Warm Start Failure - out of ideas

[FLG]

Ah yes forgot. Pretty sure the same company sells the correct injectors than.

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[Varinn]

Maybe I had bad luck, but my car absolutely refused to run when I installed a set of the m50 green tops rebuilt from MaksV on the board, did I just get a bad batch or something?

[jlevie]

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

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You can use larger injectors, but you really need a chip tuned for those injectors. The DME can adapt to 17lb injectors if, and only if, everything else in the engine management is perfect. Anything larger mandates a chip.

There is no performance advantage from larger injectors unless serious internal engine work (or FI) has increased mass flow through the engine.

[FLG]

Agreed. There just a better designed pintle and not expensive either. Worked fine for men with no issues

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[mrgraphics]

Pulled the plugs, pulled the cold start injector, cranked it a bunch. No fuel showed up in the spark plug passages. I put the plugs back in and swapped between 3 different junkyard cold start injectors with no starts.

A new twist: I was at the gym - car was at that hard to start temperature. Cranked and cranked, same story. Then I remembered I had some carb cleaner in the trunk. Sprayed some in the intake, and she fired right up - instantaneously.

After doing Jlevie's test and the car wouldn't start, I was able to repeat my carb cleaner trick.

Does that change my approach?

[jlevie]

That sounds like a problem with the cold start valve or controls, or intake leaks. A smoke test will tell if intake leaks are present.

[mrgraphics]

I'm looking for a place to do the smoke test. What would you suggest I do to test the cold start valve and controls, since it seems like I replaced all the elements that determine it's engagement (sensors on thermostat housing).

[Quadrajet]

You could just use some sort of clamp to "pinch" the fuel line that feeds it. I used a small pair of needle nose vise grips wrapped with tape. It negated that as an issue for my problem....but that's a whole other story.

[future rs]

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

I have a very intermittent issue similar to this. Please let me know if you track down the culprit. Mine will do this say... 1 time a week or less. And seems to happen a lot less now that the temperature is dropping.

[mrgraphics]

Do I need to only do an intake system smoke test, or do I have to go with the one that they plug the exhaust and pressurize every single area of the engine system? Price is considerably less for the former.

On another note, I was able to verify that my cold start injector does indeed fire. But of the three I have, the best one was not the one in my car. Now that it is we'll see if that was simply the issue.

[jlevie]

Do I need to only do an intake system smoke test, or do I have to go with the one that they plug the exhaust and pressurize every single area of the engine system? Price is considerably less for the former.

Since leaks in the block are an intake leak, you need the test where the exhaust is plugged and smoke is fed in via an adapter that replaces the AFM. Smoke pressure needs to reach 2-4psi and be held there for several minutes.

[mrgraphics]

It's the cold start injector. It's not firing when it should. I waited 3 hrs after a long drive home - the premiere witching hour for the problem. Car was cool - not cold, with next to no heat registering.

I pulled the cold start injector and pointed it into a clear bottle and plugged the hole. Car would need it to fire. No fuel came out of it.

Then I sprayed carb cleaner in the cold start valve hole, sealed it up with tape, and the car started right up. This is definitely my problem.

Hooked up a multimeter to the cold start injector plug and cranked. No voltage. Then I waited another hour and retested. . . voltage. Reminder: I have tried 3 different thermo-time switchs, including a brand new BMW one that cost me $100.

[mrgraphics]

What I think I'll do is this: Using my voltmeter, on each plug (thermo-time and cold start) I'll check for voltage on the starter circuit, connecting the ground of my multimeter to chassis.

http://www.hglmotors.co.uk/ts/pic/thermo.gif

Then I'll check for continuity between the two connectors on the other line (which is essentially the ground I believe). Question: do I need to disconnect the ECU before doing this particular test?

[mrgraphics]

Interesting results:

Cold, the plug to the Thermo Time switch has a ground and 12V. Just as it should. However, once it gets really hot in the engine bay, both sides of the plug go hot (12v). Continuity to the cold start injector is always maintained. But instead of ground, it's also getting double 12v.

I had a small fire a long time ago at the FPR, and that plug got pretty burnt - not melted but crusty. I think what is happening is that as the plug gets hot, there is a small amount of expansion that causes the 12V side to contact the ground. That also causes the Thermo Time Switch to get double 12V. Since it gets ground through the plug itself, I'm sure it's getting quite hot, which is why it takes so long to come back to a reset / cool state (it no longer corresponds to the coolant temperature.)

I'm going to cut the old burnt connector off and solder on a new one, and hopefully that fixes things.

[mrgraphics]

I rebuilt the wire harness and it's still doing the same thing (Thermal switch sending 12V along ground to cold start injector.) There is a short somewhere else.

So I simply disconnected the plug to the thermal switch, and made a ground connection jumper wire for the cold start plug. Yes, it always fires when I start, but once the car starts the cold start injector turns off. It just means on hot start it revs a bit higher than normal at first.

Yeah it's a hack, but it's also an e30.