injector pump replacement advice?

[RickInTex]

This is the sequel to the *sigh* thread I started a week or so ago, which died when I announced that I was facing a rebuild of my injection pump.  Anyway, the car is in the shop awaiting arrival of a rebuilt pump from Pacific FI; with luck it will come on Monday, and I'll get the car back later in the week.  Wouldn't you know it, but it's a totally beautiful weekend in North Texas, and exactly the right time to be taking off the hardtop for the spring.  Just my luck.

Anyway, here's the substantive part of my post.  Being an obsessive, having learned far too much from this site than is good for me about the many things that go wrong and be ill-repaired, I'm wondering about what questions to ask my mechanic, and what things to make sure get done when the pump it reinstalled.  Mind you, he's quite competent, and he's been in touch with Will Samples, who's helped me a lot.  Still, what should I make sure they do or check?

For example, since this job is a response to a running-rich problem that was impossible to fix otherwise, I would guess that an oil change is in order, in case fuel has at all diluted the oil in the crankcase.  Is that right?

What other things should be checked or adjusted when reinstalling the injector pump?

Rick
Dallas TX
1967 250SL, 4-speed

[mdsalemi]

Rick in TX,

Hopefully others will check in as well...

Obviously you want to check the entire fuel system, from the pump in back up to the new FI pump in front.

You want to make sure you are getting clean proper fuel flow.

New fuel filter should be a given.

I believe you want to ensure that all your accelerator linkages are proper.  It's a task to do that.

You want to ensure your CO is to spec for your car.  This will determine "by the book" whether you are correct as to rich/lean.

Starting with new plugs is a help.  Knowing your ignition is up to snuff is good as well.

As you have surmised there are so many intertwined issues here....its kind of hard to adjust the rich/lean if your timing is off.  Kind of hard to adjust the timing if you have bad wires or plugs.  If your mechanic is as experienced as you say he his, he'll probably have a procedure in place for this.

Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored

[rwmastel]

quote:Originally posted by RickInTex

What other things should be checked or adjusted when reinstalling the injector pump?

Rick,
Michael hit on very good points.  I'll elaborate and say you should :

 - if your 250SL has the MFI pump with the seperate oil resivoir and dip stick, make sure it has proper oil level before starting car.  Probably shipped dry from Pacific FI.
 - did you send your fuel injectors to be cleaned and tested by Pacific FI?  If not, it's a good thing to do.
 - check for rust in fuel tank.
 - check for a dirty filter screen in fuel tank.
 - check for a dirty filter screen in electric fuel pump.
 - get new flexible fuel lines (and clamps) to/from fuel tank.
 - get new cork seal for fuel gauge sender unit in fuel tank.
 - get new main fuel filter.
 - once pump is installed, check fuel pressure and flow rate of electric fuel pump.  You don't need to start car, just turn fuel pump on.  Check this where the fuel return line comes back to the fuel tank, testing the whole system.
 - get new flexible fuel lines in trunk to/from expansion tank.
 - check all fuel injection linkages for proper length (a factory setting that should never be changed), no loose ball/socket joints, no bent linkages, and proper lubrication.
 - test the cold start valve (CSV) on the intake manifold for leakage (mechanical) and proper running time (electrical).
 - check your distributor for wear, lost springs, extra play in all components, ability to hold a vacuum, etc.
 - check your large tach drive bushing.  Nothing to do with the fuel system or rich running, but causes the engine oil pump to stop if bushing wears too thin!

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

[bpossel]

Hi Rick,

Everything that Rodd and Michael stated is good advice.  I would just reemphasize making sure to test, and replace if necessary your fuel injectors.  Also make sure to test your cold start valve (CSV).  When I had my pump rebuilt, all of my injectors were bad, so I replaced mine.  Fortunatley, my CSV only needed a good cleaning.  Also, when you reinstall the injection pump, use a new paper gasket...  one less leak to deal with.  Clean, replace the spark plugs, change the oil (mine was saturated with gas).  
I have been very pleased with my rebuild.  Car is running great!
Good luck!
Bob

bpossel
Memphis, TN.
1971 280SL
1997 E320

[RickInTex]

Bob, Rodd, Michael: Thanks for all the suggestions.  I embarked on the pump replacement after eliminating a variety of other possibilities for my problems with idle, richness, etc.  The CSV was working properly, the distributor is sound, timing was where it should be, and so forth.  So some of the items mentioned have already checked out fine (unfortunately, since they would've been cheaper causes for my problems than a a tired injection pump!).

The injectors are being tested at PFI and will be replaced as needed.

I'll definitely get the oil and oil and fuel filters changed, and I'll have them check the fuel supply items suggested as well.

Thanks for all the advice!

Rick
Dallas TX
1967 250SL, 4-speed

[Tom]

Hopefully your mechanic followed the book and set the engine timing correctly before pulling the pump.  If not, your pump will go back in and the timing will be off.

I believe the BBB says set the engine timing at 20 degrees AFTER top dead center before pulling the pump.  

As I recall (Techno-Pagodites correct me here if wrong), there is also a timing indicator mark on the FI pump that should be lined up with a notch on the flange of the FI pump.  In other words, top dead center on the pump should be attained at 20 degrees after top dead center on the engine timing.  All of this is detailed in the book.

Best,

Tom

1971 280sl Tunis Beige Metallic (restored & enhanced)
1971 280sl Tobacco Brown (low mileage stock)
1970 280sl Deep Red (Project Car)