hunting idle, stalling and not starting

[47silver]

hi:

i searched this forum for information on my problem and my head is spinning for all of the fixes that i might have to do maybe your experiences will pinpoint where i have to look first.

the car 1975 911S 2.7 CIS all stock.
points with msd.
i checked timing a month ago and it was 5 atdc.


main problems:
1. cannot adjust idle, we have to use throttle lever to keep it at 1800 rpm any lower it stalls. i plugged the deceleration valve thinking that may be causing a problem but still could not adjust.
2. car bucks a little at partial throttle at lower rpm <2500 when pulling away.
3. when car is idling (well if 1800 rpm is idling) we hear slight pops as though a spark plug is not firing intermittently.
4. car would not restart after bringing engine to 180 oil and letting sit for a bit.

to get the car to run we fiddled with the fuses (#1 fuse in the front luggage bay was not completely seated, and #2 fuse in the rear fuse box was a little loose.) Unfortunately at the time i also depressed the throttle valve after taking the filter out and heard the fuel pressure. the car started.
car history
we got the car in august from a guy in indiana, and it ran nicely until it became colder outside and we have begun to experience problems. i wish i could park it for the winter but i dont want to as i like driving it too much. car goes to redline without hesitation.

i think that it possibly be:

1. fuel mixture setting too lean?
2. warm up regulator?
3. distributor contacts closing due to lack of oil?
4. deceleration valve leaking through the valve seat that would allow the two large hoses to send too much air to the throttle body?
5. spark plug wires?
6. coil?

any suggestions would be appreciated.

too cold to work on it but not too cold to drive.

gary

[RoninLB]

so then you checked for a vac. leak and ruled it out?........Ron

[47silver]

my son told me to put that on the list, i thought that it would not prevent it from starting, maybe some of the other problems, but i will check with carb cleaner.

gar

[bigchillcar]

Gar,

Wish I were cloer to you, I could probably help. I've got a '74 with CIS bone stock and work on her every weekend to keep her the pampered beauty I love...god, hope my girlfriend doesn't read that!

Anyway, the WUR definitely is possibility with the change in temperatures. As you know, it's mounted on the engine and has an internal 'thermosensor' that allows more fue from the fuel distributor to injectors when cold. It governs the pressure inside the FD...cold temp/low pressure in the WUR allows the plunger attached to the sensor plate to rise, forcing more fuel up, as the WUR warms (approx. 95 degrees), the pressure in the WUR rises and this restricts the fuel plunger, less fuel, leaner yada yada yada... You also could consider the thermotime switch/cold start valve combo, essentially a 'cold fuel injector'. These would be likely 'cold culprits', although I agree a vacuum leak could do it...spray some car cleaner around your air box , hoses, etc. while running and if the car's idle picks up, you have a vacuum leak.

Something else I'd check since you mention it. Points are funny. Have they been checked or changed recently? Not a bad idea to replace at least every 10K. Dwell needs to be 38(+ or - 3) for my car. If they start to close on you, expect pops and backfires and eventual car dying. Little adjustments mean a lot on these things. Probably the first thing I'd be doing If I were looking at your car would be pulling off the cap and rotor and taking a look to rule out ignition. What do your plugs look like? Are they white or are they black? Plugs will tell you a story about your mixture condition. Good luck and keep posting your progress...mid-year cars have got to stick together on this board! I think the rest would like to see us become extinct!
Ryan

[RoninLB]

Hey Gary.. I don't know what's wrong.. don't think it's vac. leak specific. but the injector seals dry out routinely. and the rest can be tested and adjusted. you may have a good "going over" project. get a fuel injection PSI tester, a timing light, a VOM, etc... when you do the whole system you'll know what your dealing with for the next time and secure with what you have now.. and I always have a spare coil and CD box around..........Ron

[47silver]

i am stuck tonite at my office. the car started beautifully and after reconnecting the vacuum advance line that was loose at the throttle body, i thought i found my trouble. drove the car about 5 miles to the office shut it off. spent less than 10 minutes in the office.

went back out, no start. it seems like it is flooded. i have spark, i have fuel pressure but a significant gas smell is evident, would some ether help, i am not too kean on spraying that into the car with a lot of gas in the system.

gary

[RoninLB]

Originally posted by 47silver
i went back out, no start. it seems like it is flooded. i have spark, i have fuel pressure but a significant gas smell is evident, would some ether help, i am not too kean on spraying that into the car with a lot of gas in the system.

gary

A guess.. the accumulator diaphragm is torn.. A CIS psi tester will confirm or deny...........Ron

[47silver]

does the 1975 911s have a cold start valve? i looked under pp and found a photo of one. this device may cause flooding as it may keep not let the engine lean out?

where is this located on the engine? i cannot locate in haynes or on site.

