Odd Start Issue

[lsf911]

I have a stock 83sc that has been great for several years now, no issues. On Saturday, the car wouldn’t start at first. It turned over for several attempts but did not start. I then feathered the gas pedal (which I never do) and the car started, sputtered a bit and leveled out. It ran for a minute or so, then cut out as if I turned the key off. It wouldn’t start again.
So, my first thought was a CDI failure. I checked for spark at the coil and plug wire #6 (random choice), all good there. Next, I pulled a plug and noticed it was dry. Hmmm…no fuel? I then pulled the red fuel pump relay and bypassed it with a switch (30, 87a). The fuel pump sounded good, I let it run for several seconds and I turned the ignition switch on and the car fired right up. After a few minutes I turned it off and put the red relay back in. I then started the car again, it fired right up. Took it for a ride and it ran great.
Next day, I started the car again. It didn’t fire right up but it did start after several seconds. Usually it just starts immediately.
The CIS components in the car are all relatively new/rebuilt as I went through the system a few years ago (Tony’s rebuilt WUR, new accumulator, fuel filter, injectors and seals, AAR, etc..)
At this point I am a little leery about driving the car somewhere and shutting it off. Does this sound like a bad check valve? Bad red relay?
Any thoughts on what the issue might be?
Thanks in advance!

[pampadori]

Fuel pump? Cracked airbox allowing vacuum leak? These two issues caused me similar slow to start issues on my 83 3.0 before i up-converted to EFI.

[lsf911]

Thanks for the response. It could be the fuel pump but odd that when I bypassed the red relay the pump operated fine.
I don't think it's a vacuum leak because they don't come and go.
The spark plug was dry when pulled which tells me it's a fuel delivery problem. As well as when I ran the fuel pump for several seconds the car started right up.
What does the fuel check valve do? I thought it kept the pressure in the line and prevented back flow. Is that correct? If so, wouldn't that fit this symptom I experienced?

[T77911S]

its probably the relay.

when you bypassed it you primed the system which is why it started after you put it back in.

[lsf911]

I agree but it started the next day as well. Is that still pointing at the relay?

[T77911S]

that and/or I would check residual pressures

also spin the fuel pump fuse to clean it

[lsf911]

Okay, solved the cold start issue, thermo-time switch is faulty.

It appears I have another more serious issue. The car starts, runs for a minute or 2 then cuts out as if I turned the ignition off! It will not start again unless I let it sit for a day or so then it fires up and does the same "cut-out" again.

I tested the ignition switch, power on pin 15 of CDI unit. The fuel pump runs when I lift up on the plunger or bypass the relay (30, 87a), I replaced the red relay with a new relay, same issue. It appears to be spark just cutting out but not sure.

My question...what is the usual culprit of a car that just shuts off mid run without any warning? I'm thinking my CDI unit but am looking for clarification on this. Does a CDI box work then not work then work again? If it just died it would be easier for me to figure out...

BTW my CDI is a permatune. Have had it for years now (10 years maybe).

[rwest]

Prematune units will work intermittently- generally heat soak will cause them to stop working and then when they cool down will work again- maddening.

Keep a timing light handy to check when it happens.

[lsf911]

Thanks rwest. I'm pursuing the CDI first. Will let you know what happens.

[boyt911sc]

Originally Posted by lsf911

Thanks rwest. I'm pursuing the CDI first. Will let you know what happens.

Lou,

Do you need to borrow a 6-pin Bosch CDI? I have a dozen Bosch CDI units that I use for my troubleshooting. You could use the one that is installed in my engine test stand or the one in my car. PM me your address.



Send it back to me when you are done with it. I don’t know how to test and evaluate a CDI so I just use the ones that were tested/ran in previous engine start-ups.

Tony

[lsf911]

Tony,

Thank you for the generous offer, I appreciate it.

I just sent my CDI unit to Bob Ashlock to be tested and repaired if necessary.

I'll let you know what happens.

[lsf911]

I received my rebuilt Bosch CDI unit from Bob Ashlock (great guy and super helpful) and installed it on Friday. I have been running the car for a few days now and the "cut out" problem appears to be gone.

Thanks all for the responses.
Much appreciated.

[mhackney]

Hey Lou, did you get your issue sorted? I'm always available if you want to stop by!

cheers,
Michael

[lsf911]

Hi Michael,

It appears to be sorted out, thank you. Been a while since I've seen you. You should stop by and check out my 68 project that I've been working on.

[mhackney]

Oh cool! That would be great. Are you around this weekend?

[lsf911]

I should be around most of the weekend. I'll shoot you a text message.

[boyt911sc]

Originally Posted by boyt911sc

Lou,

Do you need to borrow a 6-pin Bosch CDI? I have a dozen Bosch CDI units that I use for my troubleshooting. You could use the one that is installed in my engine test stand or the one in my car. PM me your address.



Send it back to me when you are done with it. I don’t know how to test and evaluate a CDI so I just use the ones that were tested/ran in previous engine start-ups.

Tony

I just noticed today that I attached the wrong picture. The picture I posted earlier was that of the ECU’s for SC’s and nobody seemed to notice the blunder. Anyway, here are the Bosch CDI’s:



Tony

[lsf911]

Tony,

I did notice. Thought maybe you were testing me to see if I knew the difference