Hard start when hot

[70barracuda]

Having issues with an 86 2.5 TBI. The thing will start perfect when cold but once I drive it and it gets hot, its a total pain to start. Have to crank and crank and feather the gas pedal to get it to start. Once it starts its perfectly fine. I have replaced,

CPS - no change 

Ignition box, coil, cap and rotor - no change

CTS - no change

AIT - no change 

Fuel pump - no change 

Rebuilt the tbi unit with new regulator and injector

Cleaned up all engine grounds and added new ones - no change. 

 

Its driving me nuts. The truck runs awesome and starts great when cold. Its just the hot starts that are a pain. 

[Eagle_SX4]

My experience has been that is usually a vapor lock issue. Maybe try insulating the fuel line. DEI has some stuff that is great. I was able to get some at my local auto parts store. 

 

https://www.designengineering.com/heat-sheath-aluminized-sleeving-0-5-x-36/

 

[70barracuda]

15 minutes ago, Eagle_SX4 said:

My experience has been that is usually a vapor lock issue. Maybe try insulating the fuel line. DEI has some stuff that is great. I was able to get some at my local auto parts store. 

 

https://www.designengineering.com/heat-sheath-aluminized-sleeving-0-5-x-36/

 

Thats what I also have been thinking. I have stuff to make brand new fuel lines and ill be wrapping it in that. 

[eaglescout526]

Huh. Interesting. Can’t say I’ve run into that issue where at least the CPS doesn’t solve such an issue. I’m wondering if the ISA isn’t operating properly. 

[watchamakalit]

Have we learned nothing from recent events?

 

 

Sorry for the outburst there, have your checked ignition timing?

[70barracuda]

When I turn it off the isa moves the throttle back to open so I believe its functioning. It'll only start if I feather the gas and itll slowly come to life. If I don't do anything itll just crank and crank. 

[eaglescout526]

Huh. How interesting. Ok it’s resetting. Do we know if it has been adjusted at some point in its life? I’m almost wonder if it’s working but it’s not “working” like yeah it moves and makes sound but is it opening to the correct position for next start up kind of working. Just a thought. 
 

Does it have a full cluster?

[70barracuda]

48 minutes ago, eaglescout526 said:

Huh. How interesting. Ok it’s resetting. Do we know if it has been adjusted at some point in its life? I’m almost wonder if it’s working but it’s not “working” like yeah it moves and makes sound but is it opening to the correct position for next start up kind of working. Just a thought. 
 

Does it have a full cluster?

That part i do not know. Is there a writeup for it?  

 

Yes full cluster

[70barracuda]

Found your write up on it. Ill definitely be doing this tomorrow. 

[eaglescout526]

Sweet glad ya found it!
 

As far as the full cluster, one little thing I’ve noticed with the tach is it bounces when cranking. That’s how I’ve been able to determine if it’s something in ignition. If that bounces, you should be good in terms of the ignition system. Like I’ve had a couple CPS issues and when the tach doesnt move, I unplug and plug it back in and it’ll fire right up. 

[70barracuda]

12 minutes ago, eaglescout526 said:

Sweet glad ya found it!
 

As far as the full cluster, one little thing I’ve noticed with the tach is it bounces when cranking. That’s how I’ve been able to determine if it’s something in ignition. If that bounces, you should be good in terms of the ignition system. Like I’ve had a couple CPS issues and when the tach doesnt move, I unplug and plug it back in and it’ll fire right up. 

Huh interesting but good to know. Ill add it to the list of stuff to check tomorrow. I also just got the REM hooked up today and was playing around with it so I'm sure that'll give me some good info once I figure out the menus 

[eaglescout526]

REM should provide some insight as well. 

[70barracuda]

ISA was dead on doing eagle's procedure

[eaglescout526]

Holy crap! That’s a first. Usually that’s messed with by other when they have an idle issue. 

[hgeranium]

What the heck is an ISA?

[eaglescout526]

2 minutes ago, hgeranium said:

What the heck is an ISA?

Idle Speed Actuator. It’s similar to the IAC but it’s only found on TBIs. You can find it on the GM cars and trucks and our own 2.5L. 

[hgeranium]

25 minutes ago, eaglescout526 said:

Idle Speed Actuator. It’s similar to the IAC but it’s only found on TBIs. You can find it on the GM cars and trucks and our own 2.5L. 

Good looks! I'll add that to my infinitely increasing internal inventory of acronyms

[70barracuda]

Is 18 psi a little high for the tbi unit?

[eaglescout526]

A little bit. Pretty sure output should be 15psi

[70barracuda]

8 minutes ago, eaglescout526 said:

A little bit. Pretty sure output should be 15psi

Hmmm I wonder if I'm flooding at all when trying to restart. 

[eaglescout526]

It lines up with having to feather the throttle to get it to restart. Maybe a regulator rebuild is needed along with new injector O-rings

[70barracuda]

1 hour ago, eaglescout526 said:

It lines up with having to feather the throttle to get it to restart. Maybe a regulator rebuild is needed along with new injector O-rings

All brand new. Regulator was leaking when I picked it up so I rebuilt the tbi unit top to bottom. Injector is a brand new standard brand but I did also just order a brand new ac delco because I wasn't happy with the spray pattern on the standard injector 

[eaglescout526]

Huh. How odd. Was the adjustment screw exposed on the bottom of the regulator?

[70barracuda]

No screw wasnt exposed. Had to dig the lead out. Adjusted it down to 15 psi on the dot and replaced the fuel injector. 

 

Still does it. Definitely not as bad as before but still have to Crack the throttle to get it to go. No Crack, and itll just crank and crank and crank. But the moment I Crack the throttle halfway or so, itll fire no problem. 

[eaglescout526]

Well that’s definitely progress actually. Small steps to solving this one. 
 

We’re the injector o-rings replaced?