A puzzle for you GM experts

Re: A puzzle for you GM experts

PostBy: Coalfire On: Fri Jan 21, 2011 5:35 pm

david78 wrote:Here's my problem: I have a 1996 K2500 Suburban, 5.7, 136,000 miles, automatic. It had been running great, but quit on the way home a couple nights ago, just like turning off the key. I have spark but no fuel. I had to have it hauled home. To add insult to injury, the guy driving the rollback backed into a tree limb while turning around and busted out the back glass. So now I have a three ton lawn ornament that leaks. :mad: Anyway, I couldn't hear the fuel pump run when I turned the key. I put in a new fuel pump relay and changed the filter and now when I turn the key on I can hear the pump running but still no fuel spraying into the TBI. It will start when I pour gas into the TBI, but quits as soon as that fuel is gone. I had replaced the fuel pump a couple years ago. This is my building material/coal hauler so I really need to get it running. Any ideas?



You say TBI and than you say schrader port. The throttle body injection(TBI does not have a schrader). Is this the engine with the plastic upper manifold that houses the spider injector? Or do you see two injectors in something that looks like a carburetor. I need a little more info???
Coalfire
 
Hand Fed Coal Stove: DS Machine 96K btu Circulator
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: david78 On: Fri Jan 21, 2011 7:11 pm

It's a 1996 so according to the manual it's a Central Sequential Fuel Injection system, not TBI, though it does still have a throttle body. It does have a Schrader valve.
david78
 
Baseburners & Antiques: Fuller & Warren Splendid Oak 27
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: Coalfire On: Fri Jan 21, 2011 7:16 pm

Ok that is the spider injection with the poppet nozzles. you need to be at a certain fuel pressure or they won't open.

Here is where you need a fuel pressure gauge. you will spend alot of money and time replacing parts. You can not tell if you have proper pressure br cracking the schrader. Like I said this injection system uses electronics but the nozzle that put the fuel in has to be at pressure or it will not open.
Coalfire
 
Hand Fed Coal Stove: DS Machine 96K btu Circulator
Coal Size/Type: Nut


Re: A puzzle for you GM experts

PostBy: david78 On: Fri Jan 21, 2011 7:27 pm

OK, I'll get hold of a gauge. Can you test for pressure if the engine is cranking but not running?
david78
 
Baseburners & Antiques: Fuller & Warren Splendid Oak 27
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: Coalfire On: Fri Jan 21, 2011 7:32 pm

Yes when you first turn your key on you will get a two second prime. Then when you crank your computer will ground the conrol for the fuel pump relay.
Coalfire
 
Hand Fed Coal Stove: DS Machine 96K btu Circulator
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: Coalfire On: Fri Jan 21, 2011 7:37 pm

What is strange is that it died while driving, like someone turned the key off? I am wondering if there could be a computer problem. Like a bad driver. Do you have access to wiring diagrams? Can you go to the control side of the injectors with a lab scope and monitor the injector command? If you know some one that has a labscope it would be helpful. If not you could use a test light, but that is not a hundred percent you can still get flashing but will still not work.

First things first though get back with fuel pressure numbers




Eric
Coalfire
 
Hand Fed Coal Stove: DS Machine 96K btu Circulator
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: Coalfire On: Fri Jan 21, 2011 7:39 pm

Sorry for all the posts in a row, but did you KISS the car (keep it simple stupid) sometimes thats all it is.

