SC Won't Start After Sitting for 2 Months

[OsoMoore]

My 79 911 SC won't start, and I need it out of the garage to take pictures for my collector's license plates!

I last ran the car about 2 months ago. I drove it more than 30 miles, without significant issues. I did replace the fuel pump relay because it wasn't starting evenly.

The car has been stored in my unheated garage, with temperatures ranging from 20 to 40 degrees. It had a full tank of gas and about 1/3 of the normal concentration of stabilizer (I drove it with full stabilizer concentration and then refilled the tank w/out more stabilizer). Previously I had let the car sit for 20 days and was able to start it afterwards without issues. The car normally spits a bit of white smoke on startup, and burns about a liter of oil per month - it has a very slow oil drip. I had the battery in my basement (60 degrees) and on a battery tender during that time. Its voltage was normal.

When I first attempted to start the car, I heard the normal noises - fuel pump whine, starter cranked, but no ignition. After about 4 attempts, I heard a small bit of combustion, but it wouldn't really start. At regular intervals I attempted to start it again, and each time I got more combustion. I kept retrying every 5 minutes, and eventually it would roar to life but die immediately. It reaches about 1600 RPM during its firing spurts. When it dies after starting, it dies in a coughing sort of way which vibrates the car as it stops firing. Ambient temperature was about 40 degrees F.

That was yesterday evening. This morning when I attempted to start it, I got only a little bit of combustion (no real RPMs), similar to my 10th attempt last night. The battery charge is still high, so the crank is strong.

Is this maybe an idle issue? Cold start sensor? Vacuum?

[Jdub]

Do you know with a certainty that a rodent has not found its way into the exhaust system? Has all the water in your gas tank gone to the bottom at the pickup? Any chance that the gas tank is working under a vaccum?

Pop the air filter and be sure everything is OK in there, including pushing the pressure plate up and letting it fall naturally. Consider replacing the fuel filter if not done in the last six months. Stabil (or equiv.) will scour the tank and lines and it all goes into that filter, which when plugged gives the same symptom I detect in your car - fuel starvation.

[ossiblue]

Originally Posted by OsoMoore

My 79 911 SC won't start, and I need it out of the garage to take pictures for my collector's license plates!

I last ran the car about 2 months ago. I drove it more than 30 miles, without significant issues. I did replace the fuel pump relay because it wasn't starting evenly.

The car has been stored in my unheated garage, with temperatures ranging from 20 to 40 degrees. It had a full tank of gas and about 1/3 of the normal concentration of stabilizer (I drove it with full stabilizer concentration and then refilled the tank w/out more stabilizer). Previously I had let the car site for 20 days and was able to start it afterwards without issues. The car normally spits a bit of white smoke on startup, and burns about a liter of oil per month - it has a very slow oil drip. I had the battery in my basement (60 degrees) and on a battery tender during that time. Its voltage was normal.

When I first attempted to start the car, I heard the normal noises - fuel pump whine, starter cranked, but no ignition. After about 4 attempts, I heard a small bit of combustion, but it wouldn't really start. At regular intervals I attempted to start it again, and each time I got more combustion. I kept retrying every 5 minutes, and eventually it would roar to life but die immediately. It reaches about 16000 RPM during its firing spurts. When it dies after starting, it dies in a coughing sort of way which vibrates the car as it stops firing. Ambient temperature was about 40 degrees F.

That was yesterday evening. This morning when I attempted to start it, I got only a little bit of combustion (no real RPMs), similar to my 10th attempt last night. The battery charge is still high, so the crank is strong.

Is this maybe an idle issue? Cold start sensor? Vacuum?

Several possible problems come to mind from your post. First, the bold highlight is a clue--don't know what you mean by starting unevenly, but that's a clue that something was amiss and the fuel pump replacement did not fix it.

