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hard starting LS1
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Posted by: ddot

I bought my 1998 firebird formula about a month ago it has 5.7 LS1 engine with 50,000 miles on it. Now I will get to my problem, about five times now i go to start it and it just spins and spins try after try. I then give it some gas and one or two tries later it starts. I have changed the fuel filter and put GM injector cleaner in it but it has still happened. It doesn't seem to matter if it is cold,hot wet, or dry no pattern. So if someone can tell me what is wrong or even what you think is wrong pleas do. Thanks for any help

Can someone tell me how to check fuel pressure and what a fuel pump would cost that is my last guess.

PS. LOVE THE CAR SO FAR(just think it is going to leave me stranded and not start one of these times)

Posted by: Grape Ape

The only place other than a dealer or A/C delco parts supplier(part # MU195) I know of that has it is NAPA and they get over $400 for them. That would include the pump, strainer, etc. They aren't cheap, even from Delco, but likely less than that(figure $315+).

Sounds to me like it might have a bad sensor. You may even be getting vapor lock, but that is usually a bit different in regards to the sypmtoms. If it were the fuel pump, you'd probably not get it to start at all. BUT, it could be very weak, causing hard starts. I just kinda doubt it. If you haven't, buy gas from somewhere else(93Octane if available) and go from there.

Posted by: LS1JAY

I agree with Itllrun, it sounds like a bad sensor, but if it is, you should have a SES light. If you don't have a SES light, have it scanned as it may have set a code before you bought it, if so, it will be saved in the computer as long as the battery has not been disconnected.

Posted by: StoneFox

sounds like the crankshaft position sensor

Posted by: cswrench

fuel pressure spec is 55-60 psi key on engine off. This is checked with a fuel pressure gage at the fuel rail schrader valve. after pump runs pressure should hold via a check valve in the tank. if fuel pressure bleeds down, You will have an extended cranking condition. This can be present and cause no running problems once the car is started. If pressure bleeds down you could have a multiple problems. faulty fuel pump asm,fuel injectors or a leak. (If you have a leak externally i am sure you would have noticed it!)

Posted by: ddot

I have a superchips tunner for my silverado that has the gm decoder built in, so I scanned the firebird and it was clear no codes present. But I also was thinking in the back of my head possible crankshaft sensor what do the rest of you think.

Posted by: cswrench

I have never replaced on yet on an LS1

Posted by: Grape Ape

I've never seen anything with a bad CPS actually run. Do they? Seems to me, if they would, they'd also have a horrible miss. I'm thinking something more along the lines of a problem with the TPS or maybe a screwy O2 sensor. That's the issue with sensors though... Bad or not, they're hard to diagnose sometimes. Another thing might be a problem in the ignition switch itself. Or worse, a bad ECM.

Posted by: LS1JAY

How does the car run after you finally get it started? does it idle smooth, does it run strong at WOT?

Also, does it have the stock cam?

Posted by: ddot

once is starts runs great no other problems what so ever. As far as I know it is stock like i said I have only had it about a month. so what do you think would just make it hard starting with no other symptoms.

Posted by: LS1JAY

Hmm, could it be the starter? other than the sensor theory, I just don't know.

Posted by: cswrench

Have you checked fuel pressure yet?

Posted by: ddot

no hopefully tomorrow , knock on wood but it hasn't done it in a few days now.

Posted by: ddot

I didn't get it checked out yet I'll let you know what I find out.

Posted by: ddot

Well i still haven't had anything check out but after I replaced fuel filter and put injector cleaner in, it did it only once that was the day after. Since that not a problem maybe the injector cleaner did the trick , maybe it had water in the tank, I am sure it was sitting a good 6 months on the car lot through fall and winter so I put isopropyl in the tank also. So i believe all is good.

PS. did the free ram air mod,egr mod, and should be getting a lid soon.

Posted by: GT500

when u guys say lid i dunno if its a slang word or a real part name? can someone explain wat it is? lid....throttle body that thingy that moves sideways with u rev it? im clueless

Posted by: EvilLS1

Quote:


	Originally posted by GT500 when u guys say lid i dunno if its a slang word or a real part name? can someone explain wat it is? lid....throttle body that thingy that moves sideways with u rev it? im clueless

Its the big plastic "lid" that covers the airbox. The stock lid has alot of little baffles on the inside and a silencer which restricts air flow.. An aftermarket lid is smooth on the inside and has no silencer.

