PeachParts Mercedes-Benz Forum

PeachParts Mercedes-Benz Forum (http://www.peachparts.com/shopforum/)
-   Diesel Discussion (http://www.peachparts.com/shopforum/diesel-discussion/)
-   -   Difference in primer/bleeder pumps (http://www.peachparts.com/shopforum/diesel-discussion/219747-difference-primer-bleeder-pumps.html)

vjw 04-17-2008 09:40 AM
Difference in primer/bleeder pumps
 
I have a quick question. I recently retired an '84 300D that had the screw-type primer on the lift pump. The '82 240D that I replaced it with has the straight primer pump.

I really liked the screw-type style, which seemed to act also as a bleeder. It seems that this other style pushes air back to the fuel tank to bleed. Is this true?

Stevo 04-17-2008 10:00 AM
NO, its not true

vjw 04-17-2008 11:43 AM
Any insights on how it does work? I always assumed that the screw-type released the air at the handle (based on the fact that it begins to spill diesel once the air has passed).

I am confused by where the air goes with this type primer. When I pump it I see air bubbling at the engine side of my in-line fuel filter. I'm trying to get the air out of the system or find the leak that is keeping my car from running.

Stevo 04-17-2008 11:57 AM
[QUOTE=vjw;1827290] (based on the fact that it begins to spill diesel once the air has passed).

The problem with the older style is they do spill fuel (leak) when they need replacing, they shouldn't do that.

Stevo 04-17-2008 12:06 PM
When you pump your primer pump the air exits a small hole on the primary (big) fuel filter housing, not sure where, doesn't matter, but you will hear a difference in the sound when your pumping. You can still get the old "screw down" type but I would stick with the new "black handle" one, more better:)

vjw 04-17-2008 12:16 PM
THanks Stevo

dannym 04-17-2008 02:00 PM
The black one is considered an upgrade to the older screw down type.

Danny

vjw 04-17-2008 02:49 PM
For some reason, I'm partial to the old style. Guess I'm just an old fogey who gets set in his ways... tell me I'll change my tune before I rip the old one off my previous block!

V

tangofox007 04-17-2008 04:02 PM
Quote:
Originally Posted by Stevo (Post 1827315)
When you pump your primer pump the air exits a small hole on the primary (big) fuel filter housing, not sure where, doesn't matter, but you will hear a difference in the sound when your pumping.
There is only going to be a "hole" in the filter housing if you make one by loosening a hose or fitting. The return line hollow bolt works well. The sound that you hear is most likely the relief valve on the injection pump. It just relieves excess pressure by diverting fuel (or air) into the return line.

As counterintuitive as it may seem, the large filter is the secondary filter. The inline filter upstream from the fuel pump is the primary.

1983/300CD 04-17-2008 04:48 PM
Quote:
Originally Posted by Stevo (Post 1827186)
NO, its not true
Yes it is true. The air goes to the canister filter at the three-point connection, to the cigar hose and returns to the tank.

Don't belive it? Change your fuel filter without filling it with anything. Tighten it, then hit the primer 30 times. No cracking of anything required. Where did the air go? No big mystery.

It might be more obvious if you could see through your clear fuel lines and watch the bubbles.

Jordan G 04-17-2008 04:51 PM
Quote:
Originally Posted by 1983/300CD (Post 1827572)
Yes it is true. The air goes to the canister filter at the three-point connection, to the cigar hose and returns to the tank.

Don't belive it? Change your fuel filter without filling it with anything. Tighten it, then hit the primer 30 times. No cracking of anything required. Where did the air go? No big mystery.
If I did that, my car wouldn't start:D.


Still - both new/old pumps work the same....and a leaky old-style pumps means it needs to be replaced, not that it's bleeding air as designed

1983/300CD 04-17-2008 04:54 PM
I did that earlier today. Don't tell me our cars are different?

Here's a question for you: Have you tried it?

Jordan G 04-17-2008 05:11 PM
Quote:
Originally Posted by 1983/300CD (Post 1827579)
I did that earlier today. Don't tell me our cars are different?

Here's a question for you: Have you tried it?

Having battled a rusty fuel tank - yes - I've had to change filters literally 20-25 times in the past year. The first two times, I hadn't this fine forum as a friend and I changed the secondary filter w/o filling it up. I had to pump until my fingers bled and I killed my battery once too.

I'm not saying it COULDN'T work....I've just had much better luck loosening the bolt.

1983/300CD 04-17-2008 05:16 PM
Hmm. Sounds like a problem with the condition of your car?
I have no problems whatsoever. Like I said, I did it earlier today.

But back on point, yes. The air returns to the tank.

Stevo 04-17-2008 07:23 PM
Quote:
Originally Posted by 1983/300CD (Post 1827572)
Yes it is true. The air goes to the canister filter at the three-point connection, to the cigar hose and returns to the tank.

Don't belive it? Change your fuel filter without filling it with anything. Tighten it, then hit the primer 30 times. No cracking of anything required. Where did the air go? No big mystery.

It might be more obvious if you could see through your clear fuel lines and watch the bubbles.
Huh, I had always thought it was the air escaping the system that could be herd, learn something everyday:)

vjw 04-17-2008 11:12 PM
Changing speeds a bit...

I know with some pumps, you must have enough head for them to work properly (or properly, you shouldn't be trying to raise the fluid higher than the pump's capacity). So...

If there was a column of air between the fuel tank and the engine (i.e. when you change fuel lines), would the amount of fuel in the tank make it impossible to purge the air?

I have this friend (totally hypothetical, of course) who has about 1/4 tank of diesel, has gone through the charge of two batteries and about 1000 primer strokes, and still has a car in his driveway that doesn't start. Do I... I mean.. does this guy need to get more fuel in his tank or is it likely something else?

Jordan G 04-18-2008 07:25 AM
Quote:
Originally Posted by vjw (Post 1827895)
Changing speeds a bit...

I know with some pumps, you must have enough head for them to work properly (or properly, you shouldn't be trying to raise the fluid higher than the pump's capacity). So...

If there was a column of air between the fuel tank and the engine (i.e. when you change fuel lines), would the amount of fuel in the tank make it impossible to purge the air?

I have this friend (totally hypothetical, of course) who has about 1/4 tank of diesel, has gone through the charge of two batteries and about 1000 primer strokes, and still has a car in his driveway that doesn't start. Do I... I mean.. does this guy need to get more fuel in his tank or is it likely something else?
hypothetical speaking, of course.....when my friend ran into this problem.....he cracked his injector lines and cranked patiently (waiting b/w cranks) but loooong cranks. My friends car started soon after this:D

ForcedInduction 04-18-2008 08:10 AM
Quote:
Originally Posted by vjw (Post 1827895)
I have this friend (totally hypothetical, of course) who has about 1/4 tank of diesel, has gone through the charge of two batteries and about 1000 primer strokes, and still has a car in his driveway that doesn't start. Do I... I mean.. does this guy need to get more fuel in his tank or is it likely something else?
Likely something else. The engine should be running in that amount of time even if you started with a completely dry injection system and only fuel in the tank.

vjw 04-18-2008 09:15 AM
As a test, I diesel purged the engine from a jar and it ran fine... It took four or five cranks to get the air out of the lines for just that test... I... I mean my friend, will be atr it again today.

THanks all!

V


All times are GMT -4. The time now is 02:08 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website