Drivability Issues '77 CIS
 

Hello,

Here are my symptoms: cold start takes 5-10 seconds to start (used to be quicker), very flat acceleration up to about 2500RPM (been this way for 27 years), very slight to moderate bucking/hesitation/studder when at steady speed (recent change).

I did a partial engine drop last year, removed and replaced just about every wear item, gaskets, hoses, seals and the air box.

Ignition components are all recently new except the actual distributor, timing is on and steady- I'm still suspicious of the distributor and most likely will get it rebuilt.

I decided to start testing systematically and then post my results and ask for suggestions; first thing was to try and find vacuum leaks. I started a post on that http://forums.pelicanparts.com/porsche-911-technical-forum/962257-smoke-testing-did-i-do-right.html and I would like to believe I am "leak free".

Next step is fuel pressures, which I'll list out in the next post to avoid making each post too long.

Thanks in advance for any help and suggestions.
Rutager

Did the fuel tests this morning and here are my results:

FD 0 438 100 006, WUR 0 438 140 033

Temperature was 75 degrees F.

WUR heating element 26 ohms

System pressure 4.9 bar
Cold Control Pressure 1.3 bar electrical disconnected.
Warm Control Pressure 2.8 bar after 3 minutes electrical connected.
Warm Control Pressure vacuum applied 3.6 bar.

Residual Pressure:
.9 bar after 5 minutes.
.5 bar after 15 minutes.
.2 bar after 30 minutes
.1 bar after 60 minutes.

It appears to me that only my residuals are out of spec.

Here's a picture of my gauge set up and factory listed specs.



http://forums.pelicanparts.com/uploa...1499620573.jpg
http://forums.pelicanparts.com/uploa...1499620635.jpg

Guessing you have tried seafoam in the gas tank to scrub out cooties.

Your rest pressure should not cause the operational issue.

Hi Bob,

Never put any type of fuel system cleaner in it. I almost exclusively use ethanol free gas. Only exception is on road trips, but them I burn through it pretty quick.

Rutager

How old is the accumulator / fuel filter?

Is there lateral and axial play in the distributor? Why do you want to rebuild it? (I think this is a good idea and something I want to do too) When you say ignition components are new does that include points? Is the dwell and timing set? Does it run hot at all? just some additional questions.

-Edit I see you set the timing.

I'm with Bob in that your test pressures would not account for the running problems nor the cold start issue. (BTW, I think you typo'd the fuel results--the second and third measurements should be warm pressure readings, correct?) If you cold start valve is working, you should get at least a brief firing/quick dying of the engine upon cold start. Is that happening, and have you tested the CSV? Regardless, that will not result in the problems in running.

Assuming your air leak results are correct, your symptoms look more ignition related to me, especially the flat acceleration you mention. Still, you may have a problem with fuel flow. It might be a good time to check the volume put out by the FP and pull all the injectors to perform a test to measure their spray patterns, possible leaking, and volume of fuel delivered by each.

Hi Duane,

Fuel filter was installed last year along with all new engine fuel lines. Accumulater is not original, but can't remember when I replaced it, likely ten years or more.

I had an issue with my points (tiny piece of wire broke down!) last fall leaving me stranded, so I replaced them this spring. Strangely I could get dwell to set, so just gapped with feeler gauge to spec.

Distributor looks pretty clean, although I did remove a black piece of something out of it recently. Side play seems minimal; up/down seems like a lot to me. Watching the advance with revving the engine seems smooth. I just feel like that thing has been spinning around for forty years and a rebuild couldn't hurt.

Rutager

Hi ossiblue.

Yes, warm pressures, I referred to them as electrical connected, which then heats up, I'll edit to avoid me confusing people.

Car takes awhile to crank, but once it starts, it stays running. Hot starts are immediate though. Car will start every time under all circumstances.

I will say that it on occasion idles low for a bit- running while the starter is still operated and if I let the key back, it runs on its own and then idles at 950 or so.

Thanks,
Rutager

If the CSV is working, you should not have excessive cranking upon cold start. Have you checked it out?

Can you clarify the last bold portion in your post? Is the engine running while you still have the starter engaged? I can't really understand the situation you describe.

Just for kicks, I did residual just on the system (4.9 bar) and when pump is turned off, it dropped immediately to 2.9 bar then at ten minutes it was at 1.8 bar, twenty minutes 1.6 bar.

Of course, the tester might be faulty too?

