Installing Injection Pump Issue

[JimVillers]

Our engine rebuild is almost complete (230SL, R11 injection pump).  Everything is installed and looks beautiful.  Now the issue.

The engine will not start.  Everything points to the injection pump that is not providing fuel to the injectors.  We installed a "rebuilt" injection pump that had not been in a car for at least 20 years but was felt to be a good pump.

I pulled the fuel line to the cold start valve and got good flow with a fuel pressure of 12psi.  The engine would fire and "run" (rev to 3000RPM or so) while spraying starting fluid into the throttle body.  As I loosened an injection line, I initially got a little fuel and air bubbles from the connection.  I have not been able to observe any fuel flow from the injection line while cranking the engine.  

We have the original injection pump available but wanted to see if there were any more ideas to get this pump to work before swapping injection pumps.

[ja17]

Hello Jim,

The first thing I would do is check the rack in the pump to see if it is free. You can inspect it by going through the small bore in the front end of the pump. The rack should have a cylindrical metal cover or a rubber cover. Some early racks have a threaded screw hole you can wind a screw in and pull and push the rack if it is free. If not it should move aboput a 1/4" when the accelerator linkage is moved all the way.  You should also be able to push back on the rack and it should move back.

Next remove all the spark plugs, priming those long injector lines will take some cranking. Crack the lines at the injectors and crank away with full throtttle. As fuel emerges at each injector line, tighten it down. When all lines respond with fuel, install the plugs and it should start. Run the engine for short a short period and check oil pressure, temperature and look for leaks.  Several short start and runs are best allowing the engine to cool a bit in between. You will be making "tweeks and adjustments" during these initial trials. The last start cycle should allow engine to warm completely to temp. Make sure the thermostat is opening (radiator will become hot on top) or an air lock will cause overheating. Top off coolant again. Loosen radiator cap and re-torque the cylinder head after first warm up (according to BBB), re-torque again between 300 and 800 miles.   First test drive should be short. Let engine cool down. Pay attention to how the new hot engine starts and shuts down. Tight starting or abrupt shut down indicates internal binding which is somewhat normal unless severe.  Short warm-up and  cool down cycles will allow parts to "break in" without damage.


Happy motoring!

Joe Alexander
Blacklick Ohio

[JimVillers]

Joe ... Your were right on.  I checked the rack movement with the cap at the front of the injector pump and found that it was not moving freely.  I ran it in and out a dozen times or so to see if it would loosen and it did a little but was not free like the old pump (nice to have a spare on the bench to compare with). 

I set the rack full forward and cranked the engine until saw some gas at the injector lines.  After tightening the injector couplings, I tried firing the engine, no results, a little starting fluid and it fired right up and continued running.  I ran it for about 30 seconds.  Moved the rack in about half way and fired it up again.  This time it would rev smoothly and idle at about 1000 RPM.  Oil pressure was pegged. 

The power steering fluid belched some fluid and when inspecting I found lots of air mixed into the fluid.  I assume that this is just the fluid getting pumped through the system.  I had turned the wheel left and right to circulate the fluid.  I'll bleed the system when the engine works.

I checked the rack again and it would move but not easily.

My thoughts are to keep moving the rack and occasionally starting the engine until it is free.  Any other ideas?

 

[JimVillers]

The joy of success.  After working with the control shaft, it became looser and looser until it began to move with the accelerator.  I started the engine and set the timing with a light and the engine now starts and runs normally. 

I bleed the power steering with a tube from the top of the steering box bleed screw into the reservoir.  Lots of bubbles and milky fluid but it slowly cleared up.

Next challenge, a water leak and some fluid coming from the auto transmission (hopefully just an over full condition until I could run it through the gears to circulate the fluid).

[ja17]

Good deal !

Yes, if you dumped the entire amount of ATF in the trans at first, it will usually belch some out the vent. I normally add about 4 quarts run it through the gears so some gets pumped into the torque converter then add the rest.

The power steering pump will bleed itself if you run the engine, then turn the engine off and allow the foam bubles to escape, refill the fluid, start the engine, top off the fluid while running, turn the wheel from left to right while running, top off once more. Should be fine. Re-check fluid level first opportunity.
However can't go wrong just bleeding it either.

A bit of 2cycle motor oil in the first tank of fuel will lube thing up a bit.  I add some to the fuel and run the engine before winter storage on my old injected cars, keeps things from getting stuck!