930 Engine RUNS!...Sort of...Fuel questions inside

[cowtown]

(Background: I recently put this 930 engine into a '75 - new seals, rings, bearings, headstuds, etc. It hasn't run since Reagan's first term).

Well, with two people aiming fire extinguishers at the rear end, I gingerly turned the key and BAM! the 930 roared to life
...for about 10 seconds. Then it died, and we couldn't get it started again.

The fuel system is flooding the cylinders. If I turn the ignition to get the fuel pump to spin, gas will be pumped into the engine and quickly lock it up. I pulled the plugs and ejected the gas. Started again...then died...same thing. I don't want to keep trying it like this because I'm sure the oil's scrubbed off the cylinders and I have a bunch of gas in the oil supply.

Do I start with the fuel distributor, or injectors? My thinking is that the fuel distributor should not let any gas to the injectors unless the plate is depressed, right? (930 plate goes down, not up).

The plate's all the way at the top when the fuel pump is running but the engine is not started.

I'm going to go read my Bosch FI book now, but could use any advice you guys can give me. What to check, how to check it.
Thanks!

[logician]

Hi,

My '86 930 has a second fuel pump which I believe is needed to overcome the boost pressure. I suspect that a 3.0 would have the same secondary pump. So, have you transplanted the whole fuel system, including fuel pump and accumulator, into your '75? I'm thinking the secondary pump might be necessary in order to get all the fuel pressures correct -- critical for CIS systems.

-Juan

[dean]

The fuel pump should not run with the key in the on position. It should run when cranking and when the air flap is pushed down. I would say that you have a couple problems. Fix the fuel pump running all the time. Then I would say your metering valve is stuck. Is the airflapper all the way up when it is not running?

[cowtown]

I've got more than just a couple problems, Dean

I am working on the pump running all the time...the car acted like this even with the 2.7, so it's taking me some time to figure out what was done to the wiring.

About the metering valve, the airflapper IS all the way up when not running. When I get control pressure it becomes firm with the valve all the way closed.

Do you think one or more injectors may be opening way below their rated pressure, or even stuck open?

Thanks,
Colin

[john walker's workshop]

don't worry about the pump running all the time right now.
did you notice if the piston that comes out of the bottom of the fuel distributor was free moving?
the idle adjustment allen screw, which is under a screw in plug, may need to be backed out several turns until the injectors stop spraying. did you turn it at all previously?
another possibility is a stuck fuel distributor check valve, which would create very high fuel pressure, because fuel can't get back to the tank. remove the cap, spring, and piston to see. don't loose the shims under the cap.
injectors don't usually stick in the open position. if they're gummed up, they usually dribble, spray a little sideways squirt, or don't work at all.

[cowtown]

OK John, Thanks. This gives me some things to check tonight.

--I can't see the piston on the bottom of the fuel distributor, but if I run the pump, when I push down on the flapper I can hear the fuel squirting through the injectors. It returns back to the closed position when I stop pushing down. Is this good enough?

--I haven't touched the idle allen screw since I got the engine. Who knows where it's set. Should I back it off tonight and try again? How much?

--The check valve idea is interesting. I will check this, and maybe crack the return line to see if it has any gas in it. This would make sense because There is a TON of gas in the cylinders after running the pump a very short time - like enough to totally lock up the engine.

Thanks, and I will report back!

Colin

[john walker's workshop]

if the sensor plate remains firm and returns upwards after pushing it down, then the piston would be free. if you were familiar with CIS, you could tell by moving the sensor plate, if the pressure on it was excessive.

[cowtown]

Update:

--I opened up the return line and ran the pump. I got fuel heading out of the distributor. I also blew a little 25psi air all the way to the tank with no problem. I inspected the relief valve (one shim - is that normal?) and it looks clean, and the o-ring and springs look good.

--The covered mixture adjustment screw was fully screwed in clockwise. I backed off about three full turns, and seem to have gotten to a point where the injectors are not just pouring in gas at all times.

--The bigger problem: I was wrong about the piston moving freely. It's OK when I push down the flapper about 1/2". Tonight, when I pushed it all the way down to test the injectors, then let go, it made a screaming noise and eventually SLOWWWWWLY returned upward in about 5-6 seconds.
I understand from searching there are no rebuild kits. Is it possible to R&R the piston? Looks like a big lockwasher and nut holds it in. Any pointers here?

Thanks a lot for the ongoing help!
Colin

[beepbeep]

Don't opet that distributor unless you really know what you are doing! It's not dirt-tolerant and somewhat hard to put back together. It's better to buy completly new unit, should be heaps of them outthere from EFI-conversions. I believe same unit can be found on 928 ans MB 560...

[john70t]

Not to sound like a snake-oil salesman but if the F.I. and micro-valves/springs has been dry for a long time, would a little Marvelous Mystery Oil help lube the system for furthur testing?
(A guy at the old shop used to mix a little in the spray bottles of WD-40 making it difficult to drill if you didn't know better).

It sounds like the fuel plunger/metering valve is sticking in the distributor bore. That's what the airflow lever pushes on.

[john walker's workshop]

there's a tab that keeps it from falling out, which can be bent out of the way. the piston is a precision ground piece, so be careful not to drop it, or scar it. it takes a careful wiggle to get it started back in the bore. usually, just taking it out and wiping it down with penetrating oil with your fingers will free it up. then move it in and out a few times. you don't want to buy a rebuilt one, if they're even available. $$$$

[cowtown]

Well guys, I made some progress tonight. It idles!!!

--I took out the fuel distrib. piston and relief valve again, and shot a bunch of choke cleaner in. Gently blew it out, then put fresh gas into it, and reinserted the piston. Everything LOOKED clean before, but the piston definitely slides more easily now. It actually wanted to fall out when I put the distrib. back on the engine.

--The @$#@## electronic coldstart injector, WHICH IS UNHOOKED FROM THE WIRING HARNESS, was the culprit dumping all the gas into the cylinders. Ran to Ace to get a 10x1.0 bolt to plug that distributor port. Problem solved.

--I had to keep fiddling with the mixture screw to get to the point will it will (barely) idle.

I've ordered a pressure tester, and I guess after that I have to try to borrow or buy a Gunson.

The thing still doesn't have a muffler, so I don't want to start it up too much, but MAN, what a cool sound!

Thanks,
Colin

[dean]

Excellent, I'll bet you can't wait