Warm Start Failure - out of ideas

[mrgraphics]

Here's the situation (1986 325es):

Cold - car starts right up. Hot (as in turned off and temperature needle hasn't dropped down too far) starts right up. But in that range where there is still a bit of coolant warmth, such as after 2 hours or the needle just registers on the first mark, it won't start. It'll stumble and almost catch, but then dies. There is a smell of fuel.

Once running, it runs forever without one single problem. No idle issues, no hesitations . . . beautiful. But it almost stranded me today and I'm pretty fed up. Here's everything I've done:

New . . .

• Sensors on bell housing (CPS and the other one)
• All the sensors in the thermostat housing (with oem ones, not FAE crap)
• Fuel pump (Tre 255) and 2nd pump delete
• Fuel filter
• One way value near fuel pump to maintain pressure in the fuel line after engine shutoff
• Cap and rotor
• Plugs

I've also:

• Rebuilt engine (head gasket, intake gaskets, etc.)
• Rebuilt MAF
• Swapped cold start injectors
• Swapped coils

Ideas on where to go from here? There is a direct correlation to the needle dropping to the first tick and the level of difficulty starting. At the first tick, near impossible until it gets completely cold.

[jlevie]

One possibility would be leaking injectors. After the car has sat for enough time to duplicate the problem, pull the plugs and crank over the engine with the cold start valve disconnected. If fuel sprays out of the cylinders the injectors are leaking gas into the cylinders.

[mrgraphics]

Let me make sure I've got you right:

• Turn the car on but don't start it - check temperature and see that it's in the problem area of the needle
• Pull plugs
• Pull connector off cold start injector
• Crank engine and look for fuel to come squirting out of where a plug used to be

[jlevie]

Correct.

[Varinn]

I have this exact same problem on my 1990 325i, and as Jlevie suggested I'm trying to get booked in somewhere to have them perform a smoke test and I can post back with the results when I can. It may be a bit though as I'm completely booked up for the next couple weeks with some other things and the shop I've been trying to get into has no openings this week.

When the prblem shows up for you, do you find that the car will crank extremely well and turn over really fast as if it's trying to start, but not able to catch well enough to fire up? On mine the car will normally start on say, the 2nd revolution (<1 second) but when its in the warm start period it will crank fast for about 5-6 seconds before finally firing up

[mrgraphics]

Mine will crank well, almost catch, and then nothing. Then I'll crank it for a while with no catch. Let it sit for a few minutes, it'll almost catch again . . . ad nauseum. Then if I walk away for about an hour, it'll start.

If it is a leaking injector, does that mean a complete injector replacement, or will a rebuild of seals and pintle do the job?

[Varinn]

Hmmm... That sounds slighty different then mine, for me if I crank it for the normal 1 second or so it will stumble and die, but I'm able to attempt starting again and it will do the same thing until I've done a total of 5-6 seconds cranking time. As with yours a cold and hot start are both perfectly fine, and the problem only seems to exist after 45 minutes to an hour and a half after a drive up to full temp. Any more or less cooldown time results in starting normally

[Varinn]

Levie, do you have a preference on where to get rebuilt stock injectors at a decent price, if that ends up being the issue

[Quadrajet]

Along with Jlevie's line of thought, perhaps the Cold start injector is injecting when it's warm. Just another thing to check for.

[jlevie]

Levie, do you have a preference on where to get rebuilt stock injectors at a decent price, if that ends up being the issue

I send injectors to RC Engineering for cleaning, rebuilding, and flow testing. I think the last batch ran $25/injector.

[mrgraphics]

In my situation, I did have the presence of mind to disconnect the cold start injector. It didn't make a difference.

I was also curious about injector options. . . but I can get a new injector for $31.79 at Rockauto, so I'd probably go that direction vs. rebuilding a 26 year old injector. It would be a multi-port one too, so better atomization over stock.

[FLG]

There's a company on ebay that sells rebuilt flow matched m50 17lb injectors that are good for an m20 for around 120$ a set

Sent from my Galaxy Nexus using Tapatalk 2

[mrgraphics]

FLG - are those the green top M50 17# injectors? I've done a bunch of reading, and I know I need low-impedance injectors for my 86 ETA.

[Quinthirty]

Have you tried replacing the fuel pump relay?

[mrgraphics]

I swapped the O2 heater relay and the fuel pump relay at the time of the problem, since they are the same. No difference. I guess there is an off chance that they both are bad, but unlikely.