My woodhauling Sub is down

[jimbojango]

if it'll run on ether, gasoline, or intake cleaner being sprayed into the throttle body.. it ain't the injectors or motor. its pump related. I'd put $20 on the pump

 

[kugss]

Those vortec motors are very picky about fuel pressure, just 5# less than what it should be and it will not start cold. They also had a problem with the four pron pigtail that the fuel pump plugs in to. When you buy a new pump it should come with a new flat four prong plug that you have to cut and replace the four pron square one.

 

[7sleeper]

Did you check the fuses?

7

 

[barnumb]

also you might try checking the fuel pressure regulator its mounted in the return line going back to the gas tank has a vacuum hose from the manifold if it fails you wont have enuf pressure because it will dump it all back to the tank on a good reg if you un hook the vac line pressure will go up because the reg will close and not return any fuel to the tank ,the most common failure is the diaphram perforates ,best indicator is gas smell/dripping from disconnected vac hose jk

You will change a hundred pumps before you replace one regulator.

 

[luckypete]

get under truck with a rubber mallet or a 2x4 and slap the fuel tank as somebody cranks it over, 90% of the time if the pump is going bad it will start and even get you home... been there a few times!!!!

 

[jrr344]

I would listen for the pump to come on when you cycle the key if you don't hear it pull the tank and make sure the wires to the sending unit aren't broke or the ground wire disconnected to the frame but 99% of the time it is the pump and put a new filter on and get the delphi pump lasts longer.

 

[loadthestove]

get under truck with a rubber mallet or a 2x4 and slap the fuel tank as somebody cranks it over, 90% of the time if the pump is going bad it will start and even get you home... been there a few times!!!!

:hammer: have seen this before.

 

[super3]

this is a common problem yes, now if you use aftermarket parts always remember that you get what you pay for...(cheaper is not always better ) and yes if the pump is bad it can run at (say 20psi) and truck will still not run, due to needing 60psi...

There ya go.

Put an AC Delco pump on it.

 

[Buckethead]

Without knowing the actual fuel pressure, my money is on "a bad pump."

I have an '89 GMC C3500 with a 7.4 TBI and a 2000 Chevy C2500 with the 5.7 Vortec engine. I have replaced fuel pumps in both trucks, the '89 got an after-market pump and the 2000 got a Delco pump. If I ever have to replace them again I will stick with the Delco...it seems to be better built, is much more quiet, and the fuel sender is far more accurate.

I am also much more careful about replacing fuel filters annually to help prevent premature pump failure.

Good luck with your Suburban!

 

[Highbeam]

My old 98 K1500, same vortec 5.7 which is not TBI, ate a fuel pump once. The in tank pumps on these trucks die suddenly. So I am not at all surpised about how your truck went from 100% to dead, that's how it works. My 2001 GMC yukon with the 5.3 did the same thing. In tank fuel pumps just do that.

You aren't getting fuel. There is a schrader valve up near the intake manifold that you can poke to verify adequate pressure. Key on, engine off.

Oh, one big important thing with vortec motors. If you take off the ducting that hooks to that throttle body on top. The engine won't run!! The ducting pulls air through the MAF sensor which tells the engine to inject fuel. I know this because I tried to dump seafoam into my throttle body and as soon as I removed the duct, the engine would die immediately. I had to use the brake booster line for the seafoam.

Put the freaking black plastic duct back on and I bet it will run.

 

[david78]

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. Thanks for all the replies!

 

[John D]

I read the entire thread,and I know your hunting down the problem,but post #23 said what I was going to say......check the fuses....all of the esp ECM/PCM fuses..

 

[captndavie]

My '96 Suburban 7.5 has a hard start issue. It will start fine first thing in the morning. But once it gets warmed up and you shut it off and let it sit for a little bit you have to crank on it to get it to start. I have changed plugs and wires fuel filter and the pump seems to run fine. It has 80,000 miles on it and when I changed the plugs they were nasty looking. Oh and it uses oil too. Could this be the pump also or could it be something else?

