305 SBC TBI hard winter starting (1990)

[emmett442]

There's a lot of suggestions here that are based on...almost nothing.

Hard cold start could be the result of any one or combination of problems. There's a lot of potential problems. Throwing CTS and MAP sensors at it may or may not work.


I'd start with the basics. You can smell fuel, but do you have spark? Test for it when it won't start. Some ignition components can be very temperature sensitive. The magnetic pickup coil, for instance, varies it's resistance GREATLY over winter-summer temps. This wouldn't be the first time that one failed in the cold because it dropped out of spec, yet came back alive when it got just warm enough.

Not saying that's it, but it's just an example. Need more testing. If you have spark while it won't start, you can at least eliminate that whole system.

 

[caprice_2nv]

Testing for spark first isn't a bad idea because it's one of the easiest things to do but I have doubt that it has no spark because it wouldn't take long cranking with no spark to completely flood it and then it's not likely to start at all for a while or until the plugs are removed and cleaned.

That said I did recommend testing stuff back on the first page. The CTS would be one of the first things I would want to test, it can even be done with a scanner if you have access to one.

 

[columnshift]

Originally Posted by Phishin
Have you ever "rebuilt" the TBI? It's an easy job.

What about checking the timing? You'll need a timing light and need to unplug the timing wire from the firewall cluster. It's easy peazy.


Never done that, no, how would I do it? Haven't checked the timing either - but I assume that was done when I was forced to bring it to pros in the fall to fix because I couldn't work in the cold when all crippled up.

FWIW i'm sharing a second post - my 'cold start issue' continues in the sense of below 0 it doesn't like to start, interesting that others have not had this problem so it makes me think something may be slightly out of spec. This is slightly confirmed because I had a case of hard starting when substantially warmer just a week ago... this time it was like 35F above zero, but all the sudden it didn't want to start! (from a cold start) I mean cranking for like 60 seconds no start... I heard it stumble and struggle the same way it did when colder, and the only way it fired off at all was with "violent manipulation of the throttle" (constant randomly timed stomping) while cranking it, then once it finally started up IT RAN ROUGH like it was missing multiple cylinders, just kind ofa surge surge surge/it wouldn't even stay running without me continuing to mess with the throttle, and this continued until it got to full operating temperature. Once it got to full operating temperature it was running smooth - and I shut it down and restarted three times from warm with no problem. The next day I started again from cold (at like +20F this time) and again it started fine, as it has every day since.

So one random time it didn't want to start when just above freezing - but I have to assume the computer should never have an error like that, so i'm assuming there might be something just... slowly drifting out of spec, or starting to die or who knows what. I'll make a list of what people said in this thread to check, i'm just seeing if my new story (of the hard starting at +35F) lists anything else to suggest or watch for in the future, because hopefully in the summer i'll have a chance to finally go inspect things that I just haven't had time for when going to school and endless medical appts.

FWIW relevant things that have been done on the car by it's current 160k miles - new fuel filter, new fuel pump, new distributor cap, new plug wires, new plugs. (I did the filter, a shop did the others after diagnosing why it wouldn't start so whatever would have 'normally' been checked in the course of diagnosis was checked to result in that outcome) Also it never throws any codes but then it's only OBD1 so it's not going to have much info to share with me/only things radically out of spec ever seem to throw codes on OBD1. (as I know from when my 1990 truck acted funny)

Again car is running fine now, this is more "things to check later" hoping to prevent a future stranding next winter.

Something is clearly acting intermittent or funny.

 

[columnshift]

Originally Posted by caprice_2nv
Any updates on the repair?


Only that I haven't been able to touch things between school and medical and being too cold when I can't move very well with the endless nightmare of snow we had right up until a few weeks ago.

The blizzards are finally over though, so just to share an update, my 'hard winter starting' issue has morphed into an intermittent difficult cold start issue, I thought i'd post on the end of this instead of posting a new thread for the moment though. I thought I already posted on this subject but I can't find it so i'll bring back up to speed.

Known problem are the 305 TBI doesn't like starting below 0deg F even though my pickup with a 350 TBI starts fine. It runs very rough below about 5F and wont even catch at -5F so 0F is the absolute lower limit to running.

Now since then it had a warmer day and one 'rough start' on me where it started but wouldn't keep running unless I kept manipulating the throttle, once it was warmed up it ran fine. Cold start the next day was also fine. Intermittent and no codes I had no idea what to look for but it was like 30F at that time.

This has since happened twice more, once about 3 weeks ago and another time today - once at 30F and now at something like 55F. The colder it is the rougher it runs, idle is worst but giving a little throttle to speed the engine up makes it run better. Also as soon as the engine is warm it runs perfectly fine at idle and will restart with no problem. But if I shut it off instantly (when it's a rough cold start) and try to restart it, it's rough, those are the only tests i've done so far on it. I fully expect when the engine is cold by tomorrow morning it will start normally again - this is a totally intermittent thing but it's happened three times now (and the time between 2nd and 3rd time was much sooner than 1st and 2nd).


So to summarize currently:
- intermittent cold starting roughness worse with the colder it is but still rough at 60F
- hot start always fine even below freezing
- once vehicle warmed up it runs fine (and it progressively runs better as temp increases over 5-7 min or whatever)
- more throttle seems to make it run better.
- no OBD1 codes (1990 TBI)

I wont have a chance to touch this until basically july right now, I need one of my other cars with MPG working before I risk breaking this/have other vehicles that need work first but I expect to have more of this starting problem by then unless it goes away. Also by july hopefully i'll have had a chance to go thru the garage and find all my missing tools including a timing light and other things buried by an unwanted relative's junk crowding things up. So i'll catch back up or/and people can leave other notes on things to potentially check or watch for, or simpler diagnostic things to experiment with if it happens again before I can reach my tools proper.