why would a car not start if verified to have full spark and full fuel pressure. It turns over and cranks just fine

70

Asked by Aug 20, 2016 at 01:10 AM about the 2007 Pontiac Grand Prix Base

Question type: Maintenance & Repair

I have an 07 grand prix, car just suddenly dies while driving, no stalling or anything, its as if i turned the key off.  Its random but usually only does it when its above 85 degrees or so, or hotter, outside.  When it stalls out it is getting fuel from the fuel rail, sprays up to the hood, so full pressure, I can verify the spark plugs are firing, via starting fluid, as it ran till the fluid was used up, also checked them just to see on the plug itself.  Ignition module seems to be in good working order, fuel pump turns on, but it (the car) has not wanted to start for up to 4 hours (twice), when normally it will start back up after dying after a few minutes, sometimes on the first try.  I know quite a bit about cars myself, but I have only had older cars until I got this one a couple months ago, and I personally think its the ECU, but I dont know jack about them, never had any issues with one before.  Is there any other reason why the engine would die out suddenly, run great until it just dies, with no stalling or hesitation or any type of poor run symptoms, indicating the fuel filter and pump are working at 100% function, the spark plugs and wires are all good, the ignition module is good, the coils are good, everything seems to be in good working order, verified by more than just myself, I have taken it to a few mechanics, they cannot figure it out because it wont die when I give it to them...  When I turn the engine over, it will turn over just fine, no odd noises, or anything out of the ordinary, except for the fact its a bone dry crank, no gas is getting to the cylinders, yet the engines fuel rail has fuel.  But it sounds as it normally would on the first crank or two before it should fire up, but continues to crank.  Thats about all of the information I can think of, oh, I replaced the crank shaft sensor, and cleaned out the cat bc the diagnostic tool said those were issues, and nothing comes up now when I put the diag tool on it, but it still has this issue of not wanting to drive more than 3-5 miles before dying for 10 minutes on average, and I dont want to shell out about a thousand dollars to get this fixed if its something else, please help!  One other thing I can think of too, is 95% of the time it dies is during the afternoon on my way home from work, around 3-4pm, but on the way to work at 9am it barely ever gives me trouble, but lately it has been starting to die on the way to work too, i think it is because of the heat of late (90+ past week or two) but I figure it might be worth mentioning, thank you for any help it is much appreciated.

18 Answers

55,165

Squirting fuel out of the fuel rail is not an indication of proper pressure. To get an accurate diagnosis the fuel pressure should be measured with a gauge to see if it is in spec. Are you getting fuel injector pulse when trying to start it?

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72,395

Sounds like something is getting hot, expanding, and creating a bad electrical connection. Without a trigger signal from the PCM (Computer) the fuel injectors won't spray. HTH. -Jim

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@bob: not quite sure what you mean by fuel injector pulse, but the pressure was good enough for the car to run from the fuel rail, it may not quite be full pressure, but the spark plugs sparking should ignite something inside the engine, but its as if there is absolutely not a single drop getting past the injectors it seems, as it just cranks but no fuel is being ignited, like i said not a single drop, bone dry

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@js08016: Yes that does help some, but unfortunately I have looked for anything that would be hotter than normal like a reddish tint to any metal and I didn't notice anything that hot. But as far as finding what is heating up, I could use a bit of help there. I am not quite sure where to start. I have visually inspected most all of the wires and cables that run through the car (at least what is exposed without ripping apart the interior, so pretty much the trunk and under the hood and the car itself) and I didnt notice any that were charred or burnt up, but it does seem like either the computer is failing to send the signal or the wires are failing to deliver the signal to the injectors. Is there any more you could tell me about this to help me figure out where it might be shorting out or where something would get hot enough near the wires to make it fail? Thank you for your time, its much appreciated.

