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Old 07-03-2016, 08:48 PM   #1
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Default Hard to start after sitting for a couple of weeks

Gents,

I'm posting in this forum because I did not have the problem before the Rotrex install, but it may have nothing to do with it. Maybe it's the tune.

Although I drive the '99 to and from the track, I don't drive it much otherwise. I pull her into the garage after an event, and she might sit in there for a while. If more than a couple of weeks go by, she's ridiculously hard to start. I may have to crank it for 30 to 40 seconds. It reminds me of starting a Briggs&Stratton lawn mover for the first time in the Spring. I can smell gas, so I know it's getting fuel. It seems like one cylinder catches, and it starts running at about 100 rpm. Then another cylinder fires and the revs go up, then another cylinder, and then the last. After that, it runs fine. I don't know how many days it takes, but I never have a problem just overnight. It doesn't seem to have anything to do with the temp, either. Just time.

Thanks much.

Happy Birthday America,
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Old 07-05-2016, 12:16 AM   #2
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Don't these have a returnless fuel system? Is it possible that all of the fuel is drained from the rail and not fully primed when hard starting?
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Old 07-06-2016, 06:04 PM   #3
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Gents,

The car has sat for a couple of days in the garage. All the plugs looked good. No cylinder exhibited a strong fuel smell with the plug removed. I put the plugs back in and primed the fuel pump, then I tried to start her. It took five or six seconds of cranking to get her to kick over, but then she ran fine. If she gets harder to start the longer she sits without running, what does it mean?.

The real issue is my next event is a month away, and I want to put her up on jack stands to do some things. Starting her in the garage on jack stands every few days is not my favorite thing to do.

Thanks,
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Old 07-06-2016, 06:20 PM   #4
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Old 07-06-2016, 06:28 PM   #5
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Not sure what your point is. I already have one of those.
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Old 07-06-2016, 06:45 PM   #6
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How am I supposed to know since you didn't mention it in original post?

My point since you didn't understand, was that your battery may not be as strong as it once was, or that the additional drag of the supercharger might be enough to slow cranking when the battery is not topped off.

Go ahead and disregard it then...
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Old 07-06-2016, 06:51 PM   #7
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Translation: your battery is dying
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Old 07-06-2016, 06:58 PM   #8
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I don't think so. The idea that it can crank the engine over for 30-40 seconds after sitting for a month but be too weak to light her off doesn't make any sense.
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Old 07-06-2016, 07:25 PM   #9
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That post makes it sound like you have a battery tender but are not using it and letting the car sit for extended periods of time?
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Old 07-06-2016, 07:30 PM   #10
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My friend, nothing would make me happier (in this situation 'cause there's a lot of happy things I can think of...) than to tell you you were right.

Yes, she sits without being on charge. Although I don't accept your premise, it is easy for me to test, and I will do so.

Thanks,

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Old 07-06-2016, 07:34 PM   #11
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The premise is not rocket science. If I let my car sit for too long without the charger on it, I can still get it to crank for quite some time, but if the cranking RPM is not high enough when the battery is partially discharged, it won't fire.
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Old 07-06-2016, 07:38 PM   #12
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Plug a computer into your megasquirt and watch the cranking voltage. You might even get low voltage errors.
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Old 07-09-2016, 11:27 AM   #13
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Gents,

I let the car sit for two-and-a-half days. The battery voltage had dropped from 12.57 to 12.54, which doesn't really seem out of the ordinary. I put the battery on charge this morning.with my MUS 4.3. It went almost immediately to Level 4, Absorption and stayed there for nearly two hours before showing Float. I pulled the charger and measured the voltage, 12.78. I turned the key to ON and let the fuel pump spin, then I tried to start her. The cranking rpms sounded fine, but it wouldn't catch. I let it crank for about 10 seconds, then turned it off. Waited a couple of seconds and tried again. She cranked for almost 20 seconds before it started. It ran slow briefly, then Idled normally.

I put the charger back on and it sat on Level 1, Desulfation for about five minutes before going to Absorption. I plan to let it charge and then drive her over to Advance and have the charging system tested.

One more thing... even though it's 82 degrees out, the AFR gauge is reading 10.9 at idle cold. When she warms up, she's fine, right about 14.7, but when she first starts she's really rich. Is it possible that is making the car hard to start?

Thanks,
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Old 07-09-2016, 11:49 AM   #14
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I still think you could have a prime problem. With a returnless system, the key turn prime mostly charges the head (tank side) end. The fuel rail and hardline may have air pockets. If you changed injectors or removed the fuel rail as part of the install, you may have introduced a small leak that allows air to be drawn into the fuel system over time. I know it seems like this air should clear quickly, but I have first hand experience that it doesn't necessarily purge while cranking.

My DD is an '03 Nissan SER spec-v. These cars have a known design defect where fuel drains back into the tank leaving air in the lines. When you try to simply crank the engine over in this circumstance, it can crank for an extended period of time and not fire. If you pre-prime the fuel system it will fire straight away.

If you are running an EMS that has adjustable prime duration, try bumping the number up. I am not talking about the fuel pump prime here, but the injector priming pulse. For MS in tuner studio this is located in the Startup/Idle tab.
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Old 07-09-2016, 12:06 PM   #15
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Question: is this vehicle parked on an incline with the tail pointing down?
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Old 07-09-2016, 12:16 PM   #16
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Here are some of the sub-menus from the Startup/Idle Tab. Does anything look wrong?

She's on a very slight incline with the tail lower. However, she sits level in the garage and I push her out to start so I don't stink up the garage.
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Hard to start after sitting for a couple of weeks-startup-idle.jpg  
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Old 07-09-2016, 12:39 PM   #17
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Never tuned a '99, so I do not know if those values are reasonable or not. Furthermore, the prime pulse will be a function of your injector size, so it will change WRT installed injectors.

You could try a couple of things:

- park the car on the incline head down for the entire time.
- open (and leave open) the gas cap when parked
- significantly bump the priming pulse number around the CLT you are starting at. I am thinking extreme bump for experimentation, say 3-4x.

You could do all three at the same time or split first two and third into two different trials.

Hope this helps!
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Old 07-09-2016, 04:20 PM   #18
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Arca,

I bow to your superior intellect and request insight into tonight's Powerball lottery.

After charging fine this morning, the battery failed to take a charge on two later attempts. My battery is bad. I installed the battery from my other Miata and she started normally. Given my luck, I would not assume it's just the battery, but I yield for now.

Beers on me if we ever meet.
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Old 07-10-2016, 12:03 PM   #19
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NAPA said the battery checked good. The gal behind the counter got snooty when I told her my charger said the battery was bad. Advance Auto also said the battery was good. I plan to swap batteries around again and see if she starts normally with a different battery tomorrow after I get home from work.
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Old 07-11-2016, 07:58 PM   #20
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The car sat for more than 48 hours and I expected a hard start. I hooked up a known working, but not new, battery. She started just fine. So, I have a bad battery that passes checks at both NAPA and Advance Auto.
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