Fuel Pump?

[5.0nmalecek]

I have a '90 5.0 convert mustang, all stock (for now) besides the mufflers. The fuel pump noise varys from time to time and it gets pretty loud, but other times you can't hear it almost at all. Most of the time it's pretty steady. The car just seems to lack the power a 5.0 should have, but the power seems to come back intermittently. It also starts hard, it will crank for a few seconds and start to cough and stumble until finally it seems to "catch". It only seems to do this when the car has been sitting for awhile, like after it loses fuel pressure. Although, it will start up perfectly if I prime the key to the On position a few times so the pump can build pressure. I can hear the pump whine, it is steady until like the 2nd key turn and then the pitch drops then I know the car will start up. I just need to make sure that this is the fuel pump and not something emissions related because I know I have a code for low EVP, EVR, or PFE voltage. I am going to buy a 190 lph pump off ebay if you guys give the thumbs up

 

[HISSIN50]

it sounds like the check valve in the pump and/or the pump itself are not doing too hot. but dont forget about the FPR.

do you have a FP gauge?

based on noise and age alone, a new pump would not be unwise, even if something else is at fault (not likely).

good luck.

 

[5.0nmalecek]

Thanks for replying HISSIN50 , any help is appreciated. I don't have a fuel pressure gauge I really wish I did, I'll probably just borrow one this week to make sure the fuel pressure is low. I was also considering the fuel pressure regulator, I've been eyeing those on ebay too. You also mentioned the check valve. Is that in the pump itself so if I buy a new one that is replaced as well? Please anyone who reads this post your opinion; I'm anxious to buy the fuel pump and get 'er in there.

 

[HISSIN50]

yeah, borrowing a diagnostic FP gauge would be good. that way you can monitor FP when your first turn the key on, then note how much it increases with each priming thereafter.
you can also carefully crimp the return line to confirm things (lack of pressure can be a weak pump or a fuel pressure regulator that is simply passing most of the fuel back to the tank).

the check valve is in the pump (it's just a one-way valve to keep fuel from draining back into the tank, via the pump).

good luck and bump for ya.

 

[5.0nmalecek]

This is a follow up for anyone who reads this post, I'm concluding the problems and the solutions for reference. I bought the 190lph pump off ebay, which by the way was a fair price and good quality, and installed it. I found that it wasn't the check valve that was malfunctioning but there was a small hole in the hose leading from the fuel pump in the tank. Therefore after the car had been sitting for a while fuel pressure was lost. Also the power that I seemed to "lack" was justified when I discoved the SPOUT connector was dirty and damaged so the computer saw this circuit as open, which it was. When the SPOUT circuit is open the computer disables timing advance so base timing can be set. All I can say is now it feels how a 5.0 should, and before it was fixed I almost lost to a Honda CIvic. A stock one non-Si.
Thanks again HISSIN50 for your help.

 

[HISSIN50]

Hey man, nice catch on that hose - that would have been about 100th on my list of thoughts. Kudos for posting what the fix was.

Running around at 10-14* total timing had to suck - another nice catch to find the dirty contacts.