Starts hard when engine hot

starting
engines

#1

my 1991 mitsubishi mighty-max 4x4 V6 truck tends to start with difficulty (several cranks) when the engine is hot, meaning after it reaches operating temperature and i turn it off, it will start with difficulty. cold engine, however, starts very easily (first crank). what should i tackle first?


#2

Check for inadequate fuel, and, then, check excess fuel. To check for excess fuel, hold the gas pedal to the floor while you crank. As the engine fires, let up on the gas. If it starts quickly this way, there is flooding from leaking fuel injector. A healthy dose of fuel injector cleaner may help.

If the “engine flooded start” didn’t help, spray a two second shot of Starting Fluid (or, similar product) into the air intake. If the engine starts quicker, fuel pressure may be down, etc. Change fuel filter, air filter, spark plugs, and other “forgotten” scheduled routine maintenance items.


#3

OK, I will try that. What has stopped me from your first suggestion is that I have been told not to do that since the cars is fuel-injected, but we will see how that goes. Thank You for your response.


#4

what do you mean by “with difficulty”? is it turning over more slowly? Is it turning over quickly but just not firing up?

If your timing is too fast it can cause your vehicle to crank over more slowly when it is hot
I have also seen starters that were on their way to the great graveyard in the sky do the same when hot.


#5

it turns over (cranks) very quickly but won’t fire-up. I have to crank the engine at least twice (for about 5-7 seconds each time) before it finally fires up. again, this only happens when the engine is hot. by the way, i just replaced my starter a month ago because on the origional one (135K miles) the solinoid had gone out. new starter hasn’t effected the cranking problem. i was also told about temp sensors?
would engine-timing have an effect even when the engine is cold?


#6

Ok, so it is cranking over normally but not firing up…hmmm. that rules out the starter. i am taking that the vehicle had this problem before replacing the starter then?

I would start checking for spark when it decides not to start. no spark will most likely be caused by the distributor. the quickest and easiest way to tell if you have spark is to disconnect a plug wire and use a nice long screwdriver. insert the screwdriver gently into the plugwire and hold it near(not touching and within about an inch) something metal (valve cover, brake master cylinder, etc). have someone crank the truck over and see if you are getting spark. if not, suspect a faulty distributor.

If you have spark, have someone test the fuel pressure. low fuel pressure could cause the problem…also a fuel pump relay or the pump itself. the fact that you have to try a couple of times to get it to start makes me think it’s a fuel delivery issue.


#7

In a fuel injected engine one does not need to touch the accelerator pedal IF everything is operating properly.
What hellokit is saying here is that you may have a flooded condition due to a dripping injector, or even a leaking fuel pressure regulator, and in a case like this it is perfectly acceptable to hold the pedal down as a test method.

This will allow more air in, possibly offset the gasoline that has dribbled into the engine, and allow the engine to start more quickly.

It’s 18 years old and it’s quite possible there could be a leaky injector or fuel pressure regulator problem.


#8

You might be having some vapor lock issues. On a fuel injected car, vapor lock isn’t as much of an issue because the fuel is pressurized, but when you turn the car off, the pressure releases and the gas can form bubbles in the line. This is especially exacerbated by the ethanol-blended gas required in many locales, which has a much lower vaporization point. It may just be an issue with the car not being designed with ethanol blends in mind-- my Honda does this from time to time, but only with oxygenated (i.e. ethanol-containing) gas.

One other thing to try is before you start to turn it over, turn the key to run for a few seconds and let the fuel pump finish building up to full pressure. You can even turn the key back to off and back to run again a few times as this might also help it work out any vapor bubbles in the system.