Another thing, you shouldn't be hearing the fuel pump unless you are hearing it over the noise of a cranking engine. If the fuel pump is running with the ignition in the "on" position you either have a faulty relay, disconnected wire to the intake sensor, bad intake sensor, or the plunger is stuck and not resting on the switch. If the plunger is not at its rest, then the pump will run and the injectors will shoot gas, flooding the engine--something that could account for your symptoms. This is just one possibility.

I assume you meant 1600 rpm in your post, correct? Before you do any replacing of parts, do some diagnostics. First, check the fuel pump, as mentioned above. If the pump is functioning correctly, check your fuel pressures with a gauge set. I'd suggest you go no further until you report back on the two issues mentioned above. There are other possibilities--leaking injectors, malfunctioning cold start valve, air leaks, loss of residual pressure, but save those until you do your tests (residual pressure will be covered there, though.) Report back your results and we can go from there.

[OsoMoore]

Originally Posted by ossiblue

...
Another thing, you shouldn't be hearing the fuel pump unless you are hearing it over the noise of a cranking engine. If the fuel pump is running with the ignition in the "on" position you either have a faulty relay, disconnected wire to the intake sensor, bad intake sensor, or the plunger is stuck and not resting on the switch. If the plunger is not at its rest, then the pump will run and the injectors will shoot gas, flooding the engine--something that could account for your symptoms. This is just one possibility.
...

When I turn the key to the second On position (ready to crank but not to the crank position) there is a whining noise, which I assumed was the fuel pump. It may be that it stops after a few seconds - I don't recall. Is this the sound of the pump or of something else?

The previous fuel relay replacement was made based on swapping back and forth between 2 relays. With one relay, the engine coughed and sputtered and sometimes started. With the second relay the engine started up immediately. I switched them back and forth several times with the same result, which led me to be sure one was at fault.

I will try the suggestions and reply on the results - tonight if I have time, but maybe this weekend.

[T77911S]

it could be the whine of the CIS.

have someone turn the key on and listen at the engine. if it is the CIS, shut it off, you are dumping fuel into the engine.

[OsoMoore]

Tested!
No signs of critters in the exhaust pipe. Light whispy smoke comes out after a start attempt.
Airbox seemed clean and nice. I was able to push up the valve in the back and it fell back into place smoothly.
I cleaned the fuel pump relay with some electrical contact cleaner.

The whining noise originates from the engine area. It happens even when the fuel pump relay is removed. It stays on when the key is in the "running" position.
It was suggested I try a fuel filter (possibly fouled by Stabil?), but I don't have an extra one handy.

Videos of the start attempts and the whining noise are uploading and will be linked shortly.

[Nostril Cheese]

If it is a loud and high pitched whine, DO NOT try to start the engine!

[manbridge 74]

The whining is likely normal CDI noise if coming from engine area.

[OsoMoore]

Here are the videos. The whine is not particularly loud. It has always made this noise, since I bought the car last April. Of course, that doesn't mean it is a "good" noise...
911SC Won't Start video 1 03-13-13 - YouTube
911SC Won't Start video 2 03-13-13 - YouTube

Youtube is still finishing up on the second video.

[boyt911sc]

Do you have a fuel pressure gauge? Are you getting ignition sparks? After listening to your videos would make me check the the following:
-----fuel pressures.
-----presence of good ignition sparks.
-----air/vacuum leak.

Keep us posted.

Tony

[T77911S]

Originally Posted by OsoMoore

Tested!
I was able to push up the valve in the back and it fell back into place smoothly.
.

you have to do this with the key on. with the FP running, lifting the sensor you should have a lot of resistance. if there is ANY free play, the plunger is stuck.

the CIS sounds more like a "squeal", the CD is a very hi pitched "electronic" sound.
you could here the same thing in some old TV's.

another option is to jsut pull an injector, turn the key on and check for fuel. NO fuel is good.

[OsoMoore]

Originally Posted by boyt911sc

Do you have a fuel pressure gauge? Are you getting ignition sparks? After listening to your videos would make me check the the following:
-----fuel pressures.
-----presence of good ignition sparks.
-----air/vacuum leak.

