911sc starts and dies repeatedly

[gearby]

So, a friend of mine asked me to track down an electrical issue in his 1982 SC. I guess he figured since I owned a 72, they must be the same car. Funny huh?
So, the problem was an electrical issue which quickly became something else. when I got to the car it had a completely dead battery, so I jumped the car and figured I would drive it and use the alternator to charge the battery most of the way. I went and had lunch with my wife and when I came back out, we got in the car and it started up and immediately died. Then all cranking and no firing. I towed the car back to my house, and found that I have consistent spark and it is a fuel related issue. I jumped out 87a and 30 and listen to the fuel pump and it sounded horrible. So I replaced the fuel pump and the fuel filter. Now, the car starts immediately and dies immediately after, over and over and over and over. Unfortunately I don't have the fuel pressure gauges for the CIS injection. The throttle plate moves when the car starts. It looks like the cold start injector is what is starting the motor but then it is starving for fuel. Is it possible that the new pump is putting out more pressure and its caused something to be out of adjustment to the point it won't let the engine run? I know without the gauges diagnosing this is going to be difficult.I pulled a spark plug and the plug is completely dry so I'm sure it's being starved. The engine ran fine before it broke down and the only thing that was out of the ordinary was that it would start and run erratically for several seconds before smoothing out.

[gearby]

I might add that I tried leaving the jumper in 87a and 30 to force the fuel pump to stay on in case the ignition wasn't allowing it and it didn't make a difference.

[T77911S]

you can try pushing up or pulling down on the sensor plate to see if you can keep it running that way,

you can also check for power to the warm up reg (WUR)

also check fuse 18

did it backfire.
does it have a pop off valve, if so check to see if it is seated/closed

other wise you need gauges

[Paulporsche]

As others have said, you will need the gauges.

In the meantime you may be able to do a field test. Have someone hold the sensor plate up while starting. If holding the plate up causes the revs to rise or keep going, you can enrichen the mix. If lowering the plate causes the revs to rise you can go leaner. If raising or lowering both cause the revs to fall your mixture is OK.

Obviously having a mix that is incorrect can have many causes, which is why you need the gauges to confirm. Possible causes include a worn or faulty WUR, O2 sensor (is your dome light working?) fuel injectors, vacuum leaks, fuel distributor sticking, clogged fuel filter, or even just an incorrect mixture setting.

Also, always confirm that all ignition components are good. And make sure the fuel pump relay is making solid contact.

[Dave Kost]

Is the frequency Valve vibrating?

[T77911S]

hey paul,
I don't think I have seen you here in a while.

[gearby]

Thanks for the responses. Moving the sensor plate up or down with the key on does not have any impact. However when I do that, I hear what I think is the frequency valve vibrating. My fuse on number 18 is good. I do get full Voltage at the WUR. I removed and injector line and moved the sensor plate up and I got a little dribble of gas out of the line. I attempted to start the car and got the same small dribble of gas. When I hold the sensor plate up or down while cranking it seems to have a worse effect on the engine. Kind of hard to tell since it only starts for a second but that appears to be correct so my mixture must be right.
Since everything seems to check out, I went ahead and ordered a set of gauges. Unfortunately I may never use them again and they may sit in my toolbox till the day I die. But I will hook the gauges up and get a cold pressure and return. Maybe it'll give me a reason to buy my own SC someday.

[T77911S]

remove the connector on the top rear of the AFM and turn the key and see if the pump runs

does it have gas in it

[Paulporsche]

Let us know what readings you get and we'll go from there.

Obviously it's too early to tell now, but the bimetal strip in the WUR is quite often the culprit. You should measure its resistance and report.

[gearby]

Well my one day shipping on my gauges has turned into at least two day shipping. I measured the resistance between the two electrical connections on top of the wur and I got 12.1 ohms. Is this the correct way to measure the resistance in the bi-metal strip? If not how do I do it? Thanks in advance.

[T77911S]

I think it should be around 30 ohms. tony is more up on those details than I am.

you can try manipulating the sensor plate while cranking it to see if you can keep it running.

remove the connector and see if pumps run

[boyt911sc]

Gearby,

I have been watching this post since the very beginning. And it is very difficult to offer help with very limited information you gave us. If I were in your shoes, I would check the following:
1). Fuel pressure test (cold control, warm control, system, and residual fuel pressures).
2). Connect an in inductive timing light and confirm the presence of ignition signal. This test also helps you find or see where the ignition timing is located.
3). Check for sources of significant air leak. A home-made smoke generator will locate these hard to find vacuum leaks.
4). Fuel deliver test. CSV must be good and working with a cold engine.
5). Fully charged battery.
6). Is the motor a US spec or ROW spec?

All you need is about 5~10 mins. to do the above tests. If you could make the engine to start and run for a few seconds, it would confirm the presence of ignition source. It did run and stall because you either have problem with fuel supply or too much air. Since you were able to drive the car before, do not even think of tinkering the fuel mixture setting. This is where novice CIS troubleshooters commit their first major mistake. Altering the fuel mixture setting at this point would make the troubleshooting more difficult. Focus on finding what is the problem by confirming it with a test procedure.

