QuestionQUESTION: Hi,
Got us baffled. We sent it to the dealership for the passlock because that is
all we could think could cause the problem. They found nothing with the passlock
but that the fuel pump was faulty. WE fixed this. there also was a control
module that we fixed. Still nothing. It has all the components to making a car
run= fuel pressure, spark etc. still nothing. my husband is st his wits end. I
still think its the pass lock. What else can it be. I payed the GM garage
already 159.00 for them to give me the codes we already figured on. My husband
had those codes from his own scanner. He is a ford mechanic and knows them well
but this GM has got him flumuxed because he states he cant figure out why it
wont start because it has everything that a vehicle needs to run. that is the
main reason we thought the passlock. I guess from what we read it shuts down the
injectors(but like I stated they gm tech stated they found no codes with this. I
would really appreciate any thought to this. I want my vehicle to start again!!
What else should he look for problems in? We need to know if it is a electrical issue? We asked the dealership to give us scimatics for the vehicle re:the electrical so my husband can trace pos the wires from the bcm or pcm.
Do you know where we can locate this info?
It is a 1998 4x4 envoy. vortec motor 6 cylinder fuel injectors.
ANSWER: Theresa, any time I hear no start with a Vortec motor, I think fuel pressure! This engine needs at least 60 psi minimum to start and run reliably. Check the fuel pressure first if is less than 60 psi, more than likely a pump will be needed. A second weak point is the fuel pressure regulator, a component of the central sequental fuel injection unit, located under the upper intake manifold plenum. Regualtors are known to leak and lower the fuel pressure to the point of no start. If you are looking for detailed information on any vehicle, it can be found for a price at the OEM service website. GM charges $20 for three day access to their information website. Just about any kind of technical detail can be found there, including electrical schematics. Hope this help. Don.
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QUESTION: Hi, Don
We already replaced the fuel pump this weekend and the electronic control module. We are getting fuel just to the injectors at 60-62 psi. that is why he is baffled. So where should he start to check next all wires to /from injectors and back? we did get actual manuals from the gm dealer that I was able to sign out d/t my husband is a mechanic but he is old style. he works on older and knows fords well. I keep telling him he needs to go back and get more education on all the new stuff. LOL.
ANSWER: Hello Theresa, These new vehicles are very similar to the older ones, so his experience should come in handy. However, updating skills is always a good idea especially with the way technology is changing everything we do. You still need 4 things for a motor to start and run. Assuming that the anti theft system is functioning properly, you need fuel, ignition, compression and timing. Lets start with fuel, even though the pump was changed and pressure is now at 60-62 psi, it does not mean there is fuel in the cylinders. There could be trouble with the injectors, wiring or ECM. I see you replaced the ECM, hopefully it has been programmed for this particular vehicle. If not, it will need to be, and could be your problem. Have him get a can of starting fluid and spray some into the air intake plenum at the air filter housing, while cranking the motor. If it will run on the starting fluid then fuel delivery is the problem. Next check spark at the plugs with an adjustable spark tester set to about 30,000 volts. If the gap cannot be jumped, ignition is the problem. Compression will need to be checked next, both cranking and running. From these results, timing can be assumed good or bad and then tear down for inspection. Good luck. Don.
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QUESTION: Hi Don,
Its funny about the ECM. I called the GM dealer d/t I found in their own book that the ECM needed reprogramed and asked if this could be the problem. they stated no and that that would not stop it from running but yes it will need reprogramed and that my husband has the tools and diagnostic equipment to do it. My husband was checking the amps for it but we have no real anything to tell us where it should trully range. Do you know? Next prob. will be the wires he will be checking. It does fire with the either btw per the dealership mechanics it Just wont start on its own merit. The timing is also good. It def has spark d/t my husband stated he got zapped while checking it. They stated when they checked the passlock system that there where no codes thus they felt that was not an issue. i thought that it was because it was acting like that when it first started. It would shut off when we went into a store for 10 min or more when we tryed to restatrt it. My husband and his mechanic friend stated they cant even get readings to show it is turning over but it is. It just wont start.
AnswerTheresa, I don't understand what you are asking when you state that your husband was checking the amps for the ECM but don't know the range! Amps is a measure of current, how does this relate to the programming of the ECM? If it does fire with ether, then we have either a fuel delivery or a anti theft problem. Lets make sure the anti theft or passlock system is working and not the problem. Does the light in the dash light up when you turn the key on? If it does, then does it flash when trying to start? If the answer to the first question is no, the light needs to be fixed. If the answer to the second question is yes, there is a problem with the passlock system preventing the fuel injectors operation. It sounds like the GM dealership that you took it to isn't very helpful! Don.
