Diesel Hard start after some cool-down time

mathd

mathd

solid fixture here in the forum
Ok i noticed someything latelly with the chevy 6.5 turbo.
When its totally cold it start real quick, faster then most gas engine around.
If it shut it off and re-start immediatly its fine..

Problem is, i take a ride.. get to oprerating temperature.. If i leave it say 30-minute or 1 hour. when i come back to start i have to hold the accelerator pedal. Seem like cold advance/high idle is not kicking in.

I assume its not the coolant temperature sensor since the glow plug kick in the usual 10-15 second delay(except when hot but it start right up when hot) but will check that.
I was thinking about the OPS/thats controlling the lift pump but it work when its hot, but it has 12v power checked with multimeter today.
Thinking maby a fuel system leak but it can stay week off and then start right up.
Maby the injector pump head and rotor having too wide clearance "wear" when semi-hot and it cannot put the pressure to pop the injector.. but that pump was changed last year.
New pmd/fsd too mounted on a remote cooler.
Fuel filter is new from last summer and water was drained system air purged. may try to do it again just in case
Also has 2 battery 1 years old and new injector from last summer.

Anything esle i should check?
 
Is this GM 6.5 Liter Diesel a 2000 something single turbo with no intercooler?
If it is, suspect an intermittent and failing camshaft and or a crankshaft sensor.

BR
 
yes it sounds like the crank position sensors intermittently sending defective data, and should be replaced, it would help if you had a trouble code scanner and a shop manual, some auto parts stores will do a free scan, for you.

http://www.citydiesel.net/crankshaft-po ... p-149.html

BUT IT COULD ALSO BE PMD RELATED,

http://www.ebay.com/sch/i.html?_nkw=6.5 ... diesel+pmd


eHow
Car Repair & Maintenance
Cooling System Repair & Maintenance
Remove Water Pump
How to Change the PMD in a 6.5 Diesel Engine

How to Change the PMD in a 6.5 Diesel Engine
By William Boyce, eHow Contributor

http://www.ehow.com/how_7579482_change- ... ngine.html

How to Change the PMD in a 6.5 Diesel Engine thumbnail
The PMD sits under the air filter on the fuel injection pump.

The Pump Mounted Driver (PMD) is a set of resistors that control the fuel injection pump on General Motors (GM) 6.5-liter diesel engines manufactured between 1994 and 2001. The PMD produces a considerable amount of heat, and it sits in one of the hottest places in the engine compartment. It relies on contact with the fuel injection pump to cool itself but is prone to failure, often due to overheating. Some replacement PMDs come with cooling fins; mount these PMDs away from the injection pump in a cooler location to prevent overheating.
 
It is a GM 6.5 Liter Diesel 1994 (electronic efi) single turbo with no intercooler
I will check the crankshaft position sensor. i guess any code will show up if am doing a scan? will re-check the pump timing just incase and a few more thing like Crank reference missed, cam reference missed and so on.
 
I usally do not recommend trouble shooting like this.....
But since your GM Truck is now 19 years old, if still unsure of the culprit,
Replace the Crankshaft sensor and camshaft sensor.
Each are solid state hall effect pickup sensors. They all fail eventual due to engine heat, oil intrusion,
And time.
Replace both so you dont go crazy.
To troubleshoot in a scientific manner, you need a digital storage oscilloscope or a Snap on Modis scanner.
Measure the duty cycle. Compare to new specs. Seldom published specs.
I have changed many crankshaft and camshaft sensors on GM TRUCKS CARS AND DIESELS.
Imtermittent failures common issues.

Brian
 
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