Cold start extended crank issue

allutz

Founding Member
Nov 17, 2001
170
0
16
southeast pa
Hey guys. 02 GT..Having an issue with cold start extended crank. Usually only happens first thing in am or i guess if car sits 8hrs or so after driving. A little background to help rule out different possibilities. Car has 285k..i replaced longblock 18k miles ago. 1 week before installing the KB Supercharger (5 weeks ago)the extended crank started happening..otherwise the engine runs flawlessly. Just that 4-5 sec crank first thing in the am then sputtering till it reaches normal idle. The rest of the day its a 1/2 sec crank then fires up. When i installed supercharger last month i replaced the coolant temp sensor(orig)..tps(also orig)..iac(yup,orig) and the fuel pump(had abt 180k on it). Fuel injectors are new(part of the kb kit)as is the fuel filter.Remember, the issue started BEFORE i installed the sc and before any of the other parts were replaced.... Crank and cam sensors are still orig as well as the frps but the car runs perfectly otherwise...especially under full boost!!! anyone else have or fix this problem??
 
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allutz

Founding Member
Nov 17, 2001
170
0
16
southeast pa
Also, until i installed the sc the fuel injectors were origional too! I was hoping that somewhere in all the new parts install with the sc that the cranking issue would have been resolved...but it hasnt..lol
 

wmburns

SN Certified Technician
Aug 14, 2009
5,825
501
194
Houston Texas
Try this. Cycle the key on/pause/off several times without cranking. Does this improve cold starting? If so, suspect fuel pressure leak down.

Note, there are multiple locations for fuel pressure leak down. Examples include (but not limited to):
  • fuel injectors
  • fuel pressure regulator or FRPS
  • Fuel pump check valve.
It would be handy to KNOW what the fuel pressure is before and during cranking. Do you have an ODB2 scanner?

The other possibility is a unstable/missing cam sensor signal. This causes the PCM to have to allow the motor to spin 720 degrees in order to get synced up. But likely this would happen all the time and not just after an extended cold soak.

ForScan ODB2 scanner w ELM327 USB
 

allutz

Founding Member
Nov 17, 2001
170
0
16
southeast pa
Try this. Cycle the key on/pause/off several times without cranking. Does this improve cold starting? If so, suspect fuel pressure leak down.

Note, there are multiple locations for fuel pressure leak down. Examples include (but not limited to):
  • fuel injectors
  • fuel pressure regulator or FRPS
  • Fuel pump check valve.
It would be handy to KNOW what the fuel pressure is before and during cranking. Do you have an ODB2 scanner?

The other possibility is a unstable/missing cam sensor signal. This causes the PCM to have to allow the motor to spin 720 degrees in order to get synced up. But likely this would happen all the time and not just after an extended cold soak.

ForScan ODB2 scanner w ELM327 USB
Hey thanks for replying! So fp is @30-31 when i first turn key on(thru obd scanner)then cycle key pops up to abt 40psi..still stumbles n bumbles before it starts..as noted i had already replaced the fuel pump and sender and injectors are new with the sc install and iac and tps are new also done @sc install(not to chase the issue but to not have issues after sc install being the sensors were orig and i had replaced the pump abt 180k ago). So we can rule out all those..like i said, the issue popped up the week before the sc install and is still there after no better no worse.no other symptoms whatsoever. What role would the frps have in initial cold start? When i installed sc the vac line to the frps was dry...
 

allutz

Founding Member
Nov 17, 2001
170
0
16
southeast pa
Try this. Cycle the key on/pause/off several times without cranking. Does this improve cold starting? If so, suspect fuel pressure leak down.

Note, there are multiple locations for fuel pressure leak down. Examples include (but not limited to):
  • fuel injectors
  • fuel pressure regulator or FRPS
  • Fuel pump check valve.
It would be handy to KNOW what the fuel pressure is before and during cranking. Do you have an ODB2 scanner?

The other possibility is a unstable/missing cam sensor signal. This causes the PCM to have to allow the motor to spin 720 degrees in order to get synced up. But likely this would happen all the time and not just after an extended cold soak.

