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  #1  
Old 11-07-2014, 09:12 PM
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1974 450SL d-jet fuel pump alternative/ car starts up and dies..

Some person installed 2 bosch pumps on my sl for some reason. strangely enough the car ran fine until it didn't... I basically drove it for less than 3 miles. the fuel tank is clean, injectors work when 12v is applied to them, injector nozzle "hoods" are new, fuel filter too.

I have no pressure gauge yet, I did take one injector out and hooked it up to see if it squirts. It doesn't. There's plenty fuel coming through the rail though.

would this be the pressure regulators? or the pumps not putting out enough?

is there a less costly alternative for the original pump, and what is that other round unit that "normal" 74 sl's have next to/ above the pump? some sort of fuel dampner??

such a overly complicated system, gas motors! unreliable, compared to diesels one might say.
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Old 11-07-2014, 09:21 PM
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That other round unit above the fuel pump is a fuel filter. I guess your simple diesels don't have one. You could read the manual. It is available on line.

http://www.startekinfo.com/StarTek/outside/11883/?requestedDocId=11883
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Old 11-07-2014, 09:59 PM
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Quote:
Originally Posted by rowdie View Post
That other round unit above the fuel pump is a fuel filter. I guess your simple diesels don't have one. You could read the manual. It is available on line.

Model 107
yes diesels have one too. in the engine bay usually, before the IP.

no the filter is next to it, I replaced that as mentioned. there's a "fuel-dampner" or so that should be there for some reason. That's what a mercedes mechanic told me at least. But then again, the start up and die-issue can have about 20 different causes. Which, I don't quite enjoy about gas powered vehicles compared to diesel ones...
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Old 11-07-2014, 11:08 PM
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How long does the engine run after starting before it dies?
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  #5  
Old 11-08-2014, 09:56 AM
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here is my thred on fuel pumps , this was on my 72-73
Same on 74 IIRC
http://www.peachparts.com/shopforum/sl-forum/327148-djet-fuel-pump.html
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  #6  
Old 11-08-2014, 11:08 AM
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Originally Posted by Frank Reiner View Post
How long does the engine run after starting before it dies?
A few seconds, it burns up the fuel it gets from the Cold start valve and then dies. .
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  #7  
Old 11-08-2014, 11:39 AM
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Originally Posted by meltedpanda View Post
here is my thred on fuel pumps , this was on my 72-73
Same on 74 IIRC
http://www.peachparts.com/shopforum/sl-forum/327148-djet-fuel-pump.html
I had found that thread indeed. "Buy original pump because of internal valve needed for djet system" i concluded. Having had lots of Mercedes diesels and still do, i only like them because of reLiability and low fuel consumption. Well i like the look of the sl and w126 123 &124 i must say. But as far as rust issues i don't like them at all and gas cars i just don't like period because a car to me must be reliable above all else. this sl has no rust so i like it for that, but i really don't trust it and never will, being a gas car. MeaNing I'll sell it and would rather not lose money by throwing more parts at it or keep and install the 603 our 602 i have laying around. ..nice reliable motors, no electricity needed, pump lasts as long as the engine. ..

Mind you, this is a nice SL.92.000 original miles. .
The weird thing is that it ran fine with the dual fuel pump set up. After a couple miles the junk from the fuel tank came loose as it had set for a long time. That i think killed the pumps, Well they work but i suspect don't put out enough pressure to make the injectors squirt correctly. Or at all.
Sigh yes I'll go get a fuel pressure gauge. ..
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Old 11-08-2014, 11:48 AM
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Quote:
Originally Posted by meltedpanda View Post
here is my thred on fuel pumps , this was on my 72-73
Same on 74 IIRC
http://www.peachparts.com/shopforum/sl-forum/327148-djet-fuel-pump.html
That should do it. For a lower cost but good pump, challenge is to find a Nissan 280z pump. They do show up on eBay/Amazon from time to time. The new Bosch pump hasn't seemed to make it's way to NA. But they can be bought on-line from Europe.

Regarding dampers. There is one between fuel tank and pump inlet. Just a small cylindrical can. In the engine compartment, you will find that the rails discharge into a 3-nozzle fuel pressure regulator. Then from there into another similar looking device - it is a fuel damper - just to keep pressure as steady as possible for injectors.