Ossiblue,

It's like the engine hasn't caught fully, but if I stop cranking it will run- so the revs are low enough that it doesn't out spin the starter. This is not every time or even that often.

One reason that ignition is suspect to me is that when I was trying to get the dwell set and at certain gaps, it would start up real fast, so I'm pretty sure the cold start valve works, but I will verify- just need to get a helper.

It also seems like when I time to spec, it doesn't run as well, so I have it at halfway between the timing mark and Z1.

Okay, got it.

IMO, get the ignition/timing issue settled once and for all--eliminate one of the variables. Once you are certain the ignition is in spec and cannot be a problem, move on to the fuel delivery if the issue remains. Keep us posted.

Ossiblue,

The ignition thing is troublesome to me, because it "seems" fine, but not being able to get dwell and another thing that happened is that now after I put new points in, the distributor had to be moved to the farthest side of the slot when before it was in the middle?

Any ideas? Should I just send it out for a rebuild and advance curve check to be sure?

If so, any suggested shops?

As for residual dropping off, should I test before the accumulater to see if it is the pump check valve or something else?

Thanks,
Rutager

I will add that when I accelerate anywhere in the 2500 to redline area, it goes great, no issue. Doesn't shudder up to 2500, just doesn't pick up and go.

Only poor running is at steady speed

Steady speed=constant, relatively low-volume fuel flow. Acceleration=increase in fuel flow. If poor running at steady speed was due to inadequate fuel flow, one would not think you could accelerate smoothly, as you need even greater fuel flow.

On the other hand, poor pick-up to 2500rpm could be an advance issue, and poor running at steady rpm could also be erratic timing.

Still pointing to ignition/timing advance issue, IMO.

Ossiblue,

I was just looking around at Partsklassic since they rebuild distributors and found some videos and they showed one that had points bounce and what it looked like on an oscilloscope. I have an automotive scope, so I might just see if I get a proper wave, although I'm not sure what kind of resolution mine has and if it is enough to see.

I know of a couple rebuilders, so I'll try and figure out if they do a good job and send it to one of them.

Thanks,
Rutager

Systematic testing......
 

Rutager,

You are doing great in your CIS troubleshooting. Things I like to see are:

a). Are any of the injectors leaking? Including CSV.
b). How is the spray pattern? Jet like or mist like pattern?
c). Remove all injectors (except CSV) from their fuel lines and place the ends in suitable vessels or containers. Then test run the FP. Look for any premature fuel delivery. A good FD should not deliver fuel nor drip when the plunger is at rest. CSV test with the engine installed is quite cumbersome due to accessibility.

Your cold control fuel pressure is rather low @75°F. How old is your CIS airbox? Focus on your ignition components. And finally, have a shop test your exhaust using a gas analyzer. Keep us posted.

Tony

Hi Tony,

Airbox is new last year when I renewed just about everything that I could as far as gaskets, seals and hoses.

When I put it back together last summer, I did the factory baseline FD set up with injectors in mason jars. At that time, the patterns were good, no leaks and equal quantities delivered.

I've not checked the CSV as it seems that adjusting timing/dwell would get me different quickness in starts.

I have an LM-2 AFR meter and here are my numbers I posted in another thread a couple months ago:

"I've been trying to get my car running as well as possible; 1977 911S with CIS. I did an extensive refurb last year of the CIS and at the time my WUR and fuel distributor where in spec and I also tested as many of the other bits that I could and they tested out as well.

I still think there is room for improvement; it feels like a very, very slight bucking sensation at low RPMs and a steady speed- really hard to tell if it's the engine or bumpy roads, that's how slight it is.

I had a bit of ignition trouble last fall and I now believe that I have it all sorted, so I hooked up my LM-2 with the tailpipe adapter and headed out on a 50 mile drive in 80 degree temps.

Car never got above 200 degrees. Here are my observed AFRs, what do you think?

Idle 12.8 cold 13.1 at the end of the trip.
Full acceleration 13.8.
Steady cruising on flat road at 55 mph 14.4 to 14.7.
Slight acceleration 15.4 to 15.6.

Thanks for any input or suggestions."

i would look at
ignition- advance working properly, set correctly. try a little more advance
injectors. very often over looked. I am not one for just replacing parts as a guess but you might consider replacing all 6.
you can test them. compare volume of all 6. do 2 tests, one that would simulate an idle, run it for about min. you need a battery charger on the batt.
another test for WOT. you might repeat for consistency.

check intake bolts, injectors sleeves and injector Orings for air leaks.

mixture may need to be richer.
for my 77 I would adjust It so it was on the edge of surging at idle or the RPM's dropping down then coming back up if you rev it and let off the throttle. mine liked to be on the rich side.

