Next problem. BOOM, but not running, WTF now? Options

[Dr Evil]

So here is the back ground:

I have now checked all of the injectors and they do not leak, spray patterns are consistent, as are flow amounts.

I have checked the CDI hook up and spark and found spark to be present and adequate.

I have checked and rechecked the plug wires and connections and they are correct. Firing order is 1-6-2-4-3-5 going clockwise.

So what the hell am I seeing, or more correctly hearing?

I set the engine to TDC on #1, set dizzy so notch for #1 on the lip of the dizzy is pointing directly at the retainer band for the alt/fan, and set rotor to point at said notch.

I turn the key and it catches and runs mroe than it did before, but it back fires through the air box (good thing I installed the popoff valve) with a thunderous explosion. It almost sounds like there is a plug wire on the wrong plug. I try again after moving the dizzy slightly and I get no running and another explosion.

I had the cold start valve unplugged (I think I do, it is on the right hand side and I pulled the wire out).

So I remove #1 plug and find it to be wet which matched the fuel smell I was getting the whole time. So now I am letting the engine sit for now to evaporate any excess gas.

Please help me generate a check list for what to look at and adjust. Could it be 180 out and still act like this? Do I have a rare crank that changes my firing order (ya right)?

I am wondering why this is being so damn difficult. I wonder if the shop put the cams on the wrong side, or if I am missing some pistons (IMG:style_emoticons/default/dry.gif)

[John]

I still say, check the airbox for leaks. Any leaks will make it run just as you describe.

Those six boots on the runners are a BIG PITA to check and change out.

If you can get a helper to start the car while poking around the engine comp, lift up on the plunger when it starts and see if you can keep it running that way. It doesn't take much lift. You should also be able to hear any intake leads if your head is in the eng comp while it is running.

[TROJANMAN]

have you tried posting the question on the bird board as well? (911 style (IMG:style_emoticons/default/cool_shades.gif) )

[Dr Evil]

I replaced the rubber runner boots already when I rebuilt the whole CIS system so I am not feeling that that is it.....but what do I realy know at this point.

I can not get it to run realy. It ran for about 1 second with the BOOM BOOM.

I do get what you are saying, though. If there is a leak in the box then the diaphragm will not experience the suction to move it, but the plugs are getting wet.

[Dr Evil]

have you tried posting the question on the bird board as well? (911 style (IMG:style_emoticons/default/cool_shades.gif) )

No, but I will. I actually found a few guys over there that don't suck (IMG:style_emoticons/default/biggrin.gif)

[lapuwali]

This REALLY sounds like way off ignition timing to me. Just as you say, it sounds like the plugs aren't firing in the correct order.

You might try disconnecting the CDI box and just run off straight points just to get it running. Eliminates one variable. Have you tried a timing light on the flywheel mark while cranking, just to see if it's firing No. 1 at the right time?

[Dr Evil]

Here is a helpful page that I found, http://members.rennlist.com/jimwms/CIS/CIShome.html

Here are the recommended checks:

-Sensor plate and /or plugunger not moving freely (GO)

-Auxiliary air valve does not open (Not on mine, started in '76)

-Electric fuel pump not operating (GO)

-Cold start system defective (Disengauged, GO)

-Thermo-time switch defective (No idea where this is)

-"Cold" control pressure outside tolerance (Huh?)

-Injector leaking, opening pressure too low (All good, GO)

-Injected fuel quantities unequal (Checked all good, GO)

-Basic idle setting incorrect (Oh ya...maybe I need to check this?)

[Ferg]

This lacks in any technical info but...I ran my old 2.7 six dry (out of gas) and had the same almost catch and backfire through the airbox you describe after a shamefull flatbed home, it took about 3 cycles of cranking/flooding/airing out to get fuel to everthing again, then of course the battery had had enough cranking and was weak, so check your cranking volts at the battery as well.

Ferg.

[lapuwali]

For the thermo-time switch, follow the wires from the cold start valve. One of them will go to the starter solenoid (activated during cranking only) and the other will go to the TTS, which grounds into the case. Since you've already disabled the cold start valve, this is useless, but at least you'll know where it is. (IMG:style_emoticons/default/smile.gif)

[Dr Evil]

Kinda what I was going through. I had already primed the system as seen by the injectors in the bottles so no fuel is not a problem. Battery is cranking strong and I keep topping it off.

I am thinking if I air it out tonight and adjust the idle screw maybe it will start tomarrow. It is such a friggen tease.

