97 M3 will not start until 3rd crank when cold

[Casebrius]

As title says, when cold it will not start until cranking at least 3 times. The chepo AZ scanner says O2 sensor bank 2 I believe. When the car is warm, it fires right up. Has anyone else ever experienced this? I'm trying to avoid throwing parts at it. It runs fine once started.

[NoLastName]

Not to jump to a worst-case scenario, but both times that happened to me it was a leaking head gasket. A small amount of coolant would leak into a cylinder overnight causing a misfire & hard start. Once the initial moisture was blown out the engine would run fine. The coolant also fouled my O2 sensor. Maybe pull your spark plugs and look/smell for water in a cylinder. Easy to check.

[Casebrius]

Not to jump to a worst-case scenario, but both times that happened to me it was a leaking head gasket. A small amount of coolant would leak into a cylinder overnight causing a misfire & hard start. Once the initial moisture was blown out the engine would run fine. The coolant also fouled my O2 sensor. Maybe pull your spark plugs and look/smell for water in a cylinder. Easy to check.

I sure hope thats not the case, It has about 6,000 miles on it since a head rebuild. Even if it sits for an hour and totally cools down, it hesitates starting. It has ~100K miles on the clock and I don't think it has had O2 sensors. I don't know for sure, I bought it at 94K after a friend had money shifted it. I didn't change the O2 sensors when I rebuilt it because at the time, the friend was sporting the bill and didn't want to pay the $400 for them. I guess it's time to pony up for them (O2 sensors) and take it from there. IIRC, can't you put UV dye in the cooling system and then check fluorescence with a UV light? I guess that would be the easiest way to be sure I don't have head problems.

[CMG]

My car has always had intermittent long crank to start. I researched in my case it's most likely some kind of valve in the fuel pump. Haven't dug further cuz it's not a big deal.

[flyfishvt]

Long crank times are classic symptoms of cam or crank sensors

[CMG]

Long crank times are classic symptoms of cam or crank sensors

Wouldn't that cause other bigger issues and not be intermittent?

[ihsnshaik]

HAD THE SAME EXACT PROBLEM!!! It was my fuel pump! It would crank a few times on cold and once warm it would start right away. Put in a fuel pump its pretty cheap.

[RagnarDanskjold]

I would guess a fuel delivery problem, likely a bad fuel pressure regulator or check valve in the system that's letting the pressure bleed off and drain back into the tank. Cranking re-primes the system and it starts. Hot starts would be fine because there's not enough time to drain all the fuel back.

Just a thought.

HAD THE SAME EXACT PROBLEM!!! It was my fuel pump! It would crank a few times on cold and once warm it would start right away. Put in a fuel pump its pretty cheap.

[Casebrius]

I would guess a fuel delivery problem, likely a bad fuel pressure regulator or check valve in the system that's letting the pressure bleed off and drain back into the tank. Cranking re-primes the system and it starts. Hot starts would be fine because there's not enough time to drain all the fuel back.

Just a thought.

I replaced the fuel pump about 1000 miles ago. Maybe it was a shit pump. It would seem that if I just turned ignition on it would turn fuel pump on and prime the system, but that doesn't seem to be the case. I can crank till the cows come home on the first and second tries, it still won't start. Even if I do 2 VERY quick cranks, it will always start on the third try.

[Casebrius]

Where is the fuel pressure regulator on a 97?

[NeilM]

Where is the fuel pressure regulator on a 97?

Under the car, roughly below the driver's seat, protected by a cover.

Neil

[Sps]

Not to jump to a worst-case scenario, but both times that happened to me it was a leaking head gasket. A small amount of coolant would leak into a cylinder overnight causing a misfire & hard start. Once the initial moisture was blown out the engine would run fine. The coolant also fouled my O2 sensor. Maybe pull your spark plugs and look/smell for water in a cylinder. Easy to check.

I hate to +1 on this but my 95 M3 did the same thing. Usually starts on second or third try. I just found coolant on the dip stick and now I have to do a head gasket on it or another head. Just keep that in mind. And this is the third on since 2005. Maybe a crack in it.

[rob22sf]

Under the car, roughly below the driver's seat, protected by a cover.

