110 CIS fuel distributor supply and return line placement? - PeachParts Mercedes-Benz Forum

arootbeer · #1 05-27-2007, 06:25 PM

I'm finally getting some time to start working on this M110 -> W111 swap, and I want to make sure the M110 runs before I pull it. The fuel pump on the car is burned out (verified), and the gas in the tank is of unknown condition. I don't want to pull the tank since the car is junk (the body is >50% bondo, with holes all through the pan).

I've got a new electric fuel pump, but I can't tell (and the haynes doesn't specify) which line is the supply, and which is the return, so I can rig up a bucket system to get some fuel to the engine short-term. Can someone identify the 3 lines with arrows pointing to them in the picture?

TIA!

romansek · #2 05-27-2007, 11:00 PM

Arrow on the left - return control
arrow on the center - return to the tank
arrow on the right - fuel supply from the pump

arootbeer · #3 05-28-2007, 01:52 AM

Thanks for the insight.

Is the "return control" related to the pressure sensor line on top of the distributor? I don't want to send any gas back to the tank on this car; in order to keep that from happening, do I just need to run the return line into the bucket? Is there anything else I need to bypass?

romansek · #4 05-28-2007, 03:10 AM

Just run the return line into the bucket or even better into the bottle (less mess). Pressure regulator controls the fuel distribution pressure.

arootbeer · #5 06-21-2007, 10:55 PM

Finally got the banjo bolt I needed to get the fuel return setup going tonight. Looking back, I probably could've just put a 1/2" line over the 14mm -AN fitting on the return, but whatever. Anyway, picture 1 is my setup. ~3 feet of 1/2" line to the pump inlet (which makes for a good reservoir), 6 inches of 5/16" to the distributor supply, and 1/4" from the return to the gas can.

For the first 4 or 5 tries, the fuel pump wasn't even pushing fuel through the lines; when I took the supply and return lines back off, all of the banjos were completely dry. I got that sorted out by just holding one lead to the battery and one to - on the coil (terminal 1). (I had hooked the pump electric supply up to 1 and 15 on the coil because it was a switched source...didn't really think about it until later, but that's probably why the pump wasn't pushing fuel well when I was actually trying to start the car.)

So I filled up the supply hose for the pump, and tried again. It still won't start. I tried several times. I am getting fuel through the distributor and back into the gas can. You can see the injection control plate open slightly when the engine turns over, so I don't think that's the issue.

I tried to check the coil primary resistance, but the multimeter I have is analog, and the smallest unit is 100 ohm. I was definitely getting power across the primary, because when I had the pump hooked up to 1 and 15 and turned the key on, it would run just fine until I started cranking. The spark plug wires were replaced by the previous owner, as well as the distributor cap. They're all in extremely good condition with no condensation that I could tell in any of the wires.

I haven't gone to search yet, but I think the wires may have been on incorrectly. But they may still be, although I shifted them all counterclockwise by one in accordance with what my Haynes (vaguely) shows as the correct setup. Picture 2 shows the distributor now, with the red arrow pointing to the current wire 1 position, and the blue arrow pointing to the previous wire 1 position. Is either of these the correct position?

Additional information:
I checked all of the wire positions relative to wire 1, and they are correct for the clockwise firing order 1-5-3-6-2-4. This is a transistorized ignition; it's got the control box on the fender near the coil, although I don't see any pre-resistors in evidence (that doesn't mean they're not there and I'm not looking in the right place, though).

arootbeer · #6 06-25-2007, 06:51 PM

Can anybody help me out with the plug wire setup?

Larry Delor · #7 06-25-2007, 09:45 PM

The plunger could be sticking (it is what I call the smooth metal pin that drops down, whenever the plate moves up. If you pick up the plate (equiv. of air mass meter) does the plate go back down slowly, or does it just drop and maybe bounce a hair or two?

Oh, and a vacuum leak can make starting this thing a bear too - try it maybe at full throttle...just be careful.

arootbeer · #8 06-25-2007, 11:50 PM

I'm not sure I understand. The plate goes down to open the airway, and comes back up to shut it. It does move up quite slowly, but it doesn't seem to be obstructed in any way. It will move down as quickly as I push it down.

I'm sure there are all sorts of places for a vacuum leak...the engine has some "interesting" air/vacuum plumbing done. Does the fuel distributor take vacuum at some point?

#9 06-26-2007, 12:01 AM

You need 70psi pressure in order to start the motor, which is what the oem pump was rated for.

arootbeer · #10 06-26-2007, 10:52 AM

The pump that I'm currently using is rated at 125 PSI (the P/N is a replacement for the OEM pump). I don't know that it's making that much, but it doesn't seem to be behaving improperly. Does it need to be approximately 70 PSI, or at least 70 PSI?

cheapold280ce · #11 10-12-2007, 04:33 PM

I might be missing the point here but if you just want to check motor out put some gas through the mass air sensor intake engine should run for a short time. If you get a spray bottle you can keep it running by spraying gas into the intake. At least you would have found out the ignition is working and the engine is o.k.

cth350 · #12 10-12-2007, 06:55 PM

Two naive questions...

- You do have a fuel filter between the pump and the injection system, yes?

- You didn't bypass any of the fun components, like the pressure regulator or WUR?

I've done what you're doing with a pump bypass before, but always at the tank end.

-CTH

ctaylor738 · #13 10-13-2007, 09:47 AM

I think you've got the plumbing right.

Fuel to the FD does not mean fuel to the injectors.

Run the pump crack the fittings on top of the FD and see if you get any fuel flow. If you don't try richening the mixture (turn the adjusting screw CW) a max of one turn, and see if you get some gas. Then tighten the fittings, turn the ignition on and try a start.

One other thing to check - there is a filter in the inlet to the FD. It may be clogged. It's also possible that the FD is so full of crud that it's not going to allow enough pressure to open the injectors.

arootbeer · #14 10-17-2007, 10:11 PM

Interesting to see this thread bumped as I start working on the car again. I went through and triple-checked the spark and timing tonight.

I tried pouring a small amount of gasoline into the air intake (past the metering plate), and starting the car without the pump running. No luck. Pulled plug 1, had the wife crank the car, and verified that the spark and the wind were synchronous. Put the plug back in, cranked some more while manipulating the throttle pedal. No luck. Cranked some more, sprayed some WD-40 past the metering plate. Still no luck.

Basically I want to get the engine started so I can pull it and part/scrap the '78, just to get it out of my driveway. Is there something different about the CIS setup that it won't let me put fuel in the metering passage? I even thought it might be an airflow issue, so I propped the metering plate open about a half inch.

I will be testing the fuel distributor, hopefully within the next day or two. But I'd like to be able to just get it started, even without the distributor, since part of what I'm planning is a Megasquirt conversion.

ggenovez · #15 10-18-2007, 12:00 AM

Have you pulled the #1 plug, put your finger over the plug hole and bumped the engine, until you feel pressure (compression stroke), then truned the crank until TDC.

On the Distributor, there should be a mark for the #1 plug, and turn the distibutor until the rotor lines up with the mark.

From there set the rest of the firing order

1-5-3-6-2-4.

Good luck.