Mercedes-Benz Forum banner

1 - 20 of 27 Posts

·
Registered
Mercedes Benz
Joined
·
1,754 Posts
Discussion Starter #1 (Edited)
OF the 9 MB's I have 7 are CIS. Their fuel pumps are a bit different that the one I pulled from my recently purchased '73 450. I've read that the proper fuel pressure is 2-2.1 bar. That is quite a bit less than the pressure the CIS-E gets. So I'm wanting to source the correct part (I know Fonzi! I still need to get EPC! @maynard too) but the pelicanparts shows the same as the CIS-E.

Professional (quasi of course) opinion is welcome (as well as actual professional)!

And if anyone is rebuilding theirs I'm happy to hear about that too.

Learned that mine is this: BECK/ARNLEY 1520253 Electric Pump
 

Attachments

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
9,980 Posts
That Beck-Arnley is not original. I may be a rebuilt original Bosch or even a pump from Nissan which was similar.

We have been through this many times here.

https://www.benzworld.org/forums/r-c107-sl-slc-class/2663738-new-djet-pump-now-available-mb.html

Current sources are MB who now have a different pump kit (made by Bosch) for the djets. You can buy the same Bosch pump cheaper, but then you need some accessories like a rubber sleeve to increase diameter to fit holder plus some fittings for connections.

Pelican Parts do sell both (not same as K-jet pumps) https://www.pelicanparts.com/catalog/SuperCat/3446/MBZ_3446_FULFUL_pg3.htm#item7

You can also buy a Nissan pump off eBay or elsewhere. It is same as original Bosch Djet pump. Will fit exactly and unlike the new MB/Bosch pumps, does have the proper original spec.

https://www.tascaparts.com/oem-parts/nissan-fuel-pump-17011p7211
 

·
Registered
Mercedes Benz
Joined
·
1,754 Posts
Discussion Starter #3 (Edited)
Thank you very much MB!

I have plenty 0 580 464 042 laying around too! My issue is that Dr. Djet on oldtimer said anything running more than 3 bar will damage components of the system like the injectors.
 

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
9,980 Posts
Thank you very much MB!

I have plenty 0 580 464 042 laying around too! My issue is that Dr. Djet on oldtimer said anything running more than 3 bar will damage components of the system like the injectors.
Unavita, the pump may have a higher pressure capability, but it is the fuel pressure regulator that is on the fuel return from the injectors that determines the pressure. Not the pump.

The pumps have an internal relief valve that limits the pressure. The one on the original pumps was set lower than the new MB/Bosch replacement. (Numbers in link I posted, I believe). Bosch assured me that the fuel system with rubber hoses and clamps can take the maximum relief pressure should the regulator malfunction or the return line become blocked. I still would go with the original type if I could, but the 042 would no doubt work if you already have one and can adapt it.
 

·
Registered
Mercedes Benz
Joined
·
1,754 Posts
Discussion Starter #5
To use my favorite Russian phrase, "Yesbutt"...
That is as you said a diaphram also and meant to operate under certain perimeters. Eventually a 3+ bar pump will cause a premature end to the pressure regulator, nyet?
 

·
Registered
Mercedes Benz
Joined
·
1,754 Posts
Discussion Starter #6
Does the d-jet have a crank positioning sensor or does it just use the distributor and computer to regulate injector pulse?
 

·
Registered
75, 280Sl /5speed
Joined
·
1,293 Posts
The trigger points in the dizzy control injector timing. The M110 has a crank sensor but it's just
a test port for setting TDC.
 

·
Registered
75, 280Sl /5speed
Joined
·
1,293 Posts
Unavita, the pump may have a higher pressure capability, but it is the fuel pressure regulator that is on the fuel return from the injectors that determines the pressure. Not the pump..
Can't speak to the V8, but the M110 has regulators on both the fuel in and fuel out. The one on the fuel in controls injector pressure.
There is a different setting for the return line.
 

Attachments

·
Registered
1974 450SL (always needs something!) new djet engine 1991; 1961 Besasie X-3 (being restored)
Joined
·
788 Posts
OK. Now my curiosity is killing me. A few years ago, I bought a Beck-Arnly (I think) fuel pump for my DJet 107 off EBAY, not knowing if it was right or wrong. Honestly, I didn't know there is a specific fuel pump for DJet. The pump I bought has been working just fine. So what's the deal about a fuel pump that's specific to the DJet?
 

