Fuel pump dying?

[Yo]

I have a carbed 350 with an edebrock 650 and a holley red top pump on a holley regulator set to 5.5psi. I'm running a high output 170amp alternator.

Recently I've noticed the pressure dropping to about 1.5-2.5 psi at idle. The motor almost sounds like it wants to die, but it never does. It'll do this in traffic and in park. I also noticed the last few days, cold starting has been a little more temperamental, when before it'd fire up every time.

Yesterday I drove 120 miles to pick up a couple Yamaha 650's for a bobber build I'm doing, and I noticed on the highway at about 75mph, whenever I'd give it gas to pass etc, the motor would fall flat and stumble, like it's starved for fuel. I'd have to back off and get in the right lane, and a few times, I nearly had to pull over. If I keep the rpm's below 1800 and gradually pick up speed, it'll hold, but it continues to stumble if I try to accelerate.

I also noticed the pump making some unusual clicking noises.

This only happens at highway speeds, or if the truck is nice and warm and I come off the highway, it'll hassle me.

If I let it cool off, it runs better, but eventually it behaves the same when I get back to highway speed.

Around town I don't have any problems.

I always hear that fuel pumps just die when they go out. This one seems to be slowly giving up.

Am I on the right track? Any other suggestions?

 

[POORBOYK5]

Typically "clicking" means that the pump isn't getting enough fuel to it. Check all your connections and make sure they're tight. You may be sucking air somewhere.

 

[diesel4me]

Typically "clicking" means that the pump isn't getting enough fuel to it. Check all your connections and make sure they're tight. You may be sucking air somewhere.

Very true!..also the mechanical pumps have a "rocker arm spring" that can break,it keeps the rocker arm on the pump in contact with the push rod to ensure it pumps all the time and isn't flapping loose in there..I once had one break,didn't notice any real performance issues,but the noise fooled me into thinking it had a loose timing chain slaping against the timing cover..

You might have a rust hole in the main feed line from the tank,on top of a bend--fuel may not drip out,but air will get sucked in and starve the pump for gas--I'd also inspect or replace any short sections of rubber hose in the main feed line from the tank--especially one near the rear axle,I've had more than one look perfect on the outside,but todays ethanol gas softened the inner part into a gummy rubber goo,and starved the pump for fuel...I've been seeing lots of old rubber hoses on vehicles & lawn mowers made long ago that are not compatible with ethanol causing lots of "issues"-...it'll eat some rubber tipped needle valves in carbs up too..

 

[Fordum]

If its a mechanical pump, and you are not sucking air somewhere, odds are that clicking you hear is one of the valve cartridges rattling loose inside the pump.

Most of those pumps have the intake and output valves made into one piece units. One for in and one for out. They are pressed into the body of the pump.

If its the inlet valve, it can fall back into the hole and stick for a little while and the pump will work great.
Then, when it falls out, it will pass a flow test under no pressure, but will not pass a pressure test.
The usual symptoms are plenty of power when you go to pass, but then the engine stalls about halfway past the car.
Lots of fun on the highway.

If you want to be sure, look up the specs and do a flow and pressure test. But, by the time you get a gauge, a bottle of known size, and hook everything up, you usually could have already changed the pump.

The other problem with that valve coming out, is that it hits the diaphram and will wear a hole in it sooner or later.

I would try a new pump unless they are a lot more expensive than I think they are.

Of course, make sure nothing obvious is wrong. Kinked or loose fuel line, stopped up tank vent.........

 

[Yo]

I'm going to go and check the lines for air leakage, all good advice.

Remember the Holley red top is an electric pump. I have a block off plate at the block.

I went to inspect the wiring, and the pump was wired on a simple switched 12v/ground setup. I rewired it to a 40amp relay and upped the wire guage and so far so good, I haven't been able to duplicate the issue on the highway, but something still is not right.

 

[texas4x4rebel]

Do you have a prepump fuel filter if so it may be cloged up.