Please help with my GMC truck

[Some Kind Of Monster]

We we're rolling to the lake the other day when the truck shut off. No sputtering, it just died. It is a 98 GMC Sonoma 4.3l Here is what I know. It is getting good fuel pressure, and the motor runs if your pour gas in the intake. I am guessing the injectors aren't firing, but I am unsure what to do next. Is it a computer problem? Is there a relay to check? Thanks for any help!

[GofastRacer]

Go to AutoZone and get a scanner and plug it in, beats process of elimination on that computer crap!.. BTW, is the fuel pump working???..

[YeLLowBoaT]

did you put a presure guage on the fuel system?

[79centurion]

Does it keep running or die once it is out of fuel that you dumped in?

[Kachina26]

How much fuel pressure? It takes quite a bit to opperate those poppets.

[IMPATIENT 1]

How much fuel pressure? It takes quite a bit to opperate those poppets.
yes it does! if it ain't got at least 46 psi with key on engine off, its not gonna start for ya.

[IMPATIENT 1]

you can unplug the injector connector and and check for injector pulse there, the pink wires are voltage positive, the 6 other different colored wires are the negative trigger circuits from the pcm. just hook a small test lite between a pink and another color and have someone crank it, if it lites, you've got injector pulse.
don't use a meter to test this, its needs to be tested with a load, the lite bulb is about the same resistance as a poppet, they make things called noid lites and they can be bought at any autozone or place like that.

[Some Kind Of Monster]

Yes it gets good fuel pressure, but I am not sure exactly how much. All I know is if I disconnect the fual line it shoots all over the place. I have a gauge and I'll put it on and check it tomorrow. It is throwing a SES light on the dash, so I went and rented a scanner. The scanner returned zero codes. How can that be? I also have a noid light that I can try. Is there some kind of pressure shut off that would cause the injectors to stop? I'll post up my findings after work tomorrow. Thanks for the help everyone.

[Kachina26]

Yes it gets good fuel pressure, but I am not sure exactly how much. All I know is if I disconnect the fual line it shoots all over the place. I have a gauge and I'll put it on and check it tomorrow. It is throwing a SES light on the dash, so I went and rented a scanner. The scanner returned zero codes. How can that be? I also have a noid light that I can try. Is there some kind of pressure shut off that would cause the injectors to stop? I'll post up my findings after work tomorrow. Thanks for the help everyone.
Check the pressure, shooting all over the place isn't a sign of anything on that particular setup.

[DMOORE]

Yes it gets good fuel pressure, but I am not sure exactly how much. All I know is if I disconnect the fual line it shoots all over the place. I have a gauge and I'll put it on and check it tomorrow. It is throwing a SES light on the dash, so I went and rented a scanner. The scanner returned zero codes. How can that be? I also have a noid light that I can try. Is there some kind of pressure shut off that would cause the injectors to stop? I'll post up my findings after work tomorrow. Thanks for the help everyone.
The emergency shut offs that trigger during an accident, shut the fuel pump off. So that should not be it. I've never heard of one the shut the injectors down. I'm thinking some sort of relay failed and cut power or siginal,to the injectors
Darrell.

[67weimann]

Yeah, I would guess at it being a relay somewhere in there failed and isn;t sending the pulse to the injectors. Try the test light technique. If I wasn't so far away, I'd come help you.:D

[Beer-30]

Since it runs with fuel into the throttle body, then you are giving it what it is missing. Obviously it is getting spark and air.
Whether it's TBI or CPI, there would need to be the appropriate fuel pressure (already said). If that was OK, then the injector(s) are not opening. It would be strange for all of them not to work at the same time. If there is no signal to the injector(s), you have to start tracing back toward the ECM. If wires are ok and connected, then the injector driver section of the ECM has gone.
It's gonna throw the SES light with key on/engine off.

[Some Kind Of Monster]

Ok, The injectors are firing. I confirmed this with a node lite and all six fire as I crank the motor. I am leaning towords the fuel pump now. I put a gauge on it and got about 19 lbs of pressure. Not enough?

[67weimann]

Ok, The injectors are firing. I confirmed this with a node lite and all six fire as I crank the motor. I am leaning towords the fuel pump now. I put a gauge on it and got about 19 lbs of pressure. Not enough?
I don't think that is enough pressure for EFI... it should have like twice that. I think your injectors are probably like 32# or something like that...

[YeLLowBoaT]

it needs about 50.
Just a tip...its ezer to take off the bed then it is to drop a full gas tank.

[Beer-30]

The fuel pump is so common, that it your answer.
Also, they leave without a sputter. Unit just shuts off.
A word of advice. If you don't get good deals from your local dealership, go to an AC/Delco distributor. Same quality part for usually a little less $.
For instance. The rotors on my dually were $220/ea from dealership. Kay Automotive (AC/Delco) was $170/ea - same part number.
Plus, the original pump went what, 13 years? A cheapy will go a year or two. The extra money will insure that you don't pull the bed again.
If you could find a Walbro replacement, that would be fine.

[DMOORE]

Just to be sure, I didn't see if you checked the inline fuel filter? Make sure before you pull the tank.
Darrell.

