No fuel pressure to main injectors on first start-up from long dormancy

Hello everyone! The big day is here after almost ten months of fiddling, I am trying to get my 85 QV started. Everything sounds lovely sweet and nominal . . . for about a second, and then the old girl stalls out. All indications pointed to a lean start, even though I had run the pump for a while to prime the fuel lines and CIS distributer (see previous thread "That's weird")

Key facts:
-The cold start injector is getting gas and spraying a good, steady mist.
-Based on the above, I can conclude that the pump is producing adequate pressure, and there are no restrictions or air bubbles between the pump/accumulator/filter and the bottom half of the fuel distributer.
-Engine roars to life instantly with a little starter fluid in the air inlet, but still dies a few seconds later.
-After four or five rapid start attempts with the ether (starter fluid), we got little backfire through the intake.
-We have tried pushing the metering plate down a little (with a dowel rod, after the backfire incident), during start-up when it starts to stumble, but it hasn't really helped.
-I disconnected the most #5 and #8 cylinder fuel lines. The fittings at the injectors were both dry as bone.
-With the starter engaged, no fuel was observed coming out of the disconnected fuel lines.

My tentative conclusion: stuck fuel metering plunger, resulting in zero fuel flow to the upper chambers in the fuel distributer.

If that is correct--and I am open to any other possibilities that the brilliant minds here might suggest--the next question is: how do I get the plunger un-stuck and operating normally? Thoughts?

 

To clarify, I figure rebuilding the distributer is the way this is headed; but in the immediate term (this weekend) and just to get her running, I'd love to get that plunger unstuck, even if the driving behavior is less-than-optimal.

 

First thing I would suggest is breaking open the fuel line to the cold start injector to release all the fuel pressure (wrap the fitting with a rag before loosening as fuel will squirt out) and then see if the airflow metering plate/plunger motion is smooth and easy as you deflect the airflow plate downward, and confirm it returns well/smoothly. Do you have a copy of the Mondial 8/QV WSM (covers K-Jet without Lambda) and Service Bulletin 10-13 (covers K-Jet with Lambda)?

 

My Audi ur-Quattro has a similar CIS system. It had a sticking fuel metering plunger and at times I would have to stick a long hex key down the hole for adjusting the air flow sensor plate and engaged the adjusting screw with enough side pressure to lift the sensor plate which moves the plunger. I eventually took the fuel distributor apart and cleaned the plunger. The slightest dirt or fuel gum will bind the plunger, it has diesel injector precision tolerances. The same could be done by removing the air filter box and grab the bolt head holding the sensor on the arm and moving the sensor up and down a few times. I don't know exactly about the 308/328 CIS system (I have carbs) so I can't be sure about accessing the sensor plate, on the Quattro it takes an act of God to remove the air filter housing cover. Actually accessing anything under the hood of a ur-Quattro makes a Ferrari 308/328 seem as easy as working under the hood of a full size 1970's American car.

 

I do have the 10-13 service bulletin and the WSM. The more I think about this though, I'm beginning to wonder about my conclusion. I mean, clearly, fuel pressure is not building in the upper chambers. Fuel gets to the upper chamber when the control plunger is pushed upward when the air metering plate is sucked (or pushed manually) downward (in a downdraft CIS system). With the engine off (as it has been this year) the plunger would have slid downward to rest on the metering lever roller. That is the position it would have frozen in if my initial theory was correct. If it was stuck there, wouldn't I have felt resistance when I pushed the metering plate down? I didn't. The resistance build a little once the system began to pressurize, which is what I would expect, since the top side of the plunger would be seeing some fuel pressure through the WUR. I can push the metering plate down to what feels like full travel in any case--yet no fuel is getting out to the injectors. Puzzling. Besides the plunger being stuck down, is there anything else that might explain lack of pressure/flow to all eight injectors, yet sufficient pressure to make the cold start injector spray?

At this point, I guess I won't know until I at least get the distributer off, and check the plunger for freedom of movement. I assume it's just the four slotted screws holding the thing down, yeah? Maybe tonight...

 

That's saying a lot. Remind me not to get into Audis!

 

Can't agree with you here -- if the FD plunger was stuck in the down position (slits closed), you wouldn't be able to push the airflow metering plate down (the plunger goes up when the airflow metering plate goes down). Have you double-checked that all of your fuel hose connections are in their proper locations? (My recollection is that things can be hooked up wrong.)

 

Yes, Steve, that is exactly the conclusion I am forced to come to. To the issue of having reversed the some connection during re-install, I wouldn't put it past me but the options are highly limited. I disconnected as little as possible, and lifted the entire system very carefully (two-man-carry) and placed in a box. My first thought was that I might have somehow swapped the supply and return lines, despite having labelled them. But then I double-checked the pre-removal photographs, and they indicate the same configuration. Literally, the only other fuel connection that was opened was the injectors themselves, so I am at a loss for what could be mis-configured.

In a nutshell, I'm stumped.

But at least my motor is pretty now. And it sounds awesome for the 1-2 seconds that it will run for. That gives me hope at least.

 

Check the supply and return lines. Also the WUR lines. The 8 injection lines if all on the FD outside ring and hooked to injection nozzles then you should be good.

 

Image Unavailable, Please Login UPDATE: She runs!!!

There are few better feelings in life than seeing a car finally roar back to life at the completion of a long, complicated project . . . And few things more humbling than when you realize you could have gotten her there a few days earlier if only you weren't such a cocksure idiot.

So, what have I learned today? Well, if you thoroughly clean up a the grounding wire connections on a BOSCH fuel pump, but only spin the nut on *finger-tight* you get enough 'trons to spin the pump . . . but not enough to actually fully pressurize the upper chambers of the CIS distributer. Thus, fuel to the cold start injector (a good spray pattern even) but not a drop from the main nozzles.

My take away, even if you are 100% sure that you secured all the system grounds perfectly, if you're having a problem, check them again. Someday, perhaps, I'll learn.

And in the meantime, if anyone is contemplating doing an engine-out service in their own garage, I have plenty of other points of stupid I can advise you how to avoid.