[RoninLB]

Originally posted by 47silver
does the 1975 911s have a cold start valve? i looked under pp and found a photo of one. this device may cause flooding as it may keep not let the engine lean out?

where is this located on the engine? i cannot locate in haynes or on site.

the cold start valve is the same from'75-'83, I think..find it on the intake manifold.. if I suspected a leaking valve I would remove it and leave the fuel line connected.. remove the elec. plug.. run one terminal to ground and the other to terminal to elec hot.. position the valve over a container.. turn on ignition.. TRANNY IN NEUTRAL.. lift sensor plate to start fuel pump and monitor valve.. should spray clean and not drip after disconnecting valve jumper wires.. do procedure for only a couple of seconds or you may lock the engine pistons with a flood of fuel.

and I think you may have alcohol in gas or some other winter gas mix, which causes me running problems........... Ron

[dougcl]

Gary, I think you have more than one problem. It sounds like the car is running too rich (when it runs) and it has a warm start problem.

Regarding the richness, the first thing to do is put it on a scope and get the mixture adjusted. Take it to a mechanic. Adjusting the mixture should not cost you more than $50.

Regarding the warm start problem, you need to have the system pressure checked after shutdown. The CIS system is supposed to hold the fuel pressure up to prevent vapor lock. There are several potential causes if this is indeed the problem. In the meantime, you can turn the key on, pull off the air filter, and lift up on the sensor plate to bleed the air out of the lines each time you want to start the car when it's warm.

Doug
75 911S

[47silver]

had it hauled by a great tow service fo 65 bucks on a flatbed, so it is back at home. i realize it is a chunk of metal and such but i was un-easy leaving it in an unguarded rough part of town overnght.
well, the car cranks (though battery is low now) ha, it seems like a cascade into the depths of troubleshooting, but it does not fire.
1. i checked the points. they were almost closed so i reset them to .012.
2. i found some wires that po's did hack job on the the distributor and fixed.

did these repairs after i tried to start in the am.
i think i do have the mixture problem and also the
should i try to bleed the gas in the fuel distributor again, after i recharge the battery?
should the coil read any voltage on the terminals when the key is on?

gary

[dougcl]

Gary, if you find that you cannot start the car when it is warm (after sitting for about 10 minutes, ie. after filling up, etc.) then it is likely that the system is not holding pressure like it should. In that event, you will have to bleed the fuel distributor every time you warm start. Either that or crank long enough for it to bleed itself.

Doug

[bigchillcar]

Gary,
Did you get a chance to look at any of the plugs? You have to be careful getting these in and out, but their appearance should speak to your mixture condition. If it is rich, the mixture adjusting screw is located between the fuel distr. and the sensor plate boot and can be adjusted with a 3mm allen wrench. I wouldn't go more than a click and then drive it before going any further...little bit means a lot with this screw. Wonder if you have a dwell meter and a timing light. Dwell angle and timing really need to be set at the same time. You set points initially to .012 inches, hook up the dwell meter and look for ~ 38 degrees (on my '74). If it's high or low, the gap should be adjusted higher or lower. Then check your timing mark, loosen the screw holding the distr. in place and turn one way or the other to adjust. I've actually done this by ear and landed right on the money, but it's better to have a timing light, but you may get it close enough if you want to try...for the idle timing (950 rpm's) on my car, keep your distr.'s vacuum advance plugged in. Let us know what's happening.
Ryan

[47silver]

thanks for all the info, i have not been able to check out the car will do friday i hope.

i hope that we can get spark and get the car running again. if no spark then will back step from plugs to rotor, points, coil, msd, fuse box, ill check red for power at the msd first though. after we solve that problem, then onto the fi system.

1. i would rather buy the gas analyzer for setting the mixture, does pelican carry this?
2. does pelican have the fuel pressure gauges? would rather buy them from pp than jc whitney
3. i am leaning towards a leaking cold start valve if all of the pressures work out. i reason that the cold start valve can only operate when the throttle lever up (micro-switch contacts make)and if the thermo-time switch contacts make. i do not think that 2 devices will fail on at the same time, however ill check them for operation before i check out the cold start valve.

question? can i remove the cold start valve with the engine in the car?
4. vacuum leaks: the best method is to spray carb cleaner? i have access to low range and sensitive vacuum gauges is there a chart on vacuum pressure versus rpm's that would give a good idea if i have a leak or not?

ha, after that i think ill take a break.
gary

[RoninLB]

