Help! Hot - crank no start 95 civic cx 1.5 d15b8

[WillTravel]

Starts right up when cold, runs great, but when hot if I try to re-start it'll crank but not start. There's the smell of fuel at the tail pipe. Fuel pressure gage shows a steady 38psi, vacuum gage shows pressure holding steady and not leaking down.
Does anyone have a list of things I should start checking out?

 

[nd4sped]

Through experience the hot no-start on Honda's have been due to a failed ignition coil. They expand when really hot (10+ years of use) and then contract when they cool down. Not to say this is your problem but its a good place to start as the coil is a primary component of the ignition system.

You need three things, air, fuel and SPARK.

Pull the plugs one by one and see if you have weak, strong or no spark on any cylinder. If spark looks STRONG its generally a fair chance to OK the spark plug wires. However if spark is WEAK, check resistance on the plug wires, this is really easy to do so do it regardless.

If plugs and wires are good to go, check condition of the distributor cap and rotor. If you see a lot of green growies (arc deposits or moisture oxidation) If contacts look corroded, replace as needed. (DONT THROW GOOD PARTS AWAY! - TEST TEST TEST!)


Also check the ignition coil for resistance and short to ground. This tends to be the issue when I saw this specific HOT NO START condition. (I dont turn wrenches professionally anymore)

Lastly since you will have more of the distributor apart you can also remove and test the ignition control module at most parts stores, Oriellys, Advance, Autozone, etc., generally all have ICM testers.

 

[nd4sped]

oh and welcome to the forum.

 

[WillTravel]

OK, thanks nd4sped for the insight, I'll start with testing the spark at the plugs and work back through the wires, cap, rotor, coil, and ICM.

 

[WillTravel]

Spark is good even when starting hot. I bled air out of the coolant line and that helped a lot. After that there was only a little starting hesitation when hot.
However, I drove up into the low mountains yesterday and not only did I have little up-hill power in 3rd,(D15B8-1.5L), but the reservoir coolant was drained empty, and I then found a lot of starting hesitation when hot,
I'm thinking I have an "air in the coolant" issue with either the ECT sensor or the IAC valve.
I don't see any coolant leak anywhere, so I can't explain the empty coolant reservoir that I had filled the day before.
Also, all four cylinders have 150lbs psi, so I assume the head gasket is ok.

 

[nd4sped]

When you pulled the spark plugs, what did the plugs look like?
If you don't see a coolant leak outside the engine then there is only two other places coolant will go and that is in the cylinder or int he engine block. Both are generally the result of a blown head-gasket.
You can do a leak down test on each cylinder. This requires a compressor and Leak Down Testing Tool.
I want to say we did a leak down test in this video.

 

[WillTravel]

Found the coolant leak. It was hiding on the underside of the upper radiator hose. The spark plugs are dry with just a slight bit of carbon. I guess from running too rich when I hot start it. I'll change the hoses, bleed the air out of the coolant, and see if that will fix it. Does anyone know the cold to hot voltage differences that should be coming out of the Idle Air Control Valve to the ECU?

 

[nd4sped]

Found the coolant leak. It was hiding on the underside of the upper radiator hose. The spark plugs are dry with just a slight bit of carbon. I guess from running too rich when I hot start it. I'll change the hoses, bleed the air out of the coolant, and see if that will fix it. Does anyone know the cold to hot voltage differences that should be coming out of the Idle Air Control Valve to the ECU?

The IACV does not control anything with coolant flow. The voltages at the IACV will go up and down based on engine load. The more accessories you turn on, the more air the IACV allows to bypass the throttle body to allow engine RPM to climb without throttle. This is a very small adjustment, usually about 500-1500 RPM depending on the amount of amperage needed to be produced by the alternator to power all the accessories.