911 sc starting issue

[scott.k]

Hello,
I need some help diagnosing a starting problem in my car. When I start the car, it starts and runs for a few seconds and dies out. If I start it and quickly step on the gas, ( about 4000rpms), it will stay running but as soon as I let off, it dies. I put the engine back in a couple of months ago and I had the car running since then, but it has not been running since then because I had to replace a fuel return line. To do that, I had to completely drain the fuel tank, so could it be the case that the fuel has nop been pushed through the feed line to the engine? A couple of other things that could be causes are the stupid mistake I made of taking the exhaust off with the O2 sensor still screwed in. This slightly bent the wire connection at top of sensor (not sure if the sensor still works). Would a faulty sensor cause this problem? Another thing is that Im not exactly sure the oil level, because I havnt been able to heat up the engine to test it but It wasnt a problem when I was running the car before so I dont think thats it. One other thing I forgot to mention is that the return line that I made for the replacement had slightly smaller diameter fittings that dont allow quite the same amount of flow as the stock ones but I don't thing that is a problem either.
Please let me know if you have any suggestions. One more thing that I forgot to mention but I don't it would have an effect, the small, rubber, cloth covered hose from the fuel tank to carbon canister broke and I did not get a replacement, so it is currently disconnected.
Thanks
Scott

[scott.k]

now it wont even stay on when I give it gas. It dies out in about 2 seconds

is there a was to check to make sure the fuel pump is delivering fuel to the engine?
thanks

[ossiblue]

Originally Posted by scott.k

now it wont even stay on when I give it gas. It dies out in about 2 seconds

is there a was to check to make sure the fuel pump is delivering fuel to the engine?
thanks

Lots of issues, but take only one at a time.

From what you describe, it sounds like the engine fires from the cold start valve injection and that's it. However, you mentioned in your first post about work done on the fuel system so here's what I'd suggest first.

Remove the air cleaner and turn on the ignition. Gently lift the lever inside the intake--this will cause the fuel pump to start and within a few seconds (or sooner) you should hear the injectors squeal, indicating they are injecting fuel. You have now primed the system. DO NOT HOLD THE LEVER UP LONGER THAN NECESSARY TO HEAR THE PUMP AND SQUEAL!

Replace the air filter and try to start the car. Do not pump the accelerator, simply turn the key to start. If it doesn't start immediately, or possibly on the second try, report back your findings.

Don't worry yet about the oil level.

The return line should not be a problem.

Do, however, fix the broken line to the charcoal canister as raw fumes will be escaping into the trunk area--bad mojo there. This would not contribute to your start problem, however.

[scott.k]

Originally Posted by ossiblue

Lots of issues, but take only one at a time.

From what you describe, it sounds like the engine fires from the cold start valve injection and that's it. However, you mentioned in your first post about work done on the fuel system so here's what I'd suggest first.

Remove the air cleaner and turn on the ignition. Gently lift the lever inside the intake--this will cause the fuel pump to start and within a few seconds (or sooner) you should hear the injectors squeal, indicating they are injecting fuel. You have now primed the system. DO NOT HOLD THE LEVER UP LONGER THAN NECESSARY TO HEAR THE PUMP AND SQUEAL!

Replace the air filter and try to start the car. Do not pump the accelerator, simply turn the key to start. If it doesn't start immediately, or possibly on the second try, report back your findings.

Don't worry yet about the oil level.

The return line should not be a problem.

Do, however, fix the broken line to the charcoal canister as raw fumes will be escaping into the trunk area--bad mojo there. This would not contribute to your start problem, however.

Thanks a lot for the help. I just read a similar procedure on another thread so I think I will give it a try. Should someone be turning the key all the way (in the position to start the car) when I am lifting the lever inside the intake, or should the key just be partway turned so that the cars electics are on? If the car needs to be cranking, I dont think I will hear the squeel because there is no muffler on the car. Also, if the car needs to be cranking, the car will start for a second and then go out, possibly not quite long enough for the fuel to be delivered to the injectors?

I am eager to give it a try.

Thanks
Scott

[boyt911sc]

Originally Posted by scott.k

Thanks a lot for the help. I just read a similar procedure on another thread so I think I will give it a try. Should someone be turning the key all the way (in the position to start the car) when I am lifting the lever inside the intake, or should the key just be partway turned so that the cars electics are on? If the car needs to be cranking, I dont think I will hear the squeel because there is no muffler on the car. Also, if the car needs to be cranking, the car will start for a second and then go out, possibly not quite long enough for the fuel to be delivered to the injectors?

