Car harder to start after sitting 15min

[liquidzorch]

Helo. Here is a new problem. My car used to start after about 1 second of cranking, maybe less, no matter what temp.

Then I sent my injectors to a lab to be cleaned and tested. Came back tested good. I put them back in. The I also changed the starter motor brushes.

Now In the morning it starts on first compression stroke always.

But when it is warmed up then has sat for about 15min or more, it takes about 5 seconds of cranking to start up again. The starter motor sounds better than before, it even sounds faster. When cranking it does not sound like it is struggling to ignite. It does this even when I prime the fuel pump a couple times.

In the morning it always starts great, even if I dont prime the fuel pump.

If I warm up the car, and turn it off and on again within 5 minutes it will start in less than a second. It is only after it has sat for awhile.

To me it sound like it is getting too much gas, since cold engine needs more gas it will start fast but hot engine need less gas, and thats why it needs more cranks. Thats just what I think.

The fuel pressure has been checked and ok, the ECT sensor is giving the right readings at all temperatures. It new ait, and tps sensors. The idle speed is perfect. It runs great. No problems when running.

Also I have tested spark twice when it is hard to start and the spark is nice and bright, can jump about 1 inch. So all ignition problems can be ruled out.

For everybody that might think it is the starter motor. Before all this (when it would always start quickly), I could start the car with basicly a bad battery. You could hear the starter stuggling to turn the engine, and it would still ignite on first or compression stroke. Now it turns quickly with new battery and new brushes.

This is a 93 honda civic lx, with d15b7 engine (non vtec).

[liquidzorch]

Here are two videos, the first is a first start of day, the second is after driving and waiting 20minutes after off.

[liquidzorch]

[liquidzorch]

The loud cracking sound in the second video is a problem with the camera mic, not the car jeje. The car sounds the same in morning and when warm. It just takes longer.

[RedDevil]

It is hot in Mexico right now, I guess?

My '85 Civic had severe vapour lock problems in the heat (in Holland...!) and was hard to get started when still hot. It could even stall when stationary in the heat, like in a traffic jam or just after the occasional mountain climb. Cool down, problem gone.
The problem was twofold: a small leak in the radiator had reduced its cooling capacity, so it ran hotter than intended. The gas boiled in the feed tube so the carburetors ran dry.

Under normal operation new cold fuel kept the feed tube from reaching the boiling point, but when stationary the hot engine managed to boil it.
Once the engine starts cranking the fuel pump will push new (liquid) gas in, but that will take, say, 5 seconds.

Don't know if the same applies to your engine, but I'd say check the temperature on the injector tubes and pump etc. when you experience these problems; maybe vent the hood and/or isolate the cylinder head around the injectors so that they pick up less heat.

For testing you could try cool them before you start to see if that makes the difference.

[liquidzorch]

Originally Posted by RedDevil

It is hot in Mexico right now, I guess?

My '85 Civic had severe vapour lock problems in the heat (in Holland...!) and was hard to get started when still hot. It could even stall when stationary in the heat, like in a traffic jam or just after the occasional mountain climb. Cool down, problem gone.
The problem was twofold: a small leak in the radiator had reduced its cooling capacity, so it ran hotter than intended. The gas boiled in the feed tube so the carburetors ran dry.

Under normal operation new cold fuel kept the feed tube from reaching the boiling point, but when stationary the hot engine managed to boil it.
Once the engine starts cranking the fuel pump will push new (liquid) gas in, but that will take, say, 5 seconds.

Don't know if the same applies to your engine, but I'd say check the temperature on the injector tubes and pump etc. when you experience these problems; maybe vent the hood and/or isolate the cylinder head around the injectors so that they pick up less heat.

For testing you could try cool them before you start to see if that makes the difference.

Hello. This happens in hot and cold weather, just yesterday it was a cold day, 16c. The outside temp does not change this problem. I was think vapor lock, but even if i prime the fuel pump 5 times before starting (getting liquid fuel to circulate), it still does the exact same thing. It has to be fuel related, or at least I think. What test can I do? It is hard to test since I have to use it and then let it sit.

[RedDevil]

If you can't get it to start normally, how hot is the engine?
If any part of the fuel system is too hot to touch, try to cool that gently, see if that helps.

Other than that, check the radiator for leaks and check the air filter. I have read about an air filter that was dripping oil from the oil pan venting; apparently the piston rings were leaking.
The excess air and exhaust gas that seeps by the pistons into the carter, now containing an oil mist, gets blown into the air intake trajectory. Too much of that can make the mixture overly rich, causing bad starting esp. when hot. Your air filter would be quite oily then.
Just guessing of course.

[liquidzorch]

Originally Posted by RedDevil

If you can't get it to start normally, how hot is the engine?
If any part of the fuel system is too hot to touch, try to cool that gently, see if that helps.

Other than that, check the radiator for leaks and check the air filter. I have read about an air filter that was dripping oil from the oil pan venting; apparently the piston rings were leaking.
The excess air and exhaust gas that seeps by the pistons into the carter, now containing an oil mist, gets blown into the air intake trajectory. Too much of that can make the mixture overly rich, causing bad starting esp. when hot. Your air filter would be quite oily then.
Just guessing of course.

Ok. There are no leaks in radiator, it has been months without having to add coolant. The air filter is almost new, no oil spots on it. There is no oil in intake, I removed the air filter to intake hose to let pure air in and it still took longer to start.

This only happens when car has been sitting more than 15minutes. If I start it when it is still HOT (off then on in less than a minute), it will ignite right away.

So what happens when you let the car cool down 15 minutes - 2 hours? What ever happens in that period is what makes it harder to start.

I know that the fuel pump primes, and fuel is being pumped with good pressure.

[RedDevil]

The problem needs to be something that gets cooled (by air or fuel) during operation but gradually heats up from the residual engine heat.
The fact that it starts easily within 15 minutes seems to rule out anything mounted directly to the engine block, as that would heat up immediately.

How's the heat under the hood?
It could just be that the engine is losing heat somewhere like when you have a hole in the exhaust manifold (mine rusted through at some point), a leaking gasket or a missing heat shield (mine dropped off but was salvaged and refitted) or such.

I measure intake air temperature continuously by a cheap digital in/out thermometer. I've stuck the probe in several places under the hood to check temperature in that region, you could do something like that too and see whether there is a direct relation between temperature and your problem or not.
(My thermometer sadly does not give readings above 70C. I cannot use it for testing coolant temp etc. A high upper limit is something to watch out for when selecting a thermometer for these causes).

[Occasionally6]

Before I read any of the posts, just the thread title, I was thinking: "The injectors are leaking.". After reading the posts, I still think that.

It only started after the injectors were cleaned, right?

One way to check is to pull the injectors, wipe their tips clean and pressurize the fuel system (run the fuel pump). After they have sat for a few minutes, wipe the injector tips with a facial tissue or toilet paper. That will show up even a small leak.

Do make sure that the injectors won't blow off the rail when subject to fuel pressure and in free air. Most are OK to do that with but if they're not, you'll have to wire them in place.