2.8 hard start when warm

[f85gtron]

I experience long cranking when car is warm. It fires right up when cold, or i crank it immediately after shutting it off.
The relay and pump both run for a couple seconds when ignition "on"  not sure about "run" position.

If i blip the throttle during cranking, it fires up.
Ron

[Fierofool]

At cold start, the cold start injector enriches the mixture for it to start.  The fuel pump should only run about 2 seconds before starting.  The solenoid click is an audible indication that the pump has been turned off, either due to elapsed time or setpoint pressure has been met.  Whichever comes first. 

The cold start injector is out of the loop when the engine is warm, so it sounds like you may not be getting enough fuel.  Fuel injection engines are designed so that the accelerator doesn't need to be depressed during cranking like the old carburetor engines.  Carburetors had accelerator pumps to squirt a small stream of fuel to enrich the mixture each time you depressed the pedal.  The ECM takes care of that function, but with the engine warm, the Coolant Temperature Sensor is telling the ECM that it doesn't need the cold start injector's little squirt of fuel.  I wouldn't think the ECM would enrich the mixture just based on a signal from the TPS.  I think the TPS is also supposed to be out of the loop until a run signal is obtained from the ICM. 

It could be a partially clogged fuel filter or weak fuel pump.  When the engine is warm, try turning the ignition on and when you hear the relay click, turn it off for about 10 seconds then turn it back on to see if you hear the click again.  I have done   that on my 87, having to cycle it 3 or 4 times until I didn't hear the relay.  That told me the system was up to pressure.  Then it would start. 

[f85gtron]

As you've recommended, I'll cycle the pump a couple-few times and see if that does it.
I've temporarily removed the csi in a previous effort isolate a potential leak down condition, which ended up being the regulator.

I've tested the fuel pressure before and everything checked out fine, but, what i would like to know is, what is an acceptable leak down rate in lbs/min?
Ron

[Fierofool]

I forgot about the pressure regulator and cold start injector service.  I don't think I've ever heard of any stated time, but it should be able to hold for a minute or two.  Ideal pressure is 43.5 lb at prime and it will drop to around 39-40 at idle, so it probably shouldn't drop below 40, I would think. 

[f85gtron]

I finally got around to testing the fuel system. I've got 35# at idle and 37# at ignition off after running. Then 26# after 15min and 20# after 30min. That seems acceptable.
I shot this video of the guage during a long crank start to see the behavior of the fuel system. I didn't notice anything abnormal, so i guess it's time to look elsewhere?

[Fierofool]

Ideally, you should have about 42 psi at prime-ignition on, no start.  Idle pressure should be in the range of 37+.  I don't think you should leak down as low as you're going.  Looks like you have an injector leaking.  If it were the pressure regulator leaking, I don't think you would have the higher pressures if your regulator were bad.  The injectors are rated at 15 lb/hr (about 2 gallon) at a stock regulator pressure of 43.5 psi.  A new regulator and pump and no leaks on the system should give you at least 43 psi with key on, no start.  Warm idle should then be about 40 psi or a little higher. 

[f85gtron]

It's in the video, but I've forgotten to mention that it's showing 43# + at key on. The 37# is ignition kill. My injectors (recently blueprinted and matched to 16.5#) have been checked for leaks outside the car, attached to the rail and they where dry, not a drop. 
It has always had this behavior since i bought it and in spite of any changes I've made. I'll tuck a nickel under the spring in the regulator and get the pressure up a bit, then measure again.
Ron
P.s.  Since the key on immediately jumps to 43# before the starter has a chance to engage, is the leak down really a concern, a red herring?

[Fierofool]

Why are you running 17# injectors?  Does it run rich?  Have you checked your MAP sensor and the line between it and the pump?  A slight leak could account for the low pressure when running but that leakdown is probably inconsequential since your pressure builds to spec.  Instead of putting a nickle in the regulator, try a dime.  Don has developed a way of making the stock regulator adjustable by drilling a hole in the regulator cover and install screw.  http://www.fuelinjectorconnection.com/calculator/index.html

[f85gtron]

I'm running larger injectors, at the advice if the guys at fuel injection connection, in account of an  opened up intake, ported and matched plenum and manifolds, ported heads, ported exhaust, ported logs, y pipe. 
Believe it or not, it doesn't smell as rich as it used to before i did all that work....but it's still mildly rich.
I'm wondering if the chip has been burned or someone messed with the fuel maps because when i originally got the car the ecm was exposed and the cover to the prom and chip was off.
Ron

[Fierofool]

I think I still have a stock ECM that you can swap in for a trial basis, if you want.  I can bring it to Heavy's on the 15th.  You don't need 17# injectors until you're at 160hp, like the 3.4.  I doubt you gained 10hp, so assume you're at 150hp, you would only need 16#.

My thoughts are that the mixture is a little rich, so at cold start, that's taking the place of the deleted CSI.  When the engine is warm, the air/fuel mixture is a little rich and that may be why the throttle blip throwing in a quick shot of air leans out the mixture to the level of a warm engine. 

[f85gtron]

We might just solve this mystery yet.
I would like to take you up on your offer to loan the ecm. That would help eliminate the chip burn theory.
I forgot to mention i installed 1.6 rockers too. 

[Fierofool]

The Warrior Project has a 85 Fiero Factory Helms Service Manual for sale, too.  Reduced from $50 to $30.  Maybe you could write a few new chapters to add to it. 

[f85gtron]

Got the loaner ecm installed. Exhaust smells normal, and has a lot more pep. My ecm or chip must be to blame. True to my eagle scout background, I'm always prepared and have a complete 7730 setup ready just for such an occasion;)
Thanks for everyone's help
Ron