Hard Hot Start... Sometimes

[PDXPeter]

Curious if this is a common problem or not. Occasionally my 325i seems to have no fuel in the line after being driven till warm and then shut off for 15-30 minutes. It feels like the fuel line is just empty. Once it does kick over it runs fine.

[jeffnhiscars]

Curious if this is a common problem or not. Occasionally my 325i seems to have no fuel in the line after being driven till warm and then shut off for 15-30 minutes. It feels like the fuel line is just empty. Once it does kick over it runs fine.

I had a weak fuel pump that died as soon as the car reached OT.

[PDXPeter]

I had a weak fuel pump that died as soon as the car reached OT.

I was worried about that. Fortunately I have a spare. Guess its time to look into swapping it. It only seems to do it on really hot days.

I did find some reference to a commonly failed valve downline near the pump. Couldn't verify the info though so I stopped pursing that idea.

[noid]

Does it just crank for a while and then start and run normal? If it sits for longer (hours or overnight) it starts with little cranking?

If so, I have experienced this with numerous E30's, I have chalked it up to being normal.

Probably a sweet spot between the default and live maps in the ECU, mixed with various other variables which an 80's ECU is trying to figure out.

[PDXPeter]

Does it just crank for a while and then start and run normal? If it sits for longer (hours or overnight) it starts with little cranking?

If so, I have experienced this with numerous E30's, I have chalked it up to being normal.

Probably a sweet spot between the default and live maps in the ECU, mixed with various other variables which an 80's ECU is trying to figure out.

Thats it exactly. Doesn't really cause a problem, just annoying when it happens. I figured its probably related to some tired part that could stand being swapped out.

[MrBurgundy]

Probably a weak pump, or even a leaky injector.

Smell your oil, if it smells like gas, it's most likely a leaky injector.

[15Michaeljoseph]

Fpr?

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[D.Martijn]

I also had hard starting problems when letting it sit for a couple of hours.
Turns out it was the fuel pressure regulator dripping into the vacuum line that goes to the inlet manifold. Causing it to start without fuel pressure and very rich.

[noid]

This has happened on E30's that had new OEM pumps, filters and new OEM FPR.

Think about it guys, if it were a weak pump, or a loss of pressure in the fuel system, it wouldn't start up without issue after a few hours/overnight.

[berndt]

I have the exact same problem. I’ve swapped injectors but that didn’t fix it. Now I suspect it’s the FPR, but I’ve also just learned to live with it. Starts up on the second crank every time.


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[jeffnhiscars]

This has happened on E30's that had new OEM pumps, filters and new OEM FPR.

Think about it guys, if it were a weak pump, or a loss of pressure in the fuel system, it wouldn't start up without issue after a few hours/overnight.

Bentley says a fuel pump can cause a hot no start and that was exactly the cure in my case. I suspect as they come close to being completely worn out, they are ok cold but after expanding they can bind.

Mine would ALWAYS start cold and over the course of several months went from always dying when hot and being able to restart in minutes to not being able to restart at all til it cooled down. Repeated dozens of times.

[noid]

Bentley says a fuel pump can cause a hot no start and that was exactly the cure in my case. I suspect as they come close to being completely worn out, they are ok cold but after expanding they can bind.

Mine would ALWAYS start cold and over the course of several months went from always dying when hot and being able to restart in minutes to not being able to restart at all til it cooled down. Repeated dozens of times.

Right, but this is a different issue. This isn't a case of the car dying while running.

This issue is a matter of restarting after its been shut off.

Its not even really a traditional hot start issue, because restarting shortly after shutting off wont produce the problem, nor will waiting multiple hours, nor overnight, nor will it always happen, and it will always start with prolonged cranking when it is happening.

Its a hard start problem, when mostly hot, but only during a sweet spot in time.

[jeffnhiscars]

So many details to track in these threads.

My earliest symptoms were a hard hot start after stopping and not dying while driving. Eventually it progressed to dying and not starting when hot.

We are probably saying the same thing :)

[Kershaw]

Yep, seen this. Might be an ECU issue, might be an overheated ignition coil, might be any number of issues. Most likely a combination of issues. Very common. As stated before, there's a sweet spot of 15-60 minutes that it happens. Only during this time will the car experience hard starts.

I've thrown dozens of parts at this on a former friend's e30. Every time we thought it was gone, it wasn't. Whatever, it's not a big deal.

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[PDXPeter]

I may have potentially stumbled on the solution in my case. I was installing new plug wires when I noticed that the MAF cap was loose. As it, I could pick it up and see the internal workings of the sensor. AFAIK this is supposed to be a sealed unit so I cleaned it up and sealed it with some RTV. Since then Ive been in several situations where it could have had a hard start and its fired right up.

Could have been the plug wires too... maybe. They were pretty old.