Engine Need help 90 mustang carbed 5.0

logonhappy · May 28, 2021

I bought the car about 2 months ago maybe longer anyway factory 2.3 5 spd 90 mustang hatchback swapped to a 5.0 from a 84 truck carbed true dual exhaust no cats brand new holley street warrior carb electric choke anyways the problem runs fine until randomly under load motor starts bogging then dies have to pump throttle to get it started has no problem starting after u pump throttle couple times I've set my idle mixtures screws with a vaccum gauge got my idle set around 800rpm im thinking accelertor pump needs adjusting or float bowls aren't filling up all the way please any help appreciated sorry am new here not sure if I should post here or not thanks tho

logonhappy · May 28, 2021

Also has new plugs and wires and numerous other things on it timing is good already checked that just had the motor out as needed new motor mounts along with rear main front main and oil pan gasket timing cover was ripped off before I got it as the old cam that was in it was from a 351 Windsor mech fuel pump lobe broke so has a stock cam in it now I did not do that work but I do know who did and sounds like was done correctly

RaggedGT · May 28, 2021

Do you have enough fuel pressure?

7991LXnSHO · May 28, 2021

If the Holley is not a new one, the float level and fuel bowl fuel level are easy to check.

How To Adjust Fuel And Float Level On Holley Carbs

Holley demonstrates how to properly adjust the fuel level and the float on Holley four-barrel carburetors.

www.holley.com

limp · May 28, 2021

Check the fuel tank to see if its cruddy.. I have also seen the "sock" on the end of the pickup tube get plugged or sucked into the line..

LILCBRA · May 28, 2021

Sounds like it's running lean to me. It could be any number of different scenarios.

If it's the fuel bowls, you'll need to set the float level. That's not hard and should probably at least be confirmed before going further.

Accelerator pump tuning as it is now could help a little, but it might not completely fix it. You could need a bigger accelerator pump and/or a bigger discharge nozzle.

It could just be that the carb is tuned lean for your combination. That'll require new jetting.

If you're new to the carb tuning world or just want to tune it the best that you're able, I'd suggest an air fuel gauge to nail it all down. There's a wealth of information to be gained from that one simple gauge and your engine will run great with the knowledge you're able to gain and the changes you're able to apply when using one. Reading spark plugs can get you there too, as long as you're experienced enough with it. But I've found my AF gauge to make a world of difference for my car.

General karthief · May 28, 2021

logonhappy said:
I bought the car about 2 months ago maybe longer anyway factory 2.3 5 spd 90 mustang hatchback swapped to a 5.0 from a 84 truck carbed true dual exhaust no cats brand new holley street warrior carb electric choke anyways the problem runs fine until randomly under load motor starts bogging then dies have to pump throttle to get it started has no problem starting after u pump throttle couple times I've set my idle mixtures screws with a vaccum gauge got my idle set around 800rpm im thinking accelertor pump needs adjusting or float bowls aren't filling up all the way please any help appreciated sorry am new here not sure if I should post here or not thanks tho

You likely are running out of fuel, like suggested check float level and install a fuel pressure gauge where you can see it while driving and note pressure while driving around to duplicate the issue.

logonhappy · May 28, 2021

I'm not sure what my fuel pressure is i just had the tank dropped to replace my sending unit which is for a 81 nonefi along with the tank tank looked quite clean I've been thinking about a air fuel gauge but I've looked at them not sure which one I need and it is a brand new carb as of probably a month ago the holley book did say some tuning might be necessary which I figured cause no 2 cars are the same I know how to set float level im not sure how to do anything with the accelerater pump tho I will set float levels after work and see if that helps thanks guys anymore ideas are welcome

logonhappy · May 28, 2021

General karthief said:
You likely are running out of fuel, like suggested check float level and install a fuel pressure gauge where you can see it while driving and note pressure while driving around to duplicate the issue.

Where would I connect a gauge and can run the line through my cowl on my hood and zip tie it just to see what it is

logonhappy · May 28, 2021

I'm just mind boggled as how it can go weeks running just fine not touch anything then boom the next time I drive it will just run terribly because of this issue only driveablity issue with the car I drive it to work this morning normally a 10 min drive turned into a 30 min drive lol sorry for the rant

General karthief · May 28, 2021

Do you have an adjustable regulator?

