[Aaron407]

First off, I'm not stock. I'm running a maggie with a 20A KB BAP and the stock fuel pump, and have been without any issues for about five years.

Here's the problem: about a week ago, after about a 20 minute drive, I turned the car off for about two minutes. When I came back out and tried to start the car, it sputtered a little bit to start with, but wouldn't start. It was turning over just fine, but seemed that there was either a lack of fuel or spark as it wasn't firing whatsoever other than the initial sputter. With that, though, I assumed that there was spark but the fuel pressure dropped off. I tried it a couple more times with the same result. After waiting for another minute, I tried it and it fired up completely normally. There were no issues on the rest of the drive or starting the next 5 or 6 times. Since this sounded like a flaky fuel pump relay, I swapped it with the trunk release relay. No codes tripped at any time.

Everything worked fine for about a week, then a similar issue yesterday. I started the car, but it started to die immediately. I was able to feather the throttle and get it back up to normal idle and it continued to run just fine. I got it home, shut it off, then tried to restart, and it did the same thing as the first time - sputtered a bit, then stopped sputtering and just wouldn't fire. I left it for a couple of minutes again, after which it fired up without issue yet again.

I checked the battery voltage at the battery with the car off, and the voltage was 12.0V, which obviously seemed low. I left it for about five minutes then checked again, and the voltage had risen to 12.2V for some reason. I put the car to the start position without actually starting and the voltage dropped to 11.4V, which seemed very low with minimal load on it. It still started and I confirmed the voltage at idle to be ~13.4V, which suggests that the alternator was still charging ok. After turning it off the voltage was back to 12.0V. I put my ammeter in line with the ground terminal and measured parasitic draw to confirm that there wasn't a faulted diode, and the standing load with the car off was under 1A and dropping over time as everything went into 'sleep' mode. Since the aftermarket battery was five years old, I decided to replace it, even though the old battery did still seem to take a charge with a charger. The new battery started off at 12.5V. I started the car and let it idle for about 20 minutes, after which the battery showed to be 12.65V (i.e., seems like the alternator is working). I also re-seated the fuse for the BAP and replaced the fuses for the fuel pump (20A) and theft deterrent system (2A) that can shut down the fuel pump. I confirmed that the wire splices for the BAP were not damaged, and I haven't driven the car since until I have a proper backup should it refuse to start at some point.

What I'm trying to figure out is whether or not a battery issue could cause a fueling/spark issue if there's still enough charge to allow the engine to crank. It doesn't seem like it should, but maybe the KB BAP was dropping out or something. If I still have the issue the next time I'm at home, I'll be checking fuel pressure to confirm whether it's fuel or spark related. What should the fuel pressure be at the rail within a couple of minutes of it shutting down? Beyond that, I'm wide open to suggestions from anyone and everyone for what to look at.

EDIT: I'm also going to try remote starting next time since that likely handles the security side differently.

 

[GOPHERIT]

The service manual says, that the fuel pressure (as it came form the factory) runs between 55 an 60 psi. They say that fuel pump pressure may vary slightly when the pump stops working. At that point the fuel pressure should stabilize an remain constant. Then verify that the pressure does not decrease more than 5 psi within 1 minute. It reads like if the psi drops below that 5 psi range, to suspect a fuel pump, or a leaking injector.

 

[Aaron407]

What seems strange is how it either works perfectly or seemingly not all, which has me suspecting an electrical issue. Out of curiosity, if there is an issue with the 'chip' in the key (if you can really call it that) and the fuel pump is immobilized as part of the theft deterrent system, should there be an accompanying security light or message of some kind? I was getting nothing, but I can't help but wonder if my flip key could be the issue if it's triggering the immobilizer system. I may keep my second key handy to try the next time there's an issue, as well as remote starting.

 

[GOPHERIT]

My take, is that the chip embedded in key side half of the fob, has a dedicated code (so to speak) assigned to it. Once the cars theft deterrent system has learned *it* (along with any other key fobs you have for it) only then, would the car give *those* key fobs the right to allow the theft deterrent system to command the ECM to start the car. So if you can crank, the car has recognized that key fob (either directly or by remote).

 

[Aaron407]

So, does the theft deterrent system disable the starter if there's no match, or just the fuel pump? I had thought it was just the fuel pump, but I guess there's no reason for it to prevent the starter from cranking as well. I'm still thinking the problem lies in fuel supply, but I'll have to test for pressure the next time it acts up.