Keep us posted.

Tony

I don't have a fuel pressure gauge. Is there a good way to check for strong sparks with just one person? I also need to determine the best way to check for vacuum leaks - I'll do a thread search.

Originally Posted by T77911S

you have to do this with the key on. with the FP running, lifting the sensor you should have a lot of resistance. if there is ANY free play, the plunger is stuck.

the CIS sounds more like a "squeal", the CD is a very hi pitched "electronic" sound.
you could here the same thing in some old TV's.

another option is to jsut pull an injector, turn the key on and check for fuel. NO fuel is good.

I'll do this tonight when I get home. The noise is more electronic than mechanical in nature.

[kodioneill]

My bet is wur adjustment.

[schumicat]

you can check for spark w/ one person by connecting spark tester or old plug to a plug wire and grounding it to engine where you can see/hear it when you turn key standing by door.

[OsoMoore]

Spark plugs were fouled, so I cleaned them really well. That didn't fix the no-start, but it does almost-start a little more happily.
Electrical distributor was very clean and shiny. When I lift the valve inside the top back of the airbox I get resistance and an air whooshing noise. CDI makes its little noise properly.

I'm not sure how to go about pulling a fuel injector to check for fuel. I have ordered a fuel filter that I will have in a couple of days.

[OsoMoore]

Update - new fuel filter and plugs are in, but no real change in behavior. It still catches a little but won't start. There is some combustion, but nothing sustained.
I suspect fuel or air isn't getting in in sufficient quantity. The spark plugs do get wet and smell of gas after attempting to start. Perhaps I should look for a vacuum leak next - old rubber tubes in the first cold winter in years may have cracked. The car came from North Carolina and now its in Wisconsin for the first winter.

I can also check the spark tonight.

Any other ideas?

[Paulporsche]

Provided your ignition components all check out, you need to check your fuel pressures, as others have mentioned. It's very possible your cold control pressure is too high, which yields a too lean mixture @ startup and/or your mixture is set too lean. As you suspected, vacuum leaks are very common in these old CIS cars and cause start/run problems.

All of these things might not matter if the car is in the warmer south, but up north, in winter, they make for very hard starting.

[T77911S]

verify spark again. pull a plug and place it o metal and have someone start it.

now you can do one of 2 things:
1; pull an injector, with the key on, make sure no fuel is coming out. then you can lift the sensor plate to make sure some does come out. just a quick squirt of fuel, remember its dumping fuel into the motor.

2; have someone start it as you lift and/or pull down on the sensor plate. this will very the mixture without changing the setting. if it starts, go back and check pressures.
lifting up makes it richer, pulling down leaner.



after that, fuel pressures need to be checked and airleaks fixed.
you should/may have a thermo time switch (TTS) connected between the WUR and TB. this blocks vacuum when cold to richen the mixture to help it start. this can go bad making the mixture too rich all the time.
you could also have a blockage in the return line making the mixture too lean. the inlet screen to the WUR could also be clogged.

[OsoMoore]

I pulled a spark plug wire and watched the spark using a used plug. The spark is small and white/blue. It seemed good, but I'm not exactly sure what a good spark looks like compared to a bad spark.

I will look into vacuum and fuel pressure next.

[Guardsred911]

2 things to consider. A good reputable shop the the PO used actually unplugged a wire that kept the pump from running when the Key was on the first position. Thus, when starting the car, you could click the key to the first position, hear the fuel pump run for about 5 seconds to pressure up, then start it. I never had problems starting it, and I didn't really like the idea of it running, so I plugged the wire back in (it's behind the airbox on the SC..... I believe it's a blue Bosch plug which can be felt by reaching in there and seen with a mirror and flashlight....

2 - Second point.. charge your battery up. I had similiar behavior and I charged my battery... started right up. Since then, I just use a battery disconnect when its parked..