hard to start when warm

[lukerseth]

I have a 1993 Isuzu Trooper 3.2 V6
When the engine has been running and hot, it's hard to start after sitting for a short period of time. The starter spins fine, and the motor tries to start and then just kinda dies off. It will start up on the second try, but usually has to crank for a good 2 or 3 seconds. When it starts, the rpms are slow to come up. Once running, its fine and is not lagging in power. When the engine is cold, its fires right up with no hesitation at all. My first thoughts were in the fuel department, such as a fuel filter, but I am not really sure.
Any ideas on where to start investigating??
Thanks in advance for your help!!

[keithramsay]

I doubt it would be the fuel filter (if the filter is beginging to clog, this will show up under hard acceleration--not enough gas gets through). If your V6 is fuel injected, I don't have any idea what your problem is. If it is carbureted, I would suspect the choke. The engine is hot, and the choke is open. You let it sit a while and the engine cools a little, but the choke is still open, in which case the mixture is too lean for starting. Or it could be the opposite: the choke has closed as it cools a little and the engine is warm, and when you try to start it it floods. If this is the case, when it does start you will probably get a puff of smoke out the exhaust from all that extra gas. Try this next time you are in that situation: pump the throttle once before you twist the key. This will give the choke a chance to reset, and it will shoot a little stream of gas into the intake. If this works, the choke was too open for the situation. If it doesn't work, you probably flooded the engine even worse, and you will have to adjust that choke. good luck

[jetendersandhu]

I have a 1993 Isuzu Trooper 3.2 V6
When the engine has been running and hot, it's hard to start after sitting for a short period of time. The starter spins fine, and the motor tries to start and then just kinda dies off. It will start up on the second try, but usually has to crank for a good 2 or 3 seconds. When it starts, the rpms are slow to come up. Once running, its fine and is not lagging in power. When the engine is cold, its fires right up with no hesitation at all. My first thoughts were in the fuel department, such as a fuel filter, but I am not really sure.
Any ideas on where to start investigating??
Thanks in advance for your help!![/quote]

[trooperbc]

what happened jetendersandhu, forgot your lukerseth password?

I have a 1992 isuzu trooper 3.2 V6, same as your 1993.

this is how my 1992 has acted since new almost...
the almost is :: : When it starts, the rpms are slow to come up. ::: that part doesn't happen with mine -- once mine starts it is fine.

i took it back to the dealer and even got the isuzu district service representative involved way back then. and the answer i got each and every time was ' that's normal '. to which i could only reply -- yes that's the problem, it's normal, it's just not right. i figure it sells them more starters.

anyway, i have come up with my own theory: namely, it is indicative of a hot rich start condition (like that reply relating to a carbureted engine). in this case, the culprit would be, i theorized, either the Manifold Temperature Sensor (MTS) or the Coolant Temperature Sensor (CTS). i figured since both these would cause the computer to mistakenly enrich the mixture if they sent the inaccurate temperature input data.

recently, i decided to track the CTS, mimicking the condition of a restart after sitting for various amounts of time. the way it works is, the sensor sends a different voltage signal back to the computer depending on the temperature; the computer takes this voltage (temperature) input and prescribes an air/fuel ratio according to its program.

the voltage changes should correspond to the changes in the coolant temperature. what i discovered is that in my case, these changes were not consistent, they fluctuated rather than followed a curve. they became weird exactlly in that window where starting was problematic. shortly after shutdown, the temp would spike (as expected) and starting would be fine, then it followed the imagined curve, but eventually started indicating values opposite what would be expected; then after that period it would settle in at what one would expect.

so that's my theory and that's my analysis and diagnosis. if the CTS were in an easily accessible place it would be a no-brainer to just swap it out and see what happens. but it's on the coolant crossover pipe at the rear of the engine up against the firewall and near impossible to get to, so i continue to live with the symptom until i need to take off some stuff and/or tilt the engine to get back in there. (and the time is probably coming soon since i am going to have to replace the heater core and/or the hoses also back up between the firewall and engine.)

well that's my story...and i'm sticking to it : it's the Coolant Temperature Sensor.

does it make sense to your situation?

//bc

[voya]

You are 100% right. I had same problem on mine 1993 and decided to convert to gas ( LPG) rather then messing with CTS. To access it you would need to remove intake manifold, which is credulous.