Hard Hot Start... Sometimes

[IS300E30]

1990 325is. I have this same hot start issue very rarely, but it happened last week which surprised me because it's been a long time. I went into CVS for about 10-15 minutes so I guess I hit that "sweet spot".

I have new injectors, FPR and a couple year old fuel pump. I replaced the OEM fuel pump about 4 years ago and the check valve failed on it within a couple months. Bad batch of aftermarket fuel pumps is what I heard from several sources.

Anyways, I've chalked it up to normal behavior as you have done too.

Are you saying the fuel pump from a bad batch was the cause of your hot starting issue?

[tomstin]

What is the condition of the fuel tank? I recall a discussion years ago where there was a lot of debris in the tank. When the car ran for awhile, or the fuel was low, the debris would collect on the pump sock and clog. After the car sat, the debris would disburse and the car would run fine until the next time.

[IS300E30]

What is the condition of the fuel tank? I recall a discussion years ago where there was a lot of debris in the tank. When the car ran for awhile, or the fuel was low, the debris would collect on the pump sock and clog. After the car sat, the debris would disburse and the car would run fine until the next time.

My fuel tank is new

[82eye]

Are you saying the fuel pump from a bad batch was the cause of your hot starting issue?

spectra or delphi - don't remember which - had a couple bad years. the check valve inside would fail and cause issues. both spectra and delphi are aftermarket jobber parts, but both manufactured for other brand names as well. i don't think it affected oe brands for the e30, but if you replaced with one of their pumps you could run into problems.

[IS300E30]

If my mechanic checked the fuel pressure and it held. Could the check valve in the exterior fuel pump still be bad?

Or if he checked the fuel pressure at the rail and the fuel pressure held, that then would eliminate any concern of the fuel pump being bad (or the check valve inside being bad)?

[IS300E30]

Anyone with this issue recently changed your Air Flow Meter for a refurbished one and this then started to occur, or adjusted your Air Flow Meter and then this started up?

[moatilliatta]

https://www.ftech9.com/new-products/993-ssr-pp

[laidback93]

Are you saying the fuel pump from a bad batch was the cause of your hot starting issue?

Sorry, just saw this.

The bad pump and check valve caused a more severe cold start issue. It would be a bitch to get it started while leaving work at the end of the day.

The hot start issue hadn't popped in a long time after I replaced the fuel pump again. But then it did again recently which surprised me. Always during that 10-15 minute window. Any shorter or longer than that and she fires right up.

[SpecM]

Yup, mine does this, maybe 1 time in 3, but always in the 10-30 minute window. Starts and runs like a champ otherwise.

'87 325is, new fuel tank and converted to single-pump (new VDO unit), rebuilt injectors but older FPR

[e30m3s54turbo]

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.

Thank guys.
I had bad adjustable fuel pressure regulator. The vacuum line was pouring fuel into vacuum line. That’s why it was running rich.