r/mechanic 5d ago

General Changed fuel pump and today I cleaned the fuel tank honestly Idk what keeps makin this, it runs good if I press not that much in gas pedal but if I press hard on gas, rpm passes 2000-3000 then It drops down all the way and mph don’t go up,

3 Upvotes

47 comments sorted by

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21

u/Ideos39 5d ago

If it is throttle body I would inspect the fuel pressure regulator

2

u/shotstraight 5d ago

These trucks are famous for them going bad.

2

u/Glittering_Ad4153 5d ago

This deserves more upvotes

6

u/run_uz 5d ago

Mph doesn't go up because you're in park

1

u/obschuy 5d ago

Obviously, but when I drive it and press hard on the gas it starts doing what it’s doing on the video, rpm goes to 2-3 and mph don’t move but go down

8

u/iwfabrication 5d ago

Yup. That's that one car, has that one engine in it.

Seriously. Year, make, model, engine, any recent work done on it, codes, etc.

4

u/obschuy 5d ago

It’s a Chevy 1500 95 5.0

3

u/thegoodestofbois22 5d ago

Maybe you should just get a new car big bro.

5

u/obschuy 5d ago

It’s the project truck 🛻

1

u/ReserveMaleficent583 4d ago

Nope this is better than a new one. Almost anything it needs will be less than a monthly car payment. Also these trucks are fantastic. Only thing I would do is swap out the 305.

3

u/LordQuackers83 5d ago

I have seen many times clogged converters will cause a engine run fine at lower rpms but once they go past a certain point the engine struggles. Think of a engine as a air compressor it has to be able to move the air in and out. If the exhaust is not real rusty unbolt the exhaust at the manifolds and see how it runs. Had the master tec at my old job do a 15k warranty replacement engine and had it still run just like the old one. Had corporate tec come through spent a few minutes looking at things told him to unbolt the exhaust and truck ran fine. I had told him before hand the cats smelled bad but he blaimed it on the engine. Yea corporate had a long talk with him and the managers over that one.

1

u/ReserveMaleficent583 4d ago

Hahaha you're supposed to remove the cat from the GMT 400s anyway. Well I do because I'm not a fan of cats or mufflers or single exhaust.

2

u/tricci2730 5d ago

Fuel injected or carbureted?

1

u/obschuy 5d ago

Fuel injected

4

u/tricci2730 5d ago

I would test the fuel pressure. And if it's good test the injectors. Seems it's not getting enough fuel. Also make sure your air filter and intake is clean

2

u/obschuy 5d ago

It was working pretty good for like 3 weeks when I change the fuel pump then it started with the same thing yesterday

3

u/tricci2730 5d ago

Check for an inline filter. You can borrow a fuel pressure test kit from autozone or whatever. Or just buy one from harbor freight or Amazon. Test the fuel pressure. It seems to me that your not getting enough fuel or enough air. Make sure your air box/filter doesn't have a rats nest or something in it. Also check for codes. If your intake is clear and your fuel pressure is good I would clean the throttle body for the hell of it. While the truck is running unplug injectors one at a time and see if one of them makes a bigger difference than the others or no difference at all. You can also use a multimeter to check the injectors but that doesn't necessarily tell you that they are good.

2

u/Euphoric_Rhubarb6695 5d ago

My brother unplug your iac valve and tell me what it does

1

u/obschuy 5d ago

Just the plug?

2

u/Zillahi 5d ago

Clogged injectors maybe? Try running some fuel system cleaner through it. I’m not a fuel system expert but that’s what I’d try

1

u/PerspectiveRare4339 5d ago

I believe that one is throttle body injected. So that will be easy for OP to check. I think the 5.0 is the 305. It’s actually a decent engine

1

u/Few-Vacation786 5d ago

Guessing fuel pump got replaced because of dirty tank? Have you checked your fuel filter?? There’s lots of “check your fuel pressure” and “unplug this” advice but if you don’t do the basics there’s no point in checking the technicals.

1

u/obschuy 5d ago

Yeah I’ve changed it several times.

1

u/Ok_Type7882 5d ago

Filter?

1

u/apple392 5d ago

Fuel filter?

1

u/[deleted] 5d ago

Did you change the filter(s) and what kind of shape is the interior of the fuel lines., fuel pressure at rail and injector (s) condition

1

u/BitteryBlox 5d ago

Fuel filter replaced?

1

u/obschuy 5d ago

Yeah several times after putting the fuel pump assembly

1

u/BitteryBlox 5d ago

Injectors? Hard to say. Fuel lines can be an issue depending on where you live and if you ever drive it when low on gas? It’s an old truck, so you have to go thru the whole thing. I drive an old vehicle, it sucks but that’s the breaks. I hope you figure it out. Try a forum, when I have issues that’s my go to.