·
Registered
Mercedes Benz
Joined
·
1,754 Posts
Discussion Starter #10
OK. Now my curiosity is killing me. A few years ago, I bought a Beck-Arnly (I think) fuel pump for my DJet 107 off EBAY, not knowing if it was right or wrong. Honestly, I didn't know there is a specific fuel pump for DJet. The pump I bought has been working just fine. So what's the deal about a fuel pump that's specific to the DJet?
The djet was designed to function at 2-2.1 bar the way I'm understanding the documents I'm reading. All 7 of my CIS cars have a good deal more than that. Just throwing numbers around I believe 50-75 psi is common in CIS-E and the pumps are capable of 120psi in some cases. I haven't checked the pump pressure on my CIS-KE ('91 500SL) but it's high I know as is the LH version. The fuel pressure regulator is designed to discharge gas about that 2 bar (about 25psi). I've read too much pressure in a Djet will cause premature wear of that regulator as well as the fuel injectors themselves- I'm assuming should said regulator fail.
 

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
9,980 Posts
To use my favorite Russian phrase, "Yesbutt"...
That is as you said a diaphram also and meant to operate under certain perimeters. Eventually a 3+ bar pump will cause a premature end to the pressure regulator, nyet?
No, that is not right. The pump does not create any pressure unless there is something restricting the outflow. In the case of the V-8 Djets (I don't know about the 6-cyls) the fuel pressure regulator located on the fuel line leaving the fuel rails restricts the flow. It will only see 2 bar of upstream pressure regardless of pump used. No way it will get damaged by a pump with a higher rated pressure because the pump will not reach that pressure.

Only concern with using higher pressure pumps like the CIS pumps with a djet, is the possibility of the return line or the regulator somehow getting blocked and flow getting considerably reduced, maybe to zero. Then pump will try an reach it's maximum internal relief pressure which is likely higher than the pressure the djet hoses can safely stand.

The pumps have an internal relief valve that limits this pressure. In the case of the original Djet pumps, it may be something like 6.3bar (dropping when valve opens to 3.7bar - I tested mine and fuel pressure was 55 psig with return line clamped closed.). For the new Djet pumps they say 8.3 bar (dropping to 4.8bar). So long as the hoses and clamps can stand these pressures, no problem. Theoretically Bosch says they would. Otherwise fuel leaks could occur which is a concern.

For above reasons my first choice would be an original pump (or an identical copy like the Nissan or Beck-Arnley). Second choice would be the new Bosch/MB pump based on the Bosch 042 pump - Bosch say that these have been evaluated by MB and deemed suitable for our old Djets. (make sure all hoses and clamps are in new condition). I would not use a CIS pump.
 

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
9,980 Posts
Can't speak to the V8, but the M110 has regulators on both the fuel in and fuel out. The one on the fuel in controls injector pressure.
There is a different setting for the return line.
Are those actually pressure regulators? Or is one a damper? On the V-*s, the fuel pressure regulator is on return line directly after fuel rails, It is followed by a fuel damper that just irons out fluctuations in pressure.
 

·
Registered
Mercedes Benz
Joined
·
1,754 Posts
Discussion Starter #13
No, that is not right. The pump does not create any pressure unless there is something restricting the outflow. In the case of the V-8 Djets (I don't know about the 6-cyls) the fuel pressure regulator located on the fuel line leaving the fuel rails restricts the flow. It will only see 2 bar of upstream pressure regardless of pump used. No way it will get damaged by a pump with a higher rated pressure because the pump will not reach that pressure.

Only concern with using higher pressure pumps like the CIS pumps with a djet, is the possibility of the return line or the regulator somehow getting blocked and flow getting considerably reduced, maybe to zero. Then pump will try an reach it's maximum internal relief pressure which is likely higher than the pressure the djet hoses can safely stand.

The pumps have an internal relief valve that limits this pressure. In the case of the original Djet pumps, it may be something like 6.3bar (dropping when valve opens to 3.7bar - I tested mine and fuel pressure was 55 psig with return line clamped closed.). For the new Djet pumps they say 8.3 bar (dropping to 4.8bar). So long as the hoses and clamps can stand these pressures, no problem. Theoretically Bosch says they would. Otherwise fuel leaks could occur which is a concern.