I am eager to give it a try.

Thanks
Scott

scott,

LJ (Ossiblue) has given you an excellent advise and has laid out to you the procedure. The ignition switch should be turned to on/run position (not start). When the AFS (air flow sensor) plate is lifted up, the FP will be energized and deliver fuel to the injectors. Do not lift the AFS plate longer than 2 sec. to prevent flooding in the chambers. The squealing noise is not too audible for someone not familiar to the test. This is a faint hissing sound when the injectors start to spray fuel.

Pull one one (1) injector and observe the fuel from the injector if you are not familiar with the 'sound' test. Sometimes a direct visual observation is much easier for people doing this test for the first time or new to this procedure. Keep us posted.

Tony

[scott.k]

Originally Posted by boyt911sc

scott,

LJ (Ossiblue) has given you an excellent advise and has laid out to you the procedure. The ignition switch should be turned to on/run position (not start). When the AFS (air flow sensor) plate is lifted up, the FP will be energized and deliver fuel to the injectors. Do not lift the AFS plate longer than 2 sec. to prevent flooding in the chambers. The squealing noise is not too audible for someone not familiar to the test. This is a faint hissing sound when the injectors start to spray fuel.

Pull one one (1) injector and observe the fuel from the injector if you are not familiar with the 'sound' test. Sometimes a direct visual observation is much easier for people doing this test for the first time or new to this procedure. Keep us posted.

Tony

Thanks for the help. Should I take the injector out and then run the test? I should stop holding the plate when I see fuel start to spray?
Thanks
Scott

[scott.k]

I took out the injector, and help up the lever (about 1 sec) until I saw the fuel start to spray out. Right wen it started to spray out, i released. Should have I held it for longer than that? Should I start it up?
Thanks
Scott

[scott.k]

I just started a couple of times it but it is still dying out. Do I need to prime it again, and it so, for longer?

Is it a possiblity that fuel is not coming to the engine while the car is running but it is when i lifted up the little lever thing in the air box?

When I start it, should I hold the throttle down for a while to get the circulation going?
Thanks
Scott

[boyt911sc]

scott,

Check your fuel pressures (control, system and residual). You need a fuel pressure gauge to do this. Borrow or buy a decent set of fuel pressure gauge kit. This tool is mandatory for doing fuel injection troubleshooting. Assuming that you don't have a significant vacuum/air leak which is very questionable at this point, and having the correct fuel pressures and ignition (spark) should easily make your engine start.

Without knowing the fuel pressures at this stage, troubleshooting will not be very effective or efficient. Unless you want to do the trial and error procedure which could be very expensive and time consuming.

Tony

[scott.k]

Ok, thanks
The engine does start, it just isn't running for long before dying out.
Scott

[scott.k]

Do you know what activates/controls the plate in the airbox to pump fuel through when the car is running? Maybe thats the problem?
Thanks
Scott

[scott.k]

Could I have someone lift the plate in the air box while the car is running to get gas going to the engine?

[psalt]

Do you know what activates/controls the plate in the airbox to pump fuel through when the car is running? Maybe thats the problem


scott,

Sounds like you are chasing your tail. The plate is the air flow sensor and the air that the running engine inhales lifts it and it is mechanically connected to the device that meters the fuel. When the engine dies, it stops breathing and the closed plate shuts off the fuel pump as a safety measure. If the engine was recently out, could you have swapped the FV and air flow contact wire plugs ? Does the pump run when you lift the plate with the key ON ? Do you have a manual that describes the CIS system ? If the engine fires when cranking, then dies, you have a cold running issue, not a cold start problem. This is a common problem on a lambda CIS 911SC and can be caused by several issues. If you have to pedal the throttle to keep it running, you are risking blowing the airbox. A properly set up 80SC should fire on the first turn of the key and immediately settle to a fast idle around 1500 rpm without touching the pedal. Most of the time the problem is the mixture is too lean to keep the engine running until it warms up. This can be caused by incorrect control pressure, a closed FV, vacuum leaks, or poor compression. The engine also needs a higher idle speed which is controlled by the AAR and to some extent the ignition timing. All of these things need to be diagnosed separately. If the pump runs when the plate is lifted, my advice would be to remove the sparkplugs, replace them with BOSCH normal plugs, or at least clean and gap them. Then disconnect and plug the vacuum retard line to the back of the distributor . This should give you a much stronger cold idle after firing. Try to avoid pedalling the throttle. Cold running issues with a lambda SC can be sorted out, but you must be methodical because you really only get one shot each day on a cold start.

