1978 (82) 3.0 CIS motor will not start.

[Trunkmonkey4]

Hello everyone, I have a few questions and also just want to voice my plan to get my SC running again to y'all to see if I am on the right track.

I have a 1978 SC with a 82 motor in it.

I have searched and searched on this and have many tabs open on my browser right now, I am having issues with my 911 starting AFTER it has been running. It all started about 3 weeks ago when I ran it low on fuel (Doh!). I got in it the next morning and it would not fire. I figured a clogged fuel filter or injectors. The car sat for about a week before I decided to give it another shot... It fired right up and ran normal for about two days. I was leaving class one night and it fired yet died right away (less than two seconds) and would not fire again. I got the car towed home and then it sat for another week or so.

About a week later I replaced my fuel filter and it fired up. After driving around for about 30 mins I shut it off and started to work on my land cruiser. When I got back in it to go home it did the same thing as before... tried to fire yet died and would not do anything but turn over. So I pulled the fuel pump relay and then bumped the car over to try and displace any fuel that might have been in my motor... IT FIRED up and RAN! , yet with no relay the fuel pump wasn't running so once all the extra fuel was burn it died (after about 5 seconds) . I replaced the relay and tried to fire it again and it would not start. -- Was this just a fluke incident?

I hear the fuel pump and the CIS is making its sound. The main injectors are wet with fuel(could I be running to lean?), and I have spark.

From what I have read I think I might have one of more of these issues... A bad fuel accumulator (reverse vapor lock?) , faulty cold start injector (flooding my motor after it is turned off?), or my CIS needs for TLC.

What do you guys think I should do first?



Thank you.



Ps, Here are some links that have given me some ideas on what possibly might be wrong.

Stuck at walmart.

911s running rich/ doesn't start when hot

Warm start problem on 911 SC (1978)

[OsoMoore]

You seem to have a good start on possible issues. Here are a few of my thoughts. Note that I'm no expert on the CIS, just learning.

The fuel accumulator's purpose is to maintain pressure in the fuel system so gas doesn't vaporize after the car has been running for a while and the fuel is hot. If the cold engine starts and then stops again right away, the accumulator is not the source of the problem (unless it is plugged).
My SC was having some problems similar to this, and my problem was my fuel pump relay was failing. The car would get a little gas and start, but die right away.

I suggest you get a friend and do a simple test with one of the fuel injectors. Pull the injector (be careful not to crack the hose) and hold it in a plastic bucket. Have your friend attempt to start the car. You should get a nice fuel spray into the bucket. If you don't, then the problem is in the fuel delivery somewhere.

[Luc Bernier]

had the same issues
turnet out to be the injectors,

good luck
Luc

[Trunkmonkey4]

If it was a problem with the injectors wouldn't it not run at all after I ran it low on gas i.e. sucked up crud into my fuel system?

Why would it work some times then just stop, then after sitting a few days start to work again? I would think if it was an issue with my injectors it wouldn't work at all until I replaced them.

[OsoMoore]

Originally Posted by Trunkmonkey4

If it was a problem with the injectors wouldn't it not run at all after I ran it low on gas i.e. sucked up crud into my fuel system?

Why would it work some times then just stop, then after sitting a few days start to work again? I would think if it was an issue with my injectors it wouldn't work at all until I replaced them.

The injectors may be gummed up and delivering inconsistent or insufficient fuel. This could lead to erratic running behavior. If it is the injectors, I believe they can be cleaned with some care, and without needing to buy new ones.

[Kemo]

I had similar symptoms on my previous SC. I had a 78 with an 83 motor in it, no lambda runnig in loopback. the car would start great cold. however, after driving for a while and then letting it sit for like10 min, it would turn over and never start and eventually flood out. After sitting overnight, it would start just fine. after extensive tinkering, I replaced the cold start switch on the front and the cold start injector, which was apparently stuck open. So you may be having some similar issues. if it were me, I would spend the money on a CIS pressure test kit and at least get some baseline control and system pressures at cold,warm-up, and hot. It could be that your control pressures are too high (lean) or too low (rich). Both of which can cause wierd issues.

Here is something you can do in the mean time. With the injection lines connected to the injectors, pull the injectors from the bung and place in a clear mason jar. You will need a jar for each side. remove the air filter cover and the air filter. turn the key to get the ignition and fuel pump going but dont try to start the car. Check to see if the injectors are leaking. if everything looks ok, carefully raise the air metering plate which is in the area below the air filter. by lifting it, you should get the gas flowing thru the injectors. Check each one for a decent spray pattern.

for my car, i occasionally run the gas tank down to almost empty and pour in a couple of bottles of techron or berrymans. I lift the meter plate to full throttle and run the tank down. I keep recycling the gas/techron mix a few times just to kinda clean the injectors and the system.

I also use this lifting of the plate to prime the injectors after engine drop and what not.

in any event, its pretty easy to check the pressures with the kit. This will tell alot. I dont have an easy way to test the cold start injector. its pretty hard to get to, but it shouldnt spray all the time, only when its real cold.

just recently, i was working on a 2.7 CIS and found the control pressure plunger to be somewhat stuck in the upward area of the fuel distributor, so all the injectors were flowing without lifting the plate at all... ya never know until you get in there and poke around. You almost have to become a CIS expert with these cars. But hey, once you get it sorted out, you should be good to go for many many years.

[Trunkmonkey4]

I will update this tomorrow after I get some time to mess around with the car.

One last question for the night, and I might not even be able to get a solid answer.... I have a '78 body with a '82 motor, would their fuel pump check valves be the same? I have read where some are built into the fuel pumps... (on the earlier sc's)

I just dont know what year fuel pump set up I have...