Posted by: Dirtybird

I have a 98 T/A and it does the same thing; no SES code it just takes a few cranks on any given day... When it was at the shop they checked fuel pressure, starter ect with no luck. Hmmm, your not alone evil-one.

Posted by: ddot

It still has not done it again since filter change plus injector cleaner. I think that fixed it all is still good.

Posted by: Dirtybird

What kind of filter are you running?

Posted by: ddot

just a regular napa filter nothing special. good luck

Posted by: red98ta

My 98 LS1 has been doing the exact same thing on and off for the past 2 years. Unfortunately the problem has returned. The first time this happened to me, I changed the fuel filter and the problem seemed to disappear. Later the problem returned and I bought a fuel pressure gauge and found nothing wrong with my pressure at all. Then the problem went away for awhile.

The motor spins but shows no sign of fire no matter how long it cranks. It will usually start on one of the later attempts. I killed the battery one day cranking away and bought a new battery. The problem went away again.

The next time the problem came back I was able to determine that it didn't have any spark and the car had no stored code. That brought me to the conclusion it was an electrical problem. I checked all my connections such as IGN relay, fuses and computer and the problem went away.

Now my car is doing this almost every time I start the car somewhere other than home. Does anyone have any clue what else I could check? The car runs great and has zero problem but sometimes doesn't want to fire when starting. I have been told to replace the computer and crankshaft sensor but I don't like to guess at the problem.

Any help from others having this problem would be appreciated

Posted by: ddot

would the pass lock computer chip in the key have anything to do with this , next time try your spare key let me know if this works. hope mine doesn't come back.

Posted by: red98ta

No its not the key, The passkey feature will disable the starter. I haven't determined any pattern of the time when it will start right away or when it won't. Hot, cold, age of gas doesn't seem to matter. I have always thought the computer may be the problem. I have a device called autotap that lets me hook up to the cars computer and monitor all the sensors. Everytime I hook the computer up, the car always starts. Everyone I talk to seems to think the problem is being caused by the cars computer. I know that it is not getting spark when it refuses to start, I know that it has full pressure on the fuel rail. I don't know whether the injectors are firing or not but I never smell gas or see a puff of smoke when it does start. For now I just deal with it.

Posted by: ddot

let me know if you ever figure it out good luck thank.

Posted by: red98ta

The problem turned out to be a bad ign relay under the hood. Replaced the relay and the problem is gone. The fans use the same relay.

Posted by: ddot

thanks for the info, did you replace it or the shop. where exactly is it how much was it. ,pics would be nice

Posted by: tbaum

Glad you are up and running. Just some other things to check...
If you have the stock battery, check your negative terminal. GM batteries have a habbit of corroding through to the post. (Happened on my Yukon) Also you might want to bite the bullet and install a new set of plugs and wires as well.

Posted by: ddot

Well I took my car out of winter storage and after a few weeks , this problem came back again.
On three different occasion the car was very hard starting ,it would just spin and spin. the last time my car would not start at all.
I knew the battery wasn't the best cause it went dead on me twice so I went and bought a red top put it in and still would not start then I was pissed. So I came back to this thread red it and decided to try the relay.
I pulled a relay for the fans cause they have the same part# number as the ignition
and put it in the ignition and the car started right up,then put the old one back in and the car would not start.
So I found out it was probably the relay the hole time.
THANKS

On a side note does anyone know what this relay does, does it control spark an or the gas or what.Cause I would have thought as many times I tried to start it,( I even floored it a couple of time) it would have been flooded. But when I switch the relay it stared up no problems.

Posted by: StoneFox

Quote:

Originally Posted by ddot


	On a side note does anyone know what this relay does, does it control spark an or the gas or what.Cause I would have thought as many times I tried to start it,( I even floored it a couple of time) it would have been flooded. But when I switch the relay it stared up no problems.

The accelerator peddle on fuel injected vehicles only lets air by, The computer reads how much air is coming into the engine and the injectors fire accordingly. So you couldn't have flooded it by pumping the peddle.

The ignition relay usually controls spark, The fuel pump usually has a separate relay.

Posted by: red98ta

The relay controls power to both the coils and injectors. Without this relay working, you don't get any spark and no fuel through the injectors. I have helped a lot of people with this problem lately, I am glad I could be of help.

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