For above reasons my first choice would be an original pump (or an identical copy like the Nissan or Beck-Arnley). Second choice would be the new Bosch/MB pump based on the Bosch 042 pump - Bosch say that these have been evaluated by MB and deemed suitable for our old Djets. (make sure all hoses and clamps are in new condition). I would not use a CIS pump.
Well exactly what I was saying except more succinctly, correctly, with greater... aw heck! Who am I kidding!

Anyway I happen to have a k-jet pump that I think is pumping low pressure that I could use but I love the write up on the rebuild so much I'll probably do that LOL!

But getting back to serious talk-
That all makes perfect sense to me. So it is very important to have a properly functioning regulator as it is the pump and filter. I wonder how many people miss that in their endeavor. Unfortunately I've also learned that this system is designed FOR the 4.5 motor and that means without modification it will not be seeing my 5.6. Ha Ha. Everybody love hot-rodding an old Mercedes... Right?
I do not like fudging about with cars like that. It's not like dropping in a 396 where a 350 once was.

The reason- for those that want to know- as I've learned today thanks to another forum member, the D-jet system does not have a crank positioning sensor and uses a dizzy in the distributor to tell the computer the information it needs to make the injectors pulse. Or something like that? Regardless it is designed for the size engine it's fitted to. To long a stroke changes everything I'm told.
 

·
Registered
75, 280Sl /5speed
Joined
·
1,293 Posts
Are those actually pressure regulators? Or is one a damper? On the V-*s, the fuel pressure regulator is on return line directly after fuel rails, It is followed by a fuel damper that just irons out fluctuations in pressure.
Regulator, note the adjustment screw on the bottom. Manual gives pressure settings for both.
 

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
9,980 Posts
Regulator, note the adjustment screw on the bottom. Manual gives pressure settings for both.
I don't have the 280SL .

This parts diagram shows two parts 1 and 2. 1 is a damper and 2 is the pressure regulator. Is there another regulator somewhere? Only difference from V-8s is that damper is on feed to fuel rails, not downstream of regulator.

The V-8 dampers dampers have an adjustment screw too, but it is not something that is adjusted once installed.

https://www.sls-hh-shop.de/main/de/mercedes-280-560sl-w107/07-a-b-d-jetronic-einspritzkomponenten/07-a-d-jet-einspritzkomponenten-280sl-slc

 

·
Registered
75, 280Sl /5speed
Joined
·
1,293 Posts
M110 has the same setup. #557 is the fuel pressure regulator which is on the fuel in hose and sets the fuel pressure at the injectors
#580 they call a diaphragm which is on the fuel return line and as you stated evens out the return flow.
 

Attachments

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
9,980 Posts
M110 has the same setup. #557 is the fuel pressure regulator which is on the fuel in hose and sets the fuel pressure at the injectors
#580 they call a diaphragm which is on the fuel return line and as you stated evens out the return flow.
The diagram I posted was for the M110. It has flow arrows that show the damper on the fuel inlet to the fuel rail. And the regulator, like other djets is on the fuel return to the tank.

It has to be like this for the injectors to have the required pressure.
 

·
Registered
Mercedes Benz
Joined
·
1,754 Posts
Discussion Starter #18
The diagram I posted was for the M110. It has flow arrows that show the damper on the fuel inlet to the fuel rail. And the regulator, like other djets is on the fuel return to the tank.

It has to be like this for the injectors to have the required pressure.
Can you post the key for that image. It's probably in the repair manual cdrom catalog I have but for posterity sake...
 

·
Premium Member
'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
Joined
·
9,980 Posts
Can you post the key for that image. It's probably in the repair manual cdrom catalog I have but for posterity sake...
The image I posted was from the German parts company - the link is in me earlier post.

It can be confusing, but so far as I know, all Djet fuel systems use back pressure control. The regulator is on the return line and maintains a back pressure in the fuel rails that feed the injectors. Even on the V-8s, some owners initially thought the fuel feed from the pump went to the regulator.

But not to say that a car could not have a pressure reducing valve downstream of the pump/filter and before the fuel rails. But have never seen one like that.
 

·
Registered
75, 280Sl /5speed
Joined
·
1,293 Posts
So after 13 years of believing the D-Jet worked one way, as Graham and the Bosch Yellow Book (which I have) have proven,
I find out it works the opposite. The fuel pump does indeed feed the injector ring through the diaphragm then back to the tank
through the pressure regulator. The opposite of everything I had been taught. My apologies for the confusion.
 

Attachments

1 - 20 of 27 Posts
Top