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Randall C
Randall C, ASE Master Tech
Category: Chevy
Satisfied Customers: 11917
Experience:  ASE Master, L1, 32 years, Diagnostic / Electrical Specialist
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1992 Chevy: PU..This truck wont start until fuel..throttle body

Customer Question

1992 Chevy 1500 PU with a 350. This truck won't start until fuel is dumped into the throttle body. Then the truck will continue to run until you shot if off. It is a no fuel during cranking problem.
Submitted: 6 years ago.
Category: Chevy
Expert:  quickcar replied 6 years ago.
you can try hitting the bottom of the gas tank to see if it will start, if it does then the fuel pump will need replaced. if it doesnt then you may have a bad relay fuse wire or clogged filter.
Customer: replied 6 years ago.
This isn't the problem because I said the pump energizes when the key is turned on. Also once youi add fuel thru the throttle body the injectoors fire and the truck will run until you shut it off. It is not a pump problem.
Expert:  quickcar replied 6 years ago.
im sorry that information didnt show up right away. the problem i have is that that dumping fuel into the throttle body gets it running, its possible then the you have an issue with the oil pressure switch. your trucks computer uses it to prime the fuel system.
Expert:  quickcar replied 6 years ago.
ill get this switch over to the chevy category and maybe someone else can help
Expert:  Randall C replied 6 years ago.

hello, we can not rule out a pump leaking back, not working during crank, etc but do understand you hear it. Since there is not a fuel pressure test port, testing pressure requires special tool.. We now to to check some other basics.

I need to know if you have a 12 volt testlight. If not, can you get one. this is important


LMK thanks

Customer: replied 6 years ago.
I do have a 12 volt test light. The only oil pressure swith I can find is the one wire switch just above the pan rail on the passanger side. I don't understand how a one wire swicth would work in this circitry. Do you know if there is another one? If there is I couild check it. Otherwise walk me thru the test you want me to preform with the test light.
Expert:  Randall C replied 6 years ago.

I need you to pull off the plugs to both injectors. Do the test when you know vehicle will NOT start.


Using your testlight, turn key just to ON/RUN. Probe both injector plugs. The wires with same color going to BOTH injectors should be hot all the time.


Then,,,,, I need you to reverse your testllight meaning.. the probe end on battery POS and the clip end to one of the OTHER wires going to injectors, crank engine. I need to know if the testlight blinks.


All of the must be done under no start. We need to start there and then move on. LMK Thanks

Customer: replied 6 years ago.
Your not going to believe this. The left side has a white and a green wire. The right side has a red and a blue wire. I turned the key to the on/run position and tested all four wires. The white wire was hot on the drivers (left) and the red wire was hot on the passenger (right) side. I then shot off the key and tried to duplicate the test. Nothing was hot!!!!
When my wife returned from work I tried the cranking test you asked me to preform and nothing lights up. I then tried to restart the truck by sqirting gas into the intake again. The truck fires but won't keep running like it did yesterday and earlier today. Our condition has changed. Now we got to figure it out because I can't drive it to town. Keep smiling. I await yoiur next tip. Denny
Expert:  Randall C replied 6 years ago.
Next post from me will be a wiring diagram. I will assure you, one wire on ECH injector MUST be hot with key on. Let me get diagrams and send. back shortly
Customer: replied 6 years ago.
I appreciate the help and I would gladly supply a bonus if we can get this little problem fixed. I am available this morning. Thanks. Denny
Expert:  Randall C replied 6 years ago.
The RED and WHITE wires are the power wires./ Turn key to run and check for voltage on them LMk thanks
Customer: replied 6 years ago.
I checked for power on the red and white wires with the key in th on position. As I said yesterday, there is no power NOW. When we started yesterday both of those wires were hot. Now are no longer. I have rechecked them at least 10 times because I find it hard to believe. I also listened for the fuel pump to energize when the key was turned on this morning and it did. Since the wires are no longer hot the truck will not continue to run once you dump in fuel. If this is easier over a phone my number is XXXXX My background is in engine rebuilding for the last 20 years. I am not very good at electronics. The code that the computer set when this started was 54 which is fuel circuit. Denny
Expert:  Randall C replied 6 years ago.

We are not permitted to call nor can I view your number ther is a power feed problem somewhere, It should run on gas in t body even if no poer to injectors. This now tells me you have lost spark as well. I have to think where to go next.


One thing I need to to check is see if you have 12 volts tto both side of the INJ A/B fuse in fuse box.with key on

Customer: replied 6 years ago.
Let me clarify. As long as I dump gas into the intake it runs. I have spark. But yesterday when I would dump in gas it would run, then the injectors would fire and it would continue to run and I could drive it with no proboems. I took it for aXXXXX
Expert:  Randall C replied 6 years ago.

Sorry , you said since wires mot hot, would not continue to run. I took that as it was not running at all with gas put in.


Please check the power to fuse i noted. We have to find out why the red/white are not hot

Customer: replied 6 years ago.
Good call. I checked and found that fuse burnt. I replaced it and now the white and red wires at the injectors are hot again when the key is on the on/run position.
Expert:  Randall C replied 6 years ago.
Ok, now go back and check the OTHER 2 wires for blinking testlight with a reverse testlight
Customer: replied 6 years ago.
OK I reversed the test light and checked the other 2 wires while cranking the engine over. No blinking light of any kind. This seems to be where the problem lies. Where does this trigger voltage come from and what does it pass through to get to the injectors. I may not have told you this but I was cleaning under the hood before putting the truck up for my son. The truck has not had much use as my son spent 2 tours in Afghanistan and the truck sat outside, on base for all that time. After cleaning, the engine fired and ran 3 different times with no glitches or misses. It was the fourth attempt at starting where the problem began. It may be related and it may not.
Expert:  Randall C replied 6 years ago.

There is a timing connector under the hood shown below. Single wire that you unplug to set timing. I need you to locate it , unplug and the see if it will stay running



Expert:  Randall C replied 6 years ago.
I have to step out for awhile. Do the test I mentioned, then check the 5 amp fuse marked CRANK . If all is good. then we need to suspect the PCM has gone bad. The PCM controls the injector pulse. You can try tapping fairly hard on the PCm located behind dash on passenger side. Tap fairly hard but no too hard as to dent or damage,. seiif the vehicle will stay running after that if so, you need anew PCM. I will submit as answer in case you isolate the problem But will be back later. thanks
Customer: replied 6 years ago.
I removed the glove box and tapped on the PCM. The truck still won't start. A new PCM is going to cost me $100. Is there any other way to isolate it to be sure and do you have to remove the entire dash to change the PCM?
Customer: replied 6 years ago.
A friend told me that the ignition modual has a start side and a run side and it could also be the problem. Does the ignition modual have any control over firing the injectors during the cranking process?
Expert:  Randall C replied 6 years ago.
Yes, this is whay I need you to disconnect the inline timing connector to se if it will run unhooked. This is a basic test that needs to be done. LMk thanks
Customer: replied 5 years ago.
The holiday is over and I'm back. I apologize because I thought I had answered your question about the timing connection but in looking back I see I did not. Yes I unplugged the timng connection and the truck continues to run.
Expert:  Randall C replied 5 years ago.
so where are you at with the truck. You still turn it off and you have to use spray to keep running?
Customer: replied 5 years ago.
Same as last week. No start until you squirt in fuel. Then it starts and runs until you shut it off.
Expert:  Randall C replied 5 years ago.
Ok, thanks. I am very sorry for delays but have been dealing with a family 911 and on/off a little more. I should be back online first in am with more thoughts. Thanks

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