 

[LumberjkChamp]

My '96 Suburban 7.5 has a hard start issue. It will start fine first thing in the morning. But once it gets warmed up and you shut it off and let it sit for a little bit you have to crank on it to get it to start. I have changed plugs and wires fuel filter and the pump seems to run fine. It has 80,000 miles on it and when I changed the plugs they were nasty looking. Oh and it uses oil too. Could this be the pump also or could it be something else?

I know someone who has the same issue with a '98 one ton chevy truck. Starts great cold, but if its warm it cranks a while. I have some questions for you. When it cranks, is the cranking speed normal? Sometimes the starter might be worn and not spinning the engine over like it should. How about the battery? A weak battery sometimes can be the cause. Are the batt. connections in good condition? This could also cause slow cranking and hard starting.

Maybe provide a few more details about the situation. It is hard to diagnose a problem without details. When you ask if its oil use is due to the pump, I'm assuming you mean the fuel pump. In that case it is not the fuel pump that is the cause for oil usage. I would first look for leaks (for this you have to clean and degrease the motor and take it for a short drive). If everything is leak free you then might have a oil burning problem. A more in depth diagnosis in this instance would be in order (could be worn or cracked piston rings, worn valves, valve seats, valve stem seals, etc). At 80,000 miles I would think it would be just leaking oil. That motor barely has 1,000 hours on it. I have a '95 suburban with 215,000 miles and it doesn't burn a drop of oil. Check the area between the transmission bellhousing and the rear of the engine (this would be the rear main seal, my sub. is developing a leak here).

Also, what does the 7.5 denote in your above post? Do you mean litres? If that is the case you have a 7.4. I'm just trying to be thourough.

 

[duane9835]

Not being a smart ass or anything:messed:
Do you have fuel in the tank and are you sure the guage works????

True story a co workers truck "late 90s chevy" died the other day and he checked all the simples and determined the fuel pump was bad.... Instead of pulling the tank out in the snow he opted to cut a hole in his bed to access the pump, when he pulled the pump out of the tank he took a look down in the tank with a flash light and it was bone dry...... LMAO!!!!!! The guage said 1/2.....

 

[LumberjkChamp]

Not being a smart ass or anything:messed:
Do you have fuel in the tank and are you sure the guage works????

True story a co workers truck "late 90s chevy" died the other day and he checked all the simples and determined the fuel pump was bad.... Instead of pulling the tank out in the snow he opted to cut a hole in his bed to access the pump, when he pulled the pump out of the tank he took a look down in the tank with a flash light and it was bone dry...... LMAO!!!!!! The guage said 1/2.....

Can you say "bad sending unit." That is not a funny story. At least he didn't have to drop the tank.

 

[jrr344]

You need to check your fuel pressure, but usually if its the pump it will be hard to start when it sits for a while and start easy after it is already started. Is your ses light on?

 

[captndavie]

Sorry for the confusion. I wasn't referring to the oil use, I meant was my hard start a potential fuel pump problem. I just threw in the thing about the oil use to give more thorough info.

A little more info about the vehicle. It is a 454. It was a FBI vehicle and seems to have been well cared for. I got maint records with it and talked to the last guy who was assigned to it. It was even stored indoors when not in use! It had 69,000 on it this past summer when I got it. Still smells new inside, for real!

I can say this about the vehicle, it seems to turn over fine. Get in it first thing in the morning and it fires right up. However the battery was dead when I got it. Charged it up and no other problems other than hard start when warm.

One of the reasons I mentioned the oil use is because when I worked for the forest service we had a couple different trucks that had intake problems and I am thinking one of them was using oil due to it? I am not sure of this. I am wondering if this could be my problem for both issues. Could there be an intake leak where it would be sucking oil in and the leak have an effect that would cause the hard start issue?

 

[captndavie]

Oh and shes a little oily underneath but it doesn't leave a puddle at all. Haven't seen a drop on the ground.

No to the ses light.

 

[david78]

My problem was the pump. Replaced it yesterday with a Delphi; started right up and is running fine.