1975Coupe

Hello all,

So when I bought my car, about 7 months ago, I noticed when I was above 3000 RPM it would lose power/stutter/run rough/accelerate then lose power in weird little bursts. If I kept the petal down the engine would do this so much that I would lose speed and engine revs. I figured out that if I pushed in the clutch, let the engine come back to idle, then let out the clutch and got back on it it would run fine. This only happened occasionally near or over 3000 RPM and seemed to be tied to whenever the tank was near or below 1/4. Now it is happening earlier in the revs, 2200+ or higher, and at all fuel levels. I put carb and fuel cleaner in every time I fill it up. I'm looking for suggestions as to where to diagnose the issue. My gut tells me it's a carb/fuel delivery issue, ie the carb is gunked up or the fuel filter is dirty but what does the forum think?

Jebbysan

Change out your fuel filter ASAP.

Jebby

REELAV8R

I had similar symptoms when my fuel pump was failing. It was just pumping less and less as time went on and fuel starvation occurred at lower and lower power levels.

1975Coupe

Well this weekend I changed the oil and filter, changed the fuel filter, and changed the air filter. I drove it to work this morning and plan on doing some spirited driving home to see if it suffers the same issue or not. I couldn't replicate it this weekend, so I guess we'll see. Thanks for your help guys.

1975Coupe

Well two more days and I haven't seen the issue again. I ran it hard this morning as well. Here's to hoping the fuel filter change is what did it. Thanks.

1975Coupe

Hello all,

Well the issue came back and was happening anytime I was over 2500 RPM. I had taken it out for some relaxing sprints before putting it away for the winter. It ran fine at first and then was happening constantly. So what do you guys think the issue could be? Fuel Pump? Fuel Sock issues? Something else?

Big2Bird

Both times I have seen this, it was the fuel sock collapsed. Bits of sock get sucked into the pump, keeping the check valves open. I would change them both. Sock, then pump, then filter again.

BKbroiler

Similar to previous responses, probably the sock or the fuel pump. In a 75, the pump is the less difficult repair.

REELAV8R

Still thinking fuel pump. And as BK says it's the next easiest job.

1975Coupe

Well if I'm going to change the pump I might as well change the sock when I'm in there as well. Any good links with info on changing the fuel pump? I can wrench myself but I really like to follow directions.

Also I see the following pump on Wilcox https://willcoxcorvette.com/corvette...76-replacement

Will I need anything else?

Big2Bird

The sock is in the fuel tank, and is a part of the fuel sender. You want to change it first. Then either flush the line, or drive it awhile before changing the pump to clear the line. Then the filter.

OR, Do all at once and flush the fuel line out well.

1975Coupe

Thanks. I just do it all at once. The cost is cheap and if it eliminates the problem I'm all the happier.

cobrachuck

You will need to drop the tank to do this here is a pic of sending unit & sock
Replace the pre formed fuel lines @ the fuel pump as well
Good luck
http://www.fullthrottlecorvette.com/..._thumbnail.jpg

1975Coupe

So Wilcox has the fuel pump for $44, Ecklers has it for $55, and Amazon has it for $23. Is there any reason NOT to buy the one from Amazon?

resdoggie

Yes, it's probably junk. I would get the KNOWN correct pump from Wilcox, if that indeed is your problem. Have you tested your fuel pump for it's rated capacity?

Big2Bird

Rock Auto. Delphi, $30.

1975Coupe

I went ahead and just purchased it from Wilcox. They have been very helpful in the past and have earned my money.

I did some research and the tank seems rather easy. Disconnect the lines. Drop the tank. Remove the sender. Replace the sock. Then repeat to put it back. Does that sound right?

Also I read that some people were putting a spring around the end of the sender piper inside the sock to stop the sock from collapsing or getting sucked up into the sender. Is that something you guys have ever done?

resdoggie

Be sure to let us now how it all worked out.

Big2Bird

I wouldn't bother. It took 40 years for it to crumble. Just change it again in another 40 years.

1975Coupe

I will. The car is in storage, I'm in Ohio, so didn't want the weather to get to it. I'm planning on getting it out of storage in late February and doing all of this. Right now I've got the following scheduled:

- Change fuel pump
- Change fuel filter
- Change Sender filter/strainer
- Oil Change
- New Tires (old ones were from 2001)
- Swap out center console (old one is broken into three pieces and just hanging there)
- Install new custom made shift plate/cover with ashtray removed and cup holder/usb plug instead (being custom made by a friend of mine)

March should be interesting.