Hard Start After Long Periods of Off-Time.

[Aaron Anderson]

I have a 2006 Kia Optima EX V6.
Lately, my vehicle has been giving me a hard, or slow, start in the mornings. (after being off for like 12 hours)
It turns over faithfully ever time (so far), but this problem continually occurs. It doesn’t occur if the vehicle has only been off for around 9 hours because it turns over right away when I get out of work.

I went ahead and replaced my spark plugs to see if it would help. (they needed to be replaced anyway)
Problem appeared to stop for a day or two and then came back.
I’ve had the battery, charger, starter, and alternator tested with positive results.
I left the vehicle overnight at a local mechanic to test the fuel pump pressure (perhaps it wasn’t off long enough) with positive results.
Just to be on the safe side, I replaced my gas cap with a brand new one.

Please note that I was not raised around working on cars and have very limited knowledge regarding them…
However, it appears to me to be a loss of fuel pressure. (turning the key to the “on” position a few times helps the problem, but doesn’t make it go away)
I don’t want to just replace things based on shooting in the dark, because I’d rather not burn through my money.
On the same note, I’d rather not get bent over by a mechanic that may change me a bunch of money to find inconclusive results.

To give you an explanation of my engine knowledge:
I understand the combustion cycle, from engineering school, but absolutely do not know my way around an actual engine. (thank you, modern education system for not teaching me useful life skills)

I greatly appreciate any insight and would be happy to clarify any details to the best of my ability.

(I’ve thought about replacing the fuel pump or the fuel pump relay, but I don’t want to make hasty decisions)

Thanks in advance!

Topic

[Aaron Anderson]

It appears to turn over at a normal rate, but the last turn is slow (or hesitates). If that makes sense.

As I said in the original post, time appears to play a huge factor.
If the car sits for 9 hours or less, no problems. (typically)
If it sits for a few hours longer, hard start.

I basically can’t tell if it is going to be a hard start until that last turn, if that helps.

[Aaron Anderson]

I’m planning on trying to test a few of these things this weekend, but I’ve got a lot going on.

Trying to start with the small stuff like parasitic draw/battery that won’t hold a charge, then move to the fuel pump/relay, and then troubleshoot from there if the pressure seems OK?

[James]

You could start with the fuel pressure test in the video that I showed you and/or checking the fuel pump relay. It could be a battery problem, but as mentioned before it seems more an more like a fuel pressure issue (assuming your car cranks normally in the morning, but for a longer period of time) it is pretty obvious when there isnt enough power getting to the starter. Up to you if you start with the battery and then move to the fuel system, but the pattery/parasitic draw isn’t a bad thing to test

[Aaron Anderson]

Noted.

Am I understanding that previous video correctly in him saying that the fuel pump itself needs replaced if the “check valve” is not maintaining pressure?
That seems an awful lot like what is happening, but I haven’t had a chance to get a gauge on the rail.

[James]

I beleive so, however I have little experience with this job (mostly information from a friend who did this job). Maybe someone who has done this fix can offer more insignt. I have read that some people have been able to replace the check valve while keeping the pump. But i think the pump needs to come out to do the fix

[Aaron Anderson]

Sounds like it’ll be fun…

I am skeptical though. In most of the videos and forums about check valves, the pressure drop happens very rapidly.
As suggested earlier, after 9 hours of sitting, it starts right up.

Again, this is all speculation, until I get to the actual tests.

[James]

I would attempt the test over 9 hours to see if it drops slowly, also check the relay and control functions to the pump. Also there may be an oil pressure switch involved (as seen in older GM models). I would check all of the components on the fuel pump circuit after checking for a slow pressure leak.

[James]

One more thing to note. I would highly recommend purchasing a Haynes manual. They are about 30 bucks new and will give you specific information for your car, or if you feel like spending around 80 then see if you can find a factory service manual. This information will really be helpful to you in your diagnosis of problems in your car. Good luck tracking down this issue, wish I could offer more specific expertise.

[Aaron Anderson]

Roger that.

Thanks.

One thing that I’m not sure of with a Haynes manual or factory service one… Can I get one that matches a VIN range?
I ask because my vehicle is a late ’06 with some ’06 components and some ’07 components.

[James]

Generally the haynes manual will cover a range of years (mine covers 1997-2001 explorers, mountaineers, and sport tracs i believe) I dont know much about buying FSMs, but I think they include a vin look up.

here is a link to your haynes manual: http://www.haynes.com/products/productID/828

[Aaron Anderson]

Just a quick update:
I only had time this weekend to test the battery voltages and current draw. Everything checked out.
My next step will be to read over the Haynes manual to try to help me out in my testing/service.
I’m going to try to see if I can get a pressure gauge from AutoZone or something within the next few days to check my pressure levels.
If it doesn’t appear to be my check valve–which my vehicle seems to maintain pressure for too long, without a gauge reading, for it to be–then I’m going to check to see if my pump is getting adequate voltage from the relay and potentially replace the pump.

[James]

definitely locate a wiring diagram for the pump (should be somewhere in the haynes manual) and ensure the voltages are good. Also check the pressure as well. If the pressure does leak down, then likely the fuel pump needs to be replaced. Much easier to change a relay or fuse or clean a connection then pull a fuel pump

did you find if you have an inline fuel filter outside the tank?

[Keith Castle]

A friend’s wife had a 2006.5 Sonata, so I feel your pain on the parts issue. What we found was that decoding the vin was less than helpful. One thing a Haynes manual will have lots of that will be invaluable to you is PICTURES. Knowing what parts from what years look like is a god-send.

Something these cars are kinda known for is dodgy evap components. It sounds very much like it’s that check valve, but if not I would look there next.

Fuel pressure test kits can be had fairly cheaply and easily. If it’s not something you think you’ll use often enough to warrant a purchase, ask about “renting” one instead. Most major parts houses do that now for specialty tools.

[Aaron Anderson]

I haven’t been able to check explicitly for the filter, but it seems like, according to what I’ve read, that it is in the fuel tank.
Also, the relay is actuating. That doesn’t mean it is carrying proper voltage, but it is actuating.

I’m sure I need to replace my evaporative filter, but I’m not sure how that would cause this issue?
I will try to test the pressure leak over an extended time this weekend, I hope. (won’t have that much time during the week, but can do intermediate tests)

Thanks for all of the input! The fuel filters for Kia vehicles, as I’ve read, are supposed to last the life of the vehicle and are typically in the fuel tank, with the pump. If it comes to the pump, I may replace the filter as well.

I’m hoping to kick this thing in the a__ by the end of this weekend.

[Keith Castle]

See your fuel system checks through to the end. I still think your main fault is that check valve.

I only mentioned the evap system because the one I had hands on started off with “little” weird problems like yours, and devolved into bigger weirder problems like taking 10 mins. to put gas in it and not running with the tank more than 3/4 full. Never threw a code. Something to be aware of if all else fails.

[Author]

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