Did you check all your fuses, if one is blown for the fuel system that would be a place to start



Eric
Coalfire
 
Hand Fed Coal Stove: DS Machine 96K btu Circulator
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: david78 On: Fri Jan 21, 2011 7:42 pm

So the 60-66 psi the manual calls for is after turning the key on and the 2 second prime is done?
david78
 
Baseburners & Antiques: Fuller & Warren Splendid Oak 27
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: SMITTY On: Fri Jan 21, 2011 7:45 pm

Yep - as soon as you turn the key on, it should run & the pressure will .. or should .. rise quickly.
SMITTY
 
Stoker Coal Boiler: Patriot Coal - custom built by Jim Dorsey
Hand Fed Coal Stove: Harman Mark III (not currently in use)
Coal Size/Type: Rice / Blaschak anthracite
Other Heating: Oil fired Burnham boiler

Re: A puzzle for you GM experts

PostBy: david78 On: Fri Jan 21, 2011 8:15 pm

Well, I ordered a fuel pressure gauge so it'll be a few days before I can check that. It's too dang cold to work on a truck right now anyway. 8 degrees right now. :shock:
david78
 
Baseburners & Antiques: Fuller & Warren Splendid Oak 27
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: SMITTY On: Fri Jan 21, 2011 8:19 pm

Yeah that's never fun.

I remember my father & I trying to do a simple t-stat installation in my mom's '90 Pontiac LeMans, which was only a couple years old at the time ... and it was 8° out. While dad was tightening down the bolts, the pot-metal housing decided to split in 2. Dad woke the neighborhood up after that one. Can't blame him. What a joke that was! :sick:
SMITTY
 
Stoker Coal Boiler: Patriot Coal - custom built by Jim Dorsey
Hand Fed Coal Stove: Harman Mark III (not currently in use)
Coal Size/Type: Rice / Blaschak anthracite
Other Heating: Oil fired Burnham boiler

Re: A puzzle for you GM experts

PostBy: Coalfire On: Fri Jan 21, 2011 9:00 pm

david78 wrote:So the 60-66 psi the manual calls for is after turning the key on and the 2 second prime is done?



At that point you may not have enough pressure to start. Try cranking and monitor fuel pressure.
Coalfire
 
Hand Fed Coal Stove: DS Machine 96K btu Circulator
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: Jst a Vtr On: Fri Jan 21, 2011 11:13 pm

I have a 96 K1500 5.7 that did exactly the same as yours. Could hear fuel pump run and had fuel at test port. Towed it back to the shop checked pressure and found it to be low - pinched off the return at the tank - still low- removed fuel sender and pump to find the hose that joins the pump to the sender had split.
Since this was a fleet vehicle at the time and the pump itself is replaceable (napa our cost about $65.00)we just replaced the pump and the hose that came with it so their would be no question the hose would be the correct application as off the shelf fuel hose may not meet proper specs.Some GM's in that vintage used a pulsator in place of the hose also. Probably the rear window will cost more than the fuel pump but dropping the tank sucks.
Good Luck and as said before check fuel pressure first.
Jst a Vtr
 
Hand Fed Coal Stove: Salvo citation, modified as an add on forced hot air
Hand Fed Coal Furnace: Duo-matic/Olsen (In workshop)
Coal Size/Type: Pea/Nut
Other Heating: Oil fired hot air

Re: A puzzle for you GM experts

PostBy: david78 On: Mon Jan 24, 2011 12:39 pm

Well , I got a pressure gauge today and when I turn the key on I have 45 pounds. When I start cranking it actually goes down to around 40. The manual says 60-66, so I guess my pump is toast. Now comes the fun part. :mad: Thanks for all the replies! :up:
david78
 
Baseburners & Antiques: Fuller & Warren Splendid Oak 27
Coal Size/Type: Nut

Re: A puzzle for you GM experts

PostBy: Coalfire On: Mon Jan 24, 2011 1:16 pm

Don't just replace the pump. You might want to replace the sender as well. What will happen is that the wiring from the pump to the sender can burn at the connection. If you don't check this your new pump will suffer the same fate. Also check your ground for the pump and make sure that is clean.


One other note your pump does not create the pressure the regulator does, did you pinch the return line to see if the pressure goes up? what if your regulator ruptured? that would also explain no pressure build. just a thought
Coalfire
 
Hand Fed Coal Stove: DS Machine 96K btu Circulator
Coal Size/Type: Nut