Hard to start

gmc
3500

#1

Holden calais - 1990 - 124000 kilometers. Car generally starts well after an overnight stand. When started, it runs well. However after switching off for more than 30-45 minutes, after that the car is hard to start and remains so for hours; a touch on the accerlator pedal helps; rough at first before engine kicks in.

Starter motor and ignition coil changed. relays changed for ignition and fuel pump. all six fuel injectors serviced.


#2

Everyone should have these 2 things to narrow down a non running car.
A can of name brand starting fluid with straw. Follow black round tube from air cleaner to the motor and loosen at motor and spray, then try to start. If it starts trouble is fuel related.

To check spark use this between plug wire and plug.
http://search.harborfreight.com/cpisearch/web/search.do?keyword=spark+checker&Submit=Go


#3

How old are the plugs?


#4

New Spark plug.


#5

Sorry, I should have included “how old are the plug wires”


#6

Thanks for your response. Original HT cables (20 years) but tested ok by Auto-electrician. Currently suspect posssible (fuel) leaky refurbished injectors losing pressure and dripping fuel into the cyclinder head during normal turning off the engine - testing in progress by initially disconnecting fuel pump (fuse) for switching off the engine so that fuel (between pump and injectors) are used.


#7

does this worm up to “normal temp”???
should run codes see what is present…so you’re not just throwing parts at it.

but it seem s it maybe temp sensor issue, where the temp sensor is is not sending correct info to the ECM …thus causing a over fueling or under fueling on those intermediate engine temp situations…or a O2 sensor…might be a simple thermostat


#8

Thanks for your comments. This car model has limited computerised diagnostic functionality…it is not comprehensive for this situation. The 02 sensor and temp sensors appeared normal. The car runs well after starting. After turning off the engine, the car can restart easily within 45 minutes… the testing (see above) is encouraging.

Unfortunately, the mechanic had thrown parts at the problems!! I am not an expert but working together with a friendly auto-electrician. Giving up on the car is also under consideration.