Ideas on a random no-start condition?

[dsphil]

Did you replace the main relay?

[LateFan]

New in-tank Airtex fuel pump this weekend. Starts (barely), barely idles, sputtering black smoke, won't stay running...

Inside of tank looked very clean. Only a tiny bit of grit on the pickup screen below the intake pipe.

Need to re-test cold start valve now that thermo-time switch was replaced. We may not be getting a cold-start squirt.

The coil showed higher numbers than the Bentley chart shows...like 1.5 ohms vs .5 in Bentley. Am I not getting enough spark? I'll re-check that tonight.

[LateFan]

It is always a good idea to tee in a pressure gauge in the fuel line going into the fuel rail when troubleshooting fuel related problems. You can monitor the pressure during running and dying. If the pump whines then it is on its way out. Check the pump sock for particles. It could be completely clogged.

I've read that here. Part of me is thinking, just put that pressure gauge money toward new pumps.

This car sat for a while, so clogged pick-up is a possibility.

[LateFan]

Fuel pumps are often intermittent when they fail. Kinda miss mechanical fuel pumps that would leak when they went bad, similar to a water pump.
Sounds like you need at least one fuel pump. If it was for my kid, I would replace them both and a new filter. Would hate for him to get stranded in some strange place.
The rising idle is more than likely your ICV. You can ruin them by cleaning them. The best test is if they are working right.
You can drill a quarter inch hole in a penny. Pull the air meter side of the hose at the ICV. Put the penny there and re connect. It should idle at about 600rpm.
Good until you buy a new one.

I agree - the idea of this car is so he can take it on trips alone with minimal tools and trust it.

Pumps are probably next. I may do the Chevy Vega in-tank thing for budget.

I did clean the ICV - I thought that was a good thing (?). It rattles when shaken. It hums when running. It passed the multimeter tests. When I unplug it while running the engine shoots up, then nearly dies, catches itself at 800 or so, races again. With it plugged in, there is a little bit of cycling when fully warm.

I've heard about the penny thing. You're putting it on the hose to the intake boot (this is an '86 E), or on the hose to the cold start valve on the intake?

[dnguyen1963]

It is always a good idea to tee in a pressure gauge in the fuel line going into the fuel rail when troubleshooting fuel related problems. You can monitor the pressure during running and dying. If the pump whines then it is on its way out. Check the pump sock for particles. It could be completely clogged.

[bddog]

Fuel pumps are often intermittent when they fail. Kinda miss mechanical fuel pumps that would leak when they went bad, similar to a water pump.
Sounds like you need at least one fuel pump. If it was for my kid, I would replace them both and a new filter. Would hate for him to get stranded in some strange place.
The rising idle is more than likely your ICV. You can ruin them by cleaning them. The best test is if they are working right.
You can drill a quarter inch hole in a penny. Pull the air meter side of the hose at the ICV. Put the penny there and re connect. It should idle at about 600rpm.
Good until you buy a new one.

[LateFan]

Changed the crank position sensors (2). No change, but they are due for replacement anyway. I've replaced the coolant temp senders (all but the dash gauge sender, which is apparently NLA).

I replaced the fuel pump relay and ECU / DME relay - cheap and eliminates those possibilities.

We are going to check the cold start injector again with the new temp-time sender, but that will have nothing to do with warm starting problems.

I think the symptoms are pointing to fuel pumps, while I've been chasing other things. I'll check the two pumps next, but I'm not hearing any hum whatever from the in-tank pump. The under-floor pressure pump is whining intermittently (maybe strained from pulling from the tank). The tank is maybe 2/3 full, and I've learned it can run on the pressure pump alone if it's not low. We may be just on the edge of it not starting all the time.

The creeping idle still needs to be solved. No vacuum leaks anymore. It may be those water senders, but we haven't re-tested with the new ones yet. I hope it doesn't come down to the idle control module in the glove box - another expensive gadget to replace!

[JoeyZ]

Any news in this. Im running into the same issue now. It seems as though its limited to days where its cold out.

[LateFan]

Crank position sensor on the bellhousing. They're cheap so replace both if you can. My eta did the same thing you describe in post two - start, run fine till warm then...dead. It was that sensor.

BUMP

Welp... that wasn't it. Changed both out with new OEM BMW. Still random no-starts. Or, it seems it starts for an instant but won't keep running.

It almost acts like it's out of gas. We're getting some intermittent fuel pump whining - could it be not enough fuel pressure?

Does a fuel pump relay fail all at once, or can it act intermittently?

How do you test the fuel pump vs the in-tank suction pump? Is this in the Bentley?

[bddog]

A creeping idle that goes to 1200 is not normal.

[LateFan]

Is the slowly creeping high idle related to any of this? Or do we have overlapping problems?

[Cephas]

I figure if one of those goes bad the most likely result would be a rich or lean running engine. Not a no start.

[LateFan]

Interesting... CPS...I wouldn't have thought of that. Good idea.

To answer others questions, the O2 sensor is new, and the ICV has been cleaned and tested as OK. I keep trying to convince myself to replace it, but it seems to be working fine.

Another thought - what all happens over those 9 minutes...other than temperature? Could it be one of the two temp sensors that sends signal to the ECU? Once at full warm, it either sends or doesn't send the correct signal, and the computer screws up?

[Cephas]

Would they even get the car to stumble or start at all with a failed cps?

Yes. Mine was intermittent. Usually died out when the car was warm and worked again after it cooled completely down.

[Swanny]

Would they even get the car to stumble or start at all with a failed cps? Granted when mine failed it was from an 87is with just the single sensor on the crank but I had 0 fuel running through the lines because the ecu was refusing to run spark OR fuel.

Easy enough to test both. Could be an intermittent failure....