Paul

[boyt911sc]

Originally Posted by psalt

Do you know what activates/controls the plate in the airbox to pump fuel through when the car is running? Maybe thats the problem


scott,

Sounds like you are chasing your tail. The plate is the air flow sensor and the air that the running engine inhales lifts it and it is mechanically connected to the device that meters the fuel. When the engine dies, it stops breathing and the closed plate shuts off the fuel pump as a safety measure. If the engine was recently out, could you have swapped the FV and air flow contact wire plugs ? Does the pump run when you lift the plate with the key ON ? Do you have a manual that describes the CIS system ? If the engine fires when cranking, then dies, you have a cold running issue, not a cold start problem. This is a common problem on a lambda CIS 911SC and can be caused by several issues. If you have to pedal the throttle to keep it running, you are risking blowing the airbox. A properly set up 80SC should fire on the first turn of the key and immediately settle to a fast idle around 1500 rpm without touching the pedal. Most of the time the problem is the mixture is too lean to keep the engine running until it warms up. This can be caused by incorrect control pressure, a closed FV, vacuum leaks, or poor compression. The engine also needs a higher idle speed which is controlled by the AAR and to some extent the ignition timing. All of these things need to be diagnosed separately. If the pump runs when the plate is lifted, my advice would be to remove the sparkplugs, replace them with BOSCH normal plugs, or at least clean and gap them. Then disconnect and plug the vacuum retard line to the back of the distributor . This should give you a much stronger cold idle after firing. Try to avoid pedalling the throttle. Cold running issues with a lambda SC can be sorted out, but you must be methodical because you really only get one shot each day on a cold start.

Paul

Paul,

The advise you have given Scott is well said except for the last sentence. I was totally caught by surprise specially coming from someone who knows what he's talking about. This is similar to your comment (other post) about the 2 dozens circuits in a lambda system to be understood and learned. Well if you could illustrate the existence of the 2 dozens circuit outside the ECU, I think it's worth giving you a dinner for two. As as ardent enthusiast of CIS, I want to learn more about the subject.

The guy needs help and advise. Offer him something he could do to find the problem rather giving the technical description and going around discussing convoluted ideas that does not help him at all. Instead, offer him a definitive course action or steps so he could locate or identify the root cause of the problem. Just my two cents.

Tony

[mtndawg]

The first thing I would do here is jump the relay, turn the key on and crawl under the car to make sure the fuel pump is running. This is the source of the fuel, in my opinion, it's a good place to start.

[BMEPdoc]

I wholeheartedly agree with Paul's post. Pay particularly close attention to the auxilliary air valve. These motors are set-up relatively lean and it doesn't take much of a vacuum leak to rob the sensor plate on the fuel distributor of the vacuum required to move the necessary amount in order to run properly. The AAR is notorious for causing the problem you describe making the motor either hunt up and down in RPM or simply die shortly after firing when cold, many times with a pop or backfire though not always.

In simple terms, the AAR is a temperature controlled (via the thermo-time switch) vacuum leak which, in conjunction with a richer, cold start mixture provided by a properly functioning FPR allows a marginally higher cold engine RPM until stabilizing to an even, lower, warm idle. If ANY component in the system is out of operational specification, a running issue exists. If, for example, your cold control pressure is too high (lean) then pops backfires are the result. On the other hand, IF you have a vacuum leak somewhere, control pressures are superfluous as a main component (air flow sensor) isn't receiving it's proper operating orders to begin with.

Also, by now, I'd imagine the majority of CIS cars out there have the toilet seat or backfire valve fitted. With the air filter cartridge removed you'll see what looks like a... well, spring loaded toilet seat epoxied to the floor of the housing. These were fitted specifically due to the propensity for the motors to cough or backfire as a result of their lean settings (particularly when ALL vacuum related components don't function as absolutely required), leading to warpage and in some cases just flat out blown up air boxes. You may want to check see that there aren't any issues there with a piece of debris or some such thing keeping the flap from sealing properly. There was even an outfit years ago which made cast aluminum air boxes to address this issue, though, I feel the toilet seat solution is more than adequate.

