Poor hot starting.

[levi20AE]

I've been having an issue over the past year where when I start my truck cold or after not being driven for several hours it starts immediately without issue, but if I drive to run errands and the motor gets warm it will take a few cranks before it wants to starts. I have checked to see that all the lines are free of leaks and everything seems fine. The only thing I can think is that the fuel shutoff soloinoid doesn't open immediately when it is hot. Maybe it's hanging up? When the engine does start after being warm it runs like normal, it just seems like its not getting any fuel for those first few cranks. 

You guys got any other guesses why hot starting would be a problem?

Thanks

Levi.

[rabbitman]

I had a theory about this but I've forgotten it by now , does the pulling the cold start help at all?

I'll post back when/if I remember.

[wdkingery]

Yeah only thing I can say is the obvious; I've got an 86 f250 that had leaky return lines that caused just that. Poor hot starting

[regcheeseman]

go to the engine bay, find the coolant temp sensor with the blue/wht and brn wires attached and unplug it.

You will find that the glow plugs will work hot or cold, when the engine is half warm it needs maybe two seconds of glow and then turn the key.

You may be lucky and find that replacing the sensor cures the problem properly - but I just leave mine unplugged and vary the glow duration myself.

It's not the lines, not if it starts right up when the engine is properly hot but struggles when it is mid-hot

[Mark(The Miser)UK]

Classic design fault of the glowplug temp sensor circuit. It affected many mk2 VW's.
 Faster glowplugs might help, or simply disconnect water temp sensor. There is some variation, but most plugs turn off when cranking, or engine fired up. 
Perhaps a different sensor would do it . There is a 0 to 120 deg C, and a 0 to 125 deg C sensor I think.

[levi20AE]

I have swapped over to the faster glow plugs and replay.  you guys maybe on to something though because i have found that occasionally the engine will get a little warm at stop lights cause the fan doesn't always trigger on.  I think it maybe time to swap the coolant temp sensor.  Thanks again! Fingers crossed

[rabbitman]

I believe one sensor runs the guage/rad fan and the other runs the GP's.

Is that right?

[92EcoDiesel Jetta]

I believe one sensor runs the guage/rad fan and the other runs the GP's.

Is that right?

Nope, not on mine. Rad fan has it's own thermo on/off switch (not a sensor) on the bottom of the radiator, battery side.

[maxfax]

How's the battery cables? Especially the ground....

[rabbitman]

I believe one sensor runs the guage/rad fan and the other runs the GP's.

Is that right?

Nope, not on mine. Rad fan has it's own thermo on/off switch (not a sensor) on the bottom of the radiator, battery side.

You're correct, my memory just needed to get joggled. FWIW my rabbit also has the fan switch in the rad and the sensors just run the gauge and GP's. There might be more on yours I don't know.

[regcheeseman]

three sensors originally (one thermo switch in rad to control fan and two thermo resistive senders mounted into coolant pipe flange to drive dash gauge and glowplug circuit)

but the gauge and glowplug sensor were amalgamated into a single unit later in the production run.

either way just unplug the blue wire - if that sorts it - maybe invest in a new sensor (of the same rating)

If it doesn't cure it, waste no more time messing with sensors and look for the fault elsewhere

[damac]

My glowplugs don't fire at all if the engine is warm and thus far I have left it alone.  Mine will still start within 5 seconds at this time but its also an older used engine.

Does your starter speed seem to be effected at all?  Mine was when warm, you could just tell a difference.  I had some large gage wire laying around and I added a huge ground directly to the battery from the top starter mount bolt and that is what got me to where I am now.

Before this sometimes it would just crank for like 10 seconds effecting the turnover rate and had me wondering if I was going to get stuck

[regcheeseman]

My glowplugs don't fire at all if the engine is warm and thus far I have left it alone.  Mine will still start within 5 seconds at this time but its also an older used engine.

Are you happy cranking for five seconds because I wouldn't be, I'd rather my motor fire instantly than sit there killing the starter motor

[wdkingery]

my motor's got the compression of an old queer's rear.. five seconds would be pleasant! and my starter's sound has definitely changed over the past 10k miles.

[8v-of-fury]

Starters easier to replace than the plugs

and probably about the same price if you return the core I'd imagine lol.