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Hard Start When Warm

gingerdude

gingerdude

Donating Users
I'm curious if anyone else has experienced this issue.

When my engine is cold or cool it starts right up as soon as I turn the key. But if I have been driving for awhile it seems to need to crank longer in order to start. My mechanic friend said to me "Yeah I have seen this in other car with these engines." Is this typical? Any ideas what it could be?
 


mine does the same thing. I have no idea what causes it. I just give it some gas and it will turn over. my car is an L67.
 
Fuel could be boiling in the fuel rail and could have some sort of vapor lock which causes the hard start.

The 3.1's fuel rail is subject to more heat than the 3800 rail.
 
I had the same problem with my 3.1. It turned out to be the fuel pressure regulator. It shouldn't be the heat. I drive my car all over Fl. and haven't had any problems.
 
My fuel pressure regulator doesn't seem to be leaking, but I have half a mind to just change it out anyways. Maybe I'll do that after I swap in the platinums if that doesn't fix it. Was your pressure regulator showing any outward signs of failure? Mine has no leaks, the pressures are in spec when I tested with the gas pump tool, and the pressure changes when I pull the vacuum line. So it seems to pass all of the tests....
 


gingerdude said:
My fuel pressure regulator doesn't seem to be leaking, but I have half a mind to just change it out anyways. Maybe I'll do that after I swap in the platinums if that doesn't fix it. Was your pressure regulator showing any outward signs of failure? Mine has no leaks, the pressures are in spec when I tested with the gas pump tool, and the pressure changes when I pull the vacuum line. So it seems to pass all of the tests....[/QUOTE Mine car took longer to start when the engine was warm but started normally when cold. I didn't see any leaks. You have to force these to leak. With the engine warm and running take the vacuum hose off the regulator. Take the end of the hose and wick the tube opening on the regulator. You'll have to do this for a couple of minutes or so to draw the gas out of the top of the regulator (providing the regulator is leaking). These things leak internally, not externally.
Click to expand...
 
Fivefingerdeathpunch said:
Do not install platinum plugs in a 3100 or 3800, they don't like the waste spark ignition system.

Stick with Iridium or copper plugs only.[/QUOTE I have a 01 w/ a 3.1 and the owners manual says to use the double platinum AC Delco plugs. That's what came with the engine from the factory. What gives?
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I have done literally everything possible to help with starting on my 02, and just every once in a while a warm start is difficult. Seems consistent, like a certain amount of time. Like the engine has cooled off enough but maybe the coolant sensor thinks its a bit warmer so it doesn't want to start. But yeah, FPR, TB, IAC, MAF, tuneup, etc., etc. is all cleaned and/or new. But with all of that its much better than many other 3800s, I see it all the time at work. They're probably not kept up as well and they almost always hard start when warm, so I guess what I did helped.

But yes, 3800's warm hard starting has been a super common thing that I've noticed for a long time. My 06 GT however doesn't seem to be affected by anything, starts about the same anytime. The whole electrical system is changed on the 04+ though. I have seen 04+ hard start but it's almost guaranteed to be the throttle body though. It also functions as the iac.
 
I have always followed the rule of not using platinum plugs with waste spark systems. GM used several different OE plugs back in the day and mostly all are Iridium plugs.

I've seen come backs at work because of platinum plugs as they don't last as long. The iridium plugs normally have a longer life.

Even with the double platinum plugs I still do not trust them on these engines.

http://www.aa1car.com/library/sparkplugs_for_dis.htm
 


Fivefingerdeathpunch said:
I have always followed the rule of not using platinum plugs with waste spark systems. GM used several different OE plugs back in the day and mostly all are Iridium plugs.

I've seen come backs at work because of platinum plugs as they don't last as long. The iridium plugs normally have a longer life.

Even with the double platinum plugs I still do not trust them on these engines.

http://www.aa1car.com/library/sparkplugs_for_dis.htm
Click to expand...

Great article. Explains it clearly. I have about 50k on some NGK's I put in. I think I might go with some AC delco Iridiums. Thanks for the info.
 
The article is more pointing towards the single platinum plugs and not the doubles but I still feel that a problem could happen.

I just error on the side of caution when it comes to these engines now. They say the double platinum plugs are made differently using both iridium and platinum together so that it will wear less and hold up the extra spark they see every revolution.

The AC Delco 41-101 plugs are the other OE plug that is used, for sure in all 3800 powered cars.
 
I just don't know if I can buy the "these cars have a hard start sometimes" I keep hearing though. My previous car had the same 3100 and the similar 4t60e (okay maybe older versions, but essentially the exact same) and it NEVER hard started when warm. It just doesn't make any sense how the same drivetrain but several years newer would have this issue. Not to mention the misfire at idle issue I can't pin down. Something isn't right.
 
There could be a problem with your ICM (ignition control module) too. Which might explain the misfire as well as the hard starting under heat. I had this happen on an oldsmobile i had. I wouldn't go out and just buy one though as they are fairly expensive. $200.00 or so for an OEM one. I'm not sure if or how you can test these to see if they're bad. Maybe fivefingerdeathpunch can shed some light on this.
 
I'm still leaning towards the FPR starting to go bad.

I know you said you have good fuel pressure but when the engine is hot and you shut it down, the FPR should still be holding pressure for a quiet some time after the engine is off. It's that short time that fuel can either seep past it internally or it just fails to hold the pressure and the fuel starts to boil in the rail causing the long crank/hard start.

I'm just arm chair guessing here over the web but that just seems like it could be the problem. I wouldn't think the ICM is acting up so I'm not looking that direction.
 


I swapped all coils and an ICM from a vehicle that ran perfectly into my car as a test about 3 month ago and it didn't do anything for me. Now I wasn't testing for hard start at the time, but it didn't clean up my misfire at all. I'm thinking those components are good.

Be aware that my car is only sitting with 44,000 miles on the dash, it was garage kept, and driven by my grandparents. My grandpa worked for AC Delco, so he kept meticulous care of the vehicle. So I would be super surprised if electronics are failing on it given how well it was taken care of and hardly driven.
 
But yeah I have been considering swapping a new FPR in just to see if it will work. I just don't want to toss parts for no reason though.
 
Did you do that test I mentioned earlier on the FPR? That will tell you if it's bad or not instead of going through the hassle of replacing a part. You may have a bad wire or spark plug causing a misfire too. One guy on a previous post had a problem with a misfire. He found out that one of the spark pug wires was laying on top of the vacuum hose that goes from the upper plenum to the brake booster. The vacuum hose has a wire mesh in it for rigidity and was messing w/ the plug wire. Check that on yours too. A lot of times it's the simplest things.
 
I have not done the test yet, but I will and report back when I get the chance next. Hopefully in the next few days.
 
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