Crank no start only when hot: fuel related?

[Macman45]

Issue with my 2007, it starts almost immediately when cold, but borderline leaves me stranded when hot, especially after refueling when it’s hot. Will just crank and crank. Spins over freely, not strained (not a compression issue) and occasionally will sputter like it’s trying. I try cycling the key, waiting for the pump to prime, no change. Feather the gas a little and after 2-3 minutes of this drama I can get it to fire and it wants to die. Feather the gas some more and keep the R’s up, and a minute or so later it’s perfect. Runs great. Never misfires, no CELs, no problems til I cut it off and try to restart.

On its original plugs, so I’m doing plugs and fuel filter as general maintenance. Not sure where else to look for this.

 

[Dino Dino Bambino]

It sounds like your fuel lines are getting heat soaked and developing a vapor lock. Do you have LT headers? If so, ceramic coating them might help by reducing underhood heat radiation. Alternatively you could try insulating the fuel lines/injector rails with DEI Cool Tape or similar.
Have you performed any other mods recently?

 

[Macman45]

It sounds like your fuel lines are getting heat soaked and developing a vapor lock. Do you have LT headers? If so, ceramic coating them might help by reducing underhood heat radiation. Alternatively you could try insulating the fuel lines/injector rails with DEI Cool Tape or similar.
Have you performed any other mods recently?

No it’s stock SGT, so their tune and their CAI and axle backs, rest is stock 4.6. It does sound like old school vapor lock…

 

[JC SSP]

FYI Three things to make an engine run... air, fuel and ignition.

How many miles? When was the last time you changed the fuel filter?

This could be a failing fuel pump or a crank or cam sensor malfunction... If the issue is intermittent, then it becomes a little more complex as it can be something much more in-depth (ECM, harness issue, etc.).

No codes to me sounds like more fuel related. There is a Shrader valve on the driver side fuel rail. Pick up or borrow a EFI pressure gauge... next time it does it, screw the gauge on and see where your readings are... anything less than 35-40 and the pump is not pushing enough psi.

I would not just start changing sensors, take it to a reputable shop with proper scanning tools and let them do a complete analysis on it.

 

[07 Boss]

I have an '07 and I sometimes ran into this issue in the past. Sometimes after turning the car off for a short amount of time like running into the bank or picking up some beer it would crank and not start. I always just clear the cylinders and it starts right up. I haven't experienced it lately because every time I stop for those short stops I always depress the throttle before cranking and then release it, vroom. Never figured out what the issue was or is but I don't experience it anymore. I developed this method because of my traction control monkey. If I crank it twice without returning it completely to off for a second, my traction control turns on. It's usually always off. Anyways I have developed a start up procedure that I turn the ignition on, fasten harness, then crank it. Sometimes with the pedal floored.

 

[JC SSP]

I just looked at my 05’ and did not see a shrader valve. I must have confused my 87’ and now sold 96’ GT which had them. Sorry to lead you astray. Still a reputable shop should be able take analyze the issue properly.

 

[Macman45]

Update: I think it was working through some bad gas. Last time it did it, I had just filled up with fresh 93. I've done a series of hot starts, (2 minutes rest, 5 minutes rest etc), fires RIGHT up. I think water in gas or something...

 

[Macman45]

Bumping this as the problem isn’t fully gone.

Doesn’t love starting when hot, finally kicks off and the R’s drop way way down and it hesitates and recovers then is fine. Am I seeing a fuel pump and/or check valve at the pump issue? I’m tempted to toss in a good used pump assembly I have in storage just to see…

It starts excellent when cold. Mainly have the issue after getting gas when it’s only been off a few minutes. Nozzle also clicks at 2/3 full and doesn’t wanna keep filling. New issue

 

[Pentalab]

I have an aeroforce gauge plugged into my OBD port at all times. (The 3 x aeroforce gauges are mounted to the A pillar). I can monitor the fuel pressure at any time. Normal is 40 psi. Any hand held tuner, like my SCT-X3 or other scanner, will easily tell you exactly what your fuel pressure is. Start there before wasting your time. I did have an issue a few years ago. Car would run fine till I got my foot into it, then it would gag, if the boost gauge was > 0......( and fuel pressure would then drop to 5 psi). The problem was... the sock filter that covers the bottom of the oem fuel pump was completely clogged. Once that was cleaned up, it has run like a top.

 

[RoninGT]

That does sound like something to do with improper ventilation as it has problems in proportion to heat combined with your new fill up issue.