Neil

no, thats the fuel filter; on the e46 thats where it would be; cause its part of the filter; on the e36; its along the fuel rail

[marvinstockman]

Did you have the problem before you replaced the fuel pump?

[SneauxM3]

I was thinking along same lines ^^

Was it doing this prior to a new fuel pump, and have you changed the fuel filter on it yet? Mine did this and thankfully I caught it when I did because my fuel pump almost burned down the M.

My fuel filter(had procrastinated replacing, even had new filter) was still working but just barely..basically I would prime it exactly about 2-3 times until it would start, and things would be fine. Well it started taking a few more cranks to start in next month or so, already had the filter and figured hey...amazon offers Genuine BMW OEM fuel pumps with the new bracket/hanger and all for about $120, car was a 95..fuel pump could use changing either way at this time.

Well the fuel pump was struggling so hard to push fuel through the filter that it was starting to heat up one of the wires connecting at the pump, the plastic was a lil melted and slightly singed. (everyone kept trying to say CPS)

Moral of story : Have you checked the fuel filter JUST to be sure?

[Stephen Max]

no, thats the fuel filter; on the e46 thats where it would be; cause its part of the filter; on the e36; its along the fuel rail

Well, to be exact, M3s with the S50 have the fpr on the fuel rail, M3s with the S52 have the fpr down by the fuel filter. So you're both right.

[kevinwilly]

So, you know when you first turn the key and you hear the fuel pump prime? And then it shuts off?

And you know like if you have your headlights or radio on with the key in the "on" position and they shut off while cranking?

Yeah- the fuel pump does the same thing. It's doesn't actually run while you are cranking the car over. It relies on the pressure built up from priming to be enough to fire the injectors long enough to start it.

My bet is that the check valve in your fuel pump is shot and the residual pressure is bleeding down when you are out of the car for an hour or more.

[stokeman]

I have a 04 325 and I am having the same problem, however, it takes a few more than 3 cranks. I have a guy looking at it and he seems to think the fuel injectors may be corroded due to build up and thinks they may be leaking during longer periods between cranks, like over night or for several hrs. His thought is that the leaking fuel builds up and floods the engine causing harder starts. I'm going to have him clean the injectors with some professional injector cleaner and see how that works. I should know in the next few days and I will let you know how that turns out.

[ihsnshaik]

Best thing is take it to the local dealer for a diagnosis. I was fed up with something with my x5 with the blower motor or resistor. I paid 59.99 for a diagnosis (coupon) and they said the blower motor works but its on its last legs. He said since you bought the resistor from us we just changed it out for you just in case.

Issues like this its best sorted out by an expert before spending so much money on it.

If it was me I would do the Fuel filter and fuel pump together. See if that changes. I would do spark plugs just for good measure as well. Can be fuel pressure regulator as well.

I had an intermittent fuel pump that was bad. It worked like 20 percent of the time in the morning. I would prime it for 2 minutes on each start. I sold it not for that reason but it was an auto and got it for a steal. I told the guy it was the fuel pump and he had his mechanic check it out and say its the starter. He wanted some money back since I "lied" to him but I told him wait a day or two until your car is done I bet its not the fix. He calls me and apologized and indeed was the fuel pump. His INDY charged him 1200 for the whole job! I bought the car for 1100 and sold it to him for 2800. It was a clean 98 sedan 325i.

Just chime back in after your done fixing it this can help many members.

[Casebrius]

So, you know when you first turn the key and you hear the fuel pump prime? And then it shuts off?

And you know like if you have your headlights or radio on with the key in the "on" position and they shut off while cranking?

Yeah- the fuel pump does the same thing. It's doesn't actually run while you are cranking the car over. It relies on the pressure built up from priming to be enough to fire the injectors long enough to start it.

My bet is that the check valve in your fuel pump is shot and the residual pressure is bleeding down when you are out of the car for an hour or more.

I put a new fuel pump in it 3000 miles ago.

[Casebrius]

Now it's missing badly in cylinder #5. Had the codes read but it's not throwing any except for a O2 sensor. It's looking more like a bad head gasket.... How can I tell for sure? Last ditch effort is to switch #5's fuel injector to another cylinder and HOPE that cylinder starts missing.... or it look slike I'm pulling the head.... NOT a fun job.....