Also, it goes without saying. Your system control pressures MUST be with a given range of operation from cold to hot. If you don't have the gauges to verify the FPR or fuel pressure regulator is within specifcation, then you can very well be on a not-so-merry-go-round. Still:

Remember, air leaks are the enemy to a CIS system. That means anywhere a vacuum leak can occur. Injector seals, distributor vacuum diaphragms, etc. You can clamp a small pair of vice grips with which you can pinch off the vacuum line leading to the AAR to determine if it's the offender, or have a friend use pliers to selectively pinch off the lines. When you finally do get it to run, and once you get the motor up to operating temp, you can then use a can of carb cleaner and squirt a brief spray at the base of the manifold leading to the heads and check to verify the condition of the gaskets as well as where the injectors fit into manifold to determine the condition of the seals. Again, anywhere in the intake flow path. If you discover any notable change in RPM, address the seal or gasket or component.

Good luck

regards,
Jozef Schumann

[ossiblue]

Scott,

You are learning, and getting lots of advice that may be overwhelming. May I suggest you take a deep breath and focus on only one issue at this point.

So far you have successfully pressurized the fuel system by lifting the lever in the intake. That confirms the fuel pump works and fuel is being delivered to the engine.

The car fires up but dies immediately. That tells you that you have spark and the cold start valve is working.

Your next step would be to confirm the fuel pressures/delivery pressures which, as Tony posted, will require a pressure gauge set. You have a cold running problem and maybe something else but remember, the idea is to eliminate suspects--just like a detective.

Yes, there could be (and probably are) other causes but you need to follow only one path at a time, eliminate it as the problem, then move on if you haven't solved the issue. Currently you are investigating a fuel issue. Follow it to it's conclusion before you move to Lambda or timing or vacuum problems. My $.02

[psalt]

As as ardent enthusiast of CIS, I want to learn more about the subject.

Tony,

My opinion is, it may be hopeless. My advice would be to start with the difference between a noun and a verb, it makes juvenile posts look, well, more juvenile. The reason you only get one shot a day at the cold start/cold stall diagnose is that each subsequent attempt at cranking fires the cold start valve and the extra fuel pollutes the ability to solve the problem. Most of these cars will make the transition to cold running after three of four cranks and stalls, but the problem can be solved be someone who actually knows what they are doing. It is not normal for the engine to start and stall. If you have never solved this problem on a CIS lambda car, your experience would be different.

Count the pins on the later lambda system ECU's and relay, 23 is pretty close to two dozen. There is a test procedure for each one and if you follow them you should be able to learn how the system works.

Paul

[scott.k]

I just got it. It took a few more primes of the fuel system while the engine was heated and a few more starts while stepping on the gas and it is working now and holding an idle.
Thanks for the help.

I owe you one

Scott

[boyt911sc]

Originally Posted by psalt

As as ardent enthusiast of CIS, I want to learn more about the subject.

Tony,

My opinion is, it may be hopeless. My advice would be to start with the difference between a noun and a verb, it makes juvenile posts look, well, more juvenile. The reason you only get one shot a day at the cold start/cold stall diagnose is that each subsequent attempt at cranking fires the cold start valve and the extra fuel pollutes the ability to solve the problem. Most of these cars will make the transition to cold running after three of four cranks and stalls, but the problem can be solved be someone who actually knows what they are doing. It is not normal for the engine to start and stall. If you have never solved this problem on a CIS lambda car, your experience would be different.

Count the pins on the later lambda system ECU's and relay, 23 is pretty close to two dozen. There is a test procedure for each one and if you follow them you should be able to learn how the system works.

Paul

Paul,

Precisely this is the reason why I purchased several '80 and '83 CIS units to evaluate and study them. Let's go directly to your '23' pins, this is exactly why I have some doubts about your knowledge about CIS and it its electrical system. For '80 SC's, only 10 pins are utilized while the '81-'83 SC's have 11 pins connected or used. The rest of the so called 2 dozens pins are not connected or in lay man's lingo 'open'. And some spaces are blank spots.

How could it possibly have 2 dozens circuits when there are are only 11 wires connected to the ECU? Go read the factory wiring diagram and I expect you would after reading this post. This is a technical forum and our technical dispute could be solved by facts, data, and results. Give me a decent CIS engine/car (any model from '74-83) and I'll make it run!!!!! I will pay for the return shipping cost back to the owner plus the delivery shipping cost the owner incurred if I failed to deliver my promise.

People have two (2) choices for a free CIS troubleshooting work: send the motor/car to me or Paul (check with him first). Hope this will clear who is who.

Tony