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silverado won't start....sometimes


wesson123970
06-13-2006, 03:19 PM
my '91 4.3L silverado sometimes will not start....only have 2 spray starting fluid in throttle body to get it started....then it cranks and runs fine...no matter how far you drive it....this does not happen every time either...but it does happen enough to be pretty aggravating!!....i just had the fuel pump,strainer,filter,fuel pump relay replaced(i suggested to mechanic it was fuel pump....so he replaced it...didn't help)...i then replaced the fuel filter....it seems MAYBE a little better now...but still has done it 2x in 3 or 4 days..anyone have any ideas on this?

thanks,
wes

MT-2500
06-13-2006, 05:26 PM
my '91 4.3L silverado sometimes will not start....only have 2 spray starting fluid in throttle body to get it started....then it cranks and runs fine...no matter how far you drive it....this does not happen every time either...but it does happen enough to be pretty aggravating!!....i just had the fuel pump,strainer,filter,fuel pump relay replaced(i suggested to mechanic it was fuel pump....so he replaced it...didn't help)...i then replaced the fuel filter....it seems MAYBE a little better now...but still has done it 2x in 3 or 4 days..anyone have any ideas on this?

thanks,
wes

Check fuel pressure for being up to specs to start with when it no start.
MT

kenwood guy
06-13-2006, 07:12 PM
your battery might need to be replaced

wesson123970
06-14-2006, 10:22 AM
Check fuel pressure for being up to specs to start with when it no start.
MT


this is my first time on here...is the right way to replay to posts?....anyway...thanks guy...def sounds like it may be low fuel pressure...i'm just gonna have to take it to the shop...and make sure they test the fuel pressure (the guy i had working on it told me call him when it messes up again...that that was the only way he could figure it out)...thanks again
wes

MT-2500
06-14-2006, 12:05 PM
this is my first time on here...is the right way to replay to posts?....anyway...thanks guy...def sounds like it may be low fuel pressure...i'm just gonna have to take it to the shop...and make sure they test the fuel pressure (the guy i had working on it told me call him when it messes up again...that that was the only way he could figure it out)...thanks again
wes

10-4 wesson123970 you are doing it the right way. good.
Welcome to the forum on AF.
But Your post no does say no 2 post for some reason.
And it does help to catch it when it does it.
And for sure check fuel pressure and the the fuel pump for full pressure and leak down and alll of the good stuff.
Good luck and let us know how it goes.
Mt

89iroctpi5.7
06-14-2006, 06:26 PM
when it fails to start, does it, turn over fine, sputter and try, is the check eng light on , can you hear the fuel pump energize when you turn the key to on?

wesson123970
06-16-2006, 03:11 PM
when it fails to start, does it, turn over fine, sputter and try, is the check eng light on , can you hear the fuel pump energize when you turn the key to on?

hey guy,
it turns over fine...plenty of battery power and starter is fine...i can hear the fuel-pump too....never sputters...if it does, it cranks....never can tell when it's gonna do it...at first i thought it was when parked on a hill...but that's not it..will do parked in any position...again..once it cranks, it runs like a new truck

wes

89iroctpi5.7
06-18-2006, 03:26 PM
Yep my 89 camaro is doing the same thing, Runs great but sometimes the fuel injectors dont fire at start up, but if you give it some str fluid fires rt up. Is the truck throttle body or multiport injection? regardless try to see if its fireing the injectors when it dont start of if it is then the computer is not mixing the fuel rt, ex bad temp sending unit, bad air temp sending unit , bad computer.If you find out let me know Ive been trowing all kkind of parts at mine.:banghead:

Gary the Engineer
06-20-2006, 01:47 PM
My 99 was doing the same thing, however it did start, albeit hard. Then ran just fine after it started.

Check the fuel pressure regulator located on the fuel rack. Pull the vacuum line off of the regulator and sniff it for the smell of gasoline. If you smell gas in the vacuum line, your regulator is bad. Replace it. Took me 10-15 minutes to remove the old one and replace it with new.

Good luck!
Gary

MT-2500
06-20-2006, 02:50 PM
My 99 was doing the same thing, however it did start, albeit hard. Then ran just fine after it started.

