Hey Everybody,

I finally finished the 928 powered volksrod rolling chassis. Just need to paint and install the body. Anyway, it is all ready to run. I start it and if fires to life pretty readily but putts out in a second or two. I hit the starter again and it fires a little less, if I run the starter for several seconds I get a cylinder kick every once in awhile. Then it won't really fire any more. I let it sit for 20 minutes and can repeat the process. I dont smell fuel, so I suspect it might not be getting enough. One time for fun once it fired I pushed down on the MAF paddle very slightly and it idled roughly for probably a minute. as soon as I let go of the paddle it would want to die, then I'd catch it. I only was able to do that once. hoping it might help knowing that in the diagnosis. I didnt have the pair of 928 fuel pumps so I provided a constant 80 psi from a tank mounted electric pump and regulator. I have a pressure gage between that and the fuel distribution head and it says 75 psi. And there is plenty of fuel running through the head and returning to the tank. So the way I understand it the fuel pressure developed in the head is a function of the pressure regulator at the exit of the fuel distribution head. I see lots of reference to the accumulator and making sure it holds fuel pressure when the pump is off. I dont have one so the pressure bleeds back down in a few seconds. the pump comes on with the ignition though and there is full pressure when Im cranking.

I drove this engine in a 928 about 3 years ago and it ran pretty will but not great. Then I removed the injection lines and blew them out and put wd40 in the distribution head and each of the injectors. the one time I had it running for a minute all 8 headers were pretty equally hot.

Lastly, I adusted the idle screw in and out 2 turns each by 1/2 turn increments, no change. then put it back to original and adjusted the mixture screw at the front of the engine below the oil fill in and out 2 turns each by 1/2 turn increments. no change.

that's what I know, any ideas?

 

Check the control pressure at the warm up regulator.
most likely it’s too high from dried fuel in the inlet screen.

 

Neat project! Hope you get it running soon (running video..?)

Alan

 

CIS is notoriously poor at sitting around.
Sounds like you are getting cold start fuel, but no other fuel.

Remove the injectors from all 8 cylinders.
Hook them back onto their fuel lines.
Get 8 short water bottles to spray the injectors into.
Jump the fuel pump to run....no electricity to the engine, for safety.
Push down on the sensor plate and see how the injectors spray.
Repair as needed.

 

crazy project , congrats !

Now sure in this case , i would dump that old CIS junk and mount Webers....( IDA or IDF) .... that would be cool .

 

That is a super cool project. Agree that it sounds like your cold start injector is the only thing firing and you're not getting regular fuel delivered.

Go to the 928 Classics site and follow Jim's guide on how to set a baseline mixture and position of the idle screw. Essentially you're going to jumper the fuel pump and start richening the mixture until you hear the injectors squealing, which means they're delivering fuel and then you're going to lean that screw a back a bit until the noise stops and that, combined with his baseline setting on the idle screw, should get you close enough to where the car will run and can be fine tuned.

 

Based off the picture, aren't you inviting a massive vacuum leak with the air/pressure plate being exposed? typically this is sealed with airbox.

 

I don’t think airbox is sealed. It’s how air gets to the metering plate. He has no way to filter the air with this setup as pictured

 

..and what is the airbox sealed from????

 

Dirt

 

Well, more an atmosphere question, but dirt can still enter the airbox.

 

Thanks for all the help and suggestions. So far I pulled the lines from the WUR and tried to pull the screen out of the inlet. I ended up pulling off two layers of screen and there is at least one left. but couldnt figure out how to get the whole thing off. at any rate it starts and sputters and then will run if I gently pump the MAF paddle a few times and then will idle. so sounds like I'm giving it a little extra fuel with that through the main injectors. so they are working. It will idle as long as I like it really doesnt want to rev though, so sounds like I need to go through that basic tune excercise. I'll look for it.

 

OK, I dont have the gage setup referenced, but I've cleaned all the screens and I did the mixture adjust, backing the screw out and then screwing it in until I heard the fuel flow and then backing out slightly. the initial setting was 7.5 turns in from all the way out so I thought I might be able to "fix" something. turns out that is where I could here the fuel start to flow. I'm assuming that is the singing referenced to. Anyway, does that indicate any issue that I'm only at 7.5 turns instead of the normal 11 to 15? the screw at the front of the engine was at 2.5 turns out, so that's within range.

 

The noise you heard was fuel flowing, so you've set that correctly now as a starting point. It's a little odd that it was 7.5 rather than more than that, but let's get it running and then fine tune it next. With those baselined settings, does it now run?

 

I've just gone thru similar on my 78 CIS. I ended up purchasing a CIS Fuel pressure tester kit....my WUR control pressures were off. Combination of cleaning WUR, replacing fuel filter and adjusting Cold Control Pressure appear to have helped greatly.

Do you have ability to measure system and control pressure?