Just rebuilt the fuel distributor and car won't start

[fischp]

Hi all,

Re: 1981 380SL

Thanks in advance for your help. My saga originally started with a vacuum leak in the large rubber diaphragm at the bottom of my fuel distributor. Additionally, I was blowing white smoke (not a head gasket issue) that smelled of gas. I discovered two wet cylinders where the FD was apparently leaking. I just got done rebuilding the FD and installed it, along with the new rubber diaphragm. I took special care to ensure that the throat of the diaphragm was seated securely to the throttle body. I also installed a new distributor, rotor and new spark plug wires since had the top of the engine exposed.

I tested the rebuilt FD by installing it and plumbing all of the WUR and gas lines but leaving the actual 8 feeds to the injectors open. I turned on the key, position 2, and saw that gas evenly filled the cups where the fuel lines to the injectors will go. I originally had a tear in the FD membrane which was dumping gas into two cylinders. I also depressed the air metering plate and saw the fuel level rise. All looked good. I then reconnected all of the rest of the plumbing, replaced the spark plugs and wired up the spark plugs, comparing the sequence with the old cap.

Now my car doesn't start. I'm pretty sure I need to adjust the mixture or set something but I'm at a loss as to what. When I crank the car, it sounds like it wants to start but never does. Like one or two cylinders firing the rest not. I checked for spark on the #1 cylinder and it good very good. Seems like the #1 cylinder is getting too much fuel, when I unscrew the spark plug it sounds like I'm opening a soda bottle. All the rest are fine.

Also, when I crank the engine for 10 seconds or so I smell gas. There's nothing leaking anywhere that I can see.

I know it's tough doing triage across the Internet but I would sincerely appreciate any guidance. The car was running, although badly before I started so I've obviously messed up somewhere.

Thanks,

Perry

[TnBob]

Recheck your spark plug wiring.
Crack open each injector connection and insure you are getting fuel to each cylinder.
Obviously re-tighten prior to the next starting attempt.
Crazy as it sounds, make sure your distributor cap is seated correctly.

[fischp]

TnBob, thanks, I've checked the wiring twice, so next I'm going to pull the distributor cap off as well as the #1 plug and bring that piston close to TDC and go old school, ensuring that the rotor is truly pointing to the #1 spark plug wire. It definitely "feels" like a timing issue, although not sure how timing could change since I never loosened the distributor cap bolt. Hoping that all it is.

Regarding the injectors... After a few attempts that start the car I pulled all of the plugs and had my son crank the engine, just to make sure the fuel lines were bled and that I was getting gas to the cylinders. When cranking I saw a cloud of fuel shooting for each cylinder, so I think/hope that's ok.

Thanks! I'll give that a try this afternoon.

[fischp]

No luck, the plug wires are correct, based on me manually aligning TDC on the #1 cylinder with the rotor, also watching for direction of rotation on the rotor.

Any thoughts?

[TnBob]

Really doesnt sound like a motor issue nor timing.
Gotta be an adjustment in the FD which Im not familiar with ... yet.

[fischp]

Yup, I agree. I checked the entire ignition system and it all looks good, a bit crusty, but good and I have a nice strong spark.

Does anyone have any FD knowledge? I disconnected the injector lines again last night and when I turn on the ignition, the cups where the injector lines go fill up as I'd expect, and the levels change when I depress the metering plate. The spark plugs are definitely wet, too wet to start even with starting fluid. How do I lean out the FD? Any guidance, links, videos would be appreciated!

Thanks!

[Frank Reiner]

fischp:

If you remove the fuel pump relay, you will be able to crank the engine without adding any more fuel. Perhaps you will be able to dry the plugs enough to get a brief fire up on residual fuel and/or starting fluid.

Do you have a timing light? Check that #1 is in fact firing at approx 10 deg. BTDC at cranking speed.

[fischp]

Hi Frank, I'll go ahead and do that, it's a good suggestion to at least dry the plugs. Yes, I have a timing light and have also done a manual check to see that plug 1 was indeed firing around TDC by checking the position of the #1 piston and rotor. I also put the old rotor, cap and wires back just in case there were evil spirits around the new ones...

I was going to pull the relay anyway, so I'll attempt to dry the plugs.

Thanks!

