Well, decided after all that to keep my 400i

Well fellas, after going round and round on eBay and finally nailing down a buyer, I made a serious change of heart and decided I didn't want to let my 400i out of my posession, drastic I know, but every time I look at the car, I just love it (and I guess finally came to my senses about (not) selling her!). Well anyhow, since I've elected to keep her in my herd, I've got to get to the bottom of my issue with the left bank running rich, and this is what's happening:

When I start the car, I see a little fuel drip leaking from an exhaust flange on the left side of the car, so it's obviously dumping raw fuel into the exhaust (I haven't run it but a couple of minutes since this began, just trying to diagnose it). I recently put a new dizzy cap on, new rotor, new wires, new plugs in and all new injectors. I double checked the firing order on the body of the dizzy (1-12-5-8-3-10-6-7-2-11-4-9) in clockwise rotation looking down on the distributor. Also have the plug wires in the correct places (#1 starting at the right front (right side meaning when sitting in the car), going in a "U" shape with #12 ending at the left front). I have the right bank tuned fine, the plugs are a nice ash grey color but the left side is really rich, I mean REALLY rich. I have also checked that the control plunger in the fuel head is not binding (I lifted up on the sensor plate and made sure it dropped back down smoothly with a little "bounce" before it re-seated itself, which it's doing).

Before I take this any further, I need to clarify something on mixture adjustment: When I'm standing on the left side of the car, looking down onto the driver's side fuel distributor, am I correct in that turning the mixture screw (the 3mm allen screw right "behind" the fuel head) COUNTERCLOCKWISE will lean the mixture? Or is it the opposite since it is a "backflow" system (i.e. sensor plate rises instead of falls on throttle, which it does in a Mercedes)?

I'm going to set the crank to TDC and make sure the rotor arm matches up with the mark on the dizzy body, just to be sure that's totally in order, but what else could possibly be causing this?? I obviously don't want to drive the car because of risking engine damage with fuel wash in the oil. But the car was invited to our local Concours d' Elegance in June (another reason why I decided to keep her ) and I need to have her running in top form. Something that could cause one bank to overfuel, or cause the ignition system not to hit on the left bank?

Cheers,
Aaron

 

Update:

Checked the timing, it's right where it needs to be, and plenty of spark getting to the left bank, so it's something fuel related on that side. Can a bad fuel distributor cause overfueling? Adjusting the mixture doesn't seem to make any bit of difference.

??

Cheers,
Aaron
'82 GTSi
'83 400iA

 

A-HA!

Ok, I've discovered that with a 400i, there is 'firing order' and there is 'firing order'. The true firing order is of course 1-12-5-8-3-10-6-7-2-11-4-9 however, starting with #1 on the dist. cap, you do NOT follow that sequence, as you would normally with most other cars. Because of the 180 degree difference between the contacts on the rotor, the actual firing order is 180 degrees +1. Thanks to Mark from Concours Cars for this clarification!

So, beginning at #1 on the cap, the sequence of the wire connections is as follows (clockwise)...

1-7-5-11-3-9-6-12-2-8-4-10

So, now I have the car running on all 12 except that it wants to run for about 10 sec (runs well when it runs) but then just dies as if someone yanked the fuel pump relays. I'm going to check them but they are fairly recently replaced. And the round, black electrical portion of the ignition switch has been changed as well.

Continuing the hunt....

Cheers,
Aaron
'82 GTSi
'83 400iA

 

Mark,

The way you suggested is how I originally had it wired and it wouldn't run on the left bank. I spoke to Mark from Concours Cars and he said this was a very typical mistake to think that the wires are ordered the way you suggested. I checked what Mark said using the old cap and rotor and it is indeed wired how he said it was. If you take the old cap and rotor and spin the rotor inside the cap, in the same sequence that Mark said, it does, in fact fire the cylinders in the order of 1-12-5-8-3-10-6-7-2-11-4-9. BUT in order to get the rotor to fire those cylinders in that order, the wires must be connected as such (clockwise from #1 on the mark of the dizzy); 1-7-5-11-3-9-6-12-2-8-4-10. It's confusing, but it worked! When the car runs, it fires on all 12 and runs smooth as silk, the problem now is that it dies after 10 sec.. and I'm still hunting for that cause.

Cheers,
Aaron
'82 GTSi
'83 400iA

 

Well, either way, I've got the car going on all 12 except that it just shuts off, as if you were to yank the fuel pump relays. When it runs, it runs smoothly. I checked the fuel pump fuses, I see they're supposed to be 16A but someone has plugged in 20A fuses in their place. I'm going to get some correct fuses and see if that cures it. I had a similar problem on my 308 where it would just die when you were sitting at a stoplight, I found that someone had wired a 30A (!!) inline fuse in place of the proper one on the fuse block. I purchased new blocks from Birdman and wired the fuel pump circuit back the way it was supposed to be (and replaced the FP relay) and the problem hasn't reoccurred in at least 8,000 miles of driving. So I guess the problem there was that the fuse was letting too much power through and overheating the FP relay, which I'm hoping is the same problem with the 400.

The issue with the 400 certainly doesn't seem to be a hard fuel related problem, per se. More so an electrical gremlin lurking somewhere.

Cheers,
Aaron
'82 GTSi
'83 400iA

 

Steve,

Thanks for the suggestion! I shall try that and see if it isn't my gremlin! I figured it had to be something like what you're describing.

If I recall though, I didn't see a safety switch plugged into the driver's side throttle plenum, only one on the passenger's side. I did see the connection on the driver's side, but no plug (??)

Cheers,
Aaron
'82 GTSi
'83 400iA

 

Ahh gotcha. Thanks Mark.

Onto the relays!

 

Amazing what some gas will do in terms of getting an engine to stay running

 

Ok ok hardee har har you guys!!!

Yes, the tank was dry. Jeez I feel like an idiot, but a happy idiot at that!

Of course, now after swallowing $104.00 :0 worth of premium, my gas gauge is only showing 3/4 full, and I know she took a full 30 gallons.

Cheers,
Aaron
'82 GTSi
'83 400iA