Another CIS Project

[AFB24911S]

I have read the Bosch book, Jim's Basement CIS Primer, and the excellent CIS Troubleshooting for Dummies thread. Here we go, the fear-inducing injection system!

My car:
1977 Porsche 911S Targa, original engine & stock cylinders, cam, etc., CA market, but now with an 11-blade fan and the EGR circuit cut off.

The problems:
Cold start - cranks for about 5 or 6 seconds before starting. It coughs within the first half second as if it wants to ignite right then, but then it keeps cranking until it starts.

Warmup - between minute 3 and minute 15 of driving, which is also right up until about 180°F oil temp, it bogs/hesitates at low revs under load.

Running - lots of body shake at idle, rough even at 1,000-1,100 RPM. During normal driving it makes decent power and I am getting about 20-23 mpg.

All of these problems have persisted since I bought the car about 5 years ago, but a collapsed suspension, messed up seats, and other issues took precedence. Now, I'm finally getting to the fine tuning.

My car has been at a local shop that I asked to fix these issues for the past two weeks, but they haven't solved it. After they explain what they did, I'm going to work on it.

I have the CIS pressure test tool, so I'll start with that and check pressures. As long as they are in range cold and hot, I'm going to check the check valve (LOL). If it leaks, bleeding off pressure between the pump and the fuel accumulator, it may be causing the long cranking at start. I don't think it is because I used to have the engine wired to run the fuel pump when the ignition was on. When I first bought the car, I would leave the ignition and the pump running before trying to start and it still took a while to crank. But, easy to verify. Is it possible that a fuel line between the pump and the accumulator could be letting in air? I never smell fuel or see it leaking. What about fuel tank air leaks? I bought a new gas cap, might as well put that on (but mostly because it was shiny and $12).

Then, I'm going to check the cold start valve. First to see if it sprays in a nice pattern, then to see if it leaks when it shuts off. I've got six gorgeous plastic volumetric cylinders for that.

If that thing does its job right, I'll move on to the AAR and the AAV. Last I checked the AAR was good, but it's worth checking again. I only looked through it to see if it was closing, but even if it is it could be leaking, right? I'll try blowing through it or pulling vacuum through it while hot. Same thing with the AAV, but I'm not sure the test I tried to perform 5 years ago was correct. Jim's Basement website says it's supposed to just cough until vacuum comes up, so I'll try to pull some vacuum on it and see if it flows or holds. Thinking a rubber cup attachment and some electrical tape will be my friends here.

If the cold start valve works, the AAR works, and the AAV works, I'll start chasing down vacuum leaks. Throttle body, vacuum lines, injector O-rings, both types. Plan is to spray some starter fluid around the engine bay and see if anything happens. I bought a bunch of vacuum hose to replace old, cracked ones, so I can inspect the ends of the hoses first.

Then, I can try to test the injectors for spray pattern and volume. If I find a bad fuel injector, I'll swap fuel lines at the distributor to see if the problem moves. If I haven't found a problem by then, I'll be out of ideas and send out the fuel distributor for rebuilding.

Hair-brained theories: I think the fuel pump check valve is screwed, the pump isn't pushing enough volume, or there's a serious vacuum leak. And at least one of the injectors isn't fully working, maybe just not spraying nicely at low flow rates.

Any flaws in my game plan? Other, better ideas?

[930cabman]

I'll bet your cold enrichment circuit is not working.

Report back with results of the pressure tests.

When operating properly, these CIS systems are the best. Getting them there can be a challenge.

[PeteKz]

Good game plan. I would swap it around a little. Given your rough idle, and that it runs better under load, I more strongly suspect vacuum leaks, so I would focus on that earlier in the troubleshooting tree.

I like to do the easy tests first. I would take off the air filter and look carefully around the air box for any cracks or suspect areas, then I would spray starting fluid around the manifold/head gaskets and the injector sleeves to see if that makes any difference in running at idle. If it does make a difference, then focus on those areas and other vacuum leaks generally.

Since you already have the CIS gauge/vavle, it's easy to hook that up, so that is the second thing I would try. You read the CIS primer and other threads, so you know what do to here.

Be methodical.

