79sc, new fuel pump, intermittent no starting

[ronb]

Hi, new owner, getting a lot of info and insight from this website...2 weeks with my new 79sc, was hard to start, finally died. Replaced the fuel pump which made a big difference, it would start right up with a roar. A cold snowy northeast night...it would not start (nor the next morning). Fuel pump was working, could hear it hum...next morning, would not start. Flatbedded to mechanic...sat in the sun, started right up. Cannot get it to duplicate. As this is my daily driver until salt goes down, I do not want to be stranded. Any thoughts? (replaced the fuel filters etc when I did the pump). thanks, ron b.

[davis911s]

Hi Congrats on the "new" car, you will love it!

As for your starting Problem do a search for any starting problems, it could be blocked fuel lines, bad fuel. Did it sit for a long time before you bought it? Could be contaminated fuel. Also Cold Start valve may be shot (not sure if your car has one).

Best thing is check the archives using the search feature,

Good luck

Shawn

[wckrause]

Is this only a problem when cold? Does the car fire at all, or does it just crank and crank? When it does start, does it idle ok? Does it ever backfire when cold?

[ronb]

Thanks for your quick replies. It does not fire at all, just will crank. It idles fairly well for an 22 year old car, occaissionally I had to rev it quite high for it not to stall, but then it would settle right in. No more than 1 backfire when it was hard to start (there's a pop off, which didn't pop ever). It was slightly harder to start when cold, but not to excess, ie maybe 3 or 4 cranks, and it would fire

[Rot 911]

Sure sounds like water in the fuel line froze.

[wckrause]

Search the archives for the word "thermotime". You should be able to find info on troubleshooting the thermotime switch and the cold start injector. That would be a good place to start. If you have access to a CIS tester, ($50 at JCWhitney.com) then you can verify proper fuel pressures.

If your car won't start again, make sure that you're getting a spark before digging into CIS components.

[davis911s]

Like Bill said check to ensure you have spark. I would also check your distributor cap to see if there are possibly any cracks or wetness. Sometimes this will cause intermitent problems.

Find out if it is spark or fuel related. let us know.

Shawn

[Titleist 911]

It could be a number of things - bad grounds, CD unit - but the solution to the intermittent starting (and stalling) problems with my '78 SC was the replacement of the green wire to the base of the distributor.

[ronb]

Now that the weather has warmed back up (30s and 40s) car starts right up. Any other thoughts since it seems to be cold specific?

[wckrause]

A 30 degree cold start is a good time to verify that your cold start equipment is working properly. Your car should start and warm up in the following manner.

On a stone cold engine.

1. Turn key to start -- engine should crank for one or two seconds as fuel pressure comes up.
2. Engine should fire strong, and begin to idle at around 1600 to 1800 rpm. Idle should be smooth but may flucuate a little as the mixture changes.
3. The rpm may rise a little, but then it should gradually reduce to normal idle of 950 rpm over a period of a couple of minutes.

This warm up process shouldn't require any input from you other than turning the key.

Also, you should get decent throttle response shortly after starting the car.

[ronb]

With the exception of having to tap the throttle to get the engine to fire, your description is an accurate rendering of how it starts, except when it didn't.

[wckrause]

What happens if you don't tap the throttle? Any chance your throttle linkage is sticking, maybe your throttle isn't closed all the way unless you tap it a little?

[ronb]

without a tap or 2 it will start to catch, then miss. eventually it will catch, just requires 3 - 4 cranks; I thought it less wearing on the system to tap the throttle. If it started like this 100% of the time...there wouldn't be a problem.

Throttle does not seem to be sticking.

Right now it has crapped out - ie no start at all - when the temp has gone down to 20 degrees or less, once with snow. Once the temp is back up to 30+ it starts right up.

As of this post the thermotine has tested ok, as have the various cold start components. With the exception of the infamous green wire I'm stumped (as is the mechanic). Green wire being changed out. However testing the system by getting stuck on cold snowy nights is not a great option, esp when with my wife who prefers the heated seats in her ride (we got stranded 3 times in 10 days...)

RB

[ronb]

An update - car started fine 25 or 30 times in daily around town use. Could not get it NOT to start, so was unable to really diagnose....until, once again, late at night, coming out of a bar w my wife in 20 degree weather....no start. Other than stopping going to hear music late at night....I still am stymied. Some other observations though when it did not start....the starter motor would crank and the tach needle would flip over quite high. I spoke to the mechanic who looked at it...his conjecture now is that there's a problem with the distributor, although I checked it out and he did as well. I'm out of my depth here...could there be some sort of ignition malfunction? Why would the tach react like that? Or is that something to ignore.

And naturally, the next day...after flatbedding again...it started right up (and before it went on the flatbed, we tried to start it).

[ronb]

A pattern in the no starting is finally appearing.
15 - 18 starts w/o problem
Then no start - tach needle flips, horn does not work, car cranks, no firing at all
Tap the distributor, a long crank, a very hard start requiring feathering of the throttle, not possible to rev over 1k. Eventually catches.
If sitting and idling without input on the throttle...revs rolling up and down from 600 - 1500, in a rhythm, as if an injector is opening and closing.

2 separate problems here? Or...is it just that i need a new horn?

Any help is appreciated, so far both mechanics who have looked at it cannot help, and it is certainly beyond my diagnostic skill level at this point.

The suggestion was made to simply replace the ignition with an electronic ignition - any thoughts? I'm out here in a rural area and sort of have to depend on this car as a daily driver for awhile as my truck coincedentally has a blown rear seal.

Help!

[Jdub]

I am afraid I am not of much help on this one, but I do think that you will need to baseline the car by replacing certain parts that, unless you have docs that show they are new, are commonly replaced in a tune up.

So first off, the fuel filter should be replaced. Left side engine bay as you face car, behind and to the left of the black hose running from the blower motor to the engine duct.

Other bits: 'plugs, wires, cap, rotor. Adjust valves, air filter, and of course an oil/oil filter change AFTER you drop 20oz of Techron in a near-empty tank and drive the living bejabbers out of it.

Finally, do I understand correctly that the car only refuses to fire when freezing (<32degree)? I wonder about the battery...

John

[ronb]

All those items have already been replaced.
On the list to replace immed:
thermotime
cold start valve
(both of these have been tested however and work, so I am still stabbing about in the dark)