Question about 1997 GMC Sonoma
Have you checked the fuel pressure at the injectors ?
Are the plugs getting spark ?
Posted on Jan 14, 2013
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Posted on Jan 02, 2017
SOURCE: starts fine cold then starts
The computer runs the fuel mixture rich when cold and then leans out as it warms up into closed loop, a common problem is the regulator leaking, if you remove the upper part of the intake and then turn key on and watch for fuel leaks, another trick is to remove the throtlebody and use a light to see if fuel is puddling up on the top of the intake, make sure to dissconnect module connectors to avoid a false start or spark that will cause a fire, i would almost bet its the regulator, hope this helps,
Posted on Dec 07, 2010
Should be attached to the fuel rail. The fuel rail connects all of the fuel injectors. The regulator will have a vacuum line on it.
Posted on Dec 09, 2009
Testimonial: "thanks for the help and it fixed the problem."
SOURCE: MY 1999 SONOMA WONT START
Re:"truck try to start but,look like not caching all cylinders cause while
crank, if i puhs acelerator to the floor then try to start i remove
plugs they, are wet i clean then reinstall,"
If you are saying that the cylinders are flooding and there is misfire, check the coil packs. This get tested reading Ohms on primary and secondary coils, reading volts in. Ohms on primary coil terminal (B+) must be in range of 0.3-1Ohms, secondary resistance reads between 5K and 15K. There are different kind of coil packs for this engine. Their ratio is always about 90:1, to return 45K Volts. On this one impedances should be 0.2 ohm primary resistance; 6.7 KOhms secondary resistance.
Other way to test coil packs is swapping the two packs in this engine (not swapping spark cables, swapping the modules).
Also do a code scan. If there is misfire this is reported as P03xx OBDII code.
Reading codes you can also find out if there is any rich or lean code detected by the O2 sensor. If car is not starting at all there will be no mixture code reported from O2 sensors, as there is no ignition.
Regarding mixture, if ignition and distribution is OK, check the factors that determine mixture. Check MAP/MAF sensor and IAT sensor. Test starting with new air filter , test with no fuel cap and check the vacuum. If vacuum has a hole it will **** air in the mixture, mixture will be lean, you have pressure but the engine does not ignite even if there is spark.
To test vacuum use the fuel gauge in vacuum lines and spray carb cleaner on hoses, if there is a hole pressure will go up.
If still nothing check and eventually replace the AC delco EGR valve. Valve stuck open is a common failure, car will not start, engine will flood. In that case the mixture is rich.
PS:Please stop telling everybody "if you dont know dont answer" There are two kind of answers, the ones from people who does not have a clue and go for the few bucks, and the one from people that may help you. There is no way to filter them. Most of the answers are from experts but some idio t is also posting. Simply discard the bad ones and stick to the good ones.
You should stick with an expert and keep troubleshooting, not keep arguing.
I know you are discarding everything, and probably going for r., but who cares. I am out of here.
All the best, good luck with your GM engine.
Posted on Sep 16, 2010
A VERY COMMON CAUSE OF THAT IS THE ENGINE COOLANT TEMPERATURE SENSOR, YOU WILL NEED TO VERIFY PROPER OPERATION WITH A LIVE DATA SCANNER, BEFORE U TURN IT ON IN MORNINGS OR COLD, COLD ENGINE LOOK FOR CTS READING IT MAY READ -40 DEGREES, IF SO THEN SENSOR IS MALFUNCTIONING, BUT WILL NOT SET A "SERVICE ENGINE SOON" LAMP WARNING. OTHER WAY TO CHECK IS TO DISCONNECT SENSOR, I AM ASSUMING THAT WEATHER IS ABOVE 20 DEGREES. LET ME KNOW IF THIS HELPS, CAN ASSIST YOU FURTHER WITH UPDATES
Posted on Mar 03, 2011
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