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Hard Starting Getting worse every day - Fuel Pump: Check Valve? Relay?- Advice Requested

2005 Toyota Sienna
Car is hard to start after sitting overnight. Once started it runs fine - does not hesitate at all.
The starting is getting gradually worse each day - today it took 20 cranks to start
When I turn the key to on (but not crank) I do not hear the fuel pump hum - that makes me think the relay or supporting fuses are bad - I swapped with Horn relay and no difference.

My key symptom that I cant figure out is the fact that has gotten gradually worse over 2 months. From 2 extra cranks to fire up to now 20 cranks.

Could it just be the filter?
Once again it runs fine once started and startup all day long and run fine all day long. Just a problem after sitting overnight.

Lead me to think check valve problem, but why would that get gradually worse?

Any help on what I can rule out and best course of action?


The next time you go to start the vehicle, turn the ignition on so the dash lights come on for two seconds and then turn the ignition off.

Repeat this twenty times and then try starting the engine.

If the engine starts right up, it points to a problem with the anti drain-back valve on the fuel pump.


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Thanks I will try that.
I have already tried this turning on the ignition, then off again about 4-5 times. What is happening each time I do that. Will doing it 20 times be a different result? Thanks again!

Each time the ignition is turned on, the fuel pump runs for two seconds and then turns off.

So, each time the ignition is turned on, the fuel pump has a chance prime the fuel system and build the proper fuel pressure.


I also think its the flow back check valve. But can I rule out the EFI Fuel Pump Relay? If that was bad, would it ever start?

If you don’t hear the fuel pump from the driver’s seat, try listening at the gas filler with the flap held open. The pump should run a couple seconds each time you switch from Off to Run. If it is not, that’s an important clue.

Would a separate way to power the fuel pump (analogous to a pre-luber for oil) make sense? I have a mechanical which I had to replace, took me a long time to attribute my starting problems to it instead of electrical ('cause I don’t know so much). I tried pumping it by hand.

I had the mechanic check it out and he says the fule system and pressure is fine. He suggested a Fuel Treatment to clean injectors? Sounds like a long shot. What do you think?

It won’t hurt, but it won’t likely help, either. Fuel injectors clogged enough to cause hard starting would cause other driveability problems.

Did you try @Tester’s suggestion? Did your mechanic test fuel pressure after the car had been sitting overnight?

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Does the fuel pump run a few seconds each time you turn the key from Off to Run (not all the way to Start)?

Id be suspicious of the fuel pump, the fuel filter…or water in the fuel… The key on several times is just as @Tester mentioned. The vehicle would not run at all if fuel pump relay failed. You should be able to hear the fuel pump prime on each key on event. Check that… If you dont get a prime each time…then look toward your fuel pump relay. If you do get a prime…look into your fuel filter…and then pump…


The fuel pump, or its main relay, or the ignition switch each can be intermittent. That’s why it’s important to know if the pump runs with each Run/Off/Run cycle.

Injector cleaning seems like a long shot. Clogged injectors usually causes some combination of loss of power at higher speeds and/or surging/stalling at lower speed neighborhood driving. There’s some possibility the injectors are leaking and causing a flooded condition I suppose. Try holding the accel pedal all the way to the floor next time; if that helps, consistent w/a flooded engine condition. Check the spark plugs tips to see if they are wet w/fuel.

Did your shop do a fuel pressure hold test? Or just measure the fuel pressure when the engine is running? For this problem you need the hold test too. That’s done by starting the engine with the pressure gauge installed, once normal operating temperature is reached, turning the engine off, then measuring how long it takes for the fuel pressure to leak down a specified percentage of the running pressure.

I can’t speak to your 05 Sienna, but my 90’s Corolla doesn’t turn on the fuel pump w/the key in “on”. It only turns it on in “start” or w/the engine running For my car that’s normal.

If I had that problem first thing I’d do is check if I had spark when it was taking a long time to crank. That’s a very easy test to do, and if it shows a spark problem, eliminates the much more complicated fuel system testing entirely.