Still need more CIS help!

[radcon]

I recently posted a thread regarding problems with my '80 SC and it's resistance to start easily and the fact that it will not rev during the first 3 - 5 minutes of running.

cold/hot starting issues

I am at a complete loss. I have to crank the car forever to get it to start, then it is still hard to keep it running. Once it will stay running on it's own, it will not rev and it will pop and backfire under acceleration for the first several minutes. Once it's warmed up, it runs perfect. What gives? Is it something with the cold starting attachments(AAV, AAR, etc.)? Could it be a severe air leak that is only present when cold but goes away when warm?

I only have 41 days left in Hawaii and I need to get this fixed ASAP!!!

[Doug Zielke]

You have 41 days?
Then go get a CIS fuel pressure test kit, and the Probst book on Bosch Fuel Injection Systems. Without these tools you are looking for the proverbial needle......

[john walker's workshop]

warmup regulator is probably too lean w/cold. search adjustable warmup regulator, or adjustable wur, to find how to make it run richer w/cold.

[Hladun]

You must do a proper pressure test of the WUR using the CIS pressure tester. Don't just replace the WUR unless you want to throw money away.

Also, is the thermotime switch working and is it properly connected? On my car the two leads can be reversed, and if they are the cold start valve won't work. This is important; the cold start injector only works when the engine is cranking, so if you have backfiring once the engine runs it can't be the fault of the thermotime switch/cold start valve.

[radcon]

Already have the pressure gages and my WUR has already been modified to make it adjustable. All the pressure check out fine. Is there anyway that the pressures could be indicating in the proper range, but the WUR could still be screwed up?

Some have indicated that the accumulator could be bad and causing my hard starting. But once the car is running, could a bad accumulator be causing the stumbling and inability to rev?

[Hladun]

The accumulator can affect starting, but once the engine is running its just a pulsation damper and therefore shouldn't affect running. Have you taken out the air filter and checked to see that the flapper rises when the engine is revved? It may be binding when its cold and frees up as the engine warms up.

[bigchillcar]

The accumulator dampens the system, otherwise the fuel pump would move too great a volume of fuel before the system is ready (restrictions actually create 'pressure'). It thus holds pressure as well when you turn off the car to make warm starting possible, otherwise you'd have vapor in the lines and cranking, cranking, cranking. Does the car start differently when very warm? If it starts fine your accumulator is fine.

I agree that the backfiring is probably evidence of a too lean condition. I think I replied to this on your earlier thread. If your cold-start system is malfunctioning, either or both your thermotime and cold-start valve, your initial cranking mixture is too lean - if the engine block is < 95 degrees, as determined by the thermotime switch which controls the cold-start valve.

If > than 95 degrees because the car was recently run, then the WUR, which functions to lean the mixture appropriately after the cold-start valve gets things started, has already established things and pressure/mixture are correct.

This system is my best guess. Look, if the car runs perfect when warm, you probably don't have a vacuum leak which might cause it run lean, but you can spray carb cleaner around your airbox, intake, etc. and listen for a change in idle to diagnose a leak. CIS depends on vacuum to operate properly - it won't without it.

I think the sensor plate was mentioned here by hladun. That's worth checking out. Remove the airbox cover/filter and work the throttle linkage from the rear and watch to see if the plate rises with throttle.
Ryan

[mr.bch]

I had something similar happen to my 81 SC last month. Turned out that the the OXS and interior lights fuse (4th down from the top of the panel, I think) had oxidized at the point where it was clipped into the fuse block. It didn't blow, but wasn't making contact. Cold started like a biatch. Popped and backfired when trying to rev. Nurse it till warm and it would work (almost) fine. $380 dollars of electrical trouble shooting and $0.25 for a new fuse and it runs like a dream...

And who said you can't buy nuthin' for a quarter anymore...!

