Cj_ls1

When I go start my car everyday iv noticed if it's been sitting for more then 15-20 mins it won't start on the first attempt even tho I here my fuel pump prime it will crank and crank until I cycle off then when I do it again it fires up immediately with no hesitation. I learned the little trick tho if I prime it cycle prime it again it starts no problems! I'm confused tho because I herd with are fuel pumps there all or nothing I had a 94 lt1camaro an it worked fine until 1 day it just wouldn't start at all this 1 gives me no problems while driving never shuts off I have full power and everything.. Iv changed fuel filter fuel relay my starter is good I don't get it and the original owner told me it's been doing it since 30k miles it now has 43k wouldn't it have gone out if it was a faulty pump? Btw it's a 98 trans am a4

LS6427

iTrader: (2)

So this only happens when the car is HOT.....but it's been sitting 15-20 min after it has gotten HOT....?

And when I say HOT I mean up to operating temp.

I was gonna say clean the MAF. But if you can turn the key to ON, then OFF, then ON again.....which will prime the fuel pump twice......then it will start right up....that's strange.

.

Cj_ls1

Yes at operating temp it wil fire up no problem some days even when it's cold an I haven't driven for a day I'll try my luck an it will fire up right away but it's rare. I'm not understanding an I want to take to get a diagnostic but I know there going to tell me it's this and that jus to charge more so I wanted to get an idea wat I'm dealing with

NOS LS1

iTrader: (3)

This is usually caused by a bad in-tank fuel pressure regulator that is bleeding off fuel pressure. That factory fuel pressure regulator is supposed to hold fuel pressure after you shut the car off so it will start easily later on or the next day.

My car does the same thing. Lonnie at Lonnies Performance told me this on the phone. He is a sponser here on LS1 Tech.

Cj_ls1

So do I have to replace the whole fuel pump? I had my mechanic replace my fuel regulator I don't know if it was the (In tank) sound the same lol what did he recommend?

dailydriver

I believe that on the LT1/4 cars the fuel pressure regulator is up near the fuel rails/intake in the engine bay, but I could be wrong.

It is DEFINITELY a PIA tank drop deal on the LS1 4th gens.

SteveWs6

iTrader: (1)

Do you have a check engine light on? If you're going to condemn the fuel pump first i'd at least check fuel pressure and stuff before just replacing it. It could also be the temp sensor, crank or cam position sensor. But those would kick on a check engine light.

Cj_ls1

No check engine light only my coolant light comes on an it's after 15 mins of driving I was told it was a bad sensor

SteveWs6

iTrader: (1)

I'd def just put a temp sensor in there and start form there.

JLFIII

iTrader: (1)

I had virtually the same symptoms you are describing on my 98 T/A...turned out to be the fuel pump.

NOS LS1

iTrader: (3)

Put a fuel pressure gage on the car & check your fuel pressure while the engine is running. Should be at least 55-58 psi. The factory fuel pressure regulator is designed to hold fuel pressure when you shut the car off so that when you go to start the car later or the next day...it will fire right up. I have the same problem with my car & i was told that its the in tank fuel pressure regulator that is bleeding down fuel pressure. The pressure bleed off is usually the fuel pressure regulator. Fuel Regulator Diaphragm could have a hole in it. Its common.
I was told to only use a factory gm regulator. GM Regulator is much better than after market reg.

It would be a very good idea to upgrade your fuel pump to the Racetronix / Walbro intank 255 LPH Fuel pump with hotwire kit if you plan on making additional H.P. in the future.

Dont forget to do the " Trap Door Modification " if you decide to install a new intank regulator & fuel pump. This Trap door modification gives you much eaiser access to the fuel pump so you dont have to drop your fuel tank.
Use the search box on this site to look up trap door mod.

Click on this link for trap door modification info ... https://ls1tech.com/forums/lt1-lt4-m...-mod-pics.html

Blk98ls1

iTrader: (3)

I just finished dealing with this exact problem, it is a check valve inside of the fuel pump. It stays open and allows the fuel to drain back into the tank while the car is sitting. Change the fuel pump and it will fire up right away. I went with a racetronix fuel pump from tickperformance.com, they have free shipping over $100 and the pump is $150. Some people buy the wire harness to provide extra power to the pump directly from the alternator, I chose not to as the pump provides more than enough fuel without the extra juice provided by the harness. Let me know if you have any questions. I used the "trap door" method to replace the pump. Should you ever need to replace the pump again it would take a few minutes.

Cj_ls1

Thanx man, will do!

dailydriver

Is there a sticky, or an older thread somewhere that details the "trap door" method???

NG_LT1

Here you go,

http://www.camaroz28.com/forums/fuel...-style-810959/

dailydriver

THANKS!!

michakaveli

Did you replace the in tank check valve? Or is the valve located in the fuel pump?