QuestionQUESTION: Car cranks but unless you give it a little gas it won't start. Friend told me to turn key on/off 2-3 times to see if it would start easier. It did start a little quicker but still had a bit of trouble. Once car starts it smoothes out & runs just fine. It seems to start right back up when shut off, but if it sits you have to give it gas. Is there a check valve in the fuel pump that keeps the fuel line filled completely or is there other issues?
ANSWER: Hi, Rocky. There is indeed a check ball in the fuel pump which prevents fuel pressure from bleeding back to the tank through the pump. In addition, the fuel pressure regulator should retain pressure as well. In fact, if your pressure is bleeding off while the car is off, the fuel pressure regulator is the more likely culprit. But this typically results only in an extended-crank symptom. Typically the engine will start after extensive cranking regardless of whether you're applying the accelerator.
My first question is whether the engine is cranking at normal speed? If it's cranking slowly, you may simply have a weak battery. In some cases, opening the throttle will make the engine easier to crank, in turn allowing the battery voltage and cranking speed to rise just enough during cranking that the engine will start.
Other potential problems that can cause an engine to start only if the accelerator is depressed:
-- Stuck open EGR valve. This will typically also result in poor idle.
-- Faulty coolant temperature sensor (reading too cold).
-- Stuck open purge valve. This can cause the engine to run poorly for a short period of time after starting if the vehicle has been left sitting for a significant period of time. It also frequently causes difficulty starting after refueling.
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QUESTION: I neglected to tell you that i just replaced the radiator because of a small leak in the upper tank. the car overheated several times on the way home. I let it cool & refilled it everytime it started to overheat. Do you think that it could've damaged the coolant sensor? If not it sounds like a fuel pump to me. what's your best guess?
AnswerThat's possible, Rocky. While I don't think I've ever seen the coolant sensor damaged by heat on a Hyundai, I've seen it on other cars. I don't particularly think that's your problem. Similarly, while the fuel pump (or fuel pressure regulator) could be the issue, I don't particularly think that's going to be the issue either.
My fear is that you've damaged the cylinder head from overheating. The mode of failure is typically that the valves no longer fully seat, often causing excessive cranking or the necessity to apply the accelerator to start the engine when cold. I'd suggest doing a compression test and cylinder leakage test on the engine when cold to see if you're losing compression and determine where it is going.