BTW, later model SLs had a dual pump higher pressure system, but never a djet.
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  #9  
Old 11-08-2014, 11:58 AM
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lovedieselsd:

The question about run time was to introduce the possibility that one of the ignition primary circuit resistors may have failed. When the key is turned to START, one of the resistors is bypassed. If the engine runs when the key is in START but dies when released to the RUN position, look to a failed resistor.
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Old 11-08-2014, 12:04 PM
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There should be a line out of the fuel tank to the damper cage. Damper cage is just a hollow can. From it there is a line to the FP inlet. Out from the FP to the filter then line to the fuel rail.
Sounds like you are getting fuel to the fuel rail and the cold start valve is working. You are not getting a signal from the ECU to fire the injectors. Could be the impulse sender (trigger points) in the distributor. Remove check the wiring connection and clean them. Could also be the transistorized ignition (switch gear). Pertronics conversion which eliminates the regular points under the cap and the switch gear is an option. Under $100.00.
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  #11  
Old 11-08-2014, 12:42 PM
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For D jet info, have a look at Porsche 914 sites.

The cold start inj only operates at very low temps ( 30* F ? ) and is wired to a thermo time switch. If someone rewired things it might act differently.

Cranking 2x in a row should be enough to shut the cold inj off. Unplug the wire and see if you still get start / stall.

Check for power at the ignition coil in the run position. Also, D jet needs to see a coolant temp signal otherwise it won't operate.
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  #12  
Old 11-11-2014, 12:09 PM
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Quote:
Originally Posted by Graham View Post
That should do it. For a lower cost but good pump, challenge is to find a Nissan 280z pump. They do show up on eBay/Amazon from time to time. The new Bosch pump hasn't seemed to make it's way to NA. But they can be bought on-line from Europe.

Regarding dampers. There is one between fuel tank and pump inlet. Just a small cylindrical can. In the engine compartment, you will find that the rails discharge into a 3-nozzle fuel pressure regulator. Then from there into another similar looking device - it is a fuel damper - just to keep pressure as steady as possible for injectors.

BTW, later model SLs had a dual pump higher pressure system, but never a djet.
I was wondering what that2nd unit was in there. do these break? I blew air through it...
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  #13  
Old 11-11-2014, 12:13 PM
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Quote:
Originally Posted by Frank Reiner View Post
lovedieselsd:

The question about run time was to introduce the possibility that one of the ignition primary circuit resistors may have failed. When the key is turned to START, one of the resistors is bypassed. If the engine runs when the key is in START but dies when released to the RUN position, look to a failed resistor.
great info! That is these two resistors on the dr side firewall I assume? It will run for longer though, when it gets some more fuel from the cold start valve. i.e. turning the key a couple times before actually starting it. Ifound a set on a '72 350sl, I could try them. but first I'm going to have these pumps run in reverse with diesel going through. and buy me a pressure tester..
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  #14  
Old 11-11-2014, 12:21 PM
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Quote:
Originally Posted by rowdie View Post
There should be a line out of the fuel tank to the damper cage. Damper cage is just a hollow can. From it there is a line to the FP inlet. Out from the FP to the filter then line to the fuel rail.
Sounds like you are getting fuel to the fuel rail and the cold start valve is working. You are not getting a signal from the ECU to fire the injectors. Could be the impulse sender (trigger points) in the distributor. Remove check the wiring connection and clean them. Could also be the transistorized ignition (switch gear). Pertronics conversion which eliminates the regular points under the cap and the switch gear is an option. Under $100.00.
trigger points I heard my remote mechanic say before. the 350sl I found at the junkyard had a rectangular piece missing on the distributor, I assume that's where these are?
I can check that easy indeed. there also was a vacuum line from the intake to some sort of round thing on dr side firewall loose. that wasn't it though.
I happily replace a head on a 603, install a 1.9 instead of a 1.6 diesel into a vw vanagon or repair a cell phone but gas engines I just don't like at all.... too much can fail I think. not wanting to bash them, it's just not my thing at all.
all the help is greatly appreciated though!!
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  #15  
Old 11-11-2014, 12:27 PM
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Originally Posted by 97 SL320 View Post
For D jet info, have a look at Porsche 914 sites.

The cold start inj only operates at very low temps ( 30* F ? ) and is wired to a thermo time switch. If someone rewired things it might act differently.

Cranking 2x in a row should be enough to shut the cold inj off. Unplug the wire and see if you still get start / stall.

Check for power at the ignition coil in the run position. Also, D jet needs to see a coolant temp signal otherwise it won't operate.
that my mechanic told me as well. I have a spare blue sensor. will try that. so how many more "points of failure" can there be??? perhaps a couple more sensors and some earth magnetism to stay away from? I'll push the car a couple meters away from where I was working on it
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