TBI Question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

HotRod73 · 01-03-2007, 12:19 AM

I know this may sound dumb, but when my 87' swb with the 305 tbi is cold you have to pump gas a few times to get it to start then it runs fine, is this normal? i know on carbs you do but i thought fuel injected didnt require that, i havent really checked it when its hot to see if still same because i havent really driven it much but just thought ide ask, thanks...

TireSmoke420 · 01-03-2007, 03:38 AM

my sister thinks she has to do that with my truck when she drives it... bfore i took the engine outta it. but if you turn the key on and let the pump pump for a second bfore cranking it should fire right up

twoodson · 01-03-2007, 09:50 AM

I agree, I just turn the key on and you can hear the pump priming and then I can start it without touching the gas pedal.

Russell · 01-03-2007, 01:21 PM

All you are doing when you open the throttle blades is that, opening the throttle blades... The injectors don't base their rate of fire on starting on the throttle position, if anything, if you hold the throttle blades too far open, it cuts the fuel out.

My guess would be that your idle speed is probally a tad low if it will not fire even after about 5 seconds of cranking...

gflo383 · 01-03-2007, 02:02 PM

the fuel pressure regulator could be bleeding fuel, causing a loss of fuel pressure after it sits for a bit. this is very common on the multiport FI GM cars, not sure about the TBI, but i thought i would suggest it.

flooring a FI vehicle upon start up is a way to "UN FLOOD" it. like previously stated, it opens the throttle blades and cutts off fuel.

HuggerCST · 01-03-2007, 02:20 PM

Can you hear the fuel pump run when you turn the key on? I have seen a bad fuel pump relay cause similar problems.

Beefcake · 01-03-2007, 02:48 PM

my 89 tbi needs no peddle pump. Just starts right up, first crank.

HotRod73 · 01-03-2007, 02:56 PM

this truck hasnt been started in about 2 months... i can hear the pump running when i turn the key but i tried to crank for a few seconds and i hit the pedal once or twice and she fired up...

73stepside · 01-04-2007, 06:14 AM

i had to do that with my camaro when it was below 30* and it sat all night. it doesn't hurt anything.

HotRod73 · 01-04-2007, 11:55 AM

i tried last night and i let the pump run till it stopped and then turnd the key it took few seconds and finaly started

HuggerCST · 01-04-2007, 12:31 PM

I had an s-10 do that once, and it was a bad fuel pump check valve. I put a fuel pressure gauge on it, and the fuel pressure would instantly drop when the key was turned off. It should hold some pressure for a while. I changed the fuel pump and never had another problem.

TireSmoke420 · 01-09-2007, 08:21 AM

i had a 88 iroc and it did the same thing. i found out on it though if i just put the pedal to the floor when cranking it started up that way

Russell · 01-09-2007, 01:37 PM

Also check your fuel filter, that can cause delayed starting...

My 89 alway used to crank for almost 5 seconds before it started cold, went away immediately after changing the filter

lurch115 · 01-09-2007, 11:56 PM

another thing to look at besides the fuel regulator would be the screens on the bottom of the injectors...i have a '90 Caprice police interceptor that has a TBI 350 in it and had the same problem....how ever the screens not only had gummed up pretty bad, but the injectors were well used at 230,000 miles....i changed them and it starts right off now....

01-03-2007, 12:19 AM	#1
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	TBI Question I know this may sound dumb, but when my 87' swb with the 305 tbi is cold you have to pump gas a few times to get it to start then it runs fine, is this normal? i know on carbs you do but i thought fuel injected didnt require that, i havent really checked it when its hot to see if still same because i havent really driven it much but just thought ide ask, thanks... __________________ 1973 Chevrolet C20 (Under Construction)

01-03-2007, 03:38 AM	#2
TireSmoke420 One of the few GMC'ers Join Date: Jul 2005 Location: Des Moines, Iowa sometimes Butler, PA Posts: 146	Re: TBI Question my sister thinks she has to do that with my truck when she drives it... bfore i took the engine outta it. but if you turn the key on and let the pump pump for a second bfore cranking it should fire right up __________________ 87' Silverado 4x4 "Young, Dumb And Full Of Cum"

01-03-2007, 09:50 AM	#3
twoodson Registered User Join Date: Jul 2003 Location: Lancaster, TX Posts: 291	Re: TBI Question I agree, I just turn the key on and you can hear the pump priming and then I can start it without touching the gas pedal.

01-03-2007, 01:21 PM	#4
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Re: TBI Question All you are doing when you open the throttle blades is that, opening the throttle blades... The injectors don't base their rate of fire on starting on the throttle position, if anything, if you hold the throttle blades too far open, it cuts the fuel out. My guess would be that your idle speed is probally a tad low if it will not fire even after about 5 seconds of cranking... __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap) Last edited by Russell; 01-03-2007 at 01:23 PM.