Because your car is '77 the Fuel Accumulator almost certainly is leaking, if it hasn't been replaced already. For this reason, I would focus on the FA if the residual pressure is leaking away. Even if it is not the most likely cause of hard cold starting (more typically, it causes hard warm restarts), I think it may contribute to your problems. At any rate, you will need a good FA to test for loss of residual pressure through the Check Valve, WUR, FD, etc. Prove it good, or replace it.

Keep posting your results here.

[Alan L]

+1 for air leaks as first check. It sounds like a leaness, but may not be due to WUR pressures (you will know after those checks). But air leaks are more or less constant - cracked hose etc, can only let so much unmetered air in. As you go up the throttle range and pump more fuel in, the air leak diminishes in significance. So the greatest effect is at idle. It is a higher proportion of the air flow into the engine.
Some of the hoses can be hard to get to with the engine in the car (cross your finger). Don't forget to check/spray around the base of the injectors - the O rings are a good place for leaks when old.
Alan

[AFB24911S]

Thanks for all these tips, gentlemen! Will have more tomorrow night probably.

[pmax]

"Running - lots of body shake at idle"

All cylinders firing ?

[fanaudical]

I'm kinda with PMAX on this one. A lot of perceived CIS issues are really ignition. Given "body shake" at idle, I would start with:

- Verify all cylinders are sparking strong

- Verify plugs and wires are good

- Verifying timing and points are good

Make sure that's all good before proceeding. After that:

- Spray pattern test

- Check for air leaks

- Do the pressure tests

[Dr J]

Before buying parts, I would check that all cylinders are firing. Also, I would check for loose intake manifold bolts which could let in unmetered air.

[AFB24911S]

@PMAX & @ fanaucidal,

How can I safely check for good spark from each spark plug? I had the CDI box gone through when I first bought it, I'm on my second set of new plugs, I've put a new OEM rotor cap on, and I put new points in a few years ago as well. Still, agree it's good to check.

[AFB24911S]

Is it safe to take each plug out, hold it against some grounded part of the engine, and ask a helper to crank the engine?
https://www.youtube.com/watch?v=69Km8qAKJ18

[fanaudical]

I have two ways to check spark:

#1 - As you indicated - Remove plug, connect to wire, crank motor over and watch for spark.

#2 - Use an inductive timing light, connect to each wire in turn while the motor is idling, and flash the crank pulley. This has the added benefit of giving you an idea of how stable the spark timing is as well as if you're getting erratic spark. Both contribute to poor idle.

One method of checking wire integrity (but be careful with this one): Idle the car at night. Look for sparks. Mist (with a spray bottle) some water near the wires and look again.

Another set of ignition tests: Remove the cap and verify the advance is not sticking. Verify there is no side play in the distributor shaft at the rotor. Lastly, verify there is very little axial play on the rotor shaft.

The reason for the spray pattern test is to verify you really have spray at all points of operation. My car developed an issue where one injector was providing a stream at idle when the other five were producing a spray. They should all spray at the same lift point of the air metering plate.

The spray test / air leak check / pressure tests should all be done and results evaluated as a whole before adjusting / changing anything.

[Schulisco]

Originally Posted by AFB24911S

I have read the Bosch book, Jim's Basement CIS Primer, and the excellent CIS Troubleshooting for Dummies thread. Here we go, the fear-inducing injection system!

Very good!
The problem is - these sources mainly explain the function of each component, but mostly they do not cover up how they interact on particular operation conditions and how they will affect other CIS components in case of failure. This in depth understanding you only get on practising on CIS systems...
In consequence you have to take care on every single CIS component on engines like yours as they might have more than a single problem.

Of course, there's are troubleshooting tables from CIS Primer and other sources. But again - this won't show you how to proceed in detail on problems. Furthermore several issues on CIS engines overlay other issues and mimic the behaviour of non existant issues. This confuses most of people working on them and they bring in other issues to solve former issues instead of sorting out the original problems. It's a complex system at first sight... but not if you got a deeper understanding ... then it's pretty simple.

Lots of things has already been written yet by others. You first should work these suggestions before proceeding with other ones. That's also one of the main problems on solving issues on a CIS: People tend to jump between several issues and components instead of solving one problem at a time.

