Weird E30 Problem

So my '90 325i has developed a hard start issue. When it's cold, it starts right up. When it's hot, it starts right up. But when it's been driven, then parked for a half hour to an hour, occasionally it's hard to start. It still starts every time, but sometimes it will crank for 10-20 seconds before starting. And still it's not every time, but it might happen once a week or so. It got a new fuel filter about a year ago and a new fuel pump and FPR about 6 months ago, so I don't think either one of those would be an issue. It kinda acts like a bad accumulator on an old CIS vehicle, but I don't think they have a fuel accumulator, do they? Every time it's happened I've been out and about, so I haven't really had a chance to do any testing/diagnosing. Any common culprits to look out for?

This is exactly what my '88 did as the fuel pump was dying.

Fuel pump relay under the hood (IIRC). Both of my former E30s suffered from this.

I have seen this after new fp and relay and I am thinking that it is the coolant temp sensor feeding bad info to the ECU, possibly combined with a slight vac leak (remember - in an e30 and oil leak is a vac leak...) but I didn't actually try to solve it since the car always started - it just needed some extra cranks.

Giant Purple Snorklewacker wrote: remember - in an e30 and oil leak is a vac leak...

That really threw me off the first time I forgot to put the oil cap back on after an oil change, and it ran like total crap! I guess I'll probably just change the CTS and the fuel pump relay since they're cheap, just to at least eliminate them, and hopefully fix the problem.

It could be the fuel pump - mine exhibited similar symptoms for months, up until the day the pump died altogether.

Crank position sensors tend to be heat sensitive too.

Is the replacement pump of sufficient quality to have a check valve? 10-20 seconds is a long time for an efi car to crank when the rest pressure goes away, but the rest of your symptoms fit.

Streetwiseguy wrote: Is the replacement pump of sufficient quality to have a check valve? 10-20 seconds is a long time for an efi car to crank when the rest pressure goes away, but the rest of your symptoms fit.

It was a brand new Bosch unit, and looked exactly like the one I took out of it, so I would assume it's of sufficient quality.

Doesn't that car have two fuel pumps?

Not necessarily, and the in-tank transfer pump shouldn't keep it from starting.

First, you need to determine if this is fuel or spark. That's step one.

Suggestions above are generally pretty good. I'd add (if spark) the white relay in the 'bonus' relay panel in between the ABS unit and the shock tower. I just spent days diagnosing one of these that would cause intermittent no starts. If you can find a buddy with an E30 to swap components around it helps. This particular relay is only $14 at the stealer.

shadetree30 wrote: Doesn't that car have two fuel pumps?

Nope, '88-up only had one. Mine's a '90. Sorry, I may have forgot to mention that.

ddavidv wrote: First, you need to determine if this is fuel or spark. That's step one.

Yeah, I know. I need to pack a few tools and a can of starting fluid with me, and check a few things out next time it happens.

Thanks for all the suggestions thus far!