I am going to throw something in the pot for grins. Vacuum pod.

On my 81 there is vacuum advance (and retard). The vacuum advance kicks in off-idle and assists the mechanical advance.

What I don't know:

- Does the vacuum advance assist max out at a certain RPM?
- Is the vacuum advance and mechanical advance additive at full advance?
- Does the 77 have vacuum advance?
- Can you fit and suck on a hose and make the inside of the distributor move?

Another thought is if you only have a retard port, suck on the hose and see if it moves the inside of the distributor.

no need to suck.

I would have to look to see if all 77s have retard, but I think they do. you know the CA guys, they make things difficult.

easy way to test vac advance/retard is to remove the retard hose at idle. RPM should go up.
connect it to the advance port. idle should go up again.

vac advance is only used for mid RPM. as RPM goes up, vacuum goes down thus the vac advance comes out or retards, but you still have mechanical advance. I think I use to set mine around 30 degrees.
check mechanical advance with vac hoses removed.
no advance can make for a bad driving car like you describe. vac advance more so at low RPM if upper RPM is good.

I am pretty sure they do as well. Vacuum advance is "newish" Thanks for putting that to bed.

You mentioned new ignition components. And when I saw your car in May I remember an aftermarket coil, and maybe new CDI box? I don't know enough about ignition tech to offer any answers, but perhaps those items aren't playing nicely with your stock dizzy? Might want to post exactly what you're running for ignition.

Hi guys,

The distributor has vacuum retard and I did check it with a vacuum pump and it moved the plate smoothly.

When I baselined the FD last summer, the injectors sprayed a nice cone type pattern, no dripping and equal volumes.

Jameel,

I have an MSD 6 CDI box and their coil, I think it is the blaster II. I took the resistor out of the rev limit rotor.

I did just order a new MSD 6AL, so I can use a standard rotor and the box does the rev limit.

I'm going to send it to Partsklassic for a rebuild. Ran out of time today to call them for instructions; will try tomorrow.

Thanks,
Rutager

did you check vacuum advance AND mechanical advance.
they have to be checked separately

Sort of! I've done some "hey, that appears to be working tests".

My 77 has a vac retard and not advance. I've applied vac and the arm moved and engine bogged down.

I've moved the throttle connection while the timing light was on and saw a smooth advance, but did not quantify it with numbers.

I'm just going to get the thing rebuilt for peace of mind-it has been spinning around for forty years after all.

look to see if you have a timing mark around 30-35 degrees,. timing should advance close to that mark.
you need to look up the timing spec for your car. some set it for idle, others full advance.
I would try setting full advance to the 30degree mark and let idle fall where it may then drive it.

it not hard to pull that dist apart and check the weights to make sure they are not stuck.

you might post the engine number or specifics about you car so someone can look the spec up,
I want to say there is one that sets the timing to 15 ATDC and one sets it to TDC, don't hold me to it.

Hi,

Just a quick "midterm" update. I installed an MSD 6AL along with a standard resistorless and non rev limiting rotor a couple weekends ago (was planning on doing it anyways to get rid of rev limit rotor). Car took a lot of cranking to start up that day, most likely because I had also done fuel tests and there was probably some air in the lines.

After it was running, I checked timing and weirdly it was several degrees back from the factory 5 degree BTDC and about 5 degrees back from where I had set it a tad advanced before the change out of ignition box (was an MSD 6)! I reset the timing to factory and next day it started up excellently, just a few turns and it caught.

Road test revealed no change in the drivability situation; distributor has been sent out to be rebuilt, we'll see what happens.

The cold pressure appears low.

http://forums.pelicanparts.com/uploa...1192844740.jpg

Agree, from chart it looks like I should be closer to 2 bar.

Okay, back at this thing and with a new problem!

Had the distributor rebuild and the curve paper they sent along looks perfect. Got it yesterday, installed today and set static advance. Went for a drive and it appeared slightly smoother past idle, but bucking/stutter still exists- no change.

Drove to the freeway and turned back at the next exit everything behaving as before, then when I took the exit ramp and stopped at the bottom, idle dropped real low and engine sounded awful- thought maybe a diesel truck pulled up behind me with straight pipes. Drove slowly and carefully the few miles back with small backfires out the exhaust.