[James Brown]

the CIS injectors are designed to close at low pressure to prevent them from dribbling fuel in the intake/cylinders after you shut off the engine. if you have a fuel pressure test set, that would help in trouble shooting the fuel pump

[James Brown]

here is a diagram of the fuel pressure in relation to the injectors and the accumulator

[HarryD]

Another possibility is that the screen in fuel tank is clogged. You may want to remove it and clean or replace it.

[TibetanT]

Hello there:

Where are you located? If anywhere near Spokane, WA let me know...I will come take a look.

However, I am with Harry on this one especially since you ran out of gas it could very well be your tank has crude in it that is causing you grief with startup.

Then again, warm start issues for these 911SCs are most likely caused by a bad, or failing, fuel accumulator. (I had the same issue until I replaced the FA.)

Of course, the best thing is to test the fuel pressure as mentioned above with proper equipment to be sure.

Good luck.

[TibetanT]

Truckmonkey:

Here are a couple pictures of 911SC fuel pumps. The silver one is for the 1978/1979 model and has an internal check valve.

The black fuel pump is for the later models, 1980-1983, with the check valve very visible in the picture.

Fuel delivery rates on these are slightly different, but probably should not effectively cause issues that I know of.

Hope this helps.

[Trunkmonkey4]

Thank you for the pictures TibetanT and James Brown... Definatly will help once I start digging into everything.


Just a update for everyone, sure 'nuff I jumped the SC off this morning (cold and rainy) and it fired right up. I dialed in the air to fuel mixture at my shop so I'm good to go there.

Just got back from the shooting range and decided to see if she would fire up, Turned over and fired first try... big plume of white smoke, but only for the first second or two.



I think the plan for now is, replace the FA, check the check valve (if I have a external one, I will replace) then if none if those fix it then I will deal with both main cylinder injectors along with the cold start injector.


Wheres the best place to buy or build a fuel pressure testing set up?

[Paulporsche]

JC Whitney has a CIS fuel pressure testing kit that many of us use. It is something like $60 or so.

Sometimes these CIS cars need to have the fuel system primed in order to get started once the fuel system has been opened up, like when you changed the fuel filter). This may be a moot point now that the engine has been restarted a few times, but might have been why it was hesitant at first.

Provided all your ignition components check out, then verifying your fuel pressures and lack of vacuum leaks are the next thing to look at.

BTW what does , "jumped the SC off this morning" mean?" Did you jump start it? Try a rolling start?

[Trunkmonkey4]

I had to jump it off via jumper cables and another car... I really need to get a red top or just hook my battery up to a charger. All these failed starts have really drained my battery.


So it started today just fine, I am scared to drive it to work or class because I feel once I actually 'use' the car it wont start for me... Guess theres only one way to find out right?


One quick question, I have replaced the fuel pump relay and since then I do not hear the whine of the fuel pump as much as I used to... Whats up with that?

[Trunkmonkey4]

Ok so the car has sat for about a week, Ive been crazy busy so no time to even see if it will start. Just tried it a few mins ago and it wont fire at all... Turns over, I pull the injectors I have fuel, I also have spark on my center plug -- I will try and test every plug tomorrow morning.

What would cause it to completely not fire and run at all now cold or hot?

It would be the basics right?.... Air, Fuel, Spark. Right?

[timmy2]

Weak battery

[Trunkmonkey4]

I am trying it when I am hooked up to my DD, I know its still weak but its started like that before.

I guess I should take it to auto zone and let them charge it to be safe.

[Trunkmonkey4]

I really need to get the 911 running, I am moving out of my current rental house and it would be a heck of alot easier if I would drive it away... and more fun.


So it could potentialy be one or more of these things:
-Fuel Accumulator
-Cold start injector
-Fuel pump check valve (internal?)


Could a bad battery really be the cause of it not starting at all? I am still thinking fuel pressure, but I guess now I have a major failure some where in the system and not just something that affects hot starts. I have a CIS pressure test kit in the mail now, that should clear some things up.

[boyt911sc]

Originally Posted by Trunkmonkey4

I really need to get the 911 running, I am moving out of my current rental house and it would be a heck of alot easier if I would drive it away... and more fun.


So it could potentialy be one or more of these things:
-Fuel Accumulator
-Cold start injector
-Fuel pump check valve (internal?)


Could a bad battery really be the cause of it not starting at all? I am still thinking fuel pressure, but I guess now I have a major failure some where in the system and not just something that affects hot starts. I have a CIS pressure test kit in the mail now, that should clear some things up.

Trunk,

I've been following this post for a while and tried to stay away until today. I know how much you wanted this car to run and drive it but it won't happen until you do a systematic investigation and tests to determine the culprit/s. By tinkering the fuel mixture setting (which you did already) without confirming the absence of any significant source in the system, you had created a bad situation worst.

Stop the quess work and start doing something sensible to get to the bottom of your problem/s. Test and confirm!!!!!!! All the CIS componnts you mentioned about could be tested and verified by DIY'ers like you or me. Don't replace parts if they are not defective unless you don't care about spending your hard earned money.

Now, let's start doing some work:
1. Check your fuel pressures (system, control, and residual).
2. Have your battery analyzed by a competent battery technician/shop.
3. Check for air/vacuum leak in the system.
4. Confirm the presence of ignition sparks during cranking.
5. The WUR, FP, FA, fuel filter, etc. could be checked without running the engine.

Why did you tweak the mixture setting in the first place? You don't need to change the mixture setting for starting an engine if the engine was running before!!!!!! The change in the mixture setting was caused by something else. You could drop your engine from a tall building and your mixture screw setting would be unchanged!!!!!

Go ahead and share with us your test results. It is very easy to make a CIS engine to run if you stop quessing. Keep us posted.

Tony