Originally Posted by AFB24911S

My car:
1977 Porsche 911S Targa, original engine & stock cylinders, cam, etc., CA market, but now with an 11-blade fan and the EGR circuit cut off.

The problems:
Cold start - cranks for about 5 or 6 seconds before starting. It coughs within the first half second as if it wants to ignite right then, but then it keeps cranking until it starts.

Takes too long to start. I suppose that the fuel pressure build up requires that time. Leads me to a bad check valve at the fuel pump. That coughing at first crank may be caused by the rest of fuel (and pressure) resides in the fuel lines and the fuel accumulator from last run.

Originally Posted by AFB24911S

Warmup - between minute 3 and minute 15 of driving, which is also right up until about 180°F oil temp, it bogs/hesitates at low revs under load.

Mixture and probably ignition timing incorrect. May caused by many reasons: vacuum leaks, misadjusted sensor plate height, not fitting control pressure, worn injector valves, bad fuel distributor, too low fuel system pressure, bad ignition and timing ... almost everything is in question then.

Originally Posted by AFB24911S

Running - lots of body shake at idle, rough even at 1,000-1,100 RPM. During normal driving it makes decent power and I am getting about 20-23 mpg.

See the list a line before.

Originally Posted by AFB24911S

All of these problems have persisted since I bought the car about 5 years ago, but a collapsed suspension, messed up seats, and other issues took precedence. Now, I'm finally getting to the fine tuning.

...

Any flaws in my game plan? Other, better ideas?

Seems to be a decent plan. Conclusion: In such issues you have to take every CIS component in suspect.

Originally Posted by AFB24911S

Then, I'm going to check the cold start valve. First to see if it sprays in a nice pattern, then to see if it leaks when it shuts off. I've got six gorgeous plastic volumetric cylinders for that.

The problem is its reachability. It sits on the backside of the airbox in the bottom case. Very poor to reach. I recommend the following: Go and check out the connections of the TTS. Put in a push button (normally opened) in parallel to the TTS to mimic the TTS and engage the CSV manually. Then start the engine and let it run, push the button then (to inject fuel) and see how the engine reacts: When the CSV works and injects fuel the engine will show it in two ways:
If it runs better => mixture is not rich enough. If it stalls or starts surging => mixture is too rich.
If nothing happens then the CSV is bad/clogged.

Such a push button at the CSV is also extremely useful to determine whether the mixture is lean or rich when cruising or accelerating. Pressing the button on such situations gives the engine some extra fuel. So you get a much better feeling what the engine needs. On accelerating extra fuel let's the engine revs better/quicker? => mixture too lean. If if bogs and stalls, mixture is too rich/rich enough. Also on cruising, starting etc.
But: Be aware of back fire which can happen anytime!!!
Therefore never do such "experiments" without a fire extinguisher in place, as well in the car!!
Carry 2 with you: A bigger and a smaller one... Push the button only short times like 0,5-1 sec or so. You get the idea...

The AAR does not closes completely like a valve. There's always a tiny hole and some leaking air through it:



As this is measured air behind the sensor plate that is no issue!

The AAV must be checked with a vacuum pump the apply vacuum on the control plug to engage it. When the throttle closes the vacuum increases and the AAV must open to give the engine a little extra air to burn the already created mixture for two reasons: To prevent banging in the exhaust and to keep the revs above 1500rpm when changing gears to make gear changes smoothier. Otherwise passengers will nod their heads....often overseen. When the engine rpms drop too quick/fell immdiately to idle rpm when releasing the throttle this clearly leads to this.

One of the most important things and most overseen: The sensor plate height in conjunction of (my description) the injection begin. This means the sensor plate height has a huge effect on the mixture overall. It's height must be adjusted meticously as Porsche/Bosch specified in the manuals. Why is that? The sensor plate height defines the working intervall from being lifted from idle up to WOT. The lower the sensor plate is adjusted, the more way the lever will travel. This enriches the mixture overall. Vice versa if the sensor plate is too high. This will lean the mixture overall. So first of (if all other things have been worked as mentioned before) make the sensor plate height adjustment is correct as specified!





