Intake Backfires on Cold Start

[Hughespj47]

I just thought I'd thrown my experience out there and see if anyone is experiencing the same issue. A little background- I live at high altitude and a cold climate. I took delivery on my Track Pack 350 in Mid-Feb, and we happened to have some snow-free roads and warm days (40+F). My GT350 is parked outside so it sees cold temps at night.

After 3 or 4 drives it would start right up and after about 5 seconds, start to die and backfire through the intake. I took it to the dealer and they thought it might be loss of fuel pressure overnight. They did a fuel injector leak down test and all was good. Logic indicated the the fuel pump check valve was probably bad so it was replaced. They started it up the next morning and it still backfired. So, they unplugged the MAF and it started much better. They then replaced the MAF and all seemed fine.

The second cold start after I got it back, I thought I heard an intake backfire. It started me thinking. I had been pretty much sitting down and then pressing the clutch and start buttons simultaneously. So lately, I've been pushing the clutch and waiting a few seconds before pressing the start button. I could swear that I hear a few clicks/ticks from the back that slow down over those few seconds. Then the engine starts normally.

CAN ANYONE VERIFY HEARING THE FUEL PUMP PRESSURIZING THE SYSTEM FOR A FEW SECONDS BEFORE COLD STARTUP? I'd be curious to know. Of course, if you've experienced the intake backfire problem, I like to hear about that, too.

Thanks EVERYONE for posting your thoughts and experiences in the Shelby forum! This has been a treasure trove of information for me!

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[350Mike]

Can't speak for the 350, but my GT primes the fuel system as soon as I press the clutch.

 

[KGTG350]

Never had mine back fire on me but in the mornings when I go to fire her up I do here the clicking noise three times. I usually engage clutch wait for the clicking noise to stop and hit ignition.

Never had an issue. Also mine stays garaged and temps are usually 50+.


KGTG350 - 16' GT350

 

[MAV]

Yes, pressing the clutch with the key fob in the car does initialize the pre-start functions such as fuel pump priming sequence , and probably some other pumps and relays as well. I've heard it on mine many times. I push the clutch and hit the button a second or two later, and I haven't had any issues.

 

[GDP]

It does pressurize the fuel system either by holding the clutch down a second or two before start. Or for auto GTs like mine the brake. Same thing when you just hit the start button to put it into accessory mode.

On all my mustangs I've let the system prime for 2-3 seconds before start. For the fuel rails to pressurize and for the electronics to warm up and boot. Same reason I try to wait 10-20 seconds before putting it into D so everything has a chance to warm up.

Though not sure how normal your situation is. If it continues I would push to have them find the cause.

 

[Hughespj47]

Yes, pressing the clutch with the key fob in the car does initialize the pre-start functions such as fuel pump priming sequence , and probably some other pumps and relays as well. I've heard it on mine many times. I push the clutch and hit the button a second or two later, and I haven't had any issues.

Thanks - looks like we ordered the same car. Good taste in Shelbys!:cheers:

 

[Hughespj47]

It does pressurize the fuel system either by holding the clutch down a second or two before start. Or for auto GTs like mine the brake. Same thing when you just hit the start button to put it into accessory mode.

On all my mustangs I've let the system prime for 2-3 seconds before start. For the fuel rails to pressurize and for the electronics to warm up and boot. Same reason I try to wait 10-20 seconds before putting it into D so everything has a chance to warm up.

Though not sure how normal your situation is. If it continues I would push to have them find the cause.

Thanks - I read the Mustang Owners Manual and the Shelby Supplement starting procedures, and nowhere does it say to press the clutch for a few seconds before start. I intend to keep an eye on the issue!

 

[GDP]

Thanks - I read the Mustang Owners Manual and the Shelby Supplement starting procedures, and nowhere does it say to press the clutch for a few seconds before start. I intend to keep an eye on the issue!

I didn't say it needed to be done. Only that I normally do. And yeah I don't believe it should be needed for backfire free operation. Hopefully it's not the symptom of a larger issue.

 

[50 Deep]

It's not an issue. All the cars do it on start up. Same with other mustangs when you put the key in the "On" position. Fuel pump primes and various other systems boot up since its time to start the party

 

[montreal ponies]

My Explorer does it when applying the brake pedal, i hear the fuel line pressurizing.

 

[mattlqx]

There's a whole bunch of clickity clackity sounds that happen when the clutch is pressed prior to hitting the ignition button. Sounds like a robot getting ready to rip my head off.

 

[Spa2k]

There's a whole bunch of clickity clackity sounds that happen when the clutch is pressed prior to hitting the ignition button. Sounds like a robot getting ready to rip my head off.

Or getting ready to give you the ride of your life!

 

[Trackaholic]

I was planning on starting a thread on this topic. I actually like to hear all the clicky stuff before firing the engine off. I typically leave my door open so I can hear it better. Makes the car seem alive when it gets itself ready to start. Still, even when I start right away I've never had an issue with stalling.

-T

 

[mephim]

I just thought I'd thrown my experience out there and see if anyone is experiencing the same issue. A little background- I live at high altitude and a cold climate. I took delivery on my Track Pack 350 in Mid-Feb, and we happened to have some snow-free roads and warm days (40+F). My GT350 is parked outside so it sees cold temps at night.

After 3 or 4 drives it would start right up and after about 5 seconds, start to die and backfire through the intake. I took it to the dealer and they thought it might be loss of fuel pressure overnight. They did a fuel injector leak down test and all was good. Logic indicated the the fuel pump check valve was probably bad so it was replaced. They started it up the next morning and it still backfired. So, they unplugged the MAF and it started much better. They then replaced the MAF and all seemed fine.

The second cold start after I got it back, I thought I heard an intake backfire. It started me thinking. I had been pretty much sitting down and then pressing the clutch and start buttons simultaneously. So lately, I've been pushing the clutch and waiting a few seconds before pressing the start button. I could swear that I hear a few clicks/ticks from the back that slow down over those few seconds. Then the engine starts normally.

CAN ANYONE VERIFY HEARING THE FUEL PUMP PRESSURIZING THE SYSTEM FOR A FEW SECONDS BEFORE COLD STARTUP? I'd be curious to know. Of course, if you've experienced the intake backfire problem, I like to hear about that, too.

Thanks EVERYONE for posting your thoughts and experiences in the Shelby forum! This has been a treasure trove of information for me!

When you push the clutch in before ignition, the fuel system pressurizes. This is similar to other late model Fords (Focus St, FiST, Mustang GT). As a bonus, if you wait about 5 seconds it allows for the Exhaust to do a sweep of the electronic valves and decreases an exhaust malfunction, if you have a window open you can hear the motor do two checks. Its pretty cool.

 

[Hughespj47]

When you push the clutch in before ignition, the fuel system pressurizes. This is similar to other late model Fords (Focus St, FiST, Mustang GT). As a bonus, if you wait about 5 seconds it allows for the Exhaust to do a sweep of the electronic valves and decreases an exhaust malfunction, if you have a window open you can hear the motor do two checks. Its pretty cool.

I agree it's cool, but if that pause is required, they should mention it or build it into the start sequence when you push the button. My MINI makes similar noises when you open the driver's door, so by the time you sit down, push the clutch and start button, it's ready. That's a smarter way to do it, IMO. My other cars are so old the pause is a non-issue.

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