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Help, No Fuel From Injectors

T

tx_sub

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Denton, TEXAS
Yay! dead truck. 91 chev sub 350 tbi
turns over but no fuel coming out of injectors.

will check: fuse, pump relay, wiring to pump, pump itself. anything else? i don't know exactly what happened, my brother was driving it when it died. i have had an on off rough idle for a while now. maybe it was the pump. thought it was the iac valve. any thoughts are greatly appreciated.
 
another possibility is temperature sensor, if it sticks on the hot side, it will keep the injectors from getting fuel. I had one get stuck on 210deg and at that temp, the motor gets leaned out, no fuel, so no start. Its the one in the manifold, not the one in the head. The one in the head is for the gauge. IIRC the sensor was like 22 bucks.
 
go to the auto parts store and ask for a node light for your gm t.b.i system. this is a light that plugs in to the injector harness and will flash when the low voltage is present at the pulsing for the injector. you need someone to crank will you watch. no light = no injector firing. back trace threw system and see the problem.
 
The ignition module sends a signal to the ECM that tells the ECM when to fire the injectors. If the module is dead, then you'll get zero fuel from the injectors. :eek:
 
swapping pumps

for those of you who cut the access panel on the interior i have a few questions. what tool did you use? a cutoff wheel scares me with sparks and gas fumes. how much clearance is there between the floor and the top of the tank and wiring. and lastly, could you give me some dimensions where to cut so my cargo area doesn't end up like swiss cheese.

thanks
 
thunder i think you are correct, i threw a code 12, no distributor reference pulse. so that's where i'll start. which fuses could be giving me problems if they are blown? as far as the dist module is concerned, just an oem replacement or aftermarket for reliability and longevity.


once again ck5 pays for itself tenfold.
 
Go with a AC delco or GM module. I have found most aftermarket dist modules are prone to early failure.

FYI A code 12 always comes up when you check the codes. It shows the ECM is functioning and in diagnostic mode. The ignition is turned on but the engine is not running so the ECM sees no distributor pulse and sets code 12. If you have a scanner and do a scan while the engine is runing and a code 12 comes up. Then it usually means a bad dist module.

If you pull your module out many auto parts like auto zone or Napa will test it for free. That might help you narrowdown the problem.
 
finally stopped raining, and i stopped drinking long enough (mardi gras in new orleans, need i say more) to play around a bit more. the pump doesn't make any noise indicating it is working. before i drop the tank, could it be the relay or a fuse i can check. thanks again folks.
 
i ran into the same problem and the ecm fuse blew the reason was the wire's that ran into the fuel injectors were getting to hot from the engine so i would check your fuse and if it's blown start from there. i had to get new heat sheilding on all my wire's and never had a problem since.
 
IIRC there is a test lead on the fuel pump relay (red wire?) that just hangs out, that you use to test the relay operation.

I don't have instructions on how to do that, but there is a connector near the fuel tank with one wire (sender and 12V for fuel pump, you want pump) that you can put power to and force the pump to run. That would tell you if it's the pump or before that.

I'm relatively sure that the fuel pump relay test has been explained on this board before.

I certainly wouldn't drop the tank before testing the pump, thats for darn sure.
 
hd-10 said:
i ran into the same problem and the ecm fuse blew the reason was the wire's that ran into the fuel injectors were getting to hot from the engine so i would check your fuse and if it's blown start from there. i had to get new heat sheilding on all my wire's and never had a problem since.
Click to expand...

ecm fuse is intact. currently looking how to test the pump relay. all your help is appreciated.
 
Pump relay is page 3
schematic

No idea if the wiring is going to be identical to yours, I think thats a camaro diagram, also no idea what year. But should be very similar at worst.

CK5 post

Also appears putting 12V to that test connector should kick the pump on if the above post is correct.
 