[radcon]

Thanks for the suggestions. I have to crank the car for quite awhile when it is cold to get it started, and I also have to crank the car quite awile to get it started when it is warmed up. The longer I leave it sit when it's warm the harder it is to start. Meaning, when I turn it off and restart it immediately, it starts back up. If I wait two or three minutes to restart, then it takes a bit of cranking to get it restarted. That makes me think that the above problem could be caused by the fuel pump check valve or accumulator. Is there anyway to troubleshoot and tell which one is the source of the hard starting?

But even if that fixes the start problem, I'm still left with the sputtering, backfiring and inability to rev for the first 3 - 5 minutes that it is running. Thats why I think there are multiple things wrong.

Regarding the Thermo-time switch and cold start valve, what is the maximum amount of time that the cold start valve will spray? Or will it keep spraying until the engine is above 95 degrees?

When I was checking things out last night, I looked through the Bentley and it said that the frequency valve should be buzzing when the car is running. What is the input to the frequency valve? Will it be buzzing even if the oxygen sensor is unplugged?

[targa80]

Radcon:

It does sound like you have several problems going at the same time. The loss of fuel pressure and having hard starting when hot is usualy caused by the check valve in the fuel pump or the accumulator leaking. Then again it might be further down the line but in most cases it is the check valve or the accumulator.

Your car is a 1980SC which means the check valve is internal to the pump. No fear they sell an external check valve but you also need to buy the bolt that will connect the fuel line banjo connector to the top of the new check valve. This is a cheap fix for a very annoying problem.

If that doesn't fix the hard start on a warm engine then the next would be the accumulator leaking down the fuel pressure. With a cis test set and fuel line adapters you can check the pressure at the accumulator and then the line coming from the fuel pump. I did this on my car 4 years ago. When I did the pump and accumulator test it failed. I then did just the fuel pump and it failed. Installed the check valve and banjo bolt. problem fixed.

As mentioned in this thread the cold start valve provides almost instant fuel to the manifold while cranking to help start the car. Pull the start valve and let spray into a jar while cranking to check functionality. After cranking and starting the cis system uses a thermal switch to provide the lambda computer a signal to force the frequency valve to open on a 60% duty cycle. This enriches the fuel mixture to prevent engine driveability problems. When the engine warms up the thermal switch opens up and the lambda system is in open loop operation and causes the frequency valve to go to a 50% duty cycle. when the O2 sensor is warmed up the lambda system goes into closed loop operation and senses voltage from the O2 sensor and adjusts the frequency valve duty cycle from 45~55% duty cycle depending on the engine demands.

Car owners who disconnect the O2 sensor force the lambda system to go into the open loop operation (50 % duty cycle) and adjust the fuel mixtue to suit there needs. This is usually done to resolve a driveability problem that has not been corrected. I have read that this setup is a better way to run the car for performance verses fuel economy. They may be right, my engine gave excellent performance along with fuel economy with the O2 sensor connected.

[bigchillcar]

Cold start valve fires for a period of between 5 to 12 seconds. And yes, with a fuel pressure tester you can insert it just downstream of the fuel pump and test to see if it holds fuel pressure. There is an acceptable pressure loss value for your engine, but I'm not near the information to be able to provide it.
Ryan

[radcon]

I think I've finally solved my hard start problem!!!! I have already checked the fuel pressures numerous times with my CIS gages and have always adjusted the pressure to the middle of the band recommended by the Bentley manual. I also have adjusted the fuel mixture once it warms up with my Gunson. I have always suspected that the backfiring and stumbling was due to a very lean condition on startup. In this thread or my previous one, someone suggested tapping in the plug a little to richen the fuel mixture. So last night, after working on some interior issues, I decided to just start her up and give the WUR a whack before calling it a night. Started her up, and of course she was running like crap. Wouldn't rev and would backfire when I could get it to rev. Armed with my hammer and punch, I tapped in the plug a mm or two and the idle instantly steadied out and it would rev just fine. Guess sometimes it might be better to set things at the extreme ends of a band than in the middle. Looks like my saga is finally over after spending many, many months looking for vacuum leaks, check for electrical shorts and adjusting fuel pressures and mixtures. Will do some fine tuning this weekend, but it looks as if everything is fine. Thanks to everyone for their help.