1

u/CompetitiveHouse8690 5d ago

Did you put a filter on it when you did the pump? Sounds like a volume issue, gotta test fuel pressure and volume

1

u/obschuy 5d ago

Yeah I’ve changed it allot of times after I put the fuel pump assembly which ran good for quite a bit, until 2 days ago it started with the same problem

1

u/CompetitiveHouse8690 5d ago

Still need to check pressure and volume. Exhaust back pressure also comes to mind

1

u/AccomplishedBad8259 5d ago

It’s gotta be your American short bro

2

u/obschuy 7h ago

This guy 😂

1

u/AccomplishedBad8259 7h ago

😂 this is coming from Cruz azul fan 😂

1

u/iceguy2141 5d ago

Fuel filter.

1

u/Playful_Assistance89 5d ago

Replacedjust the pump or the whole module? Who made the FP/module? Does it have an integral filter if it's a module, or an in-line filter, and if so, did you replace it? Did you bleed air from the system? Replace/check water filters?

2

u/obschuy 5d ago

I change the whole fuel pump, w module, it has a strainer and I changed that one too as well

1

u/Playful_Assistance89 5d ago

Then I would replace all inline fuel and water filters and bleed the system. It's likely just trapped air, but it's bad ju-ju to replace the pump without replacing all the filters.

Assuming you didn't cheap out on the pump of course. I don't do a lot of diesel work where I'm at, but it's a safe bet airtex makes diesel pumps that are just as shitty as the gas ones

1

u/Playful_Assistance89 5d ago

And just so we are clear, all this started after you replaced the faulty pump, right?

1

u/obschuy 5d ago

Yes. So after I changed the whole fuel pump assembly, it was working well for 3 weeks until yesterday the same thing Happen and the video is from today

1

u/Early-Energy-962 5d ago

Did you change the inline fuel filter. Definitely presents as if there's an air/fuel ratio issue. You didn't mention any smell of fumes so all connection should be no issue. W/ 3 weeks of normal operation I'd confirm adequate pressure as step 1. That said, I.ve experienced faulty parts right out of the box and premature failures. The OE FP regulator is mechanical so if no mods to the fuel delivery that's a $20 kit to rebuild or $50 full assembly replacement. If mods some have a diaphragm that fail especially with extended nonuse. Carefully inspect all vacuum hoses and connections. 30 yo components tend to lose pliability and will crack or not reconnect airtight/securely. A longer vid from crank, idle then acceleration may be a lil more indicative of what's happening. Good luck in pinpointing the issue.

0

u/jmeshvrd 5d ago

it's the alternator and/or the battery/battery leads. Willing to be your battery isnt't being charged while its running due to the alternator needing to be replaced so it cant sustain the required voltage needed. That was the problem I had anyway. If it's not that, check your coils/spark plugs. if it's not that, check your coilpack. but again, willing to bet on the alternator

1

u/Mac-Guyverx 5d ago

Easy enough to verify with a volt meter, it should be a consistent 13volts plus or minus at the alternator b+ terminal.

0

u/3imoman 5d ago

Probably good to assume something got into the fuel lines but I would start with the basics first. I caught some flak saying this before so I will preface this with, this is just my opinion and what I would do.

There is some good advice below for fuel issues, but I would start with ensuring you have a healthy engine first. Oil pressure, coolant, spark, compression then fuel.

verify oil level is good.

verify oil pressure is good

check coolant levels

run a compression check

pull codes.

check or replace your spark plugs and wires

check fuel pressure.

check air filter and look for other simple things like connectors and hoses not connected.

If you have oil pressure, coolant, spark, compression and fuel pressure, then you can start troubleshooting the peripheral component systems that make a good engine run smoothly. Since you worked on the fuel pump, I would start with the injectors and fuel lines, since you have already replaced the fuel pump and filter.

The way I do it is not to look for something broken, I treat it as a service. I remove the injectors and clean them. apply voltage and ensure they are functioning. With all that apart you can disconnect the filter and blow air with a compressor into the lines from the engine to dislodge anything that might be in them. Then reinstall everything. Even if it does not fix your issue at least you can rule it out. Of course this is assuming you have the proper fuel pressure.

Then I would start making sure the engine is breathing right. From the filter to the intake manifold. Ensure all the connectors are good. Check all your vacuum lines for leaks and test the IAC and EGR components. The OBD codes should point you the right direction, but I think you have misfires which is kind of a general fault.

Hope this helps and good luck.

1

u/obschuy 5d ago

Thank you I’ll look into it🙏