1 of 1 people found this helpful.
72,395

Unfortunately a bad connection may not be that obvious. I'd check all the plugs around the engine. They're all exposed to heat. Especially on the top of the motor as heat rises. HTH. -Jim

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@js08016 : By plugs around the engine are you referring to the spark plugs? or just every wire attached to the engine? Maybe it would help if I told you that I truly have no clue where the PCM or ECU is (or if they are the same thing). Every car I have had was carb. no fuel injection, so no computer, other than this one. Kinda wishing I had stuck with the el camino.. in those cars once u got fuel and spark it runs... so, if you could go into detail, if possible, It would be extremely helpful. My confusion arises from this : I assume there is some sort of cable(s) running from the PCM or ECU to the fuel injectors somewhere, and I would assume that/those cable(s) are the issue. But I do not know where the cables are that even run to the cars computer, as I am not sure where the computer is at in the car. (I assume its behind the dash somewhere or possibly behind the glovebox, or under the steering wheel, but I really dont know.) Also, I do not know exactly which set of cables are for the computer coming to the engine itself. I use process of elimination to figure it out somewhat, by eliminating the cables I know what they are for and where they go, but I could use a little direction, I am new to fuel injection/computers on the car, but I have fully restored my el camino, gutted it and rebuilt it, many years ago, wish I still had it. so I can figure out what u are talking about with just a bit more detailed information, possibly a picture would be great, just to point me to the right area on the engine. There are 2 possibly 3 cables coming to the engine that I am unsure their function, it is probably one of them, but I want to start by just replacing the wires from the computer to the engine, see if that helps, but I cannot do it without first knowing which are which and then proceeding to follow them through the car and replace them. Again, sorry for my lack of knowledge on this, and also thank you for your help.

1 of 1 people found this helpful.
72,395

That's ok. This car and your El Camino both need three things to run. Fuel, spark, and compression. This is no different than looking for an intermittent electrical problem on the El Camino. All of the electrical plugs I'm referring to are the exact same principle as in the old days. Only difference is here we have sensors and fuel injectors instead of relays and switches. The PCM (Powertrain Control Module) is most likely under the air cleaner box, if it's like my 2000 Grand Prix. You'll see a large bundle of wires going to it. The fuel injectors will each have a two way plug on each one. The fuel injectors are on the lower intake manifold. Since this is a catastrophic failure, that is all the injectors stop working at once, it has to be that the trigger signal from the PCM is being lost. The PCM normally gets devices to work by completing the individual circuits to ground. Once you know that your sensor and injector connections are clean and tight check your ground wires and straps for any looseness or corrosion. Intermittent problems are a bugger to track down. I'd suggest you get a shop manual for your Grand Prix as well. They are extremely helpful. I have ones for all of my vehicles. I'm sure this is going to be an electrical problem. Ninety percent of intermittents are. One other thing, is your Grand Prix involved in the giant GM ignition switch recall? If so, that may have something to do with this as well. HTH. -Jim

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Best Answer Mark helpful
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so I was looking around the web to find the PCM's location, seems to be in the air filter assembly, does that sound about right to you? I would go out and check right now, but its storming and i am not about to try and mess with the computer in the rain, for sure after that it will need replacing lol. But I only ask, because I am just going to replace the wire going from the air filter box to the engine and hope that is the PCM's main wire, if there is a wire there (like I said I cannot go mess with it today due to weather, so I am unsure if there is any wires on or near the air filter, as I don't recall there being anything other than fuel/AC lines and the throttle body near there)

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@js08016 : Thank you, that was very helpful, I think I know all I need to be able to figure this out, thank you very much!! I will let you know what I come up with once I can get under the hood (hopefully its not raining tomorrow), and update on what the problem was for anybody else in the future who reads this and has the same problem. And as far as the ignition recall, I am not sure if it was recalled or not. How would I find that out? Also, I believe the ignition switch to be okay, it doesn't seem faulty, but I probably wouldn't be able to tell either way, I do know its not loose or anything, as the one recall I heard about was the switch was just not tight and any touch to the key would cause it to switch off, which is not the case here, key holds tight in the "On" position, like it takes a bit of force to turn it off is what I mean by that, so its pretty tight for staying on.

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oh, also, I just thought of something that happened a few weeks ago... so the AC stopped working for one day only. I don't really care about the ac working or not.. but I am wondering, since it sounds like an electrical issue is the problem, if that has anything to do with the possible stalling issue? It just seems odd for the ac to be on, but be blowing hot, then work the next day. But since it seems like a similar "Failing sometimes" issue if its connected at all. Also, when its night time and I turn the right turn signal on, the bright lights come on, only half the time though.. which is also odd. Jw if it has anything to do with the stalling issue

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Okay, so I checked the GM website, and it was part of the recall, so I am going to call them up tomorrow and see if they have either already fixed this car or get them to do so. I could easily do it myself, but hey they will do it for free, why not let them.

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would the faulty ignition switch cause the car to not restart for a long duration though? I understand it can turn the car off, but would it also prevent it from starting back up?

