Help! LT1 hard starting

[Towu4free]

Hello all, im new to this forum ive done some searching but cannot seem to find anybody having the same problem i am...

i have a 1994 Convertable with the LT1 engine and 4L60E trans it has 125K on it.. i bought the car new years day and i knew it had this problem and figured i could diagnose it.....well i was wrong after changing the oil, trans fluid, fuel filter(really nasty) cleaning the throttlebody, and MAF Sensor the car seemed to run alot better didnt have the popping under the hood that was an issue.....but it still didnt fix my starting problem

Problem: i can turn the key and it turns over fine but no start....turn it off and turn it on again and hold the throttle to the floor it starts but very rough idleing up then its fine..if i were to go out and start it without touching the gas i dont belive it would start....im getting the car checked out tomorrow so any responses would help Thank You!

 

[bigblack]

Have you checked for codes?Sounds like it may be a maf..Just my .2 I had a iroc z with same problem years ago and that was my problem.First thing to do is check for codes

 

[Towu4free]

Have you checked for codes?Sounds like it may be a maf..Just my .2 I had a iroc z with same problem years ago and that was my problem.First thing to do is check for codes

i did check for codes but did not get any(month ago) i cleaned the maf it seemed to run better but not start any better

 

[Paul Higg]

Fuel pump? Mine went bad last summer. It would not start. Now since I had it replaced the way I start it I always turn the key to on and let it sit in the on position for maybe two seconds to let fuel pressure build up at the rail. When I start it it starts right up.

Welcome to the forum!

 

[Towu4free]

Fuel pump? Mine went bad last summer. It would not start. Now since I had it replaced the way I start it I always turn the key to on and let it sit in the on position for maybe two seconds to let fuel pressure build up at the rail. When I start it it starts right up.

Welcome to the forum!

Yes in fact it was the fuel pump!! had it diagnosed today... looses pressure within seconds...thank you for the welcome im a member of the Fullsizechevy.com forum and they arent so friendly. Can you tell me how hard it is to replace and if theres anything else i should replace? thanks oh and my email is gcfballplaya25@yahoo.com if you rather email me thanks again

 

[Paul Higg]

Well, you're welcome to the forum, you will not find a friendlier bunch of people as well as helpful. Not all of us are right 100% of the time, (well maybe Junk at 99.99%) especially me, I'm correct maybe 50%? :L But all are willing to help.

I sent you an e-mail with help.

Best regards, Paul

 

[gmjunkie]

Yes in fact it was the fuel pump!! had it diagnosed today... looses pressure within seconds...thank you for the welcome im a member of the Fullsizechevy.com forum and they arent so friendly. Can you tell me how hard it is to replace and if theres anything else i should replace?

It's a peice of Cake,You change it through the fuel door opening after the door with henge plate are removed!!
Takes less than a hour!!

Not all of us are right 100% of the time, (well maybe Junk at 99.99%)

That percentage may be a little high,Paul!! Only the most intuitive psychics are barely over 94% correct!!

 

[Paul Higg]

 

[Towu4free]

Thanks guys for all the help ill be buying an Acdelco pump today and hopefully installing tomorrow!! thanks again!

 

[Paul Higg]

You are welcome!

 

[Towu4free]

Thanks guys for all the help ill be buying an Acdelco pump today and hopefully installing tomorrow!! thanks again!

scratch that didnt find one!! any ideas?

 

[Toms007]

Carter, Bosch or Airtech are OK brands.

 

[Hib Halverson]

(snip)

Problem: i can turn the key and it turns over fine but no start....turn it off and turn it on again and hold the throttle to the floor it starts but very rough idleing up then its fine..if i were to go out and start it without touching the gas i dont belive it would start...(snip)

Yes in fact it was the fuel pump!! had it diagnosed today... looses pressure within seconds...thank you for the welcome im a member of the Fullsizechevy.com forum and they arent so friendly. Can you tell me how hard it is to replace and if theres anything else i should replace? thanks oh and my email is gcfballplaya25@yahoo.com if you rather email me thanks again

Whoa...slow down, here, people.:nono

The symptoms you cite...having to floor the throttle (puts the engine controls into "clear flood" mode) and fuel pressure rising then falling quickly IS NOT indicative of a bad fuel pump...at least, a bad pump is not the primary diagnosis.

What you probably have is one or more leaking fuel injectors. After you shut the engine off, they leak gas into the intake ports. The next time you go to start the engine, you need to go clear flood to get the engine to fire because...it's flooded.

Before you go buy and install a fuel pump, you need to get a Factory Service Manual and run the fuel pressure and injector tests listed in it. Then...you can decide to replace the pump or replace some injectors.

Lastly...here's how the fuel pump works.