This is not a fun problem to try to solve when I could be left out in the Saskatchewan cold...

 

[GOPHERIT]

If the key is turned to the full on position (cluster goes thru its standard turn on function), it tells me that the in tank fuel pump was powered up for the 2 sec commanded time period. If nothing further happens, that pump shuts down. If you then go for a start, pulses from the crank an cam sensors will command the in tank fuel pump to start again, an continue to run as long as the pulses from those sensors are being sensed by the ECM. I'm not familiar with what ever that KB BAP thing is (if its fuel related), or how it could influence the fuel pressure system. Something as innocence as a fuel purge valve that is *not* faulting itself, but might be partially stuck open at the wrong time, could allow fuel vapors to build up in the intake system, which sounds like *it* could make for a hard starting engine until the system has purged itself back to a near normal condition.

 

[Aaron407]

Thanks for the thoughts. I didn't realize that the fuel pump operating relied upon the cps signal. From what I've read, it should trigger a code if signal is lost, but maybe it needs to first be properly running before it checks it.

The KB BAP is a Kenne Bell boost-a-pump that runs in line with the fuel pump supply power to regulate it and boost voltage slightly when a hobbs switch tells it I'm in boost, ultimately to run it slightly harder to account for pressure dropoff at higher boost. Given that it's winter, though, I haven't been in boost in a long time, and the pump shouldn't be overheating. I just mentioned it because it is an intermediary in the power line for the pump, and a failure in it would cause problems.

Anyway, I'll hopefully be trying the car again in a couple of days. My wife threw her back out and I need to drop off/pick up my kids, so I'll wait until she's in a position to pick us up if my car completely stops starting.

 

[Aaron407]

Also, I've fought with issues with malfunctioning evap purge solenoids in the past, and this didn't seem the same. I'll consider it as a possibility going forward, though, since I'm open to all possibilities at this point.

 

[L78steve]

First step is install a fuel pressure gauge on the rail port.

 

[Aaron407]

I have one ready to put on the next time it acts up to see if I've dropped fuel pressure. It's not the kind that I can install and run to an inside gauge, though.

 

[Aaron407]

So, every time that it's acted up since then, I've been away from home with a schedule commitment and unable to check fuel pressure. Of course.

Anyway, I've confirmed a few things:

-It's not the evap purge solenoid sticking open. I swapped it out with another one I had on-hand from when I was troubleshooting a different issue. No change.
-The issue is actually *not* only at startup. Twice I've hit the throttle hard and it felt like it fell on its face hard until I let off the throttle.
-It's not a theft deterrent system issue related to the key. When I had the issue one morning, I tried the spare key and the remote start, neither of which made a difference.

Still no codes. I'm starting to think this is an intermittent sticking injector for the following reasons:

-When it's not starting properly, I can smell a raw gas. It still sputters a bit, but doesn't have enough power to fully fire up.
-When it has trouble starting, one injector may have stuck open a bit. Leaving it sit longer might allow it to evaporate somewhat, but trying to start it with the fuel still saturated in the cylinder would have bled off fuel pressure after priming from the other cylinders and that one would be saturated, even fouling the plug and leaving the others too lean.
-I changed the plugs today, and the #8 plug looked different from the others. Not black/wet, but different, almost a bit frosty looking.
-When watching misfires, the #8 cylinder has a few occasional misfires when at lighter throttle levels under load.
-When I've started up the engine when warm, it would make a popping sound, which I believe is generally caused by raw fuel dumped in the exhaust. When I tried it today, the popping sound from the exhaust was from the same side as the #8 bank. I recall this same effect when I was tuning transient fuel and dialed it back to remove the startup pops, so too much fuel would make sense.
-When my car has been muddy/dirty this spring, the exhaust on that same side leaves a darker mark in the dirt, suggesting that it's running richer.
-When starting with a warm engine, it seems a bit hesitant at first to climb RPM, but recovers after a second (possibly one rich cylinder?).

Anyway, I picked up a bottle of techron that I'm running through it. After putting it in the tank, I ran the engine at low load, high RPM on the highway for about 10 minutes to work the detergents through with the injectors pulsing rapidly. After getting home, I shut it off and restarted. No popping this time, and no hesitation for the RPM climb. I'm hoping that this will lead to it ultimately working if it was an intermittent injector issue, but I'll be keeping an eye on it.