Check the fuel pressure regulator located on the fuel rack. Pull the vacuum line off of the regulator and sniff it for the smell of gasoline. If you smell gas in the vacuum line, your regulator is bad. Replace it. Took me 10-15 minutes to remove the old one and replace it with new.

Good luck!
Gary

I am afraid a 99 with external regulator is a little bit diferent than the 91.

Gary the Engineer
06-20-2006, 03:26 PM
Yeah, I'm not familiar with the 91 fuel system. Sorry if my reply put you off track. I could still be off base here but the problem does sound like maybe excess fuel is flowing unregulated and may be flooding the cylinders. Yes???



Gary

MT-2500
06-20-2006, 05:15 PM
Yeah, I'm not familiar with the 91 fuel system. Sorry if my reply put you off track. I could still be off base here but the problem does sound like maybe excess fuel is flowing unregulated and may be flooding the cylinders. Yes???



Gary

Different years and different engine codes will be different fuel systems.
If it takes starting fluid or carb cleaner to start it it is more no fuel or low fuel pressure.
But to much fuel will give a hard start to.
That is why you need afuel pressure gauge to see what is going on.
MT

wesson123970
06-21-2006, 11:12 AM
guys....a while back my distributor module went bad on my truck(which has to do w/ fuel timing)..and it would run really rough....before i took to shop to find out what it was...i tried several different kinds of throttle body sprays to clean it....all were supposed to be safe for fuel injection(also used fuel injector cleaner in gas)....but i am really suspecting that it damaged the fuel pressure regulator as one of you guys mentioned!!!(my manual for truck also says don't soak regulator in any kind of cleaner!!!)...i just saw your reply..i ordered the pressure regulator yesterday and will be putting it on tomorrow!!!...yeah...i took a chance on that being what it is, but i feel like it has to be the problem...it all makes sense now...btw..the regulator is pretty easy to replace on the 91 too..it's right on top of throttle-body(i'm replacing the whole piece---spring and diaphram already inside!)..thanks to all of you for your help...i'll let you know how it turns out!

MT-2500
06-21-2006, 12:00 PM
guys....a while back my distributor module went bad on my truck(which has to do w/ fuel timing)..and it would run really rough....before i took to shop to find out what it was...i tried several different kinds of throttle body sprays to clean it....all were supposed to be safe for fuel injection(also used fuel injector cleaner in gas)....but i am really suspecting that it damaged the fuel pressure regulator as one of you guys mentioned!!!(my manual for truck also says don't soak regulator in any kind of cleaner!!!)...i just saw your reply..i ordered the pressure regulator yesterday and will be putting it on tomorrow!!!...yeah...i took a chance on that being what it is, but i feel like it has to be the problem...it all makes sense now...btw..the regulator is pretty easy to replace on the 91 too..it's right on top of throttle-body(i'm replacing the whole piece---spring and diaphram already inside!)..thanks to all of you for your help...i'll let you know how it turns out!

Proper testing before throwing parts at it will save you time and money and a lot of talking to yourself about it.:grinyes: :lol: :rofl:
MT

Rs051802
06-26-2006, 09:49 PM
Have you had your hose checked? There could be a collapsed line, either an input, or a return. A collapsed line will cause intermittent, eventual failure to deliver gas. You can disconect both from the TBi, blow some air through them, just make sue and disconnect them on the other side before doing so. Have you check to make sure your injectors are not clogged? Have someone start it while you watch it spray. There should be a very solid stream. Keep us posted, and good luck

wesson123970
06-27-2006, 03:04 PM
hey guys,

sorry it's taken me so long to get back to y'all...i replaced the pressure regulator and it didn't do any good(even though it was messed up....the spring was in 3pieces!!)...i can hear a little difference on startup(little crisper maybe?), but it still fails just as often.i don't have a pressure tester...and I'm out of ideas...AND money right now....anyone have any ideas??HELP!!