You turn on the key and the pump builds pressure. If the ECM doesn't see a tach input (telling it the engine is running) it shuts the pump off after a few seconds. If there are no leaks in the system (ie: leaking injectors) the pressure will hold for a while then drop very, very slowly.

If the injectors, regulator, fuel lines or the pumps internals are leaking, the pressure drop-off after the pump goes off will be much more rapid.

 

[Towu4free]

Whoa...slow down, here, people.:nono

The symptoms you cite...having to floor the throttle (puts the engine controls into "clear flood" mode) and fuel pressure rising then falling quickly IS NOT indicative of a bad fuel pump...at least, a bad pump is not the primary diagnosis.

What you probably have is one or more leaking fuel injectors. After you shut the engine off, they leak gas into the intake ports. The next time you go to start the engine, you need to go clear flood to get the engine to fire because...it's flooded.

Before you go buy and install a fuel pump, you need to get a Factory Service Manual and run the fuel pressure and injector tests listed in it. Then...you can decide to replace the pump or replace some injectors.

Lastly...here's how the fuel pump works.

You turn on the key and the pump builds pressure. If the ECM doesn't see a tach input (telling it the engine is running) it shuts the pump off after a few seconds. If there are no leaks in the system (ie: leaking injectors) the pressure will hold for a while then drop very, very slowly.

If the injectors, regulator, fuel lines or the pumps internals are leaking, the pressure drop-off after the pump goes off will be much more rapid.

The fuel pump did NOT fix my problem.... seems to idle a little higher but still does the same thing on start up...the fuel pump pulsator wasnt extremely tight on the line could that be a cause?

 

[Paul Higg]

Hib, please do not wave your finger at us, nor tell us to slow down. That is VERY condescending and rude. He e-mailed me and told me he had zero pressure at the fuel rail.

If you know so much as to wag your finger at so many people trying to help, why don't you quit this forum, get a job making BIG bucks as a Corvette consultant and have people PAY you for your advice. I may occasionally see people jibe at each other in jest but I have NEVER seen someone so holier-than-thou.

Just my 2 cents people.

 

[Gobbles]

I have had problems with my 90 starting just fine and then once hot it would turn like a champ and then never start. I found one of my spark plugs loose and tightened it up. Ran the car for 10 minutes or so and turned it off. No problems starting back up yet. Key word is yet. I'd double check your spark plugs and if they have never been replaced, probably work on that. Just my two cents on what I've experienced thus far. If it helps your welcome. If not, maybe someone else on here will be able to assist.

Tim

 

[Towu4free]

I have had problems with my 90 starting just fine and then once hot it would turn like a champ and then never start. I found one of my spark plugs loose and tightened it up. Ran the car for 10 minutes or so and turned it off. No problems starting back up yet. Key word is yet. I'd double check your spark plugs and if they have never been replaced, probably work on that. Just my two cents on what I've experienced thus far. If it helps your welcome. If not, maybe someone else on here will be able to assist.

Tim

Thanks Tim, mine is actually doing the opposite it doesnt start cold but starts most of the time when its warm..i did replace the plugs and wires about a week or two ago.. still nothing...thanks again

 

[Gobbles]

I've got a Haynes manual that says you should check the following if its hard to start when cold:
1. Battery Discharged or low
2. Fuel System malfunctioning
3. Injector(s) leaking
4. Distrubutor rotor carbon tracked (?)
5. Fuel pump relay faulty
6. Throttle body dirty

Also it says that if the engine rotates but will not start check the following:
1. Fuel Tank Empty (no brainer)
2. Battery discharged
3. Battery terminal conections loose or corroded
4. Leaking fuel injector(s), faulty cold start valve, fuel pump, pressure regualator
5. Fuel not reaching fuel injection system
6. Ignition components damp or damaged
7. Worn, faulty or incorrectley gapped spark plugs
8. Broken, loose or disconnected wiring in the starting circuit
9. Loose distributor is changing ignition timing
10. Broken, loose or disconnected wires at the ignition coil or faulty coil.

Not sure it any of the above are the problem, but thats just what my Haynes manual says to check for those specific problems. Hope you find the problem soon


Tim

 

[Paul Higg]

Hi Gobbles, the only reason I suggested Chris replace a fuel pump in the first place was because he told me he had no pressure at the fuel rail. Also, I had the same exact problem last summer.

I hope he can resolve it. I have spoken with him and he seems to be a very bright guy. He is 18 and this is his first Vette. He is doing his best to restore it and he really appreciates all the help and suggestions.

Paul

 

[Gobbles]

Paul, I'm not sure if he has a haynes manual, so I was simply providing info that may or may not be helpful in solving his problem. I just provided those because thats whats provided by haynes. Hope you get it solved soon.

Tim