 

[BAS G8]

GM dealers used to have a bottle of injector cleaner you hooked to the fuel rail and the engine ran on that for 15-20 mins while doing an intake/injector cleanse.
I was the best IMHO for cleaning injectors but apparently its not available any more.
Techron would be second best option but I don't think they advise using it tank after tank.
At least you seem to be on the right track solving this.

 

[L78steve]

GM dealers used to have a bottle of injector cleaner you hooked to the fuel rail and the engine ran on that for 15-20 mins while doing an intake/injector cleanse.
I was the best IMHO for cleaning injectors but apparently its not available any more.
Techron would be second best option but I don't think they advise using it tank after tank.
At least you seem to be on the right track solving this.

This was the 3M system. I used this on a Buick GN back in the 90's with leaky injectors and it cleared up the problem immediately.
I guess anything that works is eventually discontinued.

 

[BAS G8]

Yup, usually the way.
Although, GM had some kind of copy cat product available, when I got my G8 5 years ago my son ran a bottle thru it at the dealership where he worked so he must of got one of the last of the product.

 

[Aaron407]

Well, it's looking like that's not the issue. Today I hit the gas to downshift and the car fell flat on its face again. This time I held the throttle and glanced at my gauge, and the wideband showed the full lean level, the same as when it shuts off injectors for DFCO, but there was no KR. This tells me that I'm either losing all fuel from injectors shutting off for some reason, intermittently losing all fuel pressure, or losing all spark since the wideband presumably reads full lean if there's simply no combustion.

While still holding my foot on the throttle, it did end up surging back after a few seconds, then drove perfect after that. I downshifted just fine about 10 times afterward and with good AFRs, so it's not that the fuel pump is simply getting weak. It makes me wonder if it is the boost a pump, and maybe it has issues when the hobbs switch triggers it into the overvoltage operation and it sometimes just drops out. Maybe the hobbs switch is triggered on startup too, who knows. At any rate, I'm probably going to pull the BAP this weekend and bench test it, but that might not show anything either if it is the problem but needs a load to have issues.

Ugh, this problem is getting real old, real fast...

 

[Thawk]

If you have never replaced the fuel pump, it sure sounds close, you def have to rig a fuel gauge at base of windshield to view immediately when acting up, it is ok to close hood on hose as seal will give some and still read correctly, Most likely the press is diving, but until you know the actual fuel press when this happens, you will be still guessing, also G8s Injectors were one of many that did not require cleaning nor LS-9 injectors either. get the number of press when this happens and then you can go forward correctly

 

[PONY MAN]

Can't speak on the effectiveness of either Techron fuel additive (injector or fuel system cleaner) although it seems to do relatively well in their gasoline. The only fuel additive used to date with any noticeable difference is Gumout One-N-Done complete fuel system cleaner. Designed to be used once per year, has advanced p.e.a. (polyetheramine), helps pass emissions testing and maintains catalytic converter efficiency. It's not the same as their All-N-One cleaner. In the past, have used SeaFoam, B-12, Lucas, BGK, STP, and others will little to no perceived change. Best of fortune getting the issue resolved.

 

[Aaron407]

If you have never replaced the fuel pump, it sure sounds close, you def have to rig a fuel gauge at base of windshield to view immediately when acting up, it is ok to close hood on hose as seal will give some and still read correctly, Most likely the press is diving, but until you know the actual fuel press when this happens, you will be still guessing, also G8s Injectors were one of many that did not require cleaning nor LS-9 injectors either. get the number of press when this happens and then you can go forward correctly

That's the trouble - it's so random that I can't plan for it. Probably 1 out of maybe every 30+ starts will show the issue, and 1 out of ever 50 hard downshifts. Note that I can push it at WOT to 6000 rpm with solid AFRs, so I keep thinking that there's something intermittent in terms of supply power to the fuel pump. The only thing that would be different in boost (e.g., hard downshift) would be the boost-a-pump upping the voltage when the hobbs switch kicks in. I'm going to replace the BAP relay and do a full audit of the wiring this weekend if I can find time. It's hard to know if maybe there's a wire rubbing that gets jostled on some downshifts or moves from heat before starting after it's warm. Such a strange and random problem anyway.

 

[Rillo71]

OP, how many miles do you have on the car? Something else to think about, could it be the crankshaft position sensor causing problems?

 

[Aaron407]

About 83,000 miles. I've thought about the crank sensor, but figured it should kick out a code if it's failing. We do have mice in our garage occasionally, though, and maybe there's an intermittent wiring issues with the sensor. Does it need a crank relearn after replacing the sensor? I assume not, but curious nonetheless.