ForScan ODB2 scanner w ELM327 USB
could the frps actually be showing the ecm an incorrect fuel pressure causing ecm to cut fuel slightly on cold startup??
 

wmburns

SN Certified Technician
Aug 14, 2009
5,825
501
194
Houston Texas
could the frps actually be showing the ecm an incorrect fuel pressure causing ecm to cut fuel slightly on cold startup??
Why guess? Test!!!

Consider also the IF the FRPS were showing an incorrect pressure, wouldn't it stand to reason that it would be incorrect all the time? Again. Why guess? Test! Plus IF the cold soak fuel pressure is low this all but "proves" there's a fuel pressure leak some where in the system. After all the system is supposed to hold pressure between start ups.

Regarding your trouble shooting methods. it seems to me that you are ruling possible causes out simply on the basis that a part has been replaced without testing or confirming. Let me ask this. When you replaced the fuel pump did you replace the entire fuel basket or just the pump? Why does this matter? Because if just the fuel pump is replaced this means there could still be a bad check valve or a leak in the flexible line between the fuel pump and gas tank hat.

If you have an ODB2 scanner then think of ways to use it. For example. If you have a theory about what might be going on, then use the ODB2 scanner to either prove it or disprove it.
 

allutz

Founding Member
Nov 17, 2001
170
0
16
southeast pa
Wait a sec...as i said earlier i wasnt throwing parts at the problem..these were all parts that had 285k miles on them and had bought them to replace at the same time as i installed the supercharger to avoid any failures and having my engine blow up under boost . The fact that this prob started 5 days before i installed the sc is purely coincidental.. And yes..i know i can test test test..i came here to see if anyone had or has the same issue.and yes i had replaced the pump and sender(basket) together.
 

Onesick99GT

Active Member
Nov 20, 2018
359
47
38
33
Dayton, Ohio
It's definitely fuel pressure related. I would replace the frps. Then check for any fuel leaks. My guess would be a clogged fuel fuel filter, check valve on the fuel pump or a failing fuel pump. New parts can be bad and in your case a bad fuel pump. Remember it takes fuel, and spark to make combustion. Have you replaced or had your injectors cleaned. How about the ignition coils. Any vehicle over 100k miles should have brand new injectors, ignition coils and plugs done. That's the first thing I'd do buying any vehicle with 100k miles on it and more to make sure the motor is running as it should. Then pull codes if any before troubleshooting possible issues. Most of the time doing this will fix 90% of issues unless something is failing. Typically a part that contributes to make the motor run. Sensors ect ect.
 

allutz

Founding Member
Nov 17, 2001
170
0
16
southeast pa
It's definitely fuel pressure related. I would replace the frps. Then check for any fuel leaks. My guess would be a clogged fuel fuel filter, check valve on the fuel pump or a failing fuel pump. New parts can be bad and in your case a bad fuel pump. Remember it takes fuel, and spark to make combustion. Have you replaced or had your injectors cleaned. How about the ignition coils. Any vehicle over 100k miles should have brand new injectors, ignition coils and plugs done. That's the first thing I'd do buying any vehicle with 100k miles on it and more to make sure the motor is running as it should. Then pull codes if any before troubleshooting possible issues. Most of the time doing this will fix 90% of issues unless something is failing. Typically a part that contributes to make the motor run. Sensors ect ect.
Hey thanks for the reply. I havent had a chance to get back to it yet. I only get 1 shot at it per day..lol..so heres what i have... The cold start issue popped up 5 days before i installed the KB supercharger. BEFORE i installed the sc i had installed a new reman longblock, coils,plugs, airaid cai,bbk 73mm tb and bama 93oct tune..the car ran and started flawlessly for 18000 miles. Went out to start car 5 days before installing the sc and had the extended crank.. Only does it first thing in the am(or after sitting abt 8-10hrs). After it finally starts it spits n sputters a few secs then is 100% normal..i can shut it off and restart it rt away no problem. So, with the KB i also installed new fuel pump and sender,iac,tps and cts. Pump was abt 10 yrs old close to 200k and sensors were all orig with 285k on them. These were all parts i had bought BEFORE i had the cold start issue. With theKB kit the throttle body, injectors,maf,fuel filter(only had 18k on filter replaced with longblock)and spark plugs were all replaced and the KB tune loaded as well. (The maf and injectors were orig too..285k). After all that the cold start issue is still there...EXACTLY the same. No better..no worse..no codes then no codes now.. The fuel pressure @ initial key turn is @abt 30-32psi and pops up to 40 and higher with each key cycle. I can cycle key 5 times and cold start issue is still present even with fp showing 40+psi..and like i said, i can shut it down as soon as it idles normally(abt 5-10 secs) and itll fire up instantly. After that the car runs flawlessly! So you can see how i only have 1 shot a day to test things..lol.. The frps, crank sensor and cam sensors are all still orig. The crank sensor is showing rpm count the second i turn the key so im kind of ruling that out until i can find the actual spec to ohm it out. Theres no fuel present in the frps vac line(last time i had it off anyway at sc install).
The one thing i did find is that my alt voltage is jumping all over the place(12.6 to 13.9). I bought a rebuild kit and supply wire upgrade kit and will do all that today or tomorrow. I have a sneaky suspicion that that could be my issue but not really sure how that lends to a cold soak issue only and ZERO other problems. But, its something that needs to be fixed . the alt is a pa performance 130a and is 1 yr old(12000 mi).
Not sure if i missed anything....but there it is..lol
 

