power loss issues 85 300D - PeachParts Mercedes-Benz Forum

richclan · #1 11-11-2012, 01:22 PM

well i am having power loss real bad now. i think back and its been a long slow loss of power. i have read a lot of posts about the subject and am sure its a fuel starvation issue. i am going to try a few things that you guys have suggested, but i wanted to start a thread b4 i start.

what i have done so far:

tank screen is clean

tank breather tubes clogged so i have a fuel cap with a vent, works good!

new primary filter

new 2ndary filter [ i replace this filter every 2K miles or less. it seems that it isn't the problem, hence this thread]

bubbles in the line from the primer pump to the 2ndary filter

old style primer pump with the clear screw knob

when i clamp the cigar hose the bubbles vanish

no bubbles in the primary filter

crankcase pressure is nil

idle is ok

What i plan to replace:

primer pump new style cost under $20 i think this is the culprit!!

also where is the primer pump check valve thing with the spring that gets weak and you stretch it to get back to 14psi pressure??????

thanks guys

in advance

qwerty · #2 11-11-2012, 01:32 PM

Quote:

Originally Posted by richclan

also where is the primer pump check valve thing with the spring that gets weak and you stretch it to get back to 14psi pressure??????

What is your fuel pressure now?

Diesel911 · #3 11-11-2012, 03:11 PM

Quote:

Originally Posted by richclan

well i am having power loss real bad now. i think back and its been a long slow loss of power. i have read a lot of posts about the subject and am sure its a fuel starvation issue. i am going to try a few things that you guys have suggested, but i wanted to start a thread b4 i start.

what i have done so far:

tank screen is clean

tank breather tubes clogged so i have a fuel cap with a vent, works good!

new primary filter

new 2ndary filter [ i replace this filter every 2K miles or less. it seems that it isn't the problem, hence this thread]

bubbles in the line from the primer pump to the 2ndary filter

old style primer pump with the clear screw knob

when i clamp the cigar hose the bubbles vanish

no bubbles in the primary filter

crankcase pressure is nil

idle is ok

What i plan to replace:

primer pump new style cost under $20 i think this is the culprit!!

also where is the primer pump check valve thing with the spring that gets weak and you stretch it to get back to 14psi pressure??????

thanks guys

in advance

A.K.A Fuel Pressure Relief Valve or Over Flow Valve.

It is on the the side of the Fuel Injectin Pump that fraces the Engine Block. It does not appear to be much different than a Banjo Bolt until you unscrew it (2 crush washers).
Long Fuel Pressure Relief Valve/Overflow Valve Thread
http://www.peachparts.com/shopforum/showthread.php?t=234609

richclan · #4 11-11-2012, 05:33 PM

Quote:

Originally Posted by qwerty

What is your fuel pressure now?

idk i dont own a gauge, and i would have to replace the clear tubing right?

richclan · #5 11-11-2012, 05:35 PM

Quote:

Originally Posted by Diesel911

A.K.A Fuel Pressure Relief Valve or Over Flow Valve.

It is on the the side of the Fuel Injectin Pump that fraces the Engine Block. It does not appear to be much different than a Banjo Bolt until you unscrew it (2 crush washers).
Long Fuel Pressure Relief Valve/Overflow Valve Thread
http://www.peachparts.com/shopforum/showthread.php?t=234609

thanks i see it now, should i mess with it now or wait till i get the primer pump installed?

richclan · #6 11-14-2012, 06:24 PM

i just installed the new style primer pump and its better.

i still have bubbles in the line from lift pump to secondary filter.

if i crimp the cigar hose they go away.

i also checked the Fuel Pressure Relief Valve for any blockage, it was fine.

what should i do next?

Diesel911 · #7 11-14-2012, 06:52 PM

If you crimped the Cigar Hose would have stopped the Fuel return and that would have caused the Fuel Pressure in the IP to go up and your Fuel Pressure Relief/Overflow Valve would no longer control the Fuel Supply Pressure.

However, that was at Idle so you would not know if if it has an effect on your power during driving. And, I don't recommend driving with your Fuel Retun plugged off.

Have you tried cleaning the Banjo Bolt at the very End of the Intake Manifold; near the Fire Wall. If the Banjo Bolt or the line are plugged your ALDA will not get the Manifold Boost Pressure from the Turbo and will not increase the amount of Fuel to give you more power.