[396_WAYS_TO_SPIT]

Check your fuel pressure! Call me tomorrow and I can look up the specs

[67weimann]

Check your fuel pressure!
I put a gauge on it and got about 19 lbs of pressure.
:D :D

[79centurion]

Time for a fuel pump. Also replace fuel filter.
Dan

[AzMandella]

Deffinately a fuelpump.Need about 50psi.Have fun taking the bed off.Glad to hear yo got it figured out.Get that baby ready to go to Apache again.:D

[67weimann]

Hey Billy, let me know if you need some help swapping the pump out. I'll be glad to help to get you back on the road. You have to go to Apache with us...so get it done man...:D

[squirt'nmyload]

EASIER TO TAKE THE BED OFF!!!!!!!!!!!!...........dude, call me if you need help

[cfm]

Beer 30 is absolutely correct - get a Delco pump + sock. I'm in the biz and hate to comment on how quickly a lot of other new pumps from Carter, Borg Warner, etc,etc,etc bite the dust. Many within a years time.
Also as he said - they are no more expensive. No joy in replacing in tank pumps so just go Delco.
Lastly, make sure the ground wire is getting real good contact on frame. In our area rust is huge (lot of snow and tons of salt) and can cause problems here.

[396_WAYS_TO_SPIT]

Hey billy, call me today! I am a direct dealer for ac delco. We also carry carter and airtex pumps. All of my Carter pumps have a lifetime warranty as long as you keep the box! I think Acdelco's have a 1 year warranty:yuk: One of the main reasons that we stopped carrying all of the delco parts was due to the warranty change.....

[Kachina26]

Ok, The injectors are firing. I confirmed this with a node lite and all six fire as I crank the motor. I am leaning towords the fuel pump now. I put a gauge on it and got about 19 lbs of pressure. Not enough?Not even close, this system uses a poppet style injector. Kinda like the old diesels, it takes at least 44-46psi to move the ball off of its seat.
Now, does the pressure go up to say 30-40psi and drop rapidly? Let me know.
Just to be sure, I didn't see if you checked the inline fuel filter? Make sure before you pull the tank.
Darrell.Can't tell you how many times the fuel pump went terminal within days of replacing a severly plugged filter. Always warned the customer up front, thankfully I worked at a reputible shop and never got accused of doing something "funny" to induce the failure.

[IMPATIENT 1]

The emergency shut offs that trigger during an accident, shut the fuel pump off. So that should not be it. I've never heard of one the shut the injectors down. I'm thinking some sort of relay failed and cut power or siginal,to the injectors
Darrell.
gm don't have that, just fords;)

[IMPATIENT 1]

put a fuel pump module in it already!!! 19psi will not pop open the poppet injectors like stated above, it take at least 40psi to fire 1, it should have @48-52psi with a good fuel pump with key on, engine off.

[Some Kind Of Monster]

You guys were absolutely on the money! I put a new pump in and we are golden. Also replaced the filter just in case. Now it puts out about 50 psi and she fired right up. I pulled the bed again (no problem 8 bolts) and it wasn't too bad.
Remember that fuel pump my buddy bought from you Michael? It turned out that the fuel pump wasn't his problem so I put his old one in my truck to see if I could save some coin. Worked like a charm!
Thanks again everyone! I was able to drive mt truck to work today instead of my girlfriends pink beetle. You should have seen the looks....

[67weimann]

I was able to drive mt truck to work today instead of my girlfriends pink beetle. You should have seen the looks....
I can see it now...LMAO

[AzMandella]

Cool Billy glad to hear everything worked out.:D Now get your ass up to Apache at the end of April.

[396_WAYS_TO_SPIT]

Remember that fuel pump my buddy bought from you Michael? It turned out that the fuel pump wasn't his problem so I put his old one in my truck to see if I could save some coin. Worked like a charm! .
Right on! Im glad that it worked out for ya;) KEEP THE RECIEPT!!!!

[Some Kind Of Monster]

Well, Same truck, similar problem. Now a few months down the line when I feather the gas the truck works fine. If I push any harder, it bogs. I suspected fuel pump but this time I am getting almost 60lbs of pressure. What the heak could it be this time? This happened once before and I reseated the fuel pump and it went away for awhile. Should I just dump the used pump and get a new one? It just doesn’t make sense!!!

[79centurion]

Try filter first. Then check the psi under load. You might have the psi but no volume due to a plugged filter.
Dan

[67weimann]

What Dan said...:D

[Some Kind Of Monster]

Try filter first. Then check the psi under load. You might have the psi but no volume due to a plugged filter.
Dan
Filter was replaced on the first go-round. Besides the pressure check valve is on the fuel rail after the filter.
Regardless, I bit the bullet and bought the $350 fuel pump. It worked and the truck is good as new. I just can't explain why. Thanks again for all the help everyone!

[67weimann]

A plugged up filter will cause the fuel pump to fail prematurely...:D

[79centurion]

I hope you replaced the filter when you put the new pump in. That is the only way the warranty is good on them:D Also if you have alot of crap in the tank, it will plug the filter really quick. Also I was refering to checking the psi while driving. I know its after the filter, but it will tell you if the pump is keeping up with the volume your truck needs. Just becasue a pump builds 60 psi doesnt mean it can under load. Well anyways good to hear you got it fixed.
Dan