wmburns

SN Certified Technician
Aug 14, 2009
5,825
501
194
Houston Texas
I am a firm believer that EVERY trouble shooting session should start with a through review of the battery and charging system. Today's electronic cars simply won't run right without a strong battery and stable alternator.

Howto perform charging system voltage drop test

What you don't know is IF the voltage is changing because of a bad alternator/ground/battery or the voltage is changing because of excessive draw (load step) bringing the voltage down.

I would also like to know IF cracking the throttle open during cranking helps.

Next does spraying a small amount of starting fluid inside the throttle body help?
 

allutz

Founding Member
Nov 17, 2001
170
0
16
southeast pa
I am a firm believer that EVERY trouble shooting session should start with a through review of the battery and charging system. Today's electronic cars simply won't run right without a strong battery and stable alternator.

Howto perform charging system voltage drop test

What you don't know is IF the voltage is changing because of a bad alternator/ground/battery or the voltage is changing because of excessive draw (load step) bringing the voltage down.

I would also like to know IF cracking the throttle open during cranking helps.

Next does spraying a small amount of starting fluid inside the throttle body help?
Understood.. The voltage when running literally bounces all over the place constantly..last time i checked cold batt v was @ sc install and it was @12.4v then and alt output was same as when new @14.1,13.9-14v loaded, abt 6 weeks ago.(.ill check cold batt v again also before i start it today)had the issue then ,still have it now. Zero cranking issues,cranks strong and no i havent tested the starter amp draw cold..yet..didnt even think to check alt output and only came across the varying voltage while looking at other data info recently. Car also runs perfectly except for the initial extended crank in the am.Tons of variables...ill give the cracking of the throttle a shot in a few mins as i havent started car yet today. Like i said i only get one shot a day to test any given possibility..
 

wmburns

SN Certified Technician
Aug 14, 2009
5,825
501
194
Houston Texas
Something else that an ODB2 scanner could be used for to help focus trouble shooting. When the motor is stone cold do the PCM reported values of the IAT and ECT sensors nearly match ambient outside temperatures?

IF the PCM has inaccurate values for IAT or ECT this could cause the PCM's fuel enrichment program to be in error.
 

allutz

Founding Member
Nov 17, 2001
170
0
16
southeast pa
Something else that an ODB2 scanner could be used for to help focus trouble shooting. When the motor is stone cold do the PCM reported values of the IAT and ECT sensors nearly match ambient outside temperatures?

IF the PCM has inaccurate values for IAT or ECT this could cause the PCM's fuel enrichment program to be in error.
I know the ect does read near ambient..not sure abt the iat though. The iat was part of the KB supercharger kit. The install manual has you cut the 2 wires at the maf and cap off the wires at the maf and splice the 2 maf harness wires to a harness connector that runs to an iat sensor on the supercharger manifold. While i do not know the cold temp of the iat i do know that the issue was there 5 days before installing the sc and it didnt change one bit after or since...ill check on that iat temp tomorrow am..
 
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