cis issues

[liv@usfamily.net]

ok guys and gals I need some help...I am at my witts end...ISSUE... unable to keep my 1973.5 911 running....at first I thought it was a fuel issue and frankly still do...I started it up after being stored all winter in cold Minnesota..fired right up drove it home some 75 miles with out so much as a hickup....went to drive it to work a few weeks later.....ran ok..not great but ok..since then it will not stay running more than a few seconds and not at an idle at all...have to keep the accelerator pedal down and feather it to even keep it a higher rpms to stay running at all...for the last several years have always have had a warm start had issue...after running any time at all very hard to get restarted...any ways here is what I have done so far...fells like a very bad miss starts right back up but no way will it stay running...last year trying to solve the hard start issue I put a new fuel pump on ...thought it still might be loosing pressure so put a new fuel filter and fuel accumlator on..no luck new dist cap and rotor thinking it just might be a spark issue no luck..made sure my pop off valve was nice and sealed up and no air leaks all seems fine there ..now on to my real question..I always suspected maybe I had a fuel injector problem maybe leaking down in one cly and hard start due to flooding condition...so went on pp used bought a set of used 73.5 injectors to try.. and got them from a guy and all looked good right up till the time I pulled mine out and to my surprise the ones in my car are at least and inch longer and from what I can deduce and cross the number that is on them...they belong in a 74-83???? by looking at pp new parts catalog I have the 73.5 injector seals but 74 and newer injectors in my car??? tried installing the 73.5 injectors in my car and would not even fire up... went and bought a NEW set of 74-up injectors and now wondering what seals I should use on them...I am confused as which way is up any more......any one with any help would be a saint.....wife says sell the darn thing..and of course she would get the money for new shoes or purses or something silly...but have updated the out side and inside to a c2 and really would like to keep it...lol Thanks to any one that has any suggestions or could shed any light on what the prior owner might have done to baffle me in such a way,.... Brian

[Pillow]

Sounds to me like a WUR or fuel pump (pressure) issue to me.

Do you have the ability to test control pressure? Requires the wackadoo CIS testing kit.

I have not tried on a 911, but if you can access the fuel meter arm, you can manually flow test the injectors to make sure they are spraying properly and/or leaking.

CIS is pretty simple in theory but needs all the pieces in top condition to work properly. One bad part and the system goes limp.

Good Luck!

[tcar]

How's the tank after sitting for the winter?

Symptoms could also point to rust/junk in the fuel tank that clogged everything up after sitting all winter.

[ossiblue]

Sounds to me like a fuel starvation issue and, like tcar said, could be from sediment build up somewhere along the delivery route.

73.5 was the only year with the injectors in the head, all following years had them in the intake manifold, that's why the later (74+) are longer. Why you have later ones, I don't know but your engine should fire with the original length injectors if you are getting adequate pressure and flow. I'd suggest as the next step to do a system pressure check, warm control pressure check, then a flow rate test of all the injectors. These two tests will let you know if your fuel delivery system is up to spec (Pillow has outlined what you need to do to perform these tests.)

Your problem doesn't sound insurmountable but, with CIS, you need a plan and you need to move one step at a time. Let us know what you find.

[liv@usfamily.net]

I was on the same thought about the tank rust plugged up issues....trying to eliminate stuff that I can do myself with what I have before I figure out how to drop the tank ..accually I work as parts manager at a Dodge dealer and have access to hoists and willing techs to help me...but with limited knowledge of porsche repair...ok as far as the injectors go...mine seem to go into the intake manifold which leads me to think maybe the p/o switched engines??? but the does not explain the older style injection seals ..far as I can see the 74 and up injectors use just an oring....a while ago I bought a used cis system from here on pp and have "extra " parts that I will try and switch out..another troublesome thing I see is that from the porsche parts book I bought for some reason the p/o eliminated the decel vavle??? the system I bought has one and am thinking maybe I should first try and figure out just what is what and why that is missing and lines just plugged off. what I would really like to do is start from the begining and put the whole system back to what it came with from the start..being an OEM guy I figure that way I know it is all there and then can properly trouble shoot problems....great help so far and will let you guys know what I figure out as soon as I do....thanks guys