1 of 1 people found this helpful.
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rather would a faulty ignition switch**

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72,395

You're welcome. Glad to help! Thank you for the best answer click! That's interesting about the air conditioning and turn signal issues. There could be something going on in the steering column with the ignition switch. Yes, the PCM is located in the air filter box assembly on my 2000 Grand Prix as well. You'll see a LARGE bundle of wires going to it. Has the check engine light been on at all? If so and you can scan the computer (PCM) for trouble codes that would be helpful as well. Yes, please do keep us posted! I'll be curious as to what you find out. At least you know that it's a fuel problem. So that's half the battle!! HTH. -Jim

Did you get your car working again?

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Right now I am trying to figure out what to do, because the wire coming from the PCM to the injectors is part of the main wire harness, and I do not feel confident enough with the newer unfamiliar setup under the hood, so I am trying to get a mechanic to look at it, but I cannot get it to stall out when at a shop. For now I am trying to find if there is a mechanic around that might be willing just to add a new line (if thats even possible) from the pcm to the injectors, to bypass the old one, and just attach that to the wire harness on the outside of it with the same tape that the harness uses. Also, I noticed today when it stalled out on me, theres an odd odor coming off the car once it stalls out, it doesnt smell like any fluid in the car, maybe like grease. Could be the wire(s) getting hot, but I cant say it smells like electrical fire either, and I have smelled quite a few electrical fires in my time, its kind of a new smell to me, but does smell similar to grease getting a bit hot, but not quite like that either. Either way, I am pretty sure its like you say js08016 with something heating up the wire. As far as fixing it goes, thats a different story, as I got an $1800 quote for replacing the wire harness at a shop down the street, and well, thats not worth it. Any ideas/suggestions? At this point I am kind of stuck. I also would not mind at all jerry rigging it if anybody may have a suggestion as to how to do so safely? And no, no check engine light, and I used the diag. tool a while back and fixed the 2 codes that came up, which were crank sensor and clogged cat, but I fixed those a long time ago. Now no codes come up, computer says the car is fine, but obviously it isn't. And GM sent me a recall notice the other day too, so the switch is faulty, but I don't think that is why the car is not restarting if the switch is making it turn off. I could see it make it stall out, then u pull over, and turn the key it fires back up, right? But here it will stall and not start for a long time. Sometimes it does fire up right away, which I assume is when the ignition switch is at fault, bc the car restarts first try with no issues. But then the other times, it can want to not restart for a couple hours, but usually not too long. Also, for now I have not checked the wires by the fuel injectors either (to see if they are damaged from excess heat), as once I realized it was the whole wire harness, and not just a simple 8-20 pin plug to replace, I kinda just left it alone until I can figure out a simple way to just replace a few wires, not 50-100 wires. And also I really don't want to have to take apart the wire harness to follow the wires that do go to the injectors if its not as easy as unplugging the old wire and running new wire to replace it (mainly because with the electrical problems this car has, it seems to me the wires are like brittle and I don't want to ruin more stuff trying to fix this problem by messing with the whole cars wiring). And If it is that easy, then I am missing something lol, because a shop wants $1,800, so it cant be very easy to fix.. and I am not so sure I even have the capability to fix this issue, as I have never dealt with an electrical problem in a car, asides from replacing a wire or two when necessary, but that is a lot different than the main harness. Any help or suggestions would be much appreciated! Thanks in advance!

I have a 2008 Grand Prix that just quit on me when I was backing out of my driveway last week. For two days it wouldn't start then on the 3rd day it did but it had a bad miss and it smelled like rotten eggs from the exhaust. I replaced the ignition control module (took 15 min) just remove the 3 coils and it comes right out. Paid $143 for a new one at local auto parts store and installed it and it fired right up and runs great now. You can remove yours and have it tested to see if it is bad. Something for you to consider.

My 2005 Grand Prix is also just dying for no reason or warning...usually does it on my way home from work right after 4 p.m...never does it on my way to work @7 a.m...also has a fuel smell, bad gas mileage, and I'm pretty sure a gas leak...oh, and it also 98% of the time will take no more than between .02 cents & .20 cents at a time while pumping gas. What would cause that? There is a filter of some type located underneath my car, back by the tank...is that the exterior gas filter? Engine light is on and the tester says it's the O2 Sensor but also says my car has an upper and lower...but doesn't say which one is bad...would that cause all these fuel issues? Completely lost on this one...any suggestions are greatly appreciated

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