Fuel pump works...then doesn't.. then does...then...

[Erik the Awful]

I still have nothing from the pump when I put the jumper wire in place of the relay, so it kind of has to be the pump at this point, right?

That or wiring at the pump. Got a good ground? Clean connections? If the wiring's good and you have both 12v and a ground at the pump, it's the pump. Cheap pumps are notorious for crapping out quickly, but even the Delphis seem to be having problems.

If your truck is a TBI, absolutely replace it with the Vortec fuel pump. It's a drop-in, it works just fine with the stock TBI, and it has plenty of overhead if you want more power later. It's also not as stressed just doing its job so it lasts longer.

 

[Dariusz Salomon]

Measure the voltage on relay socket-tho jumping could be a good indicator of pump going. There's also an issue on relay terminals expanding when getting too hot. Pig tail is another culprit-they go(hence all new pumps have new style connectors included for you to replace the old ones).
In my case(intermittent non-starts) it was the control wire from ECM that was playing up-that's another thing you can check. Open the fusebox-jump wires after the relay terminals-measure currents there. Plus all of what the boys said-tho to this day Idk where is my pump ground (Tahoe) as all I see is the pig tail running from the pump to a fuse box. I looked at various diagrams and drawings and can't find it. Google shows nothing or I'm missing something-maybe it's a shared ground or something.

 

[thinger2]

What year truck? I assume its an OBD1.
If so, you can test the fuel pump by putting 12 volts to terminal "G" on your OBD1 connecter.
Just be carefull. Dont touch anything but that terminal and only do it long enough to hear if the pump turns on.
That terminal bypasses the relay and powers the pump directly.
I had a very similiar problem that turned out to be the cheap ass relay.
The 15 buck relay from Oriellys and Autozone is rated for 15 amps.
NAPA sells a 30 amp relay made by Echlin.
It isnt about the amperage draw, your pump would never draw 30 amps.
Its about the build quality and the plastic.
The 15 amp is white plastic made from a cheap recycled material that distorts easily and the contacts are very thin and they tend to "arc stick"
So you get intermittants where that relay doesnt work and then 2 minutes later when it cools the contacts pop loose and then it does work.
The 30 amp is made from "virgin" plastic and doesnt heat deform.
They are black plastic
The contacts are thicker as well.
And the last time I looked they were made in Wisconsin.
The 15 amp is about 15 bucks.
The 30 amp is about 25 bucks.
There is some truth about the fuel cooling the pump.
But I think it has more to do with the pump having to work harder without the volume of fuel above the intake.
And that the crud in the bottom of the tank is less diluted.
We run into this problem all the time on commercial boats.
Whatever is in your tank is constantly getting slopped around and mixed.
But the heavy crud falls to the bottom.
On a full tank that crap is stirred into enough fuel that the filter can handle it.
It is fuel diluted.
With a short tank that crap to fuel ratio is much higher and packs the filter.
Too much crud, not enough solvent.
The same thing happens while you are driving your truck down the road.
The same amount of crap is still in the bottom of the tank.
But it is a higher concentrate of crap because it doesnt have enough fuel to get strirred into.
I am in Seattle. I feel the pain of the 10% Inslee gas at 5.89 a gallon
I would put 12 volts to terminal "G" and see if the pump works.
If it works, put a new fuel filter in and a half tank of gas and a 30 amp pump relay and see what happens.
And fix the battery cables.
Any little loss of ground or voltage will stop it dead.
Dont get all wound up over Schurkey.
I did at first and then I realized that I wasnt here to make myself feel better I was here for the free education.
And he knows his ****.
He is just passionate about it.
You can learn a lot from this guy.
Even though I will bust him up at trivial pursuit.
Maybe.
Its a free education bud.

im in Seattle so if you need to find parts or whatever I am in the yards pretty often.

 

[mudpie]

Also please include year, model, engine, and transmission in your posts. It can help with diagnoses.

What year truck?

Yeah, I forget the GMT400 line goes back to '88. Somehow I have in my mind that it's just 96-99. I'm not really a Chevy guy, just a guy who happens to own a Chevy. Probably doesn't much matter now, but for anybody searching in the future it's a '96 2500HD, 5.7, updated spider and 140a alternator but otherwise all stock. It's got 468k, and I absolutely love this truck. Wouldn't trade it for anything. Other than some normal maintenance stuff, it's been 100% reliable.

Anyway, new fuel pump is in and it's running fine. Time will tell. It was running fine 3 days ago, when I thought the problem was the wiring, so I guess I'll find out. I've always heard that an electric fuel pump either works or it doesn't, so this being an intermittent problem was a bit of a curve ball. Maybe it's a testament to the quality of a Delphi pump that it put up a fight over a couple weeks rather than just dying straight away. Who knows...

For everyone who mentioned the ground, your point was well taken, and I did check it. However, I'm in the PNW and we don't have bad winters or road salt, so I kinda skipped past that because I was about 99% sure it was good, and it in fact was. Any time I work on anything, I make it a point to clean any grounds, and the contact on the wire. I appreciate the suggestion though. Actually, I appreciate everyone's suggestions and help. I know there's lots of fuel pump threads, and some forums I'm on have a lot of people who just want to yell at people to do a search. Y'all are pretty dope. Or whatever the kids are saying these days. Thank you all.

 

[thinger2]

Yeah, I forget the GMT400 line goes back to '88. Somehow I have in my mind that it's just 96-99. I'm not really a Chevy guy, just a guy who happens to own a Chevy. Probably doesn't much matter now, but for anybody searching in the future it's a '96 2500HD, 5.7, updated spider and 140a alternator but otherwise all stock. It's got 468k, and I absolutely love this truck. Wouldn't trade it for anything. Other than some normal maintenance stuff, it's been 100% reliable.