 

[Macman45]

I have an aeroforce gauge plugged into my OBD port at all times. (The 3 x aeroforce gauges are mounted to the A pillar). I can monitor the fuel pressure at any time. Normal is 40 psi. Any hand held tuner, like my SCT-X3 or other scanner, will easily tell you exactly what your fuel pressure is. Start there before wasting your time. I did have an issue a few years ago. Car would run fine till I got my foot into it, then it would gag, if the boost gauge was > 0......( and fuel pressure would then drop to 5 psi). The problem was... the sock filter that covers the bottom of the oem fuel pump was completely clogged. Once that was cleaned up, it has run like a top.

Flicked the key to Run, pump of course primed. 44 PSI on my X4. Left it along for one hour and it slowly bled down to 35.5PSI. That’s fine isn’t it? I read somewhere if it holds within 5 PSI for 5 minutes it’s fine

 

[Pentalab]

Flicked the key to Run, pump of course primed. 44 PSI on my X4. Left it along for one hour and it slowly bled down to 35.5PSI. That’s fine isn’t it? I read somewhere if it holds within 5 PSI for 5 minutes it’s fine

That should work good. IF I turn key over one position, so dash lights up ( key on-eng OFF) and wait for the aeroforce gauge to boot up, it's 50 psi. Turn key CW, and start eng, then it's 40 psi.

 

[Pentalab]

Bumping this as the problem isn’t fully gone.

Doesn’t love starting when hot, finally kicks off and the R’s drop way way down and it hesitates and recovers then is fine. Am I seeing a fuel pump and/or check valve at the pump issue? I’m tempted to toss in a good used pump assembly I have in storage just to see…

It starts excellent when cold. Mainly have the issue after getting gas when it’s only been off a few minutes. Nozzle also clicks at 2/3 full and doesn’t wanna keep filling. New issue

This sounds like a ventilation issue. Something is amiss somewhere. Esp when only being able to fill tank to 2/3. Typ folks would flip the nozzle 180 degs ( inverted) to fill the tank up to max.

 

[GriffX]

FYI: Not starting when hot is a typical crankshaft position sensor issue at my Mercedes: You can measure the electrical resistance of it, it's a coil, and when it is too low it does not produce a high enough signal to get recognized by the ECU.
Maybe it is similar here? But check it first if you can measure the crankshaft sensor, if it is a hall sensor, you can destroy it with a multimeter measuring ohms.

 

[Pentalab]

FYI: Not starting when hot is a typical crankshaft position sensor issue at my Mercedes: You can measure the electrical resistance of it, it's a coil, and when it is too low it does not produce a high enough signal to get recognized by the ECU.
Maybe it is similar here? But check it first if you can measure the crankshaft sensor, if it is a hall sensor, you can destroy it with a multimeter measuring ohms.

IF using a DVM in the ohms position, on 'auto' it will default to it's highest range, which is typ 40 megohms.....at which point you will have at least 7.7 vdc coming down the test leads. (assuming a good 9 vdc battery installed). This is why the manually selected ohms range is typ used, like starting with the lowest range, which is typ just 40 ohms.....at which point the vdc coming down the leads is far less.

Buddy found this out the hard way when testing the D-S ( drain + source) on a new LDMOS mosfet RF power transistor. They are polarity sensitive, and if you get the polarity reversed, the max that can be applied is 6.0 vdc With the dvm on ...'auto' , 7.7 vdc comes down the leads, and poof, $250.00 LDMOS device destroyed in an instant.

Dunno what the max vdc that a hall effect device can handle.

 

[Macman45]

I still think some sort of fuel delivery. When it catches and starts it hesitates with really low RPM and settles out. Starved for fuel or can’t vent? I figured a CPS would trip a code for sure

 

[Pentalab]

When the OP finally gets this sorted out, pse let us know what you found. It could help others down the road.

 

[Macman45]

When the OP finally gets this sorted out, pse let us know what you found. It could help others down the road.

I’m tryinggg lol. But yes I will. Any truth to a failing CPS? No code for it but could be a weak signal and it keeps turning the motor over til it gets a reading

 

[MrBhp]

Yes on the CPS. I've experienced similar problems on at least a couple other vehicles.

 

[Macman45]

Made some progress via the EVAP canister out back. Found a little electrical tape repair from the PO. This is the hard plastic line (not the metal line) of the two that come off the canister assembly (also NOT the vent tube). I looked up and it goes to some sensor, then onto a nipple on the passenger side of the fuel tank. Pressure relief? Soo. With this “leak” / hole of sorts. It can’t build pressure? Opposite of my issue or maybe the canister can’t suck it out. Idk. Gonna go to the boneyard and get an entire hose and see. Check pics. Again, no CEL which is shocking.