I have a problem that has numerous threads on here and on youtube, but none have solved my issue. I have trouble shot my issues, replaced parts... and no improvement.

My issue... long crank on my 1988 Camaro IROC 350 TPI. No check engine light and no codes. Car takes about 4 seconds of cranking to start, then there is a cloud of smoke at the exhaust. No other issues once car is running - runs smooth and responsive.

I have checked and replaced: fuel filter, plugs, plug wires, coil, distributor, oil pressure sending unit (above fuel filter), and ICM. I cleaned MAF and verified MAF is not problem by disconnecting sensor. confirmed all injectors have same resistance (including cold intake injector) - so rules out leakage. Checked fuel pressure on the rail and no leakage. Checked regulator... no fuel in the vacuum line. I confirmed fuel pump kicks on when ignition is cycled. Checked all relays and fuses.

i am at my wits... I checked spark, fuel, air, codes.

the strange thing... I have vacuum in my fuel tank. I remove my cap and let the hiss out... and car starts instantly.

thoughts?

Injector resistance does not rule out leakage. In fact it tells you exactly NOTHING about the flow characteristics, lack thereof,or ability of the injectors to seal when they are off. Resistance tells you something (but not everything) about the condition of the driver coil. That's all.

GD

Thanks for the clarification. I should have been more clear - in combination with fuel pressure test (holds pressure) I assume my injectors are not passing.

If you have vacuum in the tank then the tank is not venting properly. Check the vent valve and line back near the tank.

GD

What is acceptable leak down rate on the fuel rail? I loose 10psi after 5 minutes and 20psi in 10 minutes. Suspect leaking injector in that case? If it was leaking check valve in the tank it should have bled down faster.
Doesn't explain the tank vacuum tho... another gremlin to chase down.

That's pretty normal leakage rate I would say - the TPI regulator's don't seal perfectly - especially if it's original.

The only way to for-sure rule out the injectors is to remove them and test them in an injector flow bench. At that point though you may as well just replace them.

GD

after you run the car you can also pull the plugs. If you have a wet cylinder then you have a leaky injector

I think this is your smoking gun "the strange thing... I have vacuum in my fuel tank. I remove my cap and let the hiss out... and car starts instantly." if you change a variable and it solves the issue typically you have found the cause. If it consistently cranks with no issue with the fuel cap off then fix the tank vent or leave your cap off until you can replace it.

What color smoke? I would go to the spark plug and see what it looks like (post pictures of them if you would like) this should tell you if they are swimming in gas or water.

Also you can buy endoscopes that work with your phone pretty cheaply off amazon/ebay etc. Run the camera into the cylinder through the spark plug hole point the camera back to the intake valve (they usually come with mirror attachments) and see if you are getting gas dripping in with the pump running (don't crank over the engine with the camera in it our you will have a real bad day), this isn't 100% but easier than a full bench test of the injectors. On some intakes you can fish the camera in directly under the injectors but I don't know if you could do that on these cars without taking the runners off. I wouldn't start here though, start with the tank issue.

Pull vacuum line off of pressure regulator while not running. Fuel in vac line = replace diaphragm. If no fuel, view regulator while running. Any fuel from regulator = replace diaphragm. Also try cranking as soon as the pump begins to prime (during the 2 sec prime, not after). At that point you will have max pressure. See what happens.

Your smoke is probably from worn vavle seals.

I agree with check the tank vent valve. If removing the vacuum from the tank can turn on and off the problem like a light switch, there is no reason to look elsewhere.