Then in conjunction to this - check the injection begin. This is the point where the sensor plate switches on the fuel pump by being slightly lifted due to the sucked air when engine starts and idles. These two settings always must be seen in conjunction!!



Also check that the injector valves all spray the same fine moistured pattern and - very important -they spray all the same amount of fuel!! (less than 5% difference each). Otherwise some cylinders run too lean and too hot which may causes valve tickering due to prolonged valves from heat and in the end may cause serious engine damages like broken rocker arms, holes in pistons etc...

You already know the fabulous video series about the 911 2.7 CIS from Klassikats?

https://www.youtube.com/playlist?list=PLkWFofpgz2OgF9FdliKnlzuY0pygqRkMj

Heavily recommended to watch, even more than once. If you better know the CIS the more time and effort you save. Watch all the videos to the end!

Good luck! Curious what you will find out...

Thomas

[pmax]

Another method is to measure the cylinder temps.

[mike sampsel]

Originally Posted by AFB24911S

@PMAX & @ fanaucidal,

How can I safely check for good spark from each spark plug? I had the CDI box gone through when I first bought it, I'm on my second set of new plugs, I've put a new OEM rotor cap on, and I put new points in a few years ago as well. Still, agree it's good to check.

If you have a IRThermo, you can check the temp at the exhaust output at the cylinder. The cooler one(s) are not consistently firing.

[AFB24911S]

Thank you all for the great ideas! Update follows.

I picked the car up from the shop yesterday, and it ran better. Much less shake at idle. The shop said they didn't do hardly anything and that they don't understand why the car is running better, so they didn't charge me a dime. They said the pressures were in range cold and warm, so that's good, but I'll verify myself.

Took the car home, removed heat exchangers while it was warm because the nuts were easier to get off and because I didn't want to spill fuel on a hot engine. Found out the hard way that my oil crossover pipe is the wrong kind. Oh well, back on the old ones go until the right oil pipe arrives with a front fender kit from Elephant Racing.

This morning, I dove into the fuel system with the car cool. First, I did a test on the fuel pump to make sure it was delivering enough fuel: 2.25 L in 60 seconds, pass.

Just to make sure nothing weird was going on impeding flow through the accumulator and the filter, I tested again downstream of those components and got the same result.

Then, I started rigging up the CIS sensor. I attached it between the WUR and the fuel distributor by connecting to the WUR and the control pressure inlet at the fuel distributor, pulled the fuel injectors, inserted them in my six graduated cylinders, and (after a trip to a few stores for wires, connectors, an inline fuse, and a switch per the Bentley book's instructions) built a remote fuel pump switch I could use at the back of the car.

When I ran the pump, all six fuel injectors started leaking. AHA! Not good. At this point, I directed all my attention toward the injectors. I checked the CIS gauge a few times, but it read zero; I must have set it up wrong, will reread the instructions and rewatch the video.

More observations of the fuel injectors: only 5 & 6 had what I interpret to be acceptable spray patterns at most amounts of flow. The rest were bad no matter what rate of flow I chose. They all dripped and squirted awkward, not conical shapes at low flows. See video:

https://www.youtube.com/watch?v=7mXIYztCpDQ

The amount of fuel delivered, happily, was extremely consistent. The greatest % difference at an average of 110.5 mL fuel injected per cylinder was 2% (range of 108-112 mL). The color of the fuel from cylinders 2 & 3 was much darker than the other two, however. I thought that might have been because the fuel injectors sat in the bottom of those cylinders. I re-tested twice, being careful to dip a few of the other injectors deeply in the fuel and switching fuel lines between 1 & 2 and 3 & 4, but the discoloration stayed at 2 & 3 both times. Conclusion: there is some kind of corrosion causing discoloration either in the lines or in the injectors at cylinders #2 and #3. (Replacing them all anyway, but in 10 years when I rebuild the engine it'll be interesting to see if those cylinders show different wear patterns.)

That took me all day. I replaced the fuel injector seals with new rubber even though I'll have new injectors installed soon, the old rubber was very hard and contamination in cylinder head = bad. There definitely may be other problems, vacuum leaks, etc., to be found, but this big issue with injectors is a good thing to have found. Still, tomorrow I'm going to throw the old exhaust parts on tomorrow and start checking timing.

