Intermittent not starting

[Craig234]

On an older Buick LeSabre, for a long time the battery was going bad, and I viewed any problems starting as related to that. A jump and it'd start.

Then I got the new battery installed - day 1 fine. Day 2, drove locally - and then it wouldn't start to go home. Tried probably 20 times over 20 minutes before it finally started.

It was turning over fine - just not starting. This has occasionally happened.

I called the local garage about getting it diagnosed, and they said if the check engine light isn't on (I need to check that), they can't diagnose it - I need to wait until it won't start at all and then bring it in.

That's not good - it means getting stranded first and who knows how many times where it won't start for 20 minutes then does. And that makes any fix hard to confirm. Any suggestions?

 

[repoman0]

You need four things to start -- crank, fuel, spark and air. You said it cranks fine, and the intake is obviously fine since it runs once it starts. Spark is probably there too for the same reason.

I would start with fuel pressure -- buy a fuel pressure gauge and learn how to use it. I'm guessing you can narrow it down to a soft failing fuel pump or some kind of relay. I had the same symptoms on my last car. It eventually wouldn't start at all, luckily right outside of my place, and was fixed once I replaced the fuel pump.

 

[Craig234]

You need four things to start -- crank, fuel, spark and air. You said it cranks fine, and the intake is obviously fine since it runs once it starts. Spark is probably there too for the same reason.

I would start with fuel pressure -- buy a fuel pressure gauge and learn how to use it. I'm guessing you can narrow it down to a soft failing fuel pump or some kind of relay. I had the same symptoms on my last car. It eventually wouldn't start at all, luckily right outside of my place, and was fixed once I replaced the fuel pump.

It's funny, I told the repairman I know almost nothing of cars, but was guessing it might be related to fuel getting to the engine.

He said that is unlikely because any cause of that doesn't go away once it starts.

I still suspected there might be more intermittent causes.

So interesting you seem to be suggesting that also.

 

[repoman0]

It's funny, I told the repairman I know almost nothing of cars, but was guessing it might be related to fuel getting to the engine.

He said that is unlikely because any cause of that doesn't go away once it starts.

I sat in a parking lot cranking away for minutes on a few occasions during the few weeks preceding my repair and drove away fine each time, without any sputtering or check engine light once I got moving. And it seems to be a common failure mode for that particular pump, which I believe was made by Bosch. It doesn't seem like much of a surprise to me that a pump could be dead enough that it doesn't want to start from rest but has no problem continuing once it's already moving.

 

[mindless1]

A fuel pump can have a bad spot on it and may or may not work, especially depending on temperature. Once it does start spinning it tends to keep working until the next time it stops on the bad spot.

Yes an intermittent start is harder to diagnose, but it's nonsense that a competent shop can't do it without a check engine light/code. It just takes longer, and in some cases they may not find the problem but mostly from lack of trying hard enough. Fair enough for them, sometimes you have to be reactive and check it when in that state yourself.

When it won't start, push in the fuel rail valve to see if a lot of fuel comes out. Do this not after cranking but right after turning the key the first notch which energizes the fuel pump and should keep pressure in the line before it's cranked. A more thorough approach would be to get a fuel pressure gauge and hook that up. Auto parts stores like Advance Auto and Autozone have loaner tools you can get with a deposit.

I'm not suggesting it's the only possible cause. Usually a bad coil won't prevent starting, especially on an older buick which probably has a V6 so you still have 2/3rds of the cylinders firing if a coil is bad. Might be ignition controller, though that tends to die completely not intermittently but with higher temperatures (under hood, not just ambient temps) it is possible.

You need four things to start -- crank, fuel, spark and air.

A bit over simplified. You also need timing (crankshaft position sensor) and the right fuel/air mixture. A leaking intake manifold can cause too lean a mix to start, but then clear up as the engine heats up, though the usual symptom is running rough cold, not just start/no-start until it gets worse. If it's the first 2 or 3 generations of the 3800, they are known for bad intake manifold gaskets but crank sensor is also a common no-start fault, but of course it could still be the fuel pump, and I do lean towards the fuel pump being more likely for an intermittent no-start when it runs fine once it does.

http://www.aa1car.com/library/diagnose_buick_3800_engine.htm

 

[Craig234]

Interesting and more than I can do. But for what it's worth the good news is, driving once a day, it's started each time since.

 

[Herr Kutz]

My dad had an early 00's impala and it would start just fine when it was cold. However, when he shut down the car and was only inside for a few minutes before trying to restart his car, it quite often would not start. Never could figure it out until he brought it in for some body work. I think they replaced the crankshaft sensor(?) or something. No issues since then.