Hello Everyone,

I hope all is well.

Been having a startup issue for the past few months, that’s starting to get frustrating.

At the moment car needs a very long crank (5-8 seconds) to start or multiple short cranks (3-5 two second cranks). When it would start there would be a small puff of smoke. Car would idle and drive perfectly. If you switched the car off and back on within 5 minutes it fires right up. If the car was parked for 15-20 minutes the problem would be repeated. Car occasionally starts fine (1/10 times) especially when I am trying to show the problem to someone LOL.

Notes to consider:

• New battery 2 months ago
• New coils and spark plugs last month
• Car crank strength is strong and consistent whether the problem is there or not, the crank does not get weaker.

I am suspecting the following from my readings, just wanted to get some opinions before going ahead and changing parts out:

• Crank position sensor
• Wiring harness for starter motor & alternator
• Earth/Ground cables
• Fuel Pump
• Starter Motor – Not sure if it is this as the crank strength isn’t weak

I am running a syvecs ECU with a toucan display and have a fuel pressure sensor installed, when ignition is on and fuel is priming the gauge shows 4 Bar fuel pressure, it takes around 9 minutes to drop to 2 Bar fuel pressure. I will test again and see how long it takes to drop to 0.
What is the “Normal” fuel bleed off time? Should it be holding pressure for longer?

A little about the car:

• Engine rebuilt to 3.8L
• Running a flex fuel sensor
• New fuel system with 2 additional pumps in the fuel tank, each pump has its own check valve, the pumps are activated by boost and have their own fuel line and filter, the additional fuel line connects to the center of the fuel rail.
• Initially had Bosch 1650 injectors installed, suspected they were leaky, swapped them out to ID1700x and the problem is still there.

Here is a video of the starting after the car has been parked for 2 hours:

Here is another video of starting immediately after the initial start:


Here is a short video showing how quick the pressure is dropping:


I did not have this issue before the rebuild.

 

Must be your Syvecs then. I bet on stock ECU it'd start right up like before. Did you try it?

 

Thanks for the input.

I can't start it on the stock ECU as the map on the ECU doesn't match my new injectors.

 

I believe your Syvecs have a built in trigger scope. Crank and see if your crank- and cam sensor signal look correct.

 

Have someone map it for your injectors. Shouldn't be rocket science.

 

Yes I believe it should have it, It's my first syvecs so I have to read on where I would find the sensor signals on the PC interface.

If anyone can assist on where to find them, I would appreciate it.

 

try priming the fuel pumps before trying to start. key on, wait for pumps to build up fuel pressure then start it. if that is not the issue then its cold start tuning within the syvecs.

 

Hey Prodigy, Thanks for the input.

I have tried priming the engine a few times before and it would still lead to the same result, I had my tuner look into it previously his adjustments weren't making any big difference.

He is back from holidays next week, I will let him have a look again.

Does anyone have an idea if my fuel pressure is bleeding off at a normal rate? Or faster than normal.

I will try and test the check valves and see if they are working well in the next few days.

 

Usually that's pump assembly related T. The tuner can hopefully shed more light though. Good luck!

 

so you are saying that you prime it, pressure goes to whatever you have it set to but car still doesn't start?


do you smell fuel? could be cold start enrichment issue or a bad coolant temp sensor. that is what ECU uses to know to go into cold start mode.


also you can check the crank sensor on the side of the trans and make sure your ecu is getting good AND consistent signal from it. certain flywheels mess with the sensors as well.

 

I had a similar situation with my syvecs on my gtr. It could be a software/mapping issue and either too much much fuel on start up or not enough fuel. Mine was too much fuel. Hope you get it sorted either way.

 

​​​​​​​Thanks

Yes I would prime and it still wouldn't start correct. When it doesn't start correct there is a strong fuel smell regardless if I primed before or not.

Thanks for the reminder on the coolant temp sensor I remember reading about it somewhere. If it is in stock I will swap it out tommorow.

Thanks for the input Nick, once my tuner is back in town I'll let him have a look again and see if he can sort it out.

 

See in software that coolant tempo sensor are reading correct values. There is no point changing it out if it is ok.
Did the car start perfectly every time before the rebuild?

 

Here is the thing and my friends had the same issue. Standalones as they're generic unlike the oem ecu look to get the cam timing synced on startup so they crank a few times to get that to happen and figured out. Sorry to say but you'll likely never start the car like you did on the oem ecu unless syvecs literally replicates what the factory box does. My buddies have fought this for a long time on almost every known standalone known to man, not syvecs, but still same thing. If you can look at cam sync I bet my left nut that the car fires up right after that's done.

 

Just a small update:

We blocked off the new fuel system to see if it was related to the check valves or plumbing, problem is still there. I'm glad it doesn't seem to be related to the new fuel system.

I also purchased a new coolant temp sensor (19$), will try and have it installed today, but I doubt it will solve my problem as the syvecs guage and car guage are matching, but I guess 19$ wont hurt anyone.

I am leaning more towards the issue being software related now. My tuner is back in town end of the week, will have him look at it again.

Cranking Amps?:

A friend of mine also mentioned that my battery cranking amps may too low (680A?) he recommended that I use a battery with 800+ cranking Amps? Can someone on here confirm if this could be an issue? Not looking to purchase a new battery when I just purchased one last month. (Battery pic attached)

Note: We checked battery voltage during a bad crank and the voltage was perfect. Start 12.5, during crank 11.5, after start 13.5