MikeT 90 C4sixer

Since i started running it this spring, after winter storage. Got a significant buzzer in rear of car, from the tank. Fuel cap is humming pretty good as well. I did read some posts, and it sounds like it could be the pulsator? Or maybe just a dirty inlet filter (sock) on the fuel pump? FSM says that filter should last the life of the pump. Engine seems to run fine with no misses or anything. Injectors have been replaced, fuel rail serviced, and in-line filter as well since i bought the car. I always run premium fuel, and lately E0-91oct.

How hard is it to pull the fuel pump assy? Should i just run this old gas down, and put fresh fuel in? Any fuel adders could help? What is my risk if i keep driving it this way? The noise is certainly annoying!

bogus

it's easy... I would suspect the pump is on the way out.

Figure 30-40 minutes. It's all done at the gas cap area. Remove the lid, remove the cap, remove the rubber gasket, remove the bolts, drop the pressure, remove the lines, remove the assembly, swap the pumps, drop it back in. It really is that easy!

Get the Racetronix pump. Very good part. I have had one in my car for several years now.

BTW, consistently running low on fuel, or (really) long term storage, will burn up a pump.

aklim

I have always run to the empty mark and it hasn't done anything yet. Further to that, someone actually ran a test and put it on Youtube where they ran the pump for almost 10 minutes WITHOUT fuel and not a hiccup. That is an old wives tale.

https://www.corvetteforum.com/forums...post1591485340

aklim

I would run it down because when I pull the pump, if there is any debris or whatever, I want to be able to see it and remove it easily.

To do what? Lighten your wallet? Sure. Snake Oils, Whiffle Dust, Mouse Milk, etc are designed to separate you from your money.

The pump could and probably would quit in the worst place possible.

http://www.racetronix.biz/customkiti...c=FPA-010H&eq=

davewhtt

I agree with both Bogus and Aklim. It is an easy replacement and i had run tank down to 1/4 and syphoned old gas and debri out before putting in new pump( My 93 had been sitting a few years) Dave

WVZR-1

I don't believe it can be considered "Ole wives tale" UNLESS you know specifically the type of pump that's being evaluated. They ain't all the same. Most later production pumps certainly could be considered less likely to fail BUT why not just keep fuel in it?

JrRifleCoach

It is refreshing to hear you've done your homework before posting.
Submerged pumps do use the fuel to keep them cool. However the will get hot due to being recirculated from the engine compartment. So wither or not running low on fuel will contribute to premature pump failure is subjective.

My take is if the pump is making noise that it shouldn't be making, time to replace it before you get a ride home on the hook. As Bogus dialoged, the replacement is easy and straight forward. Just remember to disconnect the battery, and work in a well ventilated area. If your really into maintenance, drain/siphon the tank dry and inspect the bladder. I was able to get my arm thru the opening and wiped the tank with a clean rag to detect any bladder problems and remove any debris or water that may have settled. I did need some lube to retrieve my arm.

Good Luck

WVZR-1

For your next "adventure" -

YELLOW PAGES under "ARTIFICIAL INSEMINATION" for either an arm that's familiar with restrictive orifices or maybe for the LUBE

aklim

Any pump you know of that is susceptible? Logically speaking, would YOU want a pump that is generating that much heat that it needs to be cooled off? Besides being a danger, you are boiling off fuel unnecessarily. Besides, lets say you run out of fuel, what happens? The engine stops and the pump stops so there it ends.

Why? Because regardless of how much fuel you put in there is a certain amount of time you waste at the pump even if you just put the pump into the car and pull it out. I really loathe spending time at the gas station so the fewer times I can go there, the better. Some of the gas stations make you stand by the pump regardless of how cold or wet it is until you are done. I don't go to those places regardless of price.

aklim

I keep forgetting to ask Tom400CFI to continue his test but at 8 minutes and it still keeps running, I have little doubt that the cooling is really that important. Besides, the engine shutting off cuts off power to the pump so...

JrRifleCoach

I recall opening the fuel cap one hot day. There were contributing problems that lead to this and were later resolved. I started to notice a heavy fuel smell thru the hatch vent on a hot high altitude day. I opened the cap to find the flapper in the fuel inlet closed so tight i could not press it open with my finger. Pressing with a screw driver it finally open and I received 1 & 2nd degree burns on my arm as the fuel came whooshing out. So this is why I too am not convinced about the heat problem on C4 pumps.

Now letting them run dry....why?

aklim

Not dry although I don't think it would hurt but as low as possible before topping up the tank. There are many who swear that if you don't have a quarter tank, the pump burns. If that were true, I'd be replacing pumps every month.