Do not rely on guesswork or LUCK. You can not depend on luck all the time. The problem is there you just don’t see or recognize it. Make the culprit/s stand out to be identified by doing some test procedure/s. I would bet my MONEY on unmetered air. And I could be wrong without confirming it with a test. Keep us posted.

Tony

[mysocal911]

Originally Posted by boyt911sc

If you could make the engine to start and run for a few seconds, it would confirm the presence of ignition source.
Tony

Right, use carb cleaner to keep the engine running for about 10-15 seconds. Then you'll be able to at least check the timing.
Sounds like the engine is just running off of the CSI (cold start injector). Notice if the sensor plate is moving while cranking.
If you have fuel pressure and you move the sensor plate, you should hear the injectors injecting. Next, focus on using a fuel
pressure gauge to check the system & control pressures.

[RDM]

When was the fuel filter last changed?

[gearby]

Hi guys oh, yeah I left a few things out in order to keep my post shorter. But when the car essentially broke down I was in the Chipotle parking lot. I pulled a spark plug wire to confirm the presence of spark which it had. I then went to the auto parts store and bought some starting fluid and was able to keep the car running for several seconds using the fluid. So spark is not my issue although it did seem a bit weak to me. The sensor plate does move up and down when cranking and holding the plate either in an up position or a down position seems to have a detrimental effect. I pulled a spark plug and the plug is dry.
Once I realized I had a fuel delivery issue and it wasn't going to be a simple fix and probably beyond what Chipotle wanted me doing in their parking lot, I loaded the car onto my trailer and towed it home. I jumped out the fuel pump relay between 87a and 30. That is where I found the fuel pump making a morse code type sound, so I replaced the fuel pump and the fuel filter. When the car was in the Chipotle parking lot it would not fire at all except with starting fluid. Once I replaced the fuel pump and fuel filter it now fires right away but dies after a second. I pulled an injector line loose and started it up but I only got a dribble of fuel upon startup. I think that's all the cold start injector and the injection system isn't pumping any fuel. My gauges are arriving today and once I get some pressures I will post back. Derek. Thanks
I've confirmed all the basics except for the timing. I don't know that it's possible for the timing to be thrown off to the point that the car would drive fine one second and then not another. I can't find any significant vacuum leaks. And yes the battery is fully charged and it is a u.s. spec 3.0. I appreciate the help as this is my first foray into k-jetronic CIS.

[spuggy]

Firing and dying, firing and dying. Sounds familiar - I had exactly that after a shipping muppet ran my CIS 930 out of gas - precisely what it did. With fresh gas, took 15-20 minutes of turning it over, it firing and immediately stopping, repeat, wait a little to give the starter a break etc. Eventually, it'd run (ragged) longer and long each time, until it kept running.

Behaved as though the injector lines were full of air, which eventually got purged. With zero tools, about all I could do.

So. Check it's not out of gas. Why did your fuel pump die? Is it full of crud? Is the swirl pot in the tank? Does the new fuel pump deliver required flow to the fuel head? How about out of the fuel head to the injectors?

I'd be inclined to pull the injectors, put them in jars/bottles and check they're delivering fuel with the pump running and the AFM or fuel head piston moved. If not, work backwards from there.

It ran - and still fires - so probably can defer looking at ignition. Unless the distributor clamp is finger tight and the dizzy is slopping about in the crankcase.

[gearby]

Okay here we go. Here are the pressure readings I received
System pressure - 71 psi or 4.8 bar
Cold pressure - 17 psi at 84 degrees or 1.2 bar at 29 celsius
Warm pressure - 52 psi or 3.6 bar, peaked out at 2 minutes

I can make out an 090 on the wur which must be the type.
Not real sure what my pressures are supposed to be but I'm willing to Guess that cold pressure probably needs to be a little bit higher than 17 PSI.

[gearby]

Does anybody have any idea what would cause such a low cold system pressure?

[boyt911sc]

Originally Posted by gearby

Does anybody have any idea what would cause such a low cold system pressure?

Gearby,

The low cold control fuel pressure you got should not prevent the engine from starting. What’s preventing the engine from starting is the inability for fuel to be ignited caused by a LEAN mixture. A lean mixture condition could be less fuel or too much air. The most likely culprit is unmetered air. But you don’t know this as a fact. You can not detect or locate source/s of unmetered air by just using your naked eyes unless you are Superman. Specially in a case when the motor fails to start at all.

I am not Superman but I could locate sources of air/vacuum leaks in a 911 engine using a smoke generator in a couple of seconds. Or maybe it is something else. Test and confirm.

Tony

[boyt911sc]

Originally Posted by gearby

Does anybody have any idea what would cause such a low cold system pressure?

The low CCP you are having is the result from mechanical setting. If you could post a picture of the WUR showing the top section, I might be able find something. The other fuel pressure values are good. Could you measure the heater resistance (Ohms) of the WUR with a cold engine? Thanks.

Tony