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Cold start issues

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Warharan

15+ Year Contributor
121
0
Dec 2, 2006
Los Angeles, California
I tried searching but could find anything that was similar to mine.

I'm having cold start issues, and by cold start I mean starting the car when the car has sat for a day. I live in Los Angeles so it doesn't matter if it's 50 F or 100 F, when you first start the car it has issues starting so I have to crank it at least 4-5 times to get it to start. Once it starts, even if it runs for 3 seconds and I shut it off. If I restart it, it'll fire right up no issues. So it's that initial start when the engine is "room temp". I have checked for vacuum leaks and replaced the idle air control. I don't think it's the fuel pump cause I can hear it whine away when you turn on the car. I have even set the car to on, waited 5 seconds and tried starting and still the same thing. My guess is that it must be the tune but I can't be 100% sure.


Also, it idles strange sometimes. I'll pull up to a light and it'll drop idle to like 100-200 rpm and then pull itself back up to 900rpm. Or Sometimes it'll keep reving itself, from around 1000 to about 2000 rpm like a vroom...vroom...vroom when I'm at a light. It is extremely annoying.


It's a 96 Talon TSi AWD heavily modded. Check my profile for specs. I'm running DSMlink V2.5 with a GM MAF and translator.


Does anyone else have any other ideas or can confirm it must be the tune?

PLEASE help!!! :pray:

I can even send someone my tune to take a look at it to see if there is an idle or start issue in it.

Thanks.
 
If your running E85 cold starts are normal but can be corrected somewhat with dsmlink v3. If your running 91 oct and are seeing cold start issues its either your fuel pump, fuel injectors, or adjustable fuel pressure regulator not keeping the pressure at the rail.
Start your car then shut it off then jump out and look at your fuel pressure gauge on your afpr, if its at ZERO then something needs replaced.
-If the afpr is old sometimes the diaphram inside it won't seat and you'll lose fuel pressure that way, you can get rebuild parts for it or buy a new one. (this was my problem) Aeromotive afpr Rebuild Kit
-If the check valve inside your fuel pump goes bad you'll also lose pressure but slowly in the rail, the fuel pump will work fine though after its primed the fuel system.
-Sometimes you'll have a leaking injector and the only way I know how to troubleshoot that is to put in a new set and watch your afpr gauge and see if you lose pressure after you shut the car off.

Attach a log of your cars idling problems rolling up to a light... are you running bigger IC piping?

:dsm:
 
Last edited:
This starting issue is very common here cause unlike the rest of the world, our fuel pumps won't prime. I have had 3 wally's and all of them lost the check valve so it bleeds down in a few minutes and long crank again. To verify the fpr you can remove the return line line AFTER the system is primed to see if there is fuel bleeding out of it, otherwise it is most likely the pump. If it were an injector you would notice other things like a puff of smoke on startup or fuel in the oil. I saw a b16 rod get twizlered from a stuck injector.
 
If your running E85 cold starts are normal but can be corrected somewhat with dsmlink v3. If your running 91 oct and are seeing cold start issues its either your fuel pump, fuel injectors, or adjustable fuel pressure regulator not keeping the pressure at the rail.
Start your car then shut it off then jump out and look at your fuel pressure gauge on your afpr, if its at ZERO then something needs replaced.
-If the afpr is old sometimes the diaphram inside it won't seat and you'll lose fuel pressure that way, you can get rebuild parts for it or buy a new one. (this was my problem) Aeromotive afpr Rebuild Kit
-If the check valve inside your fuel pump goes bad you'll also lose pressure but slowly in the rail, the fuel pump will work fine though after its primed the fuel system.
-Sometimes you'll have a leaking injector and the only way I know how to troubleshoot that is to put in a new set and watch your afpr gauge and see if you lose pressure after you shut the car off.

Attach a log of your cars idling problems rolling up to a light... are you running bigger IC piping?

:dsm:



Thanks for you guys' help.

I'll check the fuel system and the apfr gauge today and see if it's any of those issues.


My IC piping is only like 2.25 or 2.5 inches (can't remember exactly). I run a water to air IC so my IC piping is very short, just about 2 feet until it hits the IC.

I didn't have this issue before. The damn timing belt jumped on a start and bent my intake valves last year. So we took the head off to replace them and installed everything again and from that day it's having this issue. I've tried thinking what it could be so the fuel issue seems logical.
 
Watch your AFR's when the RPM's drop like that at a stop light, see if they go rich or lean. Also get up to speed (about 55mph) and downshift not giving it any gas, then watch your AFR's then too... Log while you do both of these and attach them, I had a similar issue that just took a few tweaks here and there in link to fix.

:dsm:
 
Watch your AFR's when the RPM's drop like that at a stop light, see if they go rich or lean. Also get up to speed (about 55mph) and downshift not giving it any gas, then watch your AFR's then too... Log while you do both of these and attach them, I had a similar issue that just took a few tweaks here and there in link to fix.

:dsm:


I think I know what the problem is. When I set the car to the on position the fuel pump doesn't turn on.

I figure the line isn't pressurized so that's why you have to crank it 4-5 times to get it started. Once it's started, the fuel line is now pressurized so then the car starts with no issues.

So I am wondering, in DSMLink V2.5 is there a setting to tell the ECU to turn the fuel pump on X seconds to prime the system before cranking?

Also I wonder could it be due to lower compression?

The head I have had been decked a couple of times. We believe because of that and 1mm oversized valves caused the pistons to hit. So to make up for it I have a 0.5mm thicker than stock head gasket now.
 
I think I know what the problem is. When I set the car to the on position the fuel pump doesn't turn on.

I figure the line isn't pressurized so that's why you have to crank it 4-5 times to get it started. Once it's started, the fuel line is now pressurized so then the car starts with no issues.