[Dr Evil]

I did not disengauge the cold start valve. I unplugged the warm up regulator....maybe the probem. CSV is still pissing a bunch of gas into the engine.






DOH!

[lapuwali]

I may not have diengauged the cold start valve. I unplugged the warm up regulator....maybe another probem. CSV is still pissing a bunch of gas into the engine.

Mixture may be way too rich, then. Disconnect the CSV itself, as it will make things WAY too rich. Disconnecting the WUR is less likely to help (or harm) things.

Futzing with the idle mixture screw will turn it from easy to hard starting, but it's unlikely to venture into "impossible". Twirling it even a very small amount will make a big difference to idle quality, though. It also makes a huge difference to emissions, if you have to run a smog test where you are.

[So.Cal.914]

#1 cylinder at TDC, use pencil to mark location of #1 spark plug wire/nipple on

distributor cap on to the body of distributor. Pull cap and check relation of the

rotor to this mark. Rotate body to line up the rotor to the mark, if you have done

this, never mind.
(IMG:style_emoticons/default/smoke.gif)

[MecGen]

Hi

Its been a few years since I've worked on my Benz (sold) but I had a very similar problem, flooding/poof/bang. I am lucky anough to have a friend that works at Mercedes to have walked me through the diagnostics. It was the Warm up regulator that went bad, unpluging it made things worse and more confusing. This is not a good thing to do for diagnostics. I bought the "Bosch" manual thru an autoparts, which realy helped.

Hope it works out
Later

(IMG:style_emoticons/default/beerchug.gif)

[Brian_Boss]

Did you static time it to spec with a test light or multimeter?

Never mind if this was covered and I missed it.

[Thack]

Usually a big backfire like this is from a lean condition. I had a fuel computer go out in my 3.0 CIS. Get a can of starting fluid or just a bit of gas and pour it down the intake/flapper. If it fires up you know you are lean. Those fuel flow rates through the injectors just checks the injectors. You jumped the fuel relay to get the pump to flow right? What makes the injectors fire? Do you have a fuel computer? or is it fully mechanical injection?
WUR will still work if you unplug it it will just take longer to warm up since the WUR uses engine heat to reduce fuel pressure without electrical help.
Cold start valve doesn't even work unless temp is near freezing.
You are starving of fuel unless timing is off.
If you are running too rich reduce your fuel pressure and see if that helps. I have the CIS fuel pressure tester which really helps. You can email me if you have questions.

[rick 918-S]

CIS is not that fussy IMHO.
Sounds like you ran down the problem with the sticking sensor plate thing. Now your chasing goasts.
I'd start looking at the cap and wires for carbon tracking. Sandy and I were about 100 miles from home and stopped for lunch. We came out and started the car. We moved about a block when we had a back fire and the car shut off. I would not catch or fire again. I checked the "new" cap and found a deep cut caused by carbon under the coil terminal boot. I scraped the carbon out of the deep arch, Sandy applied some nail polish. One wrap of orange electrical tape, and we were off.

90% of fuel related problems are electrical.

[Thack]

Is this problem while it's hot or starting from a cold engine?

[Dr. Roger]

#1 cylinder at TDC, use pencil to mark location of #1 spark plug wire/nipple on

distributor cap on to the body of distributor. Pull cap and check relation of the

rotor to this mark. Rotate body to line up the rotor to the mark, if you have done

this, never mind.
(IMG:style_emoticons/default/smoke.gif)

what socal 914 said....
pull the #1 plug and turn engine over till #1 is at TDC. (if your assistant puts their finger over the plug hole you'll hear air rushing past their finger).
then double check that the distributors rotor is pointing to the #1 plug wire...

Rick, I gotta' remember that...... 90% of fuel problems..... LMAO....

[wilchek]

Mike,
If you don't get this thing running by Sunday I can come by and help you out. My dad is an electrician and I can grab some of his cool volt meters and varius testers so we can test the spark and everything else. Sounds like you are close be patient. We can figure out if it is an electical or timing issue, or a combination of both. Drop me a PM with you number.

Also, the WWII weekend is at the Reading airport this weekend. If you are into airplanes it is a good time to check out some crazy planes up close. They close half the runways down and turn it into a parking lot for planes that you can check out up close. Last year, I saw an old guy that was check out one of the plane. When I asked him about it he told me the whole in and outs of the whole thing and different crazy thing he did when he flew in the war. He ended with ya and we had a hell of a lot more machine guys. I think the wife and I, and maybe some friends are going to go Saturday if you are interested.