Hot Start Issues

[Dark_Horse]

Car starts great when the engine is cold. After the car warms up to operating temperature, if I shut it off, it will not restart unless I hold the accelerator to the floor. If I crank it for ~30 seconds with the accelerator to the floor it's hit and miss. Some of the time, it almost starts and then dies. Other times, it catches after about 30 seconds of cranking and runs just fine after a few blips of the throttle.

Tonight, I found that if I disconnect the battery, I can immediately restart the car when it's at operating temp.

What would be causing my hot start issues that disconnecting and reconnecting the battery would fix?

EDIT: Saw a few threads suggesting it could be ECU caps leaking. I haven't cracked the ECU open in a few years to inspect, but the caps were replaced in 2012, so I highly doubt that's the problem.

2nd suggestion I've seen is that ECU cannot read coolant temp. I've never had a problem with ECMlink reading the coolant temp, so I do not believe that's the issue either. When this problem happened, my coolant temp was 196 degrees according to ECMlink.

 

[toybreaker]

What fuel are you running?


You running link or have a data logger?

If so, check/log the coolant temp.

If there's any anomalies, check the wires on the coolant temp sender located on the t-stat housing.


Did you eliminate the fuel pressure solenoid?

 

[Dark_Horse]

I am running 91 Unleaded

I was running ECMlink at the time and it was able to read the coolant temp

The FPS has been eliminated. The vacuum source for the FPR is coming off of the intake manifold.

And how have you been? I rarely see you post. /ubbthreads/images/graemlins/smile.gif

 

[Dark_Horse]

Well, I figured out the problem. My ECU is fried. That explains the burning smell from 2 weeks ago when I went for an emissions inspection and the random hot start problems.

From my searching, it looks like that's a blown ISC driver, which means my ISC is probably bad. Some days I hate this car!

 

[ktmrider]

Glad you found your issue. There is a fairly new, and great, thread in How-To that lists all the driver info once yours is fixed/replaced.

Quoting Dark_Horse:
And how have you been? I rarely see you post. /ubbthreads/images/graemlins/smile.gif

Fo sho! Weather in CO must have thawed a bit, hope things are well TB.

 

[GSTwithPSI]

Your ISC failed. More specifically, coil pair A. Make sure there are no coolant leaks, or other obvious causes that made the ISC fail.

click

 

[prove_it]

Mike is the local ISC expert now.

 

[GSTwithPSI]

Who's Mike?

 

[Dark_Horse]

I replaced the ISC 2 years ago with the revised version because I was worried that the tan one would fry my ECU. Guess I'm sending the ECU to Tom/Dave to have it repaired.

There were no coolant leaks at the TB that I'm aware of, but I'll crack everything open this weekend and see what I can find. Since the ISC was basically new, if I had to guess, I'd say bad wiring harness caused the ISC to short out, but that's just a theory at this point. Will measure the coil resistance in the ISC to see what's going on.

 

[fuel]

ironic that the revised ISC swapped in to avoid this very issue actually in fact caused these issues. I wonder if the original tan ISCs had been left in, if this would have happened.

 

[Dark_Horse]

Finally had time to remove the black ISC and see what it Ohm'd out at.

Surprisingly, the entire thing was fried. Resistance was:

Pin 1 & 2: 1.8 Ohms
Pin 2 & 3: 0.4 Ohms
Pin 4 & 5: 1.1 Ohms
Pin 5 & 6: 1.0 Ohms

No coolant leaks anywhere near the ISC, so I've got no clue why it went out. If I had to guess, I'd say probably wiring harness, but I can't be sure.

I took my old tan ISC and that measured about 27.8 - 28 Ohms between all pins. Looks like I'm putting the tan one back in after the ECU is fixed.