01-03-2007, 02:02 PM	#5
gflo383 Registered User Join Date: Dec 2006 Location: Minnesota Posts: 130	Re: TBI Question the fuel pressure regulator could be bleeding fuel, causing a loss of fuel pressure after it sits for a bit. this is very common on the multiport FI GM cars, not sure about the TBI, but i thought i would suggest it. flooring a FI vehicle upon start up is a way to "UN FLOOD" it. like previously stated, it opens the throttle blades and cutts off fuel. __________________ 1986 IROC-Z lS1/T56 Moser 9" 78mm Turbo 1968 C10 step side, 5.3 Maggnacharger TVS1900 6L80E 2009 CCSB 5.3/6L80 4x4 http://members.cardomain.com/gflo383

01-03-2007, 02:20 PM	#6
HuggerCST Registered User Join Date: Jul 2001 Location: North Louisiana Posts: 4,501	Re: TBI Question Can you hear the fuel pump run when you turn the key on? I have seen a bad fuel pump relay cause similar problems. __________________ Wynne 70 CST short fleet Hugger orange & white, 350/350, ps, pb, air, tilt, tach/vac/speedwarning, original buckets, AM/FM, oak bed floor, shoulder belts, 3.5"/5.5" drop, 20" American Racing VN425s. Build thread 53 Chevy shortbed 69 Camaro Click here to subscribe Chevy GMC International Truck Club Louisiana Charter Member http://www.louisianaclassictruckclub.com

01-03-2007, 02:48 PM	#7
Beefcake Registered User Join Date: Mar 2003 Location: Motor City Posts: 540	Re: TBI Question my 89 tbi needs no peddle pump. Just starts right up, first crank. __________________ 72 GMC Camper Special 2500. currently has 350/350/14 bolt. 383 and 400 tranny is in the works.

01-03-2007, 02:56 PM	#8
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	Re: TBI Question this truck hasnt been started in about 2 months... i can hear the pump running when i turn the key but i tried to crank for a few seconds and i hit the pedal once or twice and she fired up... __________________ 1973 Chevrolet C20 (Under Construction)

01-04-2007, 06:14 AM	#9
73stepside Registered User Join Date: Feb 2002 Location: Moore OK 73160 Posts: 974	Re: TBI Question i had to do that with my camaro when it was below 30* and it sat all night. it doesn't hurt anything. __________________ 04 GMC Sierra RCSS 70 CST LWB 04 HD Sportster 1200 Custom

01-04-2007, 11:55 AM	#10
HotRod73 Registered User Join Date: Mar 2006 Location: Norman, Oklahoma Posts: 553	Re: TBI Question i tried last night and i let the pump run till it stopped and then turnd the key it took few seconds and finaly started __________________ 1973 Chevrolet C20 (Under Construction)

01-04-2007, 12:31 PM	#11
HuggerCST Registered User Join Date: Jul 2001 Location: North Louisiana Posts: 4,501	Re: TBI Question I had an s-10 do that once, and it was a bad fuel pump check valve. I put a fuel pressure gauge on it, and the fuel pressure would instantly drop when the key was turned off. It should hold some pressure for a while. I changed the fuel pump and never had another problem. __________________ Wynne 70 CST short fleet Hugger orange & white, 350/350, ps, pb, air, tilt, tach/vac/speedwarning, original buckets, AM/FM, oak bed floor, shoulder belts, 3.5"/5.5" drop, 20" American Racing VN425s. Build thread 53 Chevy shortbed 69 Camaro Click here to subscribe Chevy GMC International Truck Club Louisiana Charter Member http://www.louisianaclassictruckclub.com

01-09-2007, 08:21 AM	#12
TireSmoke420 One of the few GMC'ers Join Date: Jul 2005 Location: Des Moines, Iowa sometimes Butler, PA Posts: 146	Re: TBI Question i had a 88 iroc and it did the same thing. i found out on it though if i just put the pedal to the floor when cranking it started up that way __________________ 87' Silverado 4x4 "Young, Dumb And Full Of Cum"

01-09-2007, 01:37 PM	#13
Russell Professional Grade Join Date: May 2003 Location: Fort McMurray, Alberta Posts: 7,915	Re: TBI Question Also check your fuel filter, that can cause delayed starting... My 89 alway used to crank for almost 5 seconds before it started cold, went away immediately after changing the filter __________________ 1995 Chevrolet 2 Door Tahoe (6.6L LBZ Duramax / ZF6 / NP241 with 1 ton solid axle swap)

01-09-2007, 11:56 PM	#14
lurch115 Registered User Join Date: Oct 2006 Location: iowa Posts: 722	Re: TBI Question another thing to look at besides the fuel regulator would be the screens on the bottom of the injectors...i have a '90 Caprice police interceptor that has a TBI 350 in it and had the same problem....how ever the screens not only had gummed up pretty bad, but the injectors were well used at 230,000 miles....i changed them and it starts right off now.... __________________ "Horsepower is how fast you hit the wall, torque is how far you carry the wall with you." '84 chevy half ton short box 2wd, 67,000 actual miles '03 chevy 1500 HD crew cab 4x4 standard box, 6.0L

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