Got home checked ignition still seemed good and with timing light and operating throttle by hand, it advanced, so not a stuck weight or advance spring problem.

Hooked up the LM-2 at the tailpipe and I was pumping oxygen! 15-20 AFR. Visually nothing appeared to have disconnected, airbox seams looked fine- sprayed brake cleaner fluid into intake and car almost died. Sprayed it along airbox seam, fittings, injectors throttle body, boot and intake- no change in idle; doesn't mean no leak, but seems fine.

So besides a big vacuum leak, what could cause such a lean condition to develop "suddenly?" I have had some slight tailpipe backfires before this, so is it possible a component has gradually been failing, WUR or FD?

Thanks for everyone's help,
Rutager

what was the CP?
sounds like the WUR heated up and the CP went up as it should. could just be mixture setting but check WCP first.
get timing correct, set WCP, then set mixture.

make sure the LM is calibrated in open air. should read 20.3

Couple weeks ago when I did all the tests, cold pressure at 75 degrees was 1.3 bar, which from the chart is a tad low, but once warmed up, it was good.

Going out to the garage now to poke around with the mirror and flashlight to see if a hose in back came loose.

I didn't calibrate this time, but I have before- smell out the tailpipe agreed with the lean reading.

Double checked LM-2 calibration and it was spot on at 20.9

Car still was running 15 plus AFR cold. I poked around best I could and couldn't find anything that came undone. I slowly removed the booster vacuum line and engine started to die, so that isn't already sucking air.

Sprayed brake cleaner heavily around back of engine and AAR, no change in idle.

Picture my finger and thumb squeezing a blade of grass; that is how close I am to getting the Bitz kit.

I also did the slightly raising and pulling down the arm on the FD unit and both actions caused the idle to drop.

Any ideas?

I'm sure you have done these checks but let's confirm.....
Ignition-
What spark plugs are you running??
Have you visually checked them?
Copper I hope ?
Gap?
What does MSD recommend for the gap?
What type of ignition wires?
Points? Have you changed them lately? I would.

Mixture setting- Sounds like you are running lean, so I would turn the mixture screw clockwise 1/4 turn. This will richen the mixture. (The 3mm amen screw)

Also, If it were me I would go back to the CDI box. Maybe you could borrow one from a local.

Set the AFM between 13.94 (CO 1.5%) to 13.35 (CO 3.0%) at 950 RPM. This is done by turning the 3mm allen adjusting mixture screw at idle.

Let us know if this helps.

Hi Dave,

Pretty much the whole ignition has been replaced within the last year, just got the distributor rebuilt with new points and before that had put in a new set this year. Wires are Clewitt and less than 5,000 miles. MSD box just replaced two weeks ago. Not sure what type of plugs, but from Pelican and gapped to slightly bigger than stock as read in several places here. Dwell and timing spot on- well at least static timing, car started running bad on my drive to warm up, so I didn't do a 6,000 setting.

Car was running 13 AFR a couple weeks ago and then suddenly, like when it dropped from idle off the freeway went lean and started backfiring out the tailpipe, so something failed or false air is getting in to cause my problem. I did move the 3mm screw about 1/8 turn with no change.

Can't find a vac leak- doesn't mean there isn't one, or a component has failed- not sure which one?

I'll probably order the Bitz in the next day or so- so many things could be messing up my driving fun from CIS, that unless I want to keep chasing this thing and throwing money at it, I think that's my best move.

Thanks

After two blown Airbox'es due to backfires and vacuum issues, and a troublesome WUR - I was really tired of CIS.

Installed the Bitz kit during a weekend last year. Very easy. Runs flawlessly. Hugely improved throttle response. Nice gain in HP. I'll recommend Tony's kit to anyone.

Placed the order this afternoon!

I just don't need a "parttime job" trying to track down the problem, I spent over a grand last year replacing the airbox and all the hoses, seals and gaskets and have hooked up gauges and tested components several times without finding a obvious issue.

I'll be interested to see if I find anything blown or disconnected when I remove the CIS.

I'll update and possibly start a new thread on my Bitz install.

Rutager

Eagerly waiting to see how this CIS issue turns out, please keep us posted.


Sent from my iPhone using Tapatalk

I decided to remove it all and install the Bitz EFI- I will investigate the CIS once removed to see if something came loose or a hose split.