Running the engine on a test bed

Background

Before installing the engine, with its auxiliary systems mounted, in the car I wanted to check that:

• everything works as it should,
• there are no leaks
• re-tighten all screws after the engine has been run warm (including the cylinder head's), and of course
• do the first tuning of fuel and ignition system and set the valves. It takes time to prepare for this and do the provisional assembly but it was definitely worth it. This way I had full access to all sides of the engine for necessary repairs, adjustments and fine-tuning, especially if I had find any major parts that had to be removed and redone.

Above all, I don't risk scratching the paint on the car etc (which is accentuated by the small size of my garage) during this work.

Running my Mercedes-Benz 219 engine M 180 II on a home made test bed

First phase

The first phase included:

• Build the test bed, in my case consisting of a wooden pallet to bare the engine and a wooden rack for mounting ignition coil, the combi instrument etc.
• Mount and fasten the engine to the test bed
• Connect electricity, and water temperature and oil pressure gauges in the combi instrument
• Run the starter to see to that it, and the ignition, worked and that I got oil pressure

Since I have no idea how electricity works, even less on a car it took me some time to figure out how to set the ignition up. I spent many hours on the 219’s electric scheme in the workshop manual and practicing on my new cable harness to see how it looked like in reality. In order to understand a crucial part of the ignition system, the ignition switch, I also needed to consult articles on the Ponton pages, Mercedes-Benz Ponton Ignition Switch Repairs and Mercedes-Benz Ponton Rotary Light Switch. If you’re interested you can find some more pictures of the ignition switch below. I needed those to understand it better.

Finally, I came up with this scheme and it worked flawlessly (the fuse is not necessary, actually wrong, but I have it installed and it doesn’t hurt). The notations regarding cables, branches etc comes from the electric scheme in workshop manual and is there as a reference for you.

Electric scheme for test of ignition

Building the test bed itself was only to measure engine and radiator and saw and screw accordingly. The engine was lifted in place and attached with a piece of rubber and screws in the front and a strap in the rear. Electricity, (newly restored) combi instrument were attached and water temperature and oil pressure gauges as well.

With everything in place, I run the starter to check that it, and the ignition, worked as it should and that I got a good oil pressure.

YouTube video showing the first test, running the engine on the starter

 Second phase

The second phase consisted of assembling the exhaust system with mufflers (both to have a “as-real-as-possible” test environment and show some respect to my neighbors) and an improvised fuel system (rubber hose before the fuel filter and a canister). Triple checked that everything was in order including the base settings of the carburetor and pumped up fuel with the fuel pump lever. Then I hooked the ignition analyzer (?) and the timing light up, turned the ignition on, pressed the switch and held my breath. It took a couple tries but then it run and actually quite well! I had to open the idle screws from the base setting (1 turn) up to 2/2,5 turns and slightly alter the distributor advance. Run it warm and checked temperature and pressure, tightened _all_ screws on the engine but sighed over a leaking, restored water pump.

YouTube video showing the second test, running the engine on fuel

After this I made a first tightening of the cylinder head, adjusted the valves. The plugs were a bit too black but all looked the same.

Third phase

This phase was to test everything more thoroughly and over longer periods. With a warm engine, I checked the ignition advance on 800, 1500, 3000 and 4500rpm (without the vacuum advance hose). The values were perfect and stable which was an amazing experience. Before the engine restoration this was more or less impossible to achieve.

YouTube video showing the third test, verifying the engine on idle, 800rpm

During these tests, some more leaks appeared but was easily fixed by tightening related screws. The water pump was removed and gone through again (see the article Engine cooling and the section “Water pump” – “And again…”). At the time of writing this the water pump unfortunately still leaks. I had hoped that it would disappear after some time but even after 2-3h on different rpm’s it hasn’t. We’ll see what I do.

I also have a small oil leak from the distributors oiler but that may have been caused by me, not closing it well enough. We’ll see what happens with that as well. The third thing is that the heating flap, situated under the carburetor, doesn’t close even though the exhaust manifold has been hot, the flap moves freely and the thermo spiral is new and seems to be working (extends) when I test it with a hot air blower. I’ll go for that problem later as well.

YouTube video showing the forth test, verifying the engine on 3000rpm

After having gone through the ignition advance on all rpm’s the last thing was to set the fuel level in the carburetor float bowl (13-15mm in my Solex 32 PAATI). Suddenly the engine started to run very bad and stopped after some time. I thought that was strange, how could the fuel level lead to that. Went through the construction of the carburetor and how it functioned – again. Couldn’t see the relationship to this and the engine’s behavior. Realized I could pump fuel to the carburetor with lever just after the engine had run. In some way the engine didn’t get fuel enough so I took the pump of and checked everything. The rest of that story you can find in the article Fuel pump and air filter and the section “Fuel pump” – “And once again…”.

During this troubleshooting, I also tested the amount of fuel the pump gave. That you can find in the same article as above but in the section “Measuring that the fuel pump delivers enough fuel”.

Thereafter +1h of engine tests commenced. Since the plugs after the last test looked slightly "wet" I had the idling screws out 2 turns instead of 2,5. The engine run more or less perfect, from 800rpm up to 4500rpm. Never stalled or run bad (except that it maybe took 5-10 sec to stabilize after having run 4500) All ignition values stable and within limits. Cylinder head was tightened again and valves adjusted (always a couple to loose…). This time plugs 4-6 had a perfect even, dark gray color but plugs 1-3, especially the first, looked "less used"! To lean on fuel? Maybe the idling screws was a bit wrongly set by me. We’ll see…

YouTube video showing the fifth test, verifying the engine on 4500rpm

Fourth issue; during and after running the engine on 3000 and 4500rpm I have a rather high ticking sound from within the engine (some of it can be heard in the 3000rpm-video, around 45-50sec into it). It didn't sound like the valves, maybe the fuel pump tappet?! 

Fourth phase

This phase was half a days work a couple of days later. I had the engine “verified” by an experienced friend, Jan L. This included checking the valves (where he strived for a much more "tight feeling" with the feeler gauge than I have done so far), checking the ignition and fine tuning the carburetor incl CO-value. The result was absolutely an improvement, the engine is definitely more silent now, runs even smoother and the spark plugs have a perfect, even, dark gray color.

We identified, with the help of a small piece of garden hose as stethoscope, two sounds that I was wondering about now when the engine was so silent. The first one was simple, the sound of the fuel pump. The second one, a chirping sound coming from the area around the carburetor, was however a bit more tricky. We located it to below the carburetor, from within the intake pipe/manifold. Turned out to be the heating flap, probably from small movements when the exhausts hit it and probably also from the exhausts circulating around it.

The water pump seemed to have settled down and didn’t leak any more, so did the distributor. I assumed new parts etc had worn in. We’ll see if I do something about the “screws”, on the front of the engine ,that hold the chain guides, still smalllll leaks there.

After having spent nine month on getting the engine and gearbox into a shape, things I thought were already OK, I now turn to some hopefully less complex and more “productive” tasks.