wes

wesson123970
06-27-2006, 03:34 PM
well guys....the pressure regulator didn't work!....even though mine was definitely damaged(spring broken in 3pieces!)...still sometimes won't start...i'm out of ideas...and money!..i don't have a pressure tester either...any ideas anyone?..i've replaced ever fuel component i know of

thanks,
wes

MT-2500
06-27-2006, 03:40 PM
well guys....the pressure regulator didn't work!....even though mine was definitely damaged(spring broken in 3pieces!)...still sometimes won't start...i'm out of ideas...and money!..i don't have a pressure tester either...any ideas anyone?..i've replaced ever fuel component i know of

thanks,
wes

Proper testing is the key.
Some parts places will loan or rent a fuel pressure tester. Lot cheape thaan throwing parts at it.
Good luck and let us know how it goes.
MT

wesson123970
06-27-2006, 03:55 PM
thanks mt-2500.....i'll have to look into that

on another note....you said in another post that blinking A/C on control panel prob wasn't bad display, but low freon???you sure on that?

wes

MT-2500
06-27-2006, 04:28 PM
thanks mt-2500.....i'll have to look into that

on another note....you said in another post that blinking A/C on control panel prob wasn't bad display, but low freon???you sure on that?

wes

If I remember right I said low freon will trip the air cond controls and shut off compresser and make it blink.
Low freon is the first thing to check.
Depending on year and set up some you can get the codes and see why the light is blinking.
Post back in that post and I will refresh my memory or can tell you more about it.
MT

wesson123970
06-28-2006, 02:21 PM
it happened again today....had the chance to let someone else turn the engine over while i looked at the 2 injectors....neither of them were spraying anything!!...of course it cranked fine once i sprayed the starter fluid in it....apparently the injectors kick right in once the engine fires(or is rotating fast enough from firing---enough suction??)good.

MT-2500
06-28-2006, 03:11 PM
it happened again today....had the chance to let someone else turn the engine over while i looked at the 2 injectors....neither of them were spraying anything!!...of course it cranked fine once i sprayed the starter fluid in it....apparently the injectors kick right in once the engine fires(or is rotating fast enough from firing---enough suction??)good.

First things first.
The first thing to check is to check for good hot blue spark to all plugs.
If you have spark then move on to fuel pressure.
If you have spark and fuel then go for injector pulse.
You have to have all 3 before injectore will squirt fuel.

wesson123970
06-30-2006, 08:20 AM
does anyone know what causes the injectors to deliver gas on startup?...w/out pressing the accelerator???...it seems that is what's wrong....sometimes the injectors deliver...sometimes not...but always runs fine after it starts?..i know this may be due to clogged line..and i'm gonna check...but does anyone know what sends the signal to the injectors to fire when you crank the engine?

thanks,
wes

MT-2500
06-30-2006, 08:52 AM
does anyone know what causes the injectors to deliver gas on startup?...w/out pressing the accelerator???...it seems that is what's wrong....sometimes the injectors deliver...sometimes not...but always runs fine after it starts?..i know this may be due to clogged line..and i'm gonna check...but does anyone know what sends the signal to the injectors to fire when you crank the engine?

thanks,
wes

When the PCM/VCM sees ign spark it triggers the injectors.
But the key is fuel pressure in the right amount.
Even a couple of lbs low and the injector will not squirt.
Check my post on testing fuel pressure.
MT

wesson123970
07-07-2006, 07:36 AM
hey guys...still haven't figured out the intermittent starting...i've replaced everying fuel related i know of..fuel pump,strainer,fuel pump relay,regulator...i did confirm that it's not getting any fuel when it fails(nothing coming out of injectors while cranking engine)...a couple of you mentioned the fuel pressure...if it's fuel pressure,what could be causing it??

on a better note!..MT-2500...you were right about the a/c light blinking on display and not working...just needed freon!!my dad an old can of R-12, so i used that....i reset everything first, by disconnecting, then reconnecting battery so the a/c would work for a min or so(not even sure i needed to do that?) i had the can of freon on and open as i cranked truck and turned engine on...went smooth...didn't take long to empty the can..that was about a week ago now..still doing great!!thanks MT-2500...i've been going w/out a/c for 2 years now, thinking my display was bad!!
Please help w/ the intermittent starting?!!!