HarryH3 said:
The ignition module sends a signal to the ECM that tells the ECM when to fire the injectors. If the module is dead, then you'll get zero fuel from the injectors. :eek:
Click to expand...

this is what happened to me. went out to start the truck one morning and it was dead. i saw no fuel coming out so i thought that was the problem. after testing the injectors i traced it to ign. fired right up after that.
 
well, i held the relay in my hand and felt/heard the relay working with two different relays. but no pump sound or action. i know its the pump, but is there any other crazy thing it could be before i drop the tank? this sucks!
thanks guys for your help.
 
unplug the harnnes and se if power at plug at sender. if yes remove the tank. and if pump over 80-90k miles old its bad. and past life span.
 
It's hard to hear an in-tank pump at all.


Put a presure gauge on the incoming fuel line and turn key on, check presure, or run a long line into a can and turn key on, look for gas coming out. You can have presure and the injector will not fire unless it gets a reference pulse.
 
Diag TECHNICIAN says:

My $0.02
everybody is right, but.... with the cost of parts there is no need to replace things because it caused the same problem on someone elses rig, (not trying to step on anyones toes).
how do you know there is no fuel from the injectors-just guesing, if you manually put some fuel in or spray carb cleaner in does it run- i'm assuming this is what you did. If you did this and it didn't run or try to fire then i would check other things besides the pump, things that would cause no spark no fuel conditions,(i.e. ecm fuses, ecm connectors-always check connectors before changing electrical components, it feels bad when someone puts in a new ecm and it doesn't work or even fries because a connector pin is bent off -sorry, small tangent)


Anyways-
it sounds like it could be a pump, if you are not hearing any pump noise when the key is cycled then that is a safe bet, but do some other checks before you buy the pump. like was said before- check for fuel pressure when the keys on-(with your ear tightly up against the tank and someone else turning the key you should hear the pump, but still check for fuel pressure) if you don't have a gauge, get a bucket and take the fuel filter off and cycle the key, it should spray into the bucket pretty good, if it drizzles or none you have a fuel delivery problem. If you can get a gauge, check for adequete fuel psi. to be a bit more sure than the bucket gig. iF YOU DON'T HAVE A PROBLEM THERE THEN MOVE DOWN THE LINE TO THE INJECTORS AND GET THOSE NOID LIGHTS EVERYONE IS MENTIONING, OR IF YOU DON'T HAVE THE MONEY YOU CAN PULL THE INJECTORS AND TURN IT OVER TO VISUALLY SEE THAT THEY AREN'T FIRING- IF U USE A NOID LIGHT AND IT DOESN'T FLASH CHECK THE OTHER INJECTORS TOO, IF IT STILL DOESN'T FLASH THEN YOU HAVE AN ELECTRICAL PROBLEM WHETHER IT BE ECM, WIRING, ETC- IF THATS THE CASE, CHANGE FROM THE FUEL PUMP IDEA TO ELECTRICAL PROBLEM IDEA and come back here.
If you have a fuel delivery problem then start at the easiest point possible, check for power at the fuse panel, just because you can feel a relay clicking doesn't mean its working even when you change the relay with another one- unless it is new. you can bridge the relay socket(where the relay connects to) with a jumper wire so that you know you have good power to the pump, check to see you have power at the relay terminal and if you do then go to the wiring harness at the tank and probe the pump b+ wire to make sure there is power there- if there is and you have no fuel, feel comfortable dropping the tank, but drop the tank and then check for power again and check for ground, also maybe even try powering the fuel pump while out of the tank- sometimes moving connections will fix a problem, if magically it works then find any loose connections and repair, if it doesn't work no matter what you do then change it knowing its bad. Fuel pumps do go out around 100k but that is no reason to condemn them, i have seen them go much longer in the field and have replaced them for the first time in trucks at 185 k.
Overall though I think your on the right track, it sounds like a fuel pump problem but it always pays to do a little extra checking. It really sucks when you buy a part and it still doesn't start.
Let me know if ya fix it, or need more help.
 
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