[fischp]

Good news, I pulled the fuel pump relay and the engine started after about 2 seconds of cranking. I squirted a bit of either and restarted it, ran for a few seconds. Great, I have dry plugs now, thanks for the suggestion Frank! Ignition system good...

Ok, now my FD is distributing too much gas. I've tried turning the 3mm hex screw counter-clockwise to lean it out but no luck. Not sure how far it should turn but I've turned it CCW a lot... According to some of the posts I've seen here and other site, I should be able to jump past the relay to get the fuel pump to run continuously and not have gas overflowing the cups where the injector pipes go in. I'll keep messing with this but I'm at a loss. The FD wasn't that hard to rebuild, but...

Thanks to all!

[fischp]

Just to level set here, one of my original problems was that the gasket/membrane on cylinders three and fours in the FD were perforated, so I had lots of gas leaking into these cylinders, which I believe was the cause of the white smoke and unburned gas at the exhaust pipe. I carefully rebuilt the FD and now nothing freely flows out of the injector connections on the FD, at least during the first turn of my key to position #2. Where else could the gas be coming from? I guess I'm next going to jump the FP relay to see if I can see/hear any gas. The FD is a really neat piece of engineering, but it's not that complicated either... Has anyone had an issue like this?

[Frank Reiner]

fischp:

Good to hear that you were able to get it to light off. Try disabling the cold start injector, first by pulling the plug from the injector, and then if necessary, by capping/plugging the fuel line. They have been known to stick open.

[fischp]

More progress, not so good news... I pulled the fuel pump relay and wired in a long piece of cable and a toggle switch so that I can make the FP run while I'm staring at the FD. The ignition key is off, so I'm presuming that nothing is active on the car, no warm up circuitry etc. Just me and the FP. When I flip the switch and enable the fuel pump my FD looks like a fountain, leaking gas out of all of the injector connections, remember, they're still disconnected. I'm lead to believe that a properly tuned/set FD will not free flow, and only dispense gas when the metering plate is depressed, or a little sad...

Ok, I'm going to pull the FD (again) but I'm curious as to why all ports are squirting gas. If I would of messed up the FD rebuild, I would expect one or two ports to free flow, not all of them. I'll go ahead and check the plunger and make sure something's not jammed.

Thoughts and opinions? Am I correct in assuming that the FD is not supposed to dispense gas unless the metering plate is depressed? Could this be anything other than the plunger on the FD?

[TnBob]

Frank is the genius here with FD's.
Looks like timing wasnt the issue.

[fischp]

In the immortal words of Dr. Frankenstein, "It's alive!!!!"

First of all, thanks for TnBob and Frank for invaluable guidance and good ideas. As you can read from the thread above, my injectors were getting flooded when the fuel pump was running. Solution, the FD plunger wasn't down far enough in the metering body to stop/restrict fuel flow. (The FD Plunger up provides gas, plunger down stops the flow of gas.) I wound up removing the FD and the top part of the metering assembly, then re-installing the FD without the top half of the metering assembly. This enabled me to put my finger on the plunger and find where, if at all, the fuel would stop flowing. I did that then turned on the fuel pump. I allowed the plunger to go lower and lower, out of the FD, until the fuel stopped flowing from the injector cups (careful, there's a surprising amount of force pushing down on the plunger from the fuel). Ok, net net, the FD wasn't bad, I hadn't adjusted the mixture screw nearly enough to stop the flow. So I unscrewed, counter-clockwise, the mixture adjustment until it stopped, aka all the way out. Once the test was done, I "simply" reassembled everything. Once assembled, I turned on the fuel pump, and no gas came from the FD. I then turned the mixture screw clockwise until I saw the fuel start to rise in the cups, then turned the mixture screw counter-clockwise a quarter turn, a habit from my carb rebuilding days. Once that was done I reconnected the injector lines and two cranks later she was running. I did need to richen up the mixture, clockwise, to get her to idle nicely.

I'm sure I still have lots of tweaking to do, but my non-running is a runner again! Woo-hoo!!! What a good way to start the weekend.

Thanks again to all. And a note to those that are thinking about rebuilding or anything to do with the FD. It won't bite! Look at it, think about what it does and how it works and give it a try.

[TnBob]

Franks direction was sure the winner here !!