over 25 years old now.

For my 90 300E, my MAS went out and my a/c clutch wouldn't engage. Spent $30 for a matching one and all was cold again. It even had a more stable idle!

Good luck.

ROLLGUY · #21 08-13-2015, 12:57 PM

Quote:

Originally Posted by Benz Mondi

Unless you are so confident that you've fixed the issues with the MAS, that you are willing to go through all the trouble with draining the fuel and fiddling around with the fuel pump system, I would first get another matching MAS and see what happens. They are not expensive as a good, used, with warranty part. It's also good to have another one for the in-car emergency fix kit anyway, since a bad one will strand you. Remember these parts are over 25 years old now.

For my 90 300E, my MAS went out and my a/c clutch wouldn't engage. Spent $30 for a matching one and all was cold again. It even had a more stable idle!

Good luck.

Been there, done that. I found a bad primary pump, and just got finished draining the tank. I will probably replace the hose and filter while the tank is empty. I did use the hose pinch method to start with while I hooked up a hose to drain the gas into containers. I am off to the wrecking yard after lunch to get another pump. I will bring a cordless tool battery to check it while I am there. The pump off of my wrecked 280E was a little larger in diameter, so it will not work....Rich

ROLLGUY · #22 08-14-2015, 05:26 PM

I got the Pick-A-Part pump installed, put four gallons of fresh fuel in the tank, and it runs! Other than a squeaky belt and a couple lights illuminated on the dash, it seems to run good. The lights are for the washer fluid level and one other that has what looks like an oil can with wavey lines under it. It is either the level or temperature of the oil or coolant, I am not sure which. If it is a temp warning light, something is wrong with the wiring or a sensor, because it has not even warmed up yet! The coolant and oil levels are good. Now I just need to get an operating permit to get the car smog tested, and then register and drive it! (insuring it of course). Thanks to all especially Frank for your help....Rich