7991LXnSHO · May 28, 2021

If it was an older Holley, I would be sure about saying to check out the power valve. Even with blowout (backfire) protection built in, it could still be causing troubles. The accelerator pump causing trouble is more likely to be right off line or not getting enough fuel to start.
Here is a good video to make sure you have the pump adjusted right.

How To Adjust The Accelerator Pump On Holley Carburetors

How-to adjust the accelerator pump on Holley carburetors to avoid stumbling and hesitation upon acceleration. Tips include: How to check for the clearance between the accelerator pump diaphragm arm & operating lever; how-to select the correct accelerator pump nozzle size, and accelerator pump...

www.holley.com

logonhappy · May 28, 2021

General karthief said:
Do you have an adjustable regulator?

No

logonhappy · May 28, 2021

7991LXnSHO said:
If it was an older Holley, I would be sure about saying to check out the power valve. Even with blowout (backfire) protection built in, it could still be causing troubles. The accelerator pump causing trouble is more likely to be right off line or not getting enough fuel to start.
Here is a good video to make sure you have the pump adjusted right.

How To Adjust The Accelerator Pump On Holley Carburetors

How-to adjust the accelerator pump on Holley carburetors to avoid stumbling and hesitation upon acceleration. Tips include: How to check for the clearance between the accelerator pump diaphragm arm & operating lever; how-to select the correct accelerator pump nozzle size, and accelerator pump...

www.holley.com

So should I check my old carb and see what power valve it has or??? Cause it had a really old carb on it when I got it was just done for screws were rounded out fuel was leaking everywhere my intake is stained from fuel dripping on it lol

General karthief · May 28, 2021

Don't start randomly swapping parts till you check the fuel delivery system, once that is within working parameters can you look at the next step.

logonhappy · May 28, 2021

General karthief said:
Don't start randomly swapping parts till you check the fuel delivery system, once that is within working parameters can you look at the next step.

Ok so check fuel pressure first if so I have a tester that I used on fuel injected cars i assume i can use the same gauge but where do I hook it up

General karthief · May 28, 2021

You may have to install a T in the line, look into a fuel pressure regulator that has a port for a gauge.

7991LXnSHO · May 28, 2021

logonhappy said:
So should I check my old carb and see what power valve it has or??? Cause it had a really old carb on it when I got it was just done for screws were rounded out fuel was leaking everywhere my intake is stained from fuel dripping on it lol

1. Make sure your fuel delivery system is good, including the filter, 2. check float/bowl levels, 3. Them make sure your power valve is the stock 6.5 and is not ruptured.
I was thinking ahead and answering your earlier guesses. Although this is different tech than EFI, the system is simpler and you should be able to get your head around the big picture with some help.
What does the converted system use for ignition? It sounds like fuel, but if the fuel (and carb) check out, I think an intermittent heat caused ignition issue is farther down the list.

7991LXnSHO · May 28, 2021

General karthief said:
You may have to install a T in the line, look into a fuel pressure regulator that has a port for a gauge.

6 psi is ideal for a Holley carb. I have a 3-4” disc vac gauge that also reads pressure for things like this. I have unhooked the outlet side of the filter and temporarily put a 3/8” T in with good hose clamps. Maybe you can find a brass, barbed T in the plumbing section. I will not recommend using a vac line T for anything more than for testing it in the driveway.

logonhappy · May 28, 2021

7991LXnSHO said:
1. Make sure your fuel delivery system is good, including the filter, 2. check float/bowl levels, 3. Them make sure your power valve is the stock 6.5 and is not ruptured.
I was thinking ahead and answering your earlier guesses. Although this is different tech than EFI, the system is simpler and you should be able to get your head around the big picture with some help.
What does the converted system use for ignition? It sounds like fuel, but if the fuel (and carb) check out, I think an intermittent heat caused ignition issue is farther down the list.

I'm not too sure on ignition myself either stock distributor some msd knock off distributor cap and I think rotor msd wires I installed ngk vpower plugs recommended by my performance parts store that is helping me build this motor

Engine Need help 90 mustang carbed 5.0

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