[liv@usfamily.net]

also ossiblue it ran good for several years with the longer injectors in it...you seem to know what your talking about...will it hurt in any way to run the longer injectors in it? in my minds eye they should not even be fitting if the engine is a 73.5 right? I am so confused..lol really tough to figure out what I have going on and honestly when I bought the car 11 years ago I was a VERY uneducated buyer..knew I wanted a 911 and this one is what I could afford and bought it from a guy in St Loius and pretty much was happy with what I got and feel I got my moneys worth. with the connections I have in the body shops and techs at work it has been a blast to own, but now I really want to get the fuel issues and hard start problems taken care of once and for all.... want to do it right...and difficult at best to understand what th p/o did 14 years ago...

[Laneco]

Also worth checking for a big vacuum leak, particularly the line to the oil tank or the seal under the cap.

angela

[ossiblue]

Brian,

Your new information helps a lot so yes, let's start from the beginning as it's important to know what you have before diving into repairs.

First, you suspect you don't have the original engine. Please post the engine# which is stamped on the right side of the vertical fan support--if your car has the original engine, the number should be *613XXXX* with the *'s being "stars".

Second, post a picture of your engine--that will help immensely in determining if parts are missing.

Third, you will need a fuel pressure gauge set to do any serious diagnosis of the CIS system. Since you want to work on the engine yourself, be sure you have one that works for the system--well worth the investment.

Since you mentioned the engine had run well before, your current problem may not be very serious but it is important to know just exactly what you have running in your 73.5T. Let us know what you find out.

[47silver]

had same problem. the wire running from the points was grounding on the distributor cam.... only on occassion but sometimes the car would not start and when it did run bad.
also if you have an msd check the mag pickup wire area and make sure it does not short on the 2 stage rear window relay. (i posted about this today).

[Jim Williams]

Check out this photo. This is what the 73.5 head's injector ports will look like. If your injectors don't fit into a port like this, held in by only a rubber "grommet", then you have a later system than the 73.5 CIS, and maybe a larger engine.

[liv@usfamily.net]

yes that is what the port for the injector looks like on my engine. looking at pp new parts listing I was pretty sure I have a 73.5 set up looking at the injector "seal" set up...however really can't under stand first how my engine would run on 74 and newer injectors. it seems I have a lot to check out and being a hockey and softball coach for my girls I get about 20 mins at a shot to work on it..so go in bits and pieces when I get the time..all very good suggestions and will start from step 1 and properly try and diaganios amy vaccum leaks and gas cap and dist. wire issues....will keep all of you updated and as always you guys are great...what you learn on this site is truly amazing.....thaks all

[liv@usfamily.net]

hello fellas ok got my little red money pit running again..here is what went down....had a tech from work come over tonight...and looked at a few things and figured out it was either a fuel starvation issue or a vaccum leak...we figured that out by getting it to stay running by spraying carb cleaner into the air box with the air filter off....then it would stay running .. first lets say I totally checked out the pop off valve better than month ago because I had an issue with that being "sealed" a few years back and it seemed fine as soon as we sprayed the carb cleaner arround the pop off valve it ran perfect.....and ta da pulled on the pop off valve and off in my hand it came...the pop off valve was installed in the car when I got it and honestly don't think he installed it correctly. he had it epoxied on top of the "fins" in the air box. which to me limits the amount of surface that can be afixed to the body of the air box which in turn gives it more sealing power..any way marked the fins of the air box ground them down and refitted the pop off vavle to the air box with some two part high temp epoxy..and wa la after leting it cure good started off and ran as good as it ever has...however on to my next issue...the warm start issue I have always had seems to still exsist. can any one tell me what the decel valve does? seems as if the p/o took it off and blocked off the vaccum lines?? also would the wur have anything to do with a warm start issue? seems as if to me it has a "vapor" lock issue..try starting it when warm after driving in warmer temps and it wont even fire....not a back fire nothing...let it sit for say maybe 15 mins and take the air filter and cover off and will start ..grugingly but will stay running after a few start and die attempts..any more ideas? once and for all I would love to get the warm start issues solved so my loving ..long suffering wife feels confident enough that it won't leave her stranded some where when she wants to drive it...as always all the guys and gals that give me ideas are the best w/o you people I would be lost..my wife calls PP my face book freinds ..I have no face book account ..and frankly am way too boring to be of any interst to any one other than "guys" like you that can understand the fun (and headaches ) that owning a Porsche can bring to a middle aged working stiff....again..thanks to all that have helped me with my issues....well the Porsche ones any ways...

