So my dad just purchased a used 2005 suburban (our last one was an 02 that we ran into the ground) and got a good deal on it...
As with all good deals it has its qwirks, but my dad and I are handy with a wrench (OK not perfect, but on a scale of 1-10 id rate us pretty good at figuring stuff out and getting things fixed) so we figured sure why not, its a suburban, they are tough, the person we bought it from was less then mechanically inclined so its probably something stupid. Besides, we got a deal on it (even if we lose some money on repairs we still end up ahead.)
Ok, dead end now.
Heres what happens... when you crank the truck it cranks strong, but you sit there and crank it and it never fires... until you let go and drop the key back to the run position then crank again. Then it fires like a champ.
First thought was the fuel pump, so we primed it (put key in run and wait....) then cranked, same story.
So we drove it around for a bit (150 miles) hoping to trigger a code pop, nothing.
Took it to a friends dad (a retired mechanic, he has a knack for motors) who told me it must be a sensor issue (his first guess was the crankshaft position sensor), replaced that and no dice. Same story.
Took it to a local shop, had them scan it with one of their super scanners, nothing popped up on the scanners as being irregular.
Gut feeling got the better of me so I picked up a fuel pressure gauge and tried that, now I got some weird numbers....
When you first put the gauge on it reads 0 (car is off).
When the car is switched to run it reads 0. (if im correct it should have pressure here)
When you start cranking the gauge will slowly start going up, if you let it raise all the way to 45-50 it will fire and start running like a champ.
If you stop cranking early (IE when the gauge is at 25~) then drop it to run and crank it again, fires right away.
Once the truck is running, solid 60psi the whole time its running (havnt driven it with gauge on, the gauge we got has a short hose (dumb selection in hindsight) so the hood has to stay open while you ahve the gauge).
When you kill the truck the gauge rapidly drops down to about 9psi (in approx 3 sec)
From there the gauge will slowly drop to 0 (takes about 30-45 sec)
If you attempt to start the truck while the gauge is dropping, it starts fine. If you let it hit 0 psi, start cranking.
It should be noted that once the truck is running it has no problems, instant acceleration (for a suburban anyway), smooth idling, etc. I drove it to class and ran errands yesterday (150 - 200 miles) without any problems.
I checked fuel pump relay, it looked alright, was a little brown on one side, went ahead and replaced it, no dice.
Ran Chevron fuel cleaner through, no change.
Now im confoundled. What would cause those symptoms?
My first thought would be a leaking fuel check valve, but the system depressurizes so fast, and even when its in run it should be priming right?
So then I thought maybe the fuel pump? But then it would show up during drives.
Regulator? The pressure stays a solid 60 once its started.
Line/Fuel Injector? MPG is too high to be "wasting" gas... 17.9 mpg (city65/hwy35)
Maybe its not a fuel issue at all? Friends dad swears its got nothing to do with fuel and its a sensor (I would think the scans would pop something there)
Anyone have any thoughts? Im desperate here >.<
So who has the problem solved yet???. I think I started another thread or at least mentioned this two crank issue in another thread around here. You can turn it over for a minute or you can turn it over for 2 seconds. It simply refuses to start till you back off and turn the key over again
. But I have all the same stuff going on starting with fuel pump draining to zero pretty quick. Personally I believe that its a couple of injectors sticking open for whatever reason, most likely mechanical failure since cleaner doesnt do much. Still that injector cleaner only works if you run it BEFORE they clog.. But I also suspect the computer knows there is not enough fuel pressure and wont allow a start. Or else as one poster mentioned the pump is computer modulated and only runs when the car does. But the latter of the two may be untrue to some extent because I believe mine will start every time if I turn to BATT ON and leave till after all the bells stop. That still does not mean that this pump only runs on demand call...
ALso noting the seemingly random indications. I want to point out the is NOT a NO START/NO CRANK issue. But there is no rhyme or reason to it as all of the following scenarios happen...:
1. Get in one morning turn the key over and it fires right up.
2. Get in one day after getting out at gas station and it fires right up.
3. In BOTH ABOVE SCENARIOS you can get in and it will not start on first attempt no matter how long you turn it. Farting out the tailpipe.
4. On the occasions that it takes 2 start attempts which is about 65% if the time, it does not matter if the first attempt is one simple turnover of the engine first OR turning over for 30 seconds. But either way as soon as you turn it back off and try again its a normal start.
5. Strangely I overserve fuel bleed down as well. But how does that explain that you can get in and turn in 3 cranks on a no go, but as soon as you make second attempt it works... OR you can do a long first attempt and it takes a second attempt to start. THIS DOES NOT CORRELATE WITH LOW FUEL PRESSURE. In short I believe a good fuel pump will prime and start a bled down system in 2-3 turns regardless as the fuel if going to be sitting right there at the downward neck of the fuel race as worst case scenario... And not all injectors are bleeding out I dont think just because one or two are. Depending... But the fuel re-prime action doesn't have that far to go...
I believe that the issue is mechanical fuel related and this is triggering some kind of ECM computer reaction. So WHERE is this system in the electrical loop an how sophisticated is it..?
1. Can it tell if the fuel pump has no pressure backed up?
2. Or does it just see the fuel pump working too fast and shut it down.
3. Can it simply tell if an injector is stuck open?
4. Are the O2 sensors picking up leaking injector leaked fuel vapo in the exhaust pipe and telling it not to start? //if that exhaust valve happens to also be open at the time of tuning the vehicle off, and on only on a cylinder with a leaky injector?? Hence the randomness...??
And I have changed all the stuff either concomitantly as a an attempted remedy or normal failure coincidental. Hell I even changed the camshaft sensor when it joined in this night mare and turn this 2 crank COMPLETELY RANDOM. You could tell the camshaft sensor was causing additional problems because when it stopped in a whacked spot it really would not start, like even if just turned back off. I did hope that the camshaft sensor fixed it and acted like it did .... For a minute but no.... In all the reading I have done there is no reprogram required on the cam shaft sensor, but perhaps on the crank sensor yes.
Im sure its a fuel problem because its bleeding down. But that bleed down does not always trigger the first start failure. I think i found a salvage yard that will sell me a set of injectors for 80 bux. I'm thinking I will get them and test them all and then swap em... But have you seen the prices on the stupid o-ring kits... GOOD GRIEF....
ANYONE PLEASE FOR THE LOVE OF GOD.....
After that then tell me why my tahoe oil leak has started dumping all of the sudden... uggh..