So I am wondering, in DSMLink V2.5 is there a setting to tell the ECU to turn the fuel pump on X seconds to prime the system before cranking?
The fuel pump DOES NOT turn on when the key is in the ON position, this is a safety feature from the factory. The fuel pump will only come on when you actually turn the key to start the car, and yes there is a feature in link to manually turn on the pump. Its a option in the Misc tab however its for troubleshooting no start issues to make sure your pumps working and not to pressurize the line before you intend to start the car.

Your assumption about the fuel line not being pressurized is correct, thats exactly why it takes a few turns before the motor kicks on. Your fuel system should be pressurized even with the car off and in the above posts thats what I tried telling you... fuel pump, adjustable fuel pressure regulator, OR an injector is likely leaking. Like I said before start your car and then shut it off and check the fuel pressure gauge on the afpr, if its at 0 the instant you shut off the car I'd say rebuild your afpr. If it steadily drops to 0 after a few seconds then I'd be looking into putting in a different fuel pump to see if that fixes the problem.

Your cars low idle/idle surge you see at decel and at a light is more than likely related to a high airflow reading that your ECU is having a hard time correcting for. Its easily fixed by using the Idle Air Clamp tab in link, just open it up and read the "?" help section to learn how to set it up correctly.

:dsm:
 
As stated before almost every walbro pump I've installed on a dsm has had cold start issues after. Its quite common. Also on a side note your aeromotive afpr is most likely bleeding off pressure very rapidly every time you shut the car off. I emailed aeromotive about this issue and one of the tech's told me that it was normal and they aren't made to hold pressure while the car is off. Sounds like BS to me but thats what they told me. I've seen a few lucky aeromotive regulators that did hold some pressure after the car was shut off but not many.
 
As stated before almost every walbro pump I've installed on a dsm has had cold start issues after. Its quite common. Also on a side note your aeromotive afpr is most likely bleeding off pressure very rapidly every time you shut the car off. I emailed aeromotive about this issue and one of the tech's told me that it was normal and they aren't made to hold pressure while the car is off. Sounds like BS to me but thats what they told me. I've seen a few lucky aeromotive regulators that did hold some pressure after the car was shut off but not many.
Thats interesting to hear about the Aeromotive afpr, my buddies 1g running a Wally 255 and Aero afpr will hold 37psi in the rail for weeks. :coy:

:dsm:
 
The fuel pump DOES NOT turn on when the key is in the ON position, this is a safety feature from the factory. The fuel pump will only come on when you actually turn the key to start the car, and yes there is a feature in link to manually turn on the pump. Its a option in the Misc tab however its for troubleshooting no start issues to make sure your pumps working and not to pressurize the line before you intend to start the car.

Your assumption about the fuel line not being pressurized is correct, thats exactly why it takes a few turns before the motor kicks on. Your fuel system should be pressurized even with the car off and in the above posts thats what I tried telling you... fuel pump, adjustable fuel pressure regulator, OR an injector is likely leaking. Like I said before start your car and then shut it off and check the fuel pressure gauge on the afpr, if its at 0 the instant you shut off the car I'd say rebuild your afpr. If it steadily drops to 0 after a few seconds then I'd be looking into putting in a different fuel pump to see if that fixes the problem.

Your cars low idle/idle surge you see at decel and at a light is more than likely related to a high airflow reading that your ECU is having a hard time correcting for. Its easily fixed by using the Idle Air Clamp tab in link, just open it up and read the "?" help section to learn how to set it up correctly.

:dsm:


Again thanks to everybody's help.


Ah ok. Yes I did check the afpr gauge and it was 0 as soon as the car was off. I don't think it's the fuel pump because the pump was changed a couple years ago and this issue started when we replaced the vales on the head recently. So I'm guessing I have to rebuild the aeromotive. I'll go ahead and order the kit you suggested.


I'll also go ahead and make that adjustment in DSM Link.


I do have one question though. As the apfr is 0 right when you turn the car off, and obviously 0 after the car sits overnight, why does it turn on so easily even after the car has been sitting the last 2-3 even 4 hours hours as opposed to overnight/a day though when the afpr is 0 in both cases?
 
Before you go and purchase a rebuilt kit for the aeromotive check the 4 bolts that hold the top down onto the diaphram. I had an issue with mine backing themselves out. I eventually had to locktite them down and I also had to have the diaphragm replaced later on down the road.


Thats interesting to hear about the Aeromotive afpr, my buddies 1g running a Wally 255 and Aero afpr will hold 37psi in the rail for weeks. :coy:

:dsm:

He's a lucky one LOL. According to aeromotive it will not affect the performance of the regulator under load at all.
 
Again thanks to everybody's help.


Ah ok. Yes I did check the afpr gauge and it was 0 as soon as the car was off. I don't think it's the fuel pump because the pump was changed a couple years ago and this issue started when we replaced the vales on the head recently. So I'm guessing I have to rebuild the aeromotive. I'll go ahead and order the kit you suggested.


I'll also go ahead and make that adjustment in DSM Link.


I do have one question though. As the apfr is 0 right when you turn the car off, and obviously 0 after the car sits overnight, why does it turn on so easily even after the car has been sitting the last 2-3 even 4 hours hours as opposed to overnight/a day though when the afpr is 0 in both cases?
Because there is still fuel in the rail & lines right after you initially shut the car off, after a few hours the fuel eventually drains back to the tank.

:dsm:
 
Because there is still fuel in the rail & lines right after you initially shut the car off, after a few hours the fuel eventually drains back to the tank.

:dsm:


Ah ok, thank you.

I'll go ahead and check the apfr then. Thanks again for all your help. I hope it fixes the issue. :thumb:
 
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