[ossiblue]

Brian,

Good work on the pop-off valve, glad things are running smoothly.

As far as your warm start issue, two immediate possibilities come to mind--bad fuel accumulator or bad check valve at the fuel pump--either of which will cause loss of fuel pressure when engine is shut down.

Again, pressure tests using a fuel gauge set is in order. Your system should hold pressure for at least 30 minutes after shut down @ 1bar.

You have the two port fuel accumulator on your car so if it is bad, you might see fuel leaking from the bottom, but that's not a good test--use the pressure gauge. Connected to the line of the accumulator inlet, you can test the fuel pump check valve. If that test holds pressure, re-test at the accumulator outlet port to check the accumulator.

Your car, if unmodified, has the fuel pump located above the left rear wheel, a very hot location so the idea of "vapor lock" is very real and that is the partial function of the accumulator--to prevent that.

If your hot start problem is a failure of residual pressure, next time it happens, remove the air filter, turn the ignition to "run" (the fuel pump will start) and gently lift the sensor plate in the intake housing--you should hear the injectors squeal (caution, only do this for a few seconds, <10.) Your system is now primed and should start immediately. Since your pump activates with the ignition, you can accomplish a similar result by letting the pump run for a while before turning the key to "start".

Let us know what you find.

[liv@usfamily.net]

thanks again for taking the time to help me ossiblue..in my "mistakes " to correct the non running issue I bought a new fuel accumlator and installed it figuring "shot gunning " it may fix all the issues I had by gosh or by golly...so I have to say the acculator is not my issue..and last year had the fuel pump not run ..by that meaing could not hear it and had no fuel pressure at all so bought a brand new bosch fuel pump so am kinda thining that isn't my issue either can hear it run and barrowed a fuel prsssure gauge from a techany other suggestions? at work and seems to have the correct fuel pressurre and stays constant...any other suggestions?

[ossiblue]

Brian,

Sounds like you've checked out the obvious suspects. Just to be clear, you did mention testing the pressures, but did you check the residual pressure? The way your post is worded, "seems to have the correct fuel pressure and stays constant" I'm not sure if the "stays constant" is pressure with the pump running. If your system holds pressure with the pump off, then I'm a bit stumped, tough it still could be a "vapor lock" issue. Do you smell fuel when the warm start failure happens?

On another track, if the fuel delivery is good, you might try a check for spark when the warm start fails. Possibly it's a failing coil or CD unit that acts up when things get too hot.

[liv@usfamily.net]

good ideas will re check the fuel pressures at the point and times you suggested and will give you exact readings as I get them ..have not tried watching the pressure after shutting it off..at the point I checked it was more concerned with the non running issue and not with the hard start warm issue..will re do the pressure "leak down test" and see if the pressure stays up after shut down.. ...you might be on the right track with the coil warming and breaking down have heard of that in some of our cars at work having that issue with the "old style" coils we used to have on our Dodges, but since they went with the coil over plug style have not seen that..also not sure that why then it starts back up but needs "coaxing" , by that I mean pumping the accerator pedal and messing with the hand choke to re start..again thanks for all your help ossiblue..own a Chrysler product? any thing a chrysler parts manager could do to help you out? if so let me know Brian

[boyt911sc]

