98 gmc cranks but no start please help

98gmc1500 · 11-02-2009, 12:26 PM

ok guys going to pick some brains here .I have seen another post similar ,but not like my problem ..Ive got a 98 GMC 1500 4.3 vortec .
I just replaced the manual tranny with a good one . when i finished the truck started just fine and ran fine for about 10 min backed it out the shop turned it off 5 min later went to start ..then ...crank no start.

things I have done since then

i put fuel down the throttle body started and ran till fuel was gone.

so put new fuel pump still no luck

crank sensor still no luck

injector pack still no luck

sensor in distributor still no luck

all fuses are good fuel pressure good

it seems the injector pack is not getting the signal to fire ..

what other sensor send signal to injector pack to fire injectors

Please help been working on it for a week now and very frustrated..

any help would be very grateful

Mcat500 · 11-02-2009, 04:18 PM

Hey this sounds very similar to the problem I just had. Since you replaced the fuel pump, when you turn the key, can you here the pump run? If not replace the fuel pump relay in the under hood fuse box.

If not that, there is a oil pressure/fuel switch located at the back of the motor by the distributor, it will stop the fuel if low oil pressure is detected. Follow the link, on the 3 page are the details on it

98 k1500 won't start NEED HELP!!!

Hope this helps

98gmc1500 · 11-02-2009, 08:38 PM

Quote:

Originally Posted by Mcat500

Hey this sounds very similar to the problem I just had. Since you replaced the fuel pump, when you turn the key, can you here the pump run? If not replace the fuel pump relay in the under hood fuse box.

If not that, there is a oil pressure/fuel switch located at the back of the motor by the distributor, it will stop the fuel if low oil pressure is detected. Follow the link, on the 3 page are the details on it

98 k1500 won't start NEED HELP!!!

Hope this helps

yes i read it all ...I am getting great fuel pressure and i have ignition fire it runs fine when you pour fuel down the throttle body ..there is something not firing the injectors off. that is my only problem is the injectors are not coming on but the injector pack is brand new so i know it not that it is a sensor or some sort .

Mcat500 · 11-02-2009, 08:52 PM

My best guess would be the oil pressure/fuel switch. You say good fuel pressure, is it above 55 PSI?. Have you tested the electrical connection to the injector spider?

Mcat500 · 11-02-2009, 08:54 PM

Oh ya, any codes?

98gmc1500 · 11-02-2009, 09:06 PM

Quote:

Originally Posted by Mcat500

Oh ya, any codes?

no codes and yes injector spider is ok fuel pressure 64 lbs

hotrodpc · 11-02-2009, 09:23 PM

Dumb question. Do you have all your wiring harnesses to the transmission hooked up properly? Could one of them have falling off after your test run? I will not say for certain on your model, cuz honestly I do NOT know, but there are some vehicles that have transmission related spark control for smog devices. Really, with a comptuer controled vehicle I doubt this, but you also with computer contrlled vehicle, you'd be amazed at what must be connected to send or recieve signals to and from the ECM. Worth a check if you have not done so already.

98gmc1500 · 11-02-2009, 09:28 PM

Quote:

Originally Posted by hotrodpc

Dumb question. Do you have all your wiring harnesses to the transmission hooked up properly? Could one of them have falling off after your test run? I will not say for certain on your model, cuz honestly I do NOT know, but there are some vehicles that have transmission related spark control for smog devices. Really, with a comptuer controled vehicle I doubt this, but you also with computer contrlled vehicle, you'd be amazed at what must be connected to send or recieve signals to and from the ECM. Worth a check if you have not done so already.

Right now there are no Dumb questions or ideas ..lol

but yes sir i went back and checked everything out even made sure i didnt get anything caught between the bell housing and block ....i am so lost ...

hotrodpc · 11-02-2009, 10:18 PM

Great, to make sure you did not pinch something between the bell and block. That was my gonna be my next suggestion. hmmmmmmmm???

98gmc1500 · 11-02-2009, 10:29 PM

yea what puzzles me is that ir started just fine after the tranny swap then i turned it off and 10 or 15 min later go to restart and no start just crank ...

11-02-2009, 12:26 PM	#1
98gmc1500 Junior Member Join Date: Nov 2009 Posts: 11	98 gmc cranks but no start please help ok guys going to pick some brains here .I have seen another post similar ,but not like my problem ..Ive got a 98 GMC 1500 4.3 vortec . I just replaced the manual tranny with a good one . when i finished the truck started just fine and ran fine for about 10 min backed it out the shop turned it off 5 min later went to start ..then ...crank no start. things I have done since then i put fuel down the throttle body started and ran till fuel was gone. so put new fuel pump still no luck crank sensor still no luck injector pack still no luck sensor in distributor still no luck all fuses are good fuel pressure good it seems the injector pack is not getting the signal to fire .. what other sensor send signal to injector pack to fire injectors Please help been working on it for a week now and very frustrated.. any help would be very grateful

11-02-2009, 09:23 PM	#7
hotrodpc Senior Member Join Date: Jul 2008 Location: OKC, OK Posts: 3,177	Dumb question. Do you have all your wiring harnesses to the transmission hooked up properly? Could one of them have falling off after your test run? I will not say for certain on your model, cuz honestly I do NOT know, but there are some vehicles that have transmission related spark control for smog devices. Really, with a comptuer controled vehicle I doubt this, but you also with computer contrlled vehicle, you'd be amazed at what must be connected to send or recieve signals to and from the ECM. Worth a check if you have not done so already. __________________ *Winners NEVER Quit , Quitters NEVER Win !!!*

11-02-2009, 10:18 PM	#9
hotrodpc Senior Member Join Date: Jul 2008 Location: OKC, OK Posts: 3,177	Great, to make sure you did not pinch something between the bell and block. That was my gonna be my next suggestion. hmmmmmmmm??? __________________ *Winners NEVER Quit , Quitters NEVER Win !!!*

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11-02-2009, 04:18 PM	#2
Mcat500 Junior Member Join Date: Oct 2009 Posts: 17	Hey this sounds very similar to the problem I just had. Since you replaced the fuel pump, when you turn the key, can you here the pump run? If not replace the fuel pump relay in the under hood fuse box. If not that, there is a oil pressure/fuel switch located at the back of the motor by the distributor, it will stop the fuel if low oil pressure is detected. Follow the link, on the 3 page are the details on it 98 k1500 won't start NEED HELP!!! Hope this helps

11-02-2009, 08:52 PM	#4
Mcat500 Junior Member Join Date: Oct 2009 Posts: 17	My best guess would be the oil pressure/fuel switch. You say good fuel pressure, is it above 55 PSI?. Have you tested the electrical connection to the injector spider?

11-02-2009, 08:54 PM	#5
Mcat500 Junior Member Join Date: Oct 2009 Posts: 17	Oh ya, any codes?

11-02-2009, 10:29 PM	#10
98gmc1500 Junior Member Join Date: Nov 2009 Posts: 11	yea what puzzles me is that ir started just fine after the tranny swap then i turned it off and 10 or 15 min later go to restart and no start just crank ...