Originally posted by 47silver

1. i would rather buy the gas analyzer for setting the mixture, does pelican carry this?
2. does pelican have the fuel pressure gauges? would rather buy them from pp than jc whitney
3. i am leaning towards a leaking cold start valve if all of the pressures work out. i reason that the cold start valve can only operate when the throttle lever up (micro-switch contacts make)and if the thermo-time switch contacts make. i do not think that 2 devices will fail on at the same time, however ill check them for operation before i check out the cold start valve.

question? can i remove the cold start valve with the engine in the car?
4. vacuum leaks: the best method is to spray carb cleaner? i have access to low range and sensitive vacuum gauges is there a chart on vacuum pressure versus rpm's that would give a good idea if i have a leak or not?

ha, after that i think ill take a break.
gary

1. a few guys around here have the analyzer.. cost a little more than a C note.. I love mine. have to be sure the gas transducer is planted firm and keep that set/fixed adjustment. can be a kool tool. and Pelican/Warren would probably sell 50-100 of them if he carried the inexpensive gas analyzer.. but a problem may develop with guys unable to properly use it.
2. maybe a problem waiting to happen...
... and "can i remove the cold start valve with the engine in the car?" . do you know where the CS valve is? LOL

4.IMHO. vac leaks on this CIS is a PIA. so to relax me I bought a Snap-On model AC-6500 Vac Leak Detector.. I got a deal on it or I would probably have bought the OTC brand. which is the same machine, I think.. cool tool/big time. it also does exhaust leaks.. worth the price of a fun tool. Pelican may have a good one/don't know?

and from my previous thread.
"Hey Gary.. I don't know what's wrong.. don't think it's vac. leak specific. but the injector seals dry out routinely. and the rest can be tested and adjusted. you may have a good "going over" project. get a fuel injection PSI tester, a timing light, a VOM, etc... when you do the whole system you'll know what your dealing with for the next time and secure with what you have now.. and I always have a spare coil and CD box around..........Ron"

[bigchillcar]

Gary,

I don't know that Pelican offers a gas analyzer...my guess is that they do not and I'd think them rather expensive. You should be able to find a number of local shops, however that would have one in their service bay; I'd call around and ask and would think about $50 would do it.

Pelican probably sells the pressure gauge, but these aren't that uncommon and you could put together what you need even from a local hardware type store or an Autozone, etc.

The carb cleaner method isn't quantitative in that sense, but a useful diagnostic tool to identify whether you have a leak or not by listening to hear if your idle jumps up any.

Good luck. I'll try to find out a little about your cold start valve questions later.

Ryan

[47silver]

the cold start valve looks like a real fun job. dont they have an access plate in the back seat area for that? just kidding.

the analyzer that pp handles needs a weld and all of that h.m. (horse manure) so i dont want to do that. i just want one that works, i am in the control systems business we use sensors for flow, kw, demand, refrigerants etc so i would feel confident about using most any tool like that.

the snap-on model leak detector can it be used for refrigerant leaks also?

thanks

gary

[RoninLB]

Originally posted by 47silver
is there a chart on vacuum pressure versus rpm's that would give a good idea if i have a leak or not?

a chart? ...there are operating vac signals/don't know where..not to experienced w/ this CIS vac. system/never had to be.. but generally engine vac is a variable that has dependant factors, other than an extreme problem.. if you had a baseline with everything operating properly and a set of a few working vac readings, that would give you more feedback .............. Ron

[RoninLB]

Originally posted by 47silver
the snap-on model leak detector can it be used for refrigerant leaks also?


gary

yeah.. works on harmonics.. different frequencys.. and you probe around looking for a strong signal.. then you adjust sensitivity to the spot marked X.. works great for exhaust leaks also.......Ron

[Superman]

You're chasing wild geese. IMO, you need to start over and verify the proper operation of components, one by one, in a rational sequence. (I'm not calling you irrational). Ignition first. if an engine's timing is completely unknown, you can hook a test light up and static time it. Static timing should be just after TDC. On any car. Once it is running, then you check for timing with a timing light, including verification that ignition is advancing properly as rpms increase. In a recent thread, Warren said that proper testing gear should be used to test ignition secondary voltage. I agree, but if you can get a snappy white spark to jump an inch, you've got a hot spark. Check resistance and continuity to each spark plug. This is the easy system to verify. Once you have verified that ignition is working properly, then you know the remaining problems are either engine mechanical (valves, rings, etc) or they are problems with the fuel/air system. CIS fuels systems are troubleshooted (troubleshot?) using a step-by-step procedure found in any decent FI book, such as the Bosch books and others. The procedure requires a pressure gauge and hoses, fittings and one valve. If you skip a step, like fuel pressure verification, then you could chase wild geese to the tune of hundreds of dollars and dozens of hours. Since the car is new to you, with unknown running problems, I think the standard, local troubleshooting steps are for you. IMO. And as you go, you will be eliminating stuff you would otherwise continue to suspect.