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sprinkles08
sprinkles08, ASE Certified Technician
Category: Car
Satisfied Customers: 21589
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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Hard starting when warm problem was never solved. I have

Customer Question

Hard starting when warm problem was never solved. I have since changed the Engine temp sensor for the emissions system and pressure tested the fuel delivery system and it is within spec. Do you have my old file? I would still like to try and resolve it.
Submitted: 12 months ago.
Category: Car
Expert:  sprinkles08 replied 12 months ago.

Hello and welcome to JustAnswer!

If you have a hard restart only when hot and no fault codes are setting then you most likely have a weak check valve in the fuel pump causing vapor lock. When you park it with the engine hot, the high underhood heat will elevate pressure in the fuel rail. If the check valve is weak this will cause fuel to be pushed back to the tank leaving high pressure vapor in the rail rather than liquid fuel. This vapor has to either be purged out the injectors through extended cranking, or it has to collapse as the engine cools, to allow enough fuel to be pushed back in the rail for the engine to start.

Customer: replied 12 months ago.
Ok. Good sounding, interesting theory. Where is this check valve? is it replaceable?
Customer: replied 12 months ago.
Just to clairify the hard start comes after the vehicle sit for 1 to 2 hours. if it sits for ten minutes it fires up right away much like when it is cold. I can sent audio clips of the three scenarios if you think that might help.
Expert:  sprinkles08 replied 12 months ago.

The check valve is in the fuel pump and serviced with it.

If you can upload the audio that would be great.

Customer: replied 12 months ago.
when you say "service" do you mean replace?Just a thought. If it is the check valve why, after sitting overnight does it fire up right away. I have also tried turning the key to the on position in an attempt to build up the fuel pressure before turning to start and that does not help. Could a secondary check valve be mounted in the supply hose somewhere instead of changing out the fuel pump which is a big job dropping the fuel tank...Will make the audio files today
Expert:  sprinkles08 replied 12 months ago.

The fuel pump needs to be replaced if fuel is bleeding off through it.

Customer: replied 12 months ago.
is there a test for this? how long after shut down should the fuel system hold pressure or ?
Expert:  sprinkles08 replied 12 months ago.

A bleedoff test with a gauge won't tell anything in this case. What needs to be done is remove the fuel line coming into the engine and install a test T hose. The engine can be ran, the hose pinched off with pinch off pliers immediately on shutdown. There are also test hoses with a shutoff valve. When attempting to restart the engine then the valve can be opened or pinch off pliers removed and immediately try to start the engine. If it starts better then the pump will need to be replaced.

Customer: replied 12 months ago.
If I get this right we are basically putting a manual check valve right where it feeds the rail and by clamping it off it will prevent the fuel from weeping back into the tank? Won't I have to put a clamp on the return side as well?
Expert:  sprinkles08 replied 12 months ago.

If the regulator is good then it will hold pressure. If pinching off the return line allows it to start better then the regulator is bad.

Customer: replied 12 months ago.
Well there is a rubber hose for the feed and the return so I will try and find a clamp and give this a try. Thanks.
Expert:  sprinkles08 replied 12 months ago.

You'd need pinch off pliers.

http://www.sears.com/kd-tools-mini-hose-pinch-off-pliers-3-4/p-00996311000P?prdNo=2&blockNo=2&blockType=G2

Customer: replied 12 months ago.
I have a pair somewhere! You sure I do not need to pinch off both at the same time?
Expert:  sprinkles08 replied 12 months ago.

You can do whichever you'd like.

Customer: replied 12 months ago.
your service has been fine. We are not done yet. I am experimenting with the clamp pliers. I have more questions coming...
Expert:  sprinkles08 replied 12 months ago.

Not a problem.

Customer: replied 12 months ago.
we are not at the follow part yet though?
Expert:  sprinkles08 replied 12 months ago.

I'm not certain what you're asking?

Customer: replied 12 months ago.
I am digesting your information. doing the testing with the clamps as you suggested and doing more reseach on the fuel injection system. I do not have a question before you at the moment but more are coming.
Expert:  sprinkles08 replied 12 months ago.

Ok.

