Signs of weak fuel pump?

[shane96ranger]

I've been having, what seems to be, fuel starvation issues on my Ranger lately. It feels like it's missing under mid to heavy acceleration, gets really poor gas mileage, and it is gradually getting worse. Once and a while it will just seem like everything is perfectly normal for 10 to 15 minutes, then it starts its tricks again. My knee jerk reaction from my troubleshooting is the fuel pump is getting weak, and here's why:

When I start the truck, the fuel pressure takes 6-7 seconds to come up to full pressure. While it's running, if I purge the line it takes 3-4 seconds to come back up to full pressure. Does this sound like a weak pump? Are there any other tests I could do?

I'm not exactly sure how the fuel system works on my Ranger (96), but I think it's similar to the system on my Mustang where it has a return line going to the tank. With my Mustang, the pressure is almost instant when the car is started, and also when I purge the line while it is running.

Any other thoughts? BTW I have no CEL and I replaced the fuel filter already.

 

[shane96ranger]

Still scratching my head on this.

 

[bigrockets]

You should do the fuel flow test and fuel pressure test to see if it meets specs. Also could be the fuel pressure regulator. Also could be a failing fuel pump relay. You can usuelly swap the relay since there are three or four identical in the relay box. You can rent a fuel pressure kit from one of the big auto parts stores for almost free or a deposit.

 

[shane96ranger]

You should do the fuel flow test and fuel pressure test to see if it meets specs. Also could be the fuel pressure regulator. Also could be a failing fuel pump relay. You can usuelly swap the relay since there are three or four identical in the relay box. You can rent a fuel pressure kit from one of the big auto parts stores for almost free or a deposit.

Thank you for the response!! That's how I got this.

When I start the truck, the fuel pressure takes 6-7 seconds to come up to full pressure. While it's running, if I purge the line it takes 3-4 seconds to come back up to full pressure. Does this sound like a weak pump?

Sorry, should have been more specific on my test. It runs at 40psi without vacuum, 31psi with vacuum. I think the relay is loud enough I would hear it, but I'll give it a try.

EDIT - These pressure numbers are within spec, but it still takes a bit to get to pressure on start up and when I purge the line. Also, just a side note.... I compared it to my Mustang that still has the factory spec 88Lph pump in it.

 

[adsm08]

It could be a pump. Does it hold pressure once shut off?

 

[shane96ranger]

It could be a pump. Does it hold pressure once shut off?

It holds pressure. I only left it for about 15 seconds before I purged it. One other thing I found odd was; hardly any fuel comes out when I purge it. My car shoots it out pretty fast.

Thanks for the post adsm.