Hunting idle, bad gas milage, hesitation

[TurboedMJ]

Did a fuel pressure test, fuel pressure with vacuum line hooked up is about 33 lb. And with vacuum line unhooked is about 42 lb. I did notice that immediately after priming the pump or shutting the truck off the fuel pressure started dropping.

[ghetdjc320]

It’s normal to have it drop pressure in rotary vane pumps. It shouldn’t be a super fast bleed and should always hold some residual pressure. You can add a check valve inline to help keep your system primed. 

[eaglescout526]

Have you inspected the rubber hose the fuel pump is attached to in the tank?

[cruiser54]

[TurboedMJ]

No but it does have a relatively new fuel pump

 

[eaglescout526]

Doesn’t mean that hose is hole free. 

[cruiser54]

Or loose...

[TurboedMJ]

Ok, I will check that next. Can I check it without pulling the tank?

[cruiser54]

Yes

[TurboedMJ]

On 4/18/2024 at 1:01 PM, cruiser54 said:

Is this hose on the supply side of the fuel pump? Or return?

[cruiser54]

Supply. Fuel pump outlet inside the tank to sending unit mounting flange. 

[TurboedMJ]

Ok. Off hand, do you know how empty the tank has to be so that gas doesn't leak everywhere when I pull the pump?

[eaglescout526]

Bit below half. But between half and 1/4 would be best. 

[TurboedMJ]

Oh ok perfect. Will update later with results

[TurboedMJ]

The hose is brand new. 

Anything else I should check I have the pump out?

[eaglescout526]

Clamps good and tight?

[TurboedMJ]

48 minutes ago, eaglescout526 said:

Clamps good and tight?

Yeah they are. Although when I first pulled the pump, I noticed there was some fuel residue on each end of the hose. 

[eaglescout526]

Hmmm. Maybe inspect the ends where the clamps are. 

[Ωhm]

Could be just the photo, but hose looks too long, needs trimming. Could be pinched or kinked. Aeration.

[TurboedMJ]

I will put a shorter hose on.

[TurboedMJ]

I trimmed that hose and put it all back together and the issue is not fixed. Any other suggestions?

[Ωhm]

Just as a quick check look for fuel at the vacuum hose between the Fuel Pressure Regulator (FPR) and intake manifold. Leaky FPR.

 

@brucecooner

[TurboedMJ]

It's dry. 

[ghetdjc320]

Did this all start when you swapped injectors or were you experiencing these issues before the swap? Cam and/or crank sensors come to mind. Instead of grouping all issues together and trying to find a single source, try isolating one of them and tracking it down. For instance, with a bad idle, you could try disconnecting injectors one at a time and see if you notice a difference. 

[TurboedMJ]

44 minutes ago, ghetdjc320 said:

Did this all start when you swapped injectors or were you experiencing these issues before the swap? Cam and/or crank sensors come to mind. Instead of grouping all issues together and trying to find a single source, try isolating one of them and tracking it down. For instance, with a bad idle, you could try disconnecting injectors one at a time and see if you notice a difference. 

As far as I can remember it's been doing since I got the new fuel pump. The new injectors did make it run better, but that's because the ones they replaced were $50 ebay specials.