The car is a 2007 Chevy Malibu - V6 - 3.5 engine. The car is fine as long as it is going, but once the engine is turned off it won’t start again. The mechanics are dishonest - they are a nonprofit that helps out families like mine that are transitioning out of homelessness at greatly discounted prices - but they are confused about what is wrong. The mechanics ran diagnostic tests on it and based on the results:
First they replaced the relay, then the fuse panel block, and now the PCM. Nothing fixes it and it won’t start even if you try to jump start it. I am now in danger of losing my job because I can’t reliably get to work. I can’t afford to put more money into it and still not have it work.
Have them check for a faulty Crankshaft Position Sensor.
This can be easily done by connecting a scan tool to monitor the Crankshaft Position Sensor signal. Then by using a hair drier/heat gun apply the heat to the sensor to see if the signal from the sensor is lost.
Because if the computer doesn’t see a signal from the crank sensor it see’s no reason to operate the fuel/ignition system.
Get a cheap spark tester at harbor freight for five bucks. It plugs in series with the sparkplug. It lights up when there’s spark while starting.
report back.
A little more info please. Do you mean it won’t start when the engine is warm? That is, if you drive it, park it, then wait several hours until the engine cools off, then it starts ok? And by “not start”, do you mean it cranks ok – you know, the grrr grrr grrr sound – but doesn’t catch (the varoom sound)? Or do you mean it doesn’t crank at all when the engine is warm?
The mechanics aren’t necessarily dishonest as you claim, but they may be confused as you later say. I give everyone the benefit of the doubt, I assume they do the best they can with what they have. Having said that, there are guys out there who couldn’t fix a sandwich, much less a car.
There’s no diagnostic machine that tells a mechanic whether there is spark or fuel. Scan tools give information. Lots and lots of information. And turn things on and off when the operator commands them to. Other than that, it’s up to the mechanic to determine what’s wrong and why.
When you turn the key to start it, what happens? Does it crank over but not start, as a car that is out of gas would? Or does it not even crank over? When it doesn’t start what do you do to eventually get it going?
It will try to start and even sound like it is almost there, but then it doesn’t catch. It is intermittent. I can drive it and turn it off and then start it right back up and it is fine, and then I’ll do the same thing the next time and it won’t start. Another time I can drive it around for awhile then let it cool off and it starts, but then when I do that the next time it won’t start. There doesn’t seem to be any rhyme or reason to why it decides not to start.
The mechanics had it hooked up to diagnostic computers and it has had over 10 hrs of diagnostics run on it.
The first diagnostic tests showed the relay was bad, which is why they replaced it. Then when the problem still occurred they ran more diagnostics and it said it was the fuse panel block so they replaced that but the problem still occurred. Finally the last diagnostic tests said it was the PCM so they replaced that.
This garage has a really good reputation but the mechanics admit they are at a loss as to what is going on. They have been talking to other technicians in the area but no one has come up with a solution yet. Today the mechanic said that sometimes “systems aren’t really connected but they still talk to each other” which is why the diagnostic tests aren’t coming up with the right solution. He said there is a .5 voltage change in the system (I don’t understand what that means exactly) and that every time it won’t start and we have it towed back to the garage all he has to do to make it work again is reset the relay for the fuel pump (which has also been replaced but didn’t help) and then the car will start again. He said that was why they thought that replacing the fuse panel block and the relay would surely fix this.
So tomorrow I will have another towing bill to have it towed back to the garage again (they don’t do towing). I just want to have some possibilities to suggest to them that maybe they haven’t tried.
I just realized that I wrote the sentence wrong in my first post. These mechanics are definitely NOT dishonest. They are really good people, but they just can’t figure out what is wrong with our car and we are out of money to keep replacing parts that aren’t broken.
From what you say, it sounds like your team of mechanics think there’s a fuel delivery problem. This should be verified by measuring the fuel pressure at the rail (when it won’t start). If the pressure is low, then there’s definitely a fuel problem, which would be most cases either the pump or the fuel pressure regulator. It seems like they think it is the pump. This could be either a pump problem itself, which would require a pump replacement, or the electrical power going to the pump, which might just be a loose connector. The first thing to ask your mechanics - Julie - if is they’ve measured the fuel pressure at the rail during a time when it won’t start. Is it at spec?
They already tried replacing the pump once and that did not change or fix it. I don’t know about the fuel pressure at the rail but I will definitely ask them.
You should be able to get a full diagnostics at a dealer for around $100. You might ask these mechanics who are currently working on the vehicle if they could call the dealer and set something up for you, mechanic to mechanic sort of thing. Maybe make sure the dealer knows your situation and doesn’t try to rip you off.
@julieo00 These guys sound well-meaning, but they clearly aren’t getting a handle on your problem.
Who is recommending them so highly?
Perhaps it is time to look for another shop.
Replacing the PCM is quite drastic. And it didn’t even resolve the problem!
Without knowing the diagnostics involved I tend to agree with Tester about a crank position sensor. Located down low near the balancer and subject to vibration, heat, and water a CPS could certainly be behind something like this.
I wouldn’t be too hard on the mechanics. Struggling with a problem does not denote incompetence or being a crook because not all modern automotive problems are in black and white in spite of a perception that a computer or scanner may know all.
In the event this is not a CPS problem the following link may help; or not. You could bring it to the shop’s attention anyway.
The '07 Malibu certainly has an Encyclopedia Brittanica sized list of TSBs; many meaningless to the consumer and many that are applicable.
Looking over that list would certainly cause me to hesitate on the purchase of one of these cars.
What about this? The fuel pressure might turn out to be ok, there’s spark, but the injectors aren’t injecting gas. How would you tell? I think I heard someone say there’s a way to use a timing light to verify injectors are injecting, or more accurately, that the injectors are getting the electrical signal which should cause them to inject. You put the timing light clamp on the injector wire (rather than on the spark plug wire), and if the timing light lights up, that means the injector is injecting.
Anybody ever done this? On my VW Rabbit, the injectors popped right out with the aid of a screwdriver, so it was easy to tell if they were injecting or not. But newer cars, the injectors don’t pop out so easily. So it would be great if there’s a simple/fast way to veryify the injectors are injecting.