I just rebuilt my Holley carb, and have noticed that the engine starts to hesitate when under a load. As soon as I give it some gas over 40 mph, that’s when the problems start. As soon as I back off the gas everything is ok. I figure that I will check the fuel pump and make sure she is putting out enough pressure. My fuel rail that feeds off of main gas line from the pump doesn’t have a port adapter to hook up a fuel pressure gauge. So can I just undo the rubber gas line from the rail and plug in a fuel pressure gauge? Thanks
CK5
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Mechanical fuel pump pressure gauge?
- Thread starter scasey28
- Start date
If you go beyond 40 mph does it hesitate no matter what you do? If so then i would suspect a bad fuel pump. Keep in mind that the pump could have the correct pressure but not enough volume. You should be able to fill a 16oz bottle in about 15 seconds or less.
Yup...that's what mine was doing...before I set it on fire.
AJs72K5,
sorry to hear about the fire, I was just checking out the pixs you have posted of the damage. It makes me think twice about working on any fuel related problems after seeing those pictures. Also I really like how you have the fuel pressure gauge ran through the fuel rail. How did you go about running the fuel pressure gauge into the fuel rail? Also the stainless line that attached to the fuel gauge, did you run that directly to the fuel pump. Right now I'm looking into replacing the fuel pump and add in a fuel pressure gauge. Any recommendations on fuel pressure gauge/fuel pumps? Thanks
sorry to hear about the fire, I was just checking out the pixs you have posted of the damage. It makes me think twice about working on any fuel related problems after seeing those pictures. Also I really like how you have the fuel pressure gauge ran through the fuel rail. How did you go about running the fuel pressure gauge into the fuel rail? Also the stainless line that attached to the fuel gauge, did you run that directly to the fuel pump. Right now I'm looking into replacing the fuel pump and add in a fuel pressure gauge. Any recommendations on fuel pressure gauge/fuel pumps? Thanks
There's nothing wrong with a stock mechanical fuel pump. I run an MSD fuel pressure gauge on my rig, it is a small gauge that threads into my TBI fuel inlet fitting.
4X4HIGH,
Since I have a external fuel pump, switching out the pump should be no problem. I thinking a non high flow pump, or does it matter? Also the engine runs fine at 40 mph just as long I don't step on it. But as soon as I do, that’s when it starts to hesitate even on a flat street.
Since I have a external fuel pump, switching out the pump should be no problem. I thinking a non high flow pump, or does it matter? Also the engine runs fine at 40 mph just as long I don't step on it. But as soon as I do, that’s when it starts to hesitate even on a flat street.
69TowRig
1/2 ton status
I had an issue with the accelerator pump in my carb that would cause issues like that. If I was really easy on the throttle it would run fine, if I put my foot in it the truck would halfway stall then recover after a second or two and speed up.
That's was all the PO's handiwork. The gauge is part of the fuel rail and has an integrated fuel filter...it's a summit racing part. Mine will be going up for sale soon. It's sitting in a corner of the garage now since I'm going MPFI.
Yes, the braided stainless fuel line runs from the fuel pump to the fuel rail.
Don't let the fire scare you. Just be more prepared than I was...mop up any gas that spills on the manifold, and know where your fire extinguishers are.
Ok so I just got some free time and am going to do the fuel pump pressure test. The fuel pump and vacuum gauge tester i picked up is a U.S. general from harbor freight. The instructions say to unhook the out flow hose from the fuel pump and plug in the tester gauge into the pump. Since no fuel is going to the carb, won’t the engine stall out when I try and start it, since there is no gas going to it? Also, is this a common way for checking fuel pressure? I figure that I might as well learn how to do some of this stuff and save a few $$$ on paying a mechanic to do it. Thanks again.
The engine will run for a short while because there is still fuel in the bowl of the carb. You don't even need to start the engine though to get a pressure reading from the pump, all you need to do is crank the engine over long enough to see the pressure. It would be alot better though to cut the fuel line in half somewhere between the fuel pump and carb and install a fuel gauge fitting with a small gauge attached so you can read the pressure with the engine running and fuel flowing into the bowl.
Well I just swapped out the fuel pump with a new one, and took the k5 for a test drive. I wish I could say that replacing the fuel pump fixed the problem, but I did not. Again when I get up to 30-40 mph and step on it, that’s when the engine starts to hesitate. Could the carb be running to rich or lean? Would that cause this problem?
What year is this vehicle? Does it have a CAT? If there is a CAT it could be plugged which will act exactly as you describe. Quick test would be if your exhaust has a flange before the CAT that you could unbolt and then drive the vehicle to see if the problem is gone.
I wish it were that simple, however it’s a 72 blazer and since smog is not an issue, it doesn't have cats. It’s crazy, I can step on it pretty hard off the line and it runs great until around 40mph. I doubled checked the floats, replaced the fuel pump/filter, new cap and rotor. Could it maybe the secondaries in the carb aren’t opening once the engine hits a certain RPM?