MikeT 90 C4sixer

Well it seems like everyone just wants me to rip out the FP and replace that. I dont have a problem with that, just that I would really like to know if it is bad. It doesn't look too bad to pull the whole thing out, so why not just pull it out and look things over? Maybe the filter sock is plugged up, making the pump work harder. Or the pulsator is not doing its job?

As far as running your tank down low, prolly not the best idea. I am leaning towards the fuel in the tank cooling the unit. The in-tank designs are different than external pumps. I have run my C4 down to the reserve light coming on. But not for long! I would likely run the car down low as possible, before pulling the unit out.

aklim

Your pump is kinda dumb. Assuming the feed is good, it gets power or it doesn't. It over pressurizes the system which is why the regulator bleeds it back to the tank to maintain the correct (whatever that might be set at) pressure. If the pressure is set at 43 and it gets over 43, it bleeds back. If it hasn't, it obstructs the flow so the pressure builds up. So whether the "obstruction" occurs at the regulator or at the sock, it doesn't work any harder. At the sock, it just is unable to suck it into the system. If you really want to check that, the answer is easy. Stick a fuel pressure gauge onto the schrader valve and turn it on. It usually instantly jumps to whatever it is (mine is 43 for example). It should bleed off slowly once the pump stops (be it done with priming the system before start or you shut off the engine) and hold. If it doesn't, well, you go fishing for the problem. As to the pulsator, if it doesn't work, it just allows the fuel to leak out of the system back into the tank which means you don't get pressure. Many, and if you get the Racetronix pump will have you bypass it with fuel rated hose.

Look at the video. No fuel, no burn. The part that gets hot would probably not be the impeller which comes into contact with the fuel so any cooling would probably be conduction. As I said, if it could be burned, mine would have burned a hundred times over. I have had a 91 F-body and till it was totalled, it ran a full tank till empty and same with the Vette. I only changed pumps because I wanted a higher capacity one in the Vette. As I said, old wives tale.

Only way to test the pump is to hook it up to power and immerse it in fuel and have something like a fuel system with regulator to test. If you want to build it, have fun. Regardless, a noisy pump isn't good and it isn't worth $100 to test it.

JrRifleCoach

Seems you just need to run the car until the pump quits.
Good luck with that. Then post pics of your car on the flatbed.....

MikeT 90 C4sixer

Well i would buy most of that for a dollar......last i knew the pump is either on or off, with key on, engine running. It does provide lots of pressure to the rail. Regulator keeps it at 44psi, and whatever fuel does not get pushed out from the injectors, returns back to the tank. Whether or not this fuel is hot is debatable. I will put my gage on the port and watch it. Had some problems with a bad reg from FIC, a while ago. Pressure would not hold, and i had some no starts. Sent the regulator back, and put my stock one back on. All good, and i do have the adjustable cap. I think i am at 44 with 24# injectors.

I watched the video, so i get it. My pump sounds like that one in vid. If you run your car out of gas, wont you be walking? Or do you carry extra fuel when you run out?

From my FSM:

Pulsator 5.7L(VIN 8)
Figure 2
For vehicles equipped with the 5.7L engine, a pulsator is installed between the fuel pump and fuel level meter fuel feed tube. The function of the pulsator is to dampen fuel pulsation and reduce noise generated by the fuel pump.

Seems like my pulsator is not doing its job, Captain Obvious.
For a while there i was thinking you guys work for Racetronics. Looks like a good unit. I will get one when the time comes.

aklim

IIRC, the vid showed a pump that was pumping without gas and the gas and the tank around it would have some muffling effect so if it sounds like that muffled, I can only imagine how it will sound if it is out of the tank.

Yes which is why you don't run it till it is completely out although you can, just like a person can sleep with his sister. Doesn't make running out completely a good idea. You can run it to the empty mark on the gauge and it goes for a bit more. How much more is up to how it was adjusted. If it hits empty, I know I may have a gallon or so left which takes me under 20 miles so....

It might be doing the job but the problem is if your pump goes beyond a certain volume, it cannot do that job anymore. Besides, kike I said, many have removed it because it is slipped on and could get old and leak pressure so why risk it?

MikeT 90 C4sixer

OK, so today i checked the pressure with my gage. Key on, no starting, pumped up nice to about 42, and held good. FP ran normal, and stopped since i did not start car. Watched pressure hold for a few minutes, then started car, ran normal. Pump was not as noisey for some reason. Checked pressure, was 46 w/vac off, so i lowered a little to 44. I have 24# injectors, and burnt the PROM as such. Idled car for a few minutes, all good. Shut down, watched pressure for a while. Held good, took several hours to bleed down. Just have to keep my fingers crossed i guess......

aklim

Take the hose off and cap it off. Do a WOT run and see if it holds pressure.

MikeT 90 C4sixer

Are you talking about the vac hose to the regulator? For the WOT run, you want me to drive the car, or just rev it up to full throttle?