Takes a long time to start after sitting in the cold weather ---

[alwayscode390]

Thanks for the links guys!!! ---

[Hib Halverson]

Typically, on a cold start, crank time will be longer. Looking at that footage, yours seems right on the "line" between ok and a little long. I say that in part, because of the fast crank speed---you must have a Odyssey battery or something like that---which should have the engine firing in a shorter time than most other ZR1s with a battery, cables and starter in the typical condition those parts on most cars would be.

I'd run the fuel pressure tests in the factory service manual just in case you've got a leaking injector.

[alwayscode390]

OK, I will definitely check the fuel pressure soon. I appreciate the advice Hib, thanks ---

[Hib Halverson]

Originally Posted by Paul Workman

Well, 6 seconds seems a bit on the long side. Mine is about 3-4 seconds AFTER the fuel rail is charged.

Ya know, when I posted above, I didn't really time that video, but Paul must have and I agree with him, if it's six seconds, that's a bit much. My 95's start time after fuel pump shut off, is about the same as Paul's

Before rolling the ignition switch over to START, turn the switch to the "ON" position and listen to the fuel pumps. When they stop running, the rail is up to pressure, but it takes maybe a couple seconds before the rail (on my 90) is up to pressure. If I roll to the START position before the rail is charged, I can see how that might invite a backfire (NOT GOOD) at the very least. But, also add a second or two to the normal 3-4 second (cold) start time.

Once it has been started and run that day, the start time is much quicker - sometimes under a second!

My 95 has always behaved the same way. Couple of points, though...when the pumps stop running, the fuel system may or may not be at the correct pressure. The pump-cut off is not related to fuel pressure. If you've got a pump out, leaking pumps, leaking regulator or leaking injectors, its possible the fuel pressure is not at a nominal level when the cut-off occurs. The cut-off is related to how long (2 sec.) the ECM will allow the pumps to run without an rpm signal, not fuel pressure. When you turn to "run" the ECM turns on the pumps but, if it doesn't see the engine running after two seconds, it turns off the pumps.

Also, if you've got the key in start, the engine is cranking but fuel pressure is not up, the engine will not backfire nor are you inviting it to do so.

And, if nobody told you, you want to hold the switch in the START position for almost another second after it fires to let the motor rpm start coming up. This avoids backfires which tend to blow hoses off the MAP and the Fuel Pressure Regulator (for starters) at the very least, or rupture diaphrams in said parts (rare, but happens). This trick might avoid a plenum pull to re-connect a vacuum hose. Just sayin...

P.

Holding the key in "start" after the engine is running is pointless and might not be the best thing for the starter. Intake manifold backfire won't happen once the engine is running.

The infamous backfire occurs if the start cycle is interrupted but the key remains in "run" rather than going to "off". If the engine attains some rotation but not enough run, the ignition is hot and the engine is at a certain position with the right intake valve open, sometimes air-fuel mix in the plenum will ignite. The resulting "bang" sometimes takes out the MAP sensor and/or blows vacuum hoses off the nipples at the front or the rear of the intake manifold.

[scottfab]

Originally Posted by Hib Halverson

Ya know, when I posted above, I didn't really time that video, but Paul must have and I agree with him, if it's six seconds, that's a bit much.
...snip....

I'm measuring 4 sec on the video posted.

As for holding the key on a bit longer after detecting a start, the empirical
evidence is there from many owners. This eliminates the otherwise usual backfire from releasing early. I would say 1 sec to be an excessive estimate, more like 0.5 sec is all that is needed. Very repeatable.

[alwayscode390]

Just went back out, tried with priming the pumps ... and it took about 5 seconds. I don't think it made a change. I feel alright about it though at this point ---

[Paul Workman]

Originally Posted by Hib Halverson

Ya know, when I posted above, I didn't really time that video, but Paul must have and I agree with him, if it's six seconds, that's a bit much. My 95's start time after fuel pump shut off, is about the same as Paul's
My 95 has always behaved the same way. Couple of points, though...when the pumps stop running, the fuel system may or may not be at the correct pressure. The pump-cut off is not related to fuel pressure. If you've got a pump out, leaking pumps, leaking regulator or leaking injectors, its possible the fuel pressure is not at a nominal level when the cut-off occurs. The cut-off is related to how long (2 sec.) the ECM will allow the pumps to run without an rpm signal, not fuel pressure. When you turn to "run" the ECM turns on the pumps but, if it doesn't see the engine runningk after two seconds, it turns off the pumps.

Also, if you've got the key in start, the engine is cranking but fuel pressure is not up, the engine will not backfire nor are you inviting it to do so.



Holding the key in "start" after the engine is running is pointless and might not be the best thing for the starter. Intake manifold backfire won't happen once the engine is running.

The infamous backfire occurs if the start cycle in interrupted but the key remains in "run" rather than going to "off". If the engine attains some rotation but not enough run, the ignition is hot and the engine is at a certain position with the right intake valve open, sometimes air-fuel mix in the plenum will ignite. The resulting "bang" sometimes takes out the MAP sensor and/or blows vacuum hoses off the nipples at the front or the rear of the intake manifold.

I'd heard about the backfires before it happened to me once. The problem, like you alluded (sp?) to occured in that split second where it sounded like it fired, but actually failed to fully catch. Maybe it did fire on a cylinder, but missed the next one or two. In any case, I released the key, and POP! Just that quick and troubles followed.

Lucky for me it was just the MAP hose (now secured with a small tie-wrap as insurance against that happening in the future) and no further damage. Now I hold the key - perhaps not for a full second - prolly less than that, but I make it a point to hold it in START until I'm absolutely sure it is really running (i.e., more than just a single cylinder or two that fired, is my intention).

I know the bendix on the AC/Delco starters on the gen I SBC/BBCs are designed to "free wheel" when the engine starts and the speed of the flywheel over-runs the speed of the starter. I'm pretty sure it is the same for the LT5 starters, but can't say for sure. But, in reality the length of time I hold the switch in the START position is "under a second" - more like half a second or maybe less before I'm satisfied the motor is really running (for good) and the key is released. So far so good, far as my starter goes, and NO backfires since, far as I know. However, once in a while I will hear a cylinder fire and not be followed by one or more cylinders following. I'm glad I was still holding the switch in START - smoothly passing over until the motor catches for good.

Not being in a big hurry to release the switch from the START position was foretold to me, and then taught first-hand by a few experiences since...YMMV. Just sayin.

P.

[alwayscode390]

Thanks Paul ... I love words of wisdom like that.

I will definitely be thinking of this every time I start my car from now on. ---

[Tyler Townsley]

Originally Posted by alwayscode390

OK, I will definitely check the fuel pressure soon. I appreciate the advice Hib, thanks ---

In the calibration there is an 'accel pump' shot of fuel when the motor turns over in the crank cycle. There is a 'map' that is selected by the ecm and this map selects a time of the injector shot based on temp and a multipler that can be changed. I had to change this figure to get the prototype to start. There may also be other time base controls that are derived using temperature. I remember a discussion somewhere that indicated there was a time delay of this 'fuel pump' shot to allow for oil pressure and it was delayed based on temperature among other things. As has been pointed out your troubleshooting starts with a fuel pressure guage to make sure the pressure is adequite then you watch the fuel pulse timing and volume.

Tyler

[alwayscode390]

I just got back from installing a new Odyssey battery.

Not sure if it was the warm weather (70) ... or because I REALLY needed a battery ... but the car seems to love it. Starts after 1-2 seconds now , instead of 5-6 !!!



YAY!!! ---