I checked the fitment of the plate very unscientifically: when I put a light under it and looked in from the top, the light looked pretty consistent around what I could see. There was not a ton of room to get in there with a feeler gauge, will have to make some more room for myself there somehow.

Will attempt the CSV/TTS test suggested above. Another trip to the hardware store soon for a push button!

Remaining tests/things to measure:
-cold & hot system & control pressures (re-watch Klassik video for correct #s, my books don't have them for the '77)
-fuel distributor plate resting position orientation (centered, correct height)
-CSV (by wiring through TTS, need to find)
-ignition timing & dwell
-verify spark at all six plugs are sparking (bought a nifty in-line tester for $20, but if that doesn't work I'll use the light sensor on each)
-pancake-shaped AAV holds vacuum or not (the one passenger's back that's in line with the AAR)
-cylinder-shaped AAV works or not, vacuum leaks (the one just above the throttle)
-fuel pump check valve (residual pressure overnight from Wed to Thurs, using CIS gauge)

(For anyone trying to replicate the fuel pump switch who's as clueless as I was: the fuel pump relay is the big red cylindrical thing closest to the rear of the car in the fuse box in the frunk, and the terminals 30 and 87a can be identified by looking at the back of the relay. 30 goes to the pump, 87a is hot when the key is on. Connect a wire to 87a, run it to the back of the car, connect that to a switch, run another wire to the front again, inline fuse, into 30. Home Depot sells banana plugs that fit right in the relay holes, they're by the other stereo components and you just have to pinch them down a bit to fit them in.)

Again, thanks for all the support!

[fanaudical]

Great video!

Before you replace injectors, I highly recommend getting your pressure tests done and verify you're in range. A shop that couldn't find poor spray pattern also likely failed to do the pressure tests correctly. Poorly-atomizing fuel is a big reason why it won't idle right - but not the only reason. You're going to find the rest of the system is out-of-wack as soon as you replace injectors. Baseline everything first and then make changes.

It is curious you've got dark fuel from two injectors; I've never seen that...

[AFB24911S]

https://www.youtube.com/watch?v=te8k3ajnE4Y

Aha, another injector leak place! I was wondering how those bigger O-rings and the sleeve come out, this is a great video about it. I'll still spray starter fluid around the injectors to see if I get any revs at idle, if I do then I definitely have a leak there but even if I don't I might still have leaks there.

The thing to do might be to enjoy the car in as good a shape as I can for the rest of the summer (it runs pretty nice mostly, and the canyons are calling) and then to take the whole CIS apart knowing what I know after these tests to make it perfect next winter with the engine out. The transmission needs first and second synchros anyway.

[PeteKz]

Follow fanaudical's advice to baseline, then change one thing at a time.

That said, I don't think those injectors will clean up, so buy new ones. Our host's price is competitive with the cheap Amazon sites, and you can get new sleeves and O-rings with the injectors for a great package price.

Although Alan and I thought that the most likely cause for poor idle, but better running with more throttle, would be vacuum leaks, poor injector spray patterns cause similar symptoms. As the fuel flow increases, the spray pattern usually gets better, and the increased air flow better mixes the fuel, so it runs smoother.

You can replace the injectors before running the CIS pressures test because the injectors don't affect the SP or CCP or WCP. However, procedurally, it would be better to measure those first.

If you plan to just drive it for the summer, replace the injectors. You need to do that anyway, and that might solve most or all of your problem.

[pmax]

The corrosion is probably in the injectors.

They sound a bit louder and more shrill than I recall, not happy campers !

[Schulisco]

Originally Posted by pmax

The corrosion is probably in the injectors.

They sound a bit louder and more shrill than I recall, not happy campers !

Don't forget the fuel distributor. They corrode more likely than the injectors as they are made mostly of casted steel. The injectors worn out mechanically over time and this results in a bad spray pattern.
In case of corrosion on a CIS you have to check every component of the system. Especially the fuel tank is also made of steel and may corrode due to modern fuels containing ethanol which attracts water...

Thomas