Question about 1999 GMC Sonoma

5 Answers

MY 1999 SONOMA WONT START GOOD FUEL PRESSURE(50psi? good spark cranck,ok good compression when cranck try to start but wont keep running, is there anybody who can solve this problem please ,anwer only if you got experience on gm product..................... is a gmc sonoma with 4 cylinders

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  • leonel alvarado Sep 15, 2010

    INJECTORS I INSTALL the tool u mention on 2 cilinder there is,no room ligth ok i try to said flashing ok what u sugest to, do next if timing what is the solution how i nkow if timing is off( timing chain)

  • leonel alvarado Sep 15, 2010

    yes i mind noid lite is ik on 1 and 4 cylinder cause i had no room to check 2 and 3 i ,sporay carb cleaner and, no luck only try to start,i drop muffler pipe on exhaust manifold,to check for bad, cat converter same f is a timing,chain what ia the steps.to make sure is is the fix i repl crancksensor and fuel pump,if timing chain is bad i will repl if i needed to

  • leonel alvarado Sep 15, 2010

    this truck do not, have didtribuitor had coil pack mt question is ,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, same problem there is way that sombody anwer this question i will apreciate

  • leonel alvarado Sep 16, 2010

    crankshaft sensor already been replced,las guy a[tell me to check timing chain,with distribuitor cap removed is he for real this truck is distribuitor less i check dtc with scaner,no dtc display how i get my message across,with you guys my problem is simple, crank,wont star try to catch but wont stay running,i check compression, over 150psi,per cylinder new fuel pump,spark is redish,to anwer this you got to be,on the field,if u are reading manual you cant anwer this, need gm tech please dont waste ink, if you not capable on tell me how, to fix this truck

  • leonel alvarado Sep 16, 2010

    50 at the place where u check fuel pressure on every car i this is at return line,still u are not anwer my question some one on fix ya,com tell me if i soray carb cleaner will start and keep running, i already try that please donot guess cause u are wasting my time can u fix this or not cause i had many,gm that fuel, pressure where below specs.and spray carb cleaner will make engine to run donot tell old tricks,i already used them tell how to fix this o get out let, some one else fdo

  • leonel alvarado Sep 16, 2010

    GINKO I LIKE TO THANK u for ur profecional anwer make a lot,of sense i ill follow ur intruction if i get upset is ,because when u paid for some help i expect a, profetional, like your self anwer or try, to guide people on the, rigth track,but is true some times the anwer,is the rigth one and we do not make sense of it,i was auto tech foe 35 year working ,on ford ,vw and sabb,and litlle on gm long time ago,is why when sombody answer some idiot question i get mad(cause i paid for the services) thank u are great help

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  • GMC Master
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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.

G.

Posted on Sep 16, 2010

  • Ginko
    Ginko Sep 16, 2010

    Regarding your fuel pressure reading, the fuel pressure for Sonoma ranges from 60 to 65 Psi. If you read 50 Psi at the test connection on the fuel rail, that is because after more than ten years the fuel pressure regulator and the lines are clogged and restricted.

    You can replace the fuel pressure regulator, part is not expensive ($50 new, there are often cheaper OEM universal that mount 1996-2000 4 cyl engine). I don't think that 50 psi are enough to explain the engine not starting, but you never know that this along with other mixture related problem is causing the fault.

    If any solution helps, do not forget to accept afterwards. Typing and following your problem takes time.

    Read also my previous comment.

    bye.

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Your fuel pressure should be 55-61psi. This will cause your problem. Is the 50psi before or after the fuel pressure regulator?

Posted on Sep 16, 2010

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  • Master
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Most likely problem is a dead injector driver(s)
you'll need to buy a "noid" light from the parts store
you will install this at the end of the injector harness where it is connected to each injector
then while cranking you will watch the noid light
flashing = good driver

bottom line is....
****, push, bang blow and IN TIME
compression might be good but if timing is off then NO BANG!

Posted on Sep 15, 2010

  • Sean Reisdorf
    Sean Reisdorf Sep 15, 2010

    did not totally understand your last post

    did you mean you check to of the injectors with the noid lights?

    additionally, can you keep the truck running by spraying carb cleaner into the intake while cranking?

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Check up the Crankshaft Position (CKP) sensor. Replace if necessary.
The best idea is to scan the Engine Control Module (ECM) using a diagnostic tool connected to the data link connector of the car, in order to pull out all diagnostic trouble codes (DTC) stocked.

Posted on Sep 15, 2010

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Check to see if there is a crank shaft position sensor and make sure the plug is OK. Consider replacing it, since a faulty sensor/connection will prevent the engine from starting (computer's job).first remove rocker covers so you can see the rockers move.
To check if the distributor is fitted correctly.turn the engine over manually until you know you are the firing stroke on number 1 cylinder.
remove the distributor cap.and the rotor arm should be in line with number 1 cont tack in the cap.If not.. you will have to remove the distributor and line it up so that it is. also make sure that the plug leads are going to the cylinders in the correct firing order Then refit the distributor just place the rocker in place [ just to stop oil going all over the engine] and see if the engine starts.You will of course.have to readjust the ignition timing.
Check out.Keep updated.Thanks.

Posted on Sep 15, 2010

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1 Answer

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some cars about 1/2 only run the jump cranking and running.
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B: pump at 30pis cranking
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