New Buzz from Fuel Pump on 72 450 - PeachParts Mercedes-Benz Forum

meltedpanda · #1 04-18-2008, 04:43 PM

SO summer is here started to get out the ol gal , a 72 450
It has the electrci fuel pump back by the tank , under the car. Buzzing like a bee, dont remember hearing that before. No ill effects driving, but hate to be left stranded,.
Ideas, suggestions
138 K on clock and original

meltedpanda · #2 04-19-2008, 09:34 PM

Can these be "cleaned out" and what is the round thing that sits at the end between the pump and filter

Gurunutkins · #3 04-20-2008, 10:54 AM

Hi melted
mine has been buzzing for years, worried me at first but it just keeps going! I have a 73 thats close to yours, have nothing round between the pump and filter but I do have a round bit between the tank and pump. thats the swirlcan and it is supposed to take the pressure off the fuel when it hits the 90 degree bend to the pump. I dont think its critical but you could get cavitation into the pump if you dont have it.
cheers

meltedpanda · #4 04-20-2008, 08:54 PM

Ah yes that makes sense, a swirlcan,

In any respect mine is buzzing so I guess I will just watch it for now, do you know , if they fail, can the car be started - run?
Is it sudden or does it give, "I am going to die" signs?

Gurunutkins · #5 04-20-2008, 09:19 PM

Ive never had one of these die on me but in my jag with the same pump system it played up first and a good thump on the casing would get it going again but I only left it in that state for a day or 2 as i'm a big coward and was scared that it would leave me stranded.
I should think you could get it to keep going for a bit but would eventually get a catastrophic failure, certainly long enough to get you home!
cheers

meltedpanda · #6 04-20-2008, 09:26 PM

great

cth350 · #7 04-21-2008, 12:23 PM

keep your eyes open for a spare on ebay. They can be cheap or expensive. Buy the one with the better price. Once you get it, test it with kerosene (which will also lubricate it) and then put it on a shelf until you need it. -CTH

sjefke · #8 04-21-2008, 02:38 PM

Quote:

Originally Posted by cth350

keep your eyes open for a spare on ebay. They can be cheap or expensive. Buy the one with the better price. Once you get it, test it with kerosene (which will also lubricate it) and then put it on a shelf until you need it. -CTH

or better still, put it in the trunk in case the old one dies on the road. I (still) use the same trick on my MGBs as Gurunutkins on his Jag, especially if they have been sitting for a while, but those you can hammer while driving from inside. I used to take spare fuel pump always on long multiday trips. MB is another story...

Bert

meltedpanda · #9 04-21-2008, 03:05 PM

kinda like hitting the old starter when it ceases to function - right?

On the lookout for a spare

sjefke · #10 04-21-2008, 09:14 PM

Quote:

Originally Posted by meltedpanda

kinda like hitting the old starter when it ceases to function - right?

On the lookout for a spare

Starters are for sissy's

Get a stickshift and park on a hill...

Another trick with mallfunctioning fuel pump is to roll/drive over the biggest pothole and bumps you can find in the road. Did that once driving back from Belgium to Holland with malfunctioning pump at night. Works with MGs (stiff suspension rattles your bones) but MBs are way too smooth for that. I think I'll start looking for a spare pump for my Merc too...

Bert

Gurunutkins · #11 04-22-2008, 12:30 AM

my first triumph had a starter crank handle in the front for when the battery was flat thanks to lucas the prince of darkness. nothing like starting a 1200cc car with a crank handle. I, like sjefke, always tried to park pointing downhill.

if its of any use to you guys I replace my very expensive djet pump with a (much) cheaper CIS pump (i think it was about $70 on ebay new) and then plumbed it in to a pressure regulator under the trunk next to the pump that teed into the return pipe at the tank. I set the pressure at the first step to 70psi and then let the regulator on the engine hold the rest as it was supposed to.

It worked really well. I have it all apart now as I am converting both my cis and djet to megasquirt but can send pictures of the parts if it any use. the pump cost approx $70 new and the regulator $19 both on ebay versus the $400 for a new pump. I also didn't have the worries that i was buying a bad secondhand pump which often go for more than I paid for the new one.
cheers
barri

meltedpanda · #12 04-22-2008, 10:03 AM

Barri
Love to have the details on that retrofit, I have thought of using a diffrent pump but worried about the pressures
Thanks

Gurunutkins · #13 04-22-2008, 04:28 PM

HI Ron
luckily have some photos of the parts, the car is currently undergoing a megasquirt retrofit! I dont know how big the photos will be but if you need send me an email and I will send you full size pictures.

I removed the existing djet system and bolted in the cis pump and the filter. (both are shown below as stand alone systems) you dont need all of the accumulator crud etc. I plumbed straight out of the pump into the pressure regulator in the picture and out of that back into the filter. from the filter everything was the same. the overflow (pressure relief)from the blue regulator I plumbed back into the return from the engine pressure regulator (later picture) at the tank.

I set the blue regulator to run at 70psi. then at the engine end I checked my pressure in the FI ring (picture) it should be at 28 - 30 psi but mine is set to 32psi. you do this by removing the feed to the cold start injector (warm the engine first and watch for a spurt of gas when you pull the short length of pipe off) and plumb in your pressure gauge. you set it on the regulator (picture from the rear of engine) these can be different but one is a pressure damper and one a regulator. the regulator is before the return to the tankl. just undo the big bolt and set the pressure with the little one.

it was literally that easy. been working for the last year with no problems.

Gurunutkins · #14 04-22-2008, 04:31 PM

didnt know I was limited to 5 pictures! here are the rest.

you will see that I didnt completely remove the air filter in the pictures as I left the IAT sensor in place to run the engine otherwise it tends to race and you get pressure fluctuation

meltedpanda · #15 04-22-2008, 04:43 PM

very nice, and thanks for taking the time to post
a few questions
2nd picure 1st post, what is the third piece of the system, Mine is like your first photo.
You only use CIS pump and filter with the blue regulator inbetween, where did that come from? Do you have a source
Do you keep the pressure gauge in place all the time in the engine bay?
Thanks again