TBI hard start when cold

[UATahoe]

Was hoping to get some help on my 87 pickup. Here lately it has been giving me trouble starting when cold. Starts and starts until you think the battery is going to die and then it will finally fire off and run great. Subsequent starts are easy and it fires right up. The distributor, ignition module, and the starter are all brand new. Just started giving me this problem after we had a really heavy snow and about 6 inches of snow sat up on the hood for a couple days. Any ideas what can cause this?

[gchemist]

Send me a PM with your email address. I'll send you a PDF file with TBI troubleshooting info. The file has helped other TBI truck owners.

[Jake Wade]

Could be a faulty CTS(coolant temp sensor) It is located by the thermostat housing.

[UATahoe]

Thanks Gerardo!

Had read the same thing on the coolant sensor. It's new but was one of the cheapo sensors from the parts store.

[nekkidhillbilly]

if you step a little does it run ok then? tps caused issues in my tbi grand am. apparently the spring gets weak and the thing wont idle high enough when cold.

[UATahoe]

The tbi unit is a brand new fully rebuilt unit. I just have to keep cranking over and over. Eventually for some reason it fires up and then runs perfect. Can turn it off and then start it right back up. But once it cools down, back to the hard start.

[nekkidhillbilly]

push the pedal and crank so it dumps a little gas. iac and coolant are your only other sensors that cause issues. the throttle blade needs to open up a little more during cold just like a carb and choke. all 3 cause cause it not too. only other thing if low fuel pressure.

[UATahoe]

Go figure. Just went out and tried to crank it up. Been sitting since yesterday morning. Fired right up as easy as could be. It's 65 here today and beautiful so not cold. Now I am stumped.

[nekkidhillbilly]

vaccum lines can make it stall sometimes too. check those make sure there good.

[nekkidhillbilly]

yours sounds like the tps too. the grand am was the same way. pretty cheap sensor.

[UATahoe]

What's the process for checking the tps?

[gchemist]

Checking the voltage through it's range. If it has a dead spot, likely on old sensors, the engine may have a hard time starting.

[nekkidhillbilly]

Originally Posted by gchemist

Checking the voltage through it's range. If it has a dead spot, likely on old sensors, the engine may have a hard time starting.

hes right

[UATahoe]

Went back out this morning, fired right up again. I did replace the vacuum line from the tb to the MAP sensor with a new vacuum hose. The old one didnt fit well at all and was hard brittle plastic. It also didnt seem to fit on the TB well either. Was worried it might be leaking. Since replacing i havent had any trouble getting the truck to fire up. Not sure if this would really have an impact on starting or not but found it odd.

[nekkidhillbilly]

yes it would

[UATahoe]

I will keep checking it to see if the problem comes back. maybe i got lucky and got it fixed.

[nekkidhillbilly]

hope so

[Pano]

I second the temp sensor. My 87 tbi all of a sudden last year during the winter would not stay running unless I constantly pumped the throttle. Once warmed up it would run ok. Replaced the temp sensor near the thermostat housing and it instantly ran perfectly.

[UATahoe]

I will give that a shot if the problem returns. Still fires right up now. Thing is though, while it was hard to get it to fire up, once it did it ran perfectly fine with no issues.

I am thinking the map sensor was the culprit.

[UATahoe]

Should have known it wouldnt be that easy. No start this morning. Never did fire off. Battery finally died. After a few tries at cranking, i unplugged the temp sensor. No change. Still wouldnt fire off. kept trying until it died. So i guess i have to start trouble shooting from here.

Anybody have a how to on checking the voltage on the TPS?

Will also add that it got down to about 30 last night. Also rained a good bit as well. Not sure if rain or moisture is getting to the distributor cap or not. Before the snow there would be an occasional day where it would be a little hard to crank but it would still fire up fine.

[UATahoe]

Also, i did advance the timing about 5 degrees on the truck. The big toubles with starting came after. Curious now if the timing is too far advanced.

[doubleclucker]

When the distributor was changed was initial timing set back to 0 degree with brown wire unplugged?
Timing is not controlled by ecm until around 400 rpm at start up and with temperature changes timing could be the issue.

[UATahoe]

Well, a new distributor went in with a new 383 motor. Installed the distributor with the number 1 cylinder at TDC. Ran it the truck for about 6 months that way. Just recently tried advancing the timing a little. Seems like thats when the starting became really problematic.

[doubleclucker]

When you checked timing did you advance it with the brown wire unplugged?
Did you change or burn a chip for the new motor reqirements?
Sorry for the questions but we all just need a better understading of what we are reading here.
6 months ago the temperature outside was a little different and a new motors timing chain had just begun to stretch .

[UATahoe]

No worries at all on the questions! I did advance it with the EST connector unplugged. I have been working with Brian Harris for the chip. We have gone through 5 or 6 chips now trying to dial it in. I think i really need to get it fired up and adjust the timing back down a little bit. Seems like that could be my problem. I am going to give that a try this afternoon when i get home if i can get it to crank.