Fuel injector problems

[n/a]

After about 3 years of inactivity I'm trying to get my '64 230sl running.  Before I put it in storage it was running fine and nothing has been done in the meantime.  Now it won't start. I have spark and positive fuel pressure from the electric pump but fuel is not making it through the injectors.  I know fuel is getting to the injectors but not through.  I pulled the injectors and had them tested.  All opened up right at 600 psi but I can't find specs to see if this pressure is correct.  The gas in the tank had turned bad so I drained it and had cleaned and lined.  My suspicions are that fuel in the injector pump has varnished and limited output.  Does anyone know what pressure the injectors are supposed to open?  And has anyone run into the problem of bad gas in the pump?

[Raymond]

Someone will know the correct pressure, although I don't.  If all of the injectors were consistent, I would expect that they are fine.  You probably already ran compressed air through all the lines to be sure they are clear.  

In the mean time, you say you're sure fuel is getting to the injectors.  Can you turn the engine over with the injectors on the lines but not installed in the head to see if they are spraying?  Also, does the cold start valve function?

Ray
'68 280SL 4-spd Coupe

[A Dalton]

Opening pressures '

Approximately
 15-18 atm
 or  220-265 psi.

 Looking for <30 psi differential.

[n/a]

After all 6 injectors popped right at 600 psi on the bench tester we came to the same conclusion that they were probably alright.  I put a call in to Bosch looking for the correct opening pressure but they couldn’t tell me, only game me the MB matching part number (0000781123).

This afternoon I cleaned out (with carb cleaner and 130 psi of air) the pipes from the injector pump to the injectors then reconnected loosely, leaving the injectors out of the head.  I turned the motor several rotations to bleed the air out and got quite a bit of fuel leaking from the loose compression fittings, so I know I have fuel under pressure at the top of the injectors.  (The engine actually started with raw fuel leaking from the fittings down into the combustion chamber!)  I re-torqued the pipes to the injectors, put clean paper towels under the injector nozzles and cranked the engine.  No spray at all came out of any of the injectors.

On the bench tester all the nozzles had great spray patterns and were within 30 psi of opening pressure (~600psi, which seems awful high to me but not to the diesel mechanic).

With nothing else to go on I pulled the injector pump and checked for contaminates.  The pump turns over smoothly by hand, and other than a bit of greasy gunk the pump seems to be clean and has fresh gas running through it.  I’m not sure if the cold start valve is currently working but without fuel coming out of the nozzles I think that’s a secondary problem.  

Forgive my ignorance, but does 15-18 atm mean 15-18 atmospheres?  And does anyone know why Bosch can’t tell me the specs on their part number?

Thanks all!
Don

[A Dalton]

<<Forgive my ignorance, but does 15-18 atm mean 15-18 atmospheres? >

 Yes, it does..
 I also included the atm/PSI conversion for you , along with the Benz spec pressures listed according to my data.

[n/a]

Thanks for the info!  Looks like I have some bad injectors.

[A Dalton]

.. or just full of varnish..

 I would energize the CSV manually to get it to run for a few R's and see what happens...

[mrfatboy]

I believe the opening pressure for the fuel injectors should be around 225 psi.  I am not sure how much pressure the FI pump sends but aleast 225psi so they will open (normally).  600psi seems an awful lot. But if the pump is not over coming the 600psi it will never open the injectors.  I think you have the wrong injectors or they are broken.

I am by far not the guru here. Take what I say with a grain of salt.

[n/a]

We've had the car for about 30 years now (hasn't run much in the last 10) with the same injectors, in fact I think they're the original equipment.

The first thing I did was soak them in lacquer thinner overnight and cleaned them up as best I could.  I suppose a pretty heavy build up of varnish and or corrosion could be down there.  Any tricks out there to clean these things up?

[A Dalton]

Carb cleaner and an ultra-sonic bath ..

 I have seen some homebrew formulas here and there , but carb cleaner works fine for me......................


 Edit:
 Here is one homebrew .. I have not tried it, but those who have claim it works fine.

<<<1 litre ultrasonic cleaner (large jewelers or graphic type) — must be capable of heating solution to 150º+ F.  

The solutions are simple and available at any hardware store... mix 1/2 turpentine + 1/4paint remover + 1/4 acetone, bring to temp.150º+ .  >>>

[mrfatboy]

If they are the original fuel injectors.  Han's from H & R fuel injectors says that they are better then the new ones. He can clean them up like new.  Keep them around for sure.

[rwmastel]

quote:Originally posted by mrfatboy

Han's from H & R fuel injectors says that they are better then the new ones. He can clean them up like new.

H&R contact info can be found here.
http://www.sl113.org/data/show_table.asp?table_name=usr_parts_and_service_suppliers

If you're on the West coast of the USA, Pacific Fuel Injection is geographically closer.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420