Hard start when hot

[70barracuda]

9 minutes ago, eaglescout526 said:

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

We’re the injector o-rings replaced?

Yup. Top and bottom. 

[eaglescout526]

Ok that’s good. 
 

im gonna go consult my TBI manual and see if it has any suggestions. 

[eaglescout526]

Ok so pressure needs to be 14.5 PSI and on an unrelated note, that relay you asked about is the load swap relay. 
 

The TBI book says that if you have low pressure you will get hard cold starts. 
Hard starts if pressure is high. I think you doing the pressure adjustment was on the right track. 

[70barracuda]

So I'm right on the money with the pressure then. Maybe weak spark adding to it? Its a new coil but electric parts these days are a crapshoot. 

[eaglescout526]

Yeah pretty damn much. 
 

Weak spark could be a factor. From CPS to the coil. Was the coil replaced or was the whole ICM replaced?

[70barracuda]

1 hour ago, eaglescout526 said:

Yeah pretty damn much. 
 

Weak spark could be a factor. From CPS to the coil. Was the coil replaced or was the whole ICM replaced?

I did new ICM and coil. Then swapped back to my renix ICM in trying to figure this out. CPS was a renix, then swapped to a NGK high altitude one, and I also have a brand new standard normal cps I can try. 

[eaglescout526]

Interesting that the Renix CPS had issues. 
 

I was asking about the coil as I had mine give up on me only to just find the contacts were dirty. 

[70barracuda]

Got the fuel pressure as close as possible to 14.5. In desperation I moved the ISA bolt out to open the throttle a tad more. Idles at 900 now, and it will start without help. Its not a clean start but itll do it.  Going to swap in the new cps I got, new coil, and grab a spark tester. 

[eaglescout526]

That’s one way to solve the problem. Glad you got it close. Only thing I can think of is it’s electrical or TPS is out of adjustment. 

[70barracuda]

So just to follow up, found the issue. I rebuilt the throttle body as soon as I got the jeep so didnt think this would be the issue. As a hail Mary I went to rebuild the fuel regulator and found this 

Turns out it was filling the whole thing with has through the breather and I think pouring gas into the Throttle body through the air hole. What a pain

[Ωhm]

Seems you stuck with it. Great find for the problem.

[MagicJames]

On 5/24/2026 at 3:42 AM, 70barracuda said:

So just to follow up, found the issue. I rebuilt the throttle body as soon as I got the jeep so didnt think this would be the issue. As a hail Mary I went to rebuild the fuel regulator and found this 

Turns out it was filling the whole thing with has through the breather and I think pouring gas into the Throttle body through the air hole. What a pain

Would you mind telling me the exact issue here with that diaphragm? I'm doing the same rebuild with the standard kit, and don't want to make the same mistake 

[eaglescout526]

On 5/23/2026 at 5:42 PM, 70barracuda said:

So just to follow up, found the issue. I rebuilt the throttle body as soon as I got the jeep so didnt think this would be the issue. As a hail Mary I went to rebuild the fuel regulator and found this 

Turns out it was filling the whole thing with has through the breather and I think pouring gas into the Throttle body through the air hole. What a pain

How did I miss this update? How interesting! Wonder if I made a similar mistake on my XJ and didn’t realize it. Could be why I smell and see excess gas down the TB. Huh. Now I’m gonna have to investigate it. 

[Ωhm]

Leaky internal diaphragm will show up here. Vent used for FP regulator to sense ambient air pressure.

 

@54bobby