Wes

MT-2500
07-07-2006, 09:03 AM
hey guys...still haven't figured out the intermittent starting...i've replaced everying fuel related i know of..fuel pump,strainer,fuel pump relay,regulator...i did confirm that it's not getting any fuel when it fails(nothing coming out of injectors while cranking engine)...a couple of you mentioned the fuel pressure...if it's fuel pressure,what could be causing it??

on a better note!..MT-2500...you were right about the a/c light blinking on display and not working...just needed freon!!my dad an old can of R-12, so i used that....i reset everything first, by disconnecting, then reconnecting battery so the a/c would work for a min or so(not even sure i needed to do that?) i had the can of freon on and open as i cranked truck and turned engine on...went smooth...didn't take long to empty the can..that was about a week ago now..still doing great!!thanks MT-2500...i've been going w/out a/c for 2 years now, thinking my display was bad!!
Please help w/ the intermittent starting?!!!

Wes


Get a fuel pressure gauge and check for fuel pressue up to specs.
Do not leave home with out it.
MT

wesson123970
07-13-2006, 12:25 PM
well...a mechanic has my truck...had it all day yesterday....he said it cranked fine for him every time...so doesn't know what's wrong w/ it yet....i prob ought to ask him if he's checked the fuel pressure?...what do u think MT?
i'll let you guys know how it went


wes

MT-2500
07-13-2006, 01:20 PM
First things first.
The first thing to check is to check for good hot blue spark to all plugs.
If you have spark then move on to fuel pressure.
If you have spark and fuel then go for injector pulse.
You have to have all 3 before injectore will squirt fuel.

Do you have all 3?

wesson123970
07-19-2006, 07:15 AM
hey guys,

my mechanic finally fixed my truck(i hope)...he had it for 5 days and it never messed up on him....he tested the distributor module though, and it was reading wrong....replaced that....and my oil pressure sensor was bad....the oil pressure sensor sends signal to shut fuel pump off, if oil pressure gets too low....i haven't picked truck up yet, but he feels confident my problem is solved (i do too)...and he said it cranked a lot faster than before...just fires right up....

thanks for all your help guys

wes

MT-2500
07-19-2006, 09:25 AM
hey guys,

my mechanic finally fixed my truck(i hope)...he had it for 5 days and it never messed up on him....he tested the distributor module though, and it was reading wrong....replaced that....and my oil pressure sensor was bad....the oil pressure sensor sends signal to shut fuel pump off, if oil pressure gets too low....i haven't picked truck up yet, but he feels confident my problem is solved (i do too)...and he said it cranked a lot faster than before...just fires right up....

thanks for all your help guys

wes


Was the fuel pressure test ever done?
What was the readings?
Oil pressure switch will not turn off or shut off the fuel pump.
It only keeps the fuel pump running if the fuel pump relay quits.
MT

Glen A. Davis
06-03-2010, 03:26 PM
My 1999 4.3 won't start unless i put fuel in the throtle body, then it starts up and runs fine. My fuel psi is 63lb.s, fuel pump and filter is new. Has anyone heard of the key switch being faulty and not allowing the engine to start. sometimes all i need to do is turn the switch off and on a few times and it will start and run fine, HELP

MT-2500
06-03-2010, 03:35 PM
My 1999 4.3 won't start unless i put fuel in the throtle body, then it starts up and runs fine. My fuel psi is 63lb.s, fuel pump and filter is new. Has anyone heard of the key switch being faulty and not allowing the engine to start. sometimes all i need to do is turn the switch off and on a few times and it will start and run fine, HELP

Welcome to AF on your first post.
You need to start a New thread with your problem.

Start a New thread and answer questions below for more help.
What brand of fuel pump did you install?

Is that 63 lbs pressure engine off key on or engine cranking or just 63 when you lip ke a couple times?

You need 64-65 lbs engine cranking fuel pressure to squirt injectors on a cold start.

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 90 -100 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 90- 100 or more on yours.
And if it has a fast leak down after shut off you have a leak in system.
Post back all fuel pressure readings.

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