Anyway, new fuel pump is in and it's running fine. Time will tell. It was running fine 3 days ago, when I thought the problem was the wiring, so I guess I'll find out. I've always heard that an electric fuel pump either works or it doesn't, so this being an intermittent problem was a bit of a curve ball. Maybe it's a testament to the quality of a Delphi pump that it put up a fight over a couple weeks rather than just dying straight away. Who knows...

For everyone who mentioned the ground, your point was well taken, and I did check it. However, I'm in the PNW and we don't have bad winters or road salt, so I kinda skipped past that because I was about 99% sure it was good, and it in fact was. Any time I work on anything, I make it a point to clean any grounds, and the contact on the wire. I appreciate the suggestion though. Actually, I appreciate everyone's suggestions and help. I know there's lots of fuel pump threads, and some forums I'm on have a lot of people who just want to yell at people to do a search. Y'all are pretty dope. Or whatever the kids are saying these days. Thank you all.

468 K ?
Chevy guy or not youre doing something right!
Thats pretty awesome!

 

[HotWheelsBurban]

468 K ?
Chevy guy or not youre doing something right!
Thats pretty awesome!

Yes the young man who's selling me his granddad's truck, said he figures it's got another 300K in it if we continue to take care of it. I told him I know several guys on here who have done 400 thou on their 400s.
I feel like my Burb will go a good long time more, it just needs some love and attention ( not just getting sent all over Houston area every day).

 

[thinger2]

I look at it this way. A new truck is at least 70 grand.
Which after the finance boys get done with you is actually more like 90 grand.
For 20 you can put a new engine transmission transfer case diff into it .
Drive a 500 dollar honda while its being done.
And this makes me nuts.
Drive the old truck and stop trying to keep up with the Joneses.
Let them go into debt.
Why would you possibly care.
Keep the 70 friggen gees for you and your family.
Heres what I learned from my time as a salesman.
Everybody, everybody, every one of them who came in with a 2 year old car and wanted to trade up was so friggen upside down that it was laughable.
Snooty prententious posers who were so weak that they were worried about impressing strangers.
We love those people.
And they all every rolex wearing ****** bag one of them had horrible credit.
We call them "roaches"
Thats when you shine the light of their credit report on them and they scurry away.
And damn do they lie.
Back in the 90s it might take a couple of weeks for every finance company in the nation to kick the contract.
I worked for a huge dealership.
But we had to do our own repos.
Always interesting.
These people rip off the newspaper kid and the pool boy.
They cheat on their taxes
And that whole house of cards collapeses on them.
And the blame everybody else like they are innocent victims.
Roaches.
Drive an old truck, fix it yourself untill you get to old and beat up to do it anymore.
Use the money to buy a house and put the kids through school.
**** the neighbors.
Impress yourself.

 

[mudpie]

468 K ?
Chevy guy or not youre doing something right!

Well, I can't take all the credit. Or really any of it. I got the truck in 2015 with 425k on it from a guy who owned a towing company, and this is what he told me at the time....

Towing guy did some work for a mechanic who owed him money. Mechanic guy used this as his mobile repair rig, and had a utility body on it, and the door sticker indicates it was originally a cab & chassis configuration. Being a GM certified master mechanic, or whatever, and this being his work vehicle, it was meticulously maintained.

So mechanic guy gets a new truck, pulls the utility body, throws a bed on this truck, and asks the towing guy if he'd want to trade for the truck rather than the money the mechanic owes him. Towing guy says sure, then takes it to a body shop that owes him money and says hey, rather than that money you owe me, you wanna paint my truck? Body shop says sure. The unfortunate part is that towing guy had them paint it some Mopar color, but had them add some metallic something or other, so it's impossible to match, and the paint shop wasn't exactly doing a restoration quality job. I've got some places where it's starting to not stick so well and it's just a matter of time before it's going to need a paint job.

Anyway, towing guy now has a freshly painted truck hat he didn't really pay any cash out of pocket for, and his wife files for divorce. He's desperate for cash, throws it on Craigslist for $600, and I happened to see the ad like 8 minutes after he posted it. I jump in the car immediately to go see it. Bought it for $500, and I've put 43k on it since. In that time I've replaced the spider, starter, alternator, distributor, cap/rotor, plugs & wires, all front end bushings, and brakes. To say I'm pleased with the purchase would be an understatement.

I look at it this way. A new truck is at least 70 grand.
For 20 you can put a new engine transmission transfer case diff into it .
Drive a 500 dollar honda while its being done.

Assuming I could trade my truck for a new 70 grand something, that would be cool for a few years until the first time something breaks, and it has to go to the dealer because it needs a bunch of special tools to fix, or the cab has to come off, and it would cost me more than the total amount I have spent on my truck in the whole time I've had it. I just don't see the value in a new pickup.
Or for that matter, cars in general. I have a '94 Accord wagon that I paid $800 for. It's a 5 speed and it consistently gets 28.5 - 31 mpg. What am I gonna do....go spend 40 grand on something that gets 40 mpg? There's no value there. Vehicle prices are just stupid, but yeah, some people have to have the newest and coolest, and if they can afford it, great, go do whatever. But it's often not about how much you make, it's about how much you keep. My Honda get's me all the same places their car does, but I paid $800 once, not every month.

 

[tinfoil_hat]

So all-in you are still less than 3 car payments on that $70k truck.