When I first got My Car it was scary slow during acceleration. Once it got moving it drove normal.
It turned out that My Linkages was extremely sloppy and I evidently was not getting Full Throttle.
In My case the Bell Crank on the Fire Wall was OK but readjusting the Linkage to remove the slop cured it.

Later after getting the Service Manual I found that each Linkage Rod has a specific Length and I re-did the job following the Manual.

richclan · #8 11-14-2012, 06:55 PM

Quote:

Originally Posted by Diesel911

If you crimped the Cigar Hose would have stopped the Fuel return and that would have caused the Fuel Pressure in the IP to go up and your Fuel Pressure Relief/Overflow Valve would no longer control the Fuel Supply Pressure.
However, that was at Idle so you would not know if if it has an effect on your power during driving. And, I don't recommend driving with your Fuel Retun plugged off.

well i did run it at idle and up to 2500 or so rpms and still no bubbles with it crimped.

do you think the lift pump needs a rebuild or the spring is weak in the valve?

richclan · #9 11-14-2012, 09:21 PM

Quote:

Originally Posted by Diesel911

If you crimped the Cigar Hose would have stopped the Fuel return and that would have caused the Fuel Pressure in the IP to go up and your Fuel Pressure Relief/Overflow Valve would no longer control the Fuel Supply Pressure.

However, that was at Idle so you would not know if if it has an effect on your power during driving. And, I don't recommend driving with your Fuel Retun plugged off.

Have you tried cleaning the Banjo Bolt at the very End of the Intake Manifold; near the Fire Wall. If the Banjo Bolt or the line are plugged your ALDA will not get the Manifold Boost Pressure from the Turbo and will not increase the amount of Fuel to give you more power.

When I first got My Car it was scary slow during acceleration. Once it got moving it drove normal.
It turned out that My Linkages was extremely sloppy and I evidently was not getting Full Throttle.
In My case the Bell Crank on the Fire Wall was OK but readjusting the Linkage to remove the slop cured it.

Later after getting the Service Manual I found that each Linkage Rod has a specific Length and I re-did the job following the Manual.

the banjo is clear and the alda has been removed. W/O the alda i have [had lol] lots more power. i also defeated the egr and that vac line going to the turbo. the wastgate is adjusted back to stock specs. and the car was running great.

the clear line showing the bubbles if it was bad it would be leaking fuel not sucking air; right????

qwerty · #10 11-14-2012, 10:14 PM

Quote:

Originally Posted by richclan

the clear line showing the bubbles if it was bad it would be leaking fuel not sucking air; right????

All the sucking occurs on the other side of the fuel pump. That is where you should be looking for a compromised line, hose or fitting.

richclan · #11 11-15-2012, 12:24 AM

Quote:

Originally Posted by qwerty

All the sucking occurs on the other side of the fuel pump. That is where you should be looking for a compromised line, hose or fitting.

ok but no bubbles in the primary filter, so im guessing lift pump.

barry12345 · #12 11-15-2012, 08:31 AM

Take the car out with the cigar hose clamped to see if power is better. Will not hurt anything for a test. If power is better base pressure in the injection pump may be very low when cigar hose is open.

TnBob · #13 11-15-2012, 04:37 PM

Bubbles indicate the fuel system is sucking air in. How old are your fuel hoses ? Are the hoses crumbly at the fittings ? Are your clamps nice and snug ?

richclan · #14 11-15-2012, 05:28 PM

just road tested it and it ran good for about 5 miles then same power loss.

after idling for a minute got enough power to get it off the road.

i then plugged the cigar hose and ran it. it seemed just as bad maybe worse. the hose has bubbles in it even when hose plugged under load.

i just barely got it home.

i think i need to check fuel pressure next.

how can i do that without cracking the clear fuel lines. im know i cant get them around here.

richclan · #15 11-15-2012, 05:30 PM

Quote:

Originally Posted by TnBob

Bubbles indicate the fuel system is sucking air in. How old are your fuel hoses ? Are the hoses crumbly at the fittings ? Are your clamps nice and snug ?

only bubbles between lift pump and secondary filter.

new little hose and good clamps on suction side as well