Customer: replied 11 months ago.
Why do you keep sending these requests for me to rate your service?
Expert:  sprinkles08 replied 11 months ago.

I'm not, you're seeing something automated from the site due to the length of time the question has been open without a rating.

Customer: replied 11 months ago.
Ah. Ok. Will ignore. Thanks.
Expert:  sprinkles08 replied 11 months ago.

You're welcome.

Customer: replied 11 months ago.
clamping off the supply and return hoses to the rail has caused them to start weeping/leaking gas a bit so now I am replacing the hoses before more clamp testing. Preliminary test is that when both hoses were clamped it started up well after 1 1/2 hours. clamping one or the other hoses does not make a difference but need to verify this observation.
Expert:  sprinkles08 replied 11 months ago.

Let me know how it goes!

Customer: replied 11 months ago.
Surprisingly since I changed the hoses the problem seems to have gone away! I have not had time to verify it yet and I am still in disbelief but I should know by the end of the weekend. Thanks.
Expert:  sprinkles08 replied 11 months ago.

Great!

Customer: replied 11 months ago.
The problem was not solved with the new hoses and must have just been a coincidence the one time it seemed to be better. There are two other things that I have read that can effect starting which is the Idle Air Control valve and the Throttle Position sensor. I already changed the Engine Coolant Temperature sensor. Do you know if there is a way to test the IAC valve? I read I should be careful not to push the valve in or out as it can wreck it. I am starting to look at this point as the truck starts so well when cold I am thinking it is not the TP. I might try to push the accelerator pedal a quarter of the way down before turning the key to see if that makes a difference. Any thoughts? I am going to send an audio file or two from my phone separately.
Customer: replied 11 months ago.
audìo.. won't let me upload as it says it can't read the file type...
Expert:  sprinkles08 replied 11 months ago.

The TPS won't cause a starting issue but the IAC could prevent it from idling. You can try cracking the throttle open slightly when cranking to see if that allows it to start normally.

Customer: replied 11 months ago.
Nope. Opening the throttle did not help it start. the IAC is a $100 so I don't want to just replace it without knowing if it is the problem. How to test...? Also check out the "Start Mode description from the shop manual...
Expert:  sprinkles08 replied 11 months ago.

Did you find a difference in how it started when clamping the fuel lines during a hot soak?

Customer: replied 11 months ago.
very minor perhaps 20% faster start.
Expert:  sprinkles08 replied 11 months ago.

Do you have spark at the time it doesn't start?

Customer: replied 11 months ago.
I don't know. How would I test for that without risk of damaging the black box?
Expert:  sprinkles08 replied 11 months ago.

You would connect a spark tester and crank the engine.

http://www.amazon.com/Thexton-THE404-Spark-Tester/dp/B0002STSBM

Customer: replied 11 months ago.
Interesting. Never seen one of those before. Will get one and give it a try.
Expert:  sprinkles08 replied 11 months ago.

Ok.

Customer: replied 11 months ago.
ok. here is a vid of the spark tester. A very reluctant spark. Not quite sure what to make of this... The add file link is not working. I am going to try and send this and then re-try...
Customer: replied 11 months ago.
To compress the vid file I need to send it to an email address. Do you have an email address I can send it to?
Expert:  sprinkles08 replied 11 months ago.

I'm unable to give personal contact info. You could try uploading to Youtube or something similar if you can't get it to upload here.

Customer: replied 11 months ago.
https://www.youtube.com/watch?v=gAvWzpRdFnA&feature=youtu.beNo problem, let me know if this link works...
Expert:  sprinkles08 replied 11 months ago.

I'm a full time tech and at work this morning, I'll get back to you as quickly as I can.

Expert:  sprinkles08 replied 11 months ago.

Did you have a poor connection possibly? The engine started before spark was present in the tester.

Customer: replied 11 months ago.
That was weird. I had an exceptional ground as the first attempt was a complete fail I went overboard making a good ground for this test. I think I need to repeat the test and perhaps do a test when cold or just after shut down when it starts well.
Expert:  sprinkles08 replied 11 months ago.

If you're going to try again it would be a good idea to check as many cylinders are possible to see if there are certain cylinders that don't have spark and others do.

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