Originally Posted by liv@usfamily.net

good ideas will re check the fuel pressures at the point and times you suggested and will give you exact readings as I get them ..have not tried watching the pressure after shutting it off..at the point I checked it was more concerned with the non running issue and not with the hard start warm issue..will re do the pressure "leak down test" and see if the pressure stays up after shut down.. ...you might be on the right track with the coil warming and breaking down have heard of that in some of our cars at work having that issue with the "old style" coils we used to have on our Dodges, but since they went with the coil over plug style have not seen that..also not sure that why then it starts back up but needs "coaxing" , by that I mean pumping the accerator pedal and messing with the hand choke to re start..again thanks for all your help ossiblue..own a Chrysler product? any thing a chrysler parts manager could do to help you out? if so let me know Brian

Brian,

Since you work in car dealership, you probably have some tech willing to do some work for you. First and foremost, there is no 'vapor lock' in a CIS. It is a myth. And anyone wanted to take a detail discussion on this subject is welcome to discuss it separately. People familiar with carbs would probably experience this phenomenon. You need to establish two (2) important criteria for a good running CIS: fuel pressures and vacuum leak. While most troubleshooters would do the control and system pressures check, it is often ignored or overlooked the importance of vacuum for CIS. Not being able to detect a vacuum leak does not mean you don't have one. While it is helpful to use flammable liquids, it is not as effective as smoke machine or presurized gas to locate vacuum leak/s.

A while back, a member with a very good grasp about CIS refused to do 'pressure test' and insisted on working on his WUR. He explained that his mechanic looked all over the engine and found no air leak source. To make the story short, after weeks and months of discussion, the culprit was finally discovered. A big hole was present on one of the vacuum line.

It takes only about 5 psi. to lift a pop-off valve. Even a 'supposedly good running' CIS engine would show some minor air leak/s during the pressure test. A big air leak will cause running problem and you want to avoid this one.

Tony

[Paulporsche]

I think I know to whom Tony is referring (LOL). Actually, we found several things that were not quite right:

There were probably leaks @ the intake runner gaskets, which were replaced.

There was indeed an emerging hole in the AAR line. I say "emerging" because I found an extremely thin spot on the underside of the pipe where it had been rubbing on the oil cooler cover. John Walker mentioned that this is a very common thing. There was material there, but when I poked it lightly w/ a screwdriver, a 3/16" dia hole appeared.

I had several WURs, all of which seemed not to be varying their control pressures. Rebuilding w/ some new parts, verifying the current to the WUR, and resetting the control pressures, per a procedure supplied by Pelican stevemfr (and others) we finally got the thing running better than it had in years.

Tony and many other Pelicans were very helpful and patient throughout my ordeal. The only reason I hadn't done a pressure test was because I didn't have the means to do one myself, and none of the 3 mechanics who looked @ the car seemed to want to!

After verifying ignition, it seems that checking for pressure /leaks and control pressures seem to be the most important things to do. So check that WUR and report your pressures so others can comment.

Just wanted to add one more thing: You mentioned a new cap and rotor. It's always best to confirm ignition system is working correctly first before checking CIS. Did you check/change/reset your points?

Also, I may have missed it, but did you have your mixture (CO%) measured and set?

BTW the decel valve isn't necessary. Its function is to keep revs up between shifts and while coming to a stop for emissions reduction. Some people don't like that hanging idle effect so they disconnect it. The other thing about is that it is quite often a source of the vacuum leaks others have mentioned.

[liv@usfamily.net]

Thanks Paul ya I replaced the cap, rotors, wires and re checked the point gap....it really felt to me like a "miss" so right away after checking for what vaccum leaks seemed obviuos to me looked at it as spark issue cap rotor wires points...when I had an extra helper one of the techs at work come over was much easirer to work with it as I kept it running..hard to do alone....start it..run back and check some things..die. start again..run back die...was not a happy camper with it....either way..now is running...not perfectly as of yet but better now than 3 days ago..good to know on the decel valve good info...can tell it has a little lag during shifting but if its not needed....no need for the extra weight at the track right? lol just kidding...old ad from Dodge on a kid who was taking all the seats out of his brand new Challenger in 1970 and his dad freaked and asked what he thought he was doing....and he said extra weight at the track Dad..lol when I get some extra time this weekend will be putting all your guys ideas to the test Thanks again one and all who is willing to help me...Brian