Help...PMO accelerator pump injection quantity

snbush67 · snbush67's Garage

Within the past two months my car has been getting harder to start when cold. Usually it's five pumps on the gas and then start with about 3-5 seconds of lightly feathering the gas pedal to smooth it out. Now it barely catches and then I have to pump it like a crack head freak to keep it going.

I just tested the injection quantity and only one nozzle is squirting. What can I do to unclog the other nozzles? The fuel filters and lines are Not obstructed. I backed the adjustments out on the injection arm screws for full stroke, still no change.

Something is gummed up, where should I start?

The car runs and starts fine when warm.

snbush67 · snbush67's Garage

Just had to pull the top and blow through the valves. Probably an easier way?

2stroke · 2stroke's Garage

Excuse my ignorance, but is there no choke?

snbush67 · snbush67's Garage

Nope, no choke.

KTL · 12-17-2013, 04:12 PM

I'd take a closer look at your filters and hoses if you got something in the accel pump jets to clog them.

moneymanager · 12-17-2013, 04:38 PM

I think you've found them. For others, the injection quantity is governed by the adjustable screws on the outside of the accelerator pump and by the (four) float bowl control valves at the bottom of the float bowls. Pull the top of the carbs off and you'll see them. They can be removed and cleaned or blown out. It's also possible that the screws on the pump are set unevenly... releasing lots of gas to one cylinder and hardly any to another.
Not sure what your set up is but many cars start and run well with hardly any gas added by the accelerator pump.

snbush67 · snbush67's Garage

Thanks Kevin, the hoses and filters are clear. The gas in the bowls is clean. I haven't driven the car much. Not much pressure was needed to clear them out. Engine is running fine now, I had to adjust the pumps to the lowest setting again, now they are working too good.

my_911s · 03-04-2019, 06:40 PM

Quote:

Originally Posted by moneymanager

I think you've found them. For others, the injection quantity is governed by the adjustable screws on the outside of the accelerator pump and by the (four) float bowl control valves at the bottom of the float bowls. Pull the top of the carbs off and you'll see them. They can be removed and cleaned or blown out. It's also possible that the screws on the pump are set unevenly... releasing lots of gas to one cylinder and hardly any to another.
Not sure what your set up is but many cars start and run well with hardly any gas added by the accelerator pump.

Does anyone have a picture of this? one of my acceleration injector nozzle is stuck ... just want to estimate what kind of effort to clear this blockage ...

Thanks,
Jeff

Targa Time · Targa Time's Garage

Are your accelerator pump diaphrams leaking? I had to replace mine. Using gas with Ethanol in it ate them up.

snbush67 · snbush67's Garage

Quote:

Originally Posted by Targa Time

Are your accelerator pump diaphrams leaking? I had to replace mine. Using gas with Ethanol in it ate them up.

I don’t see any indications of leakage. Running like a champ. Gas here in Hawaii is Crap but I do run seafoam through it occasionally. Maybe that’s helpin?

juanbenae · juanbenae's Garage

pmo now suggests a "hatchet" pump activation lever modeled after another model weber carb. IDS possibly? they are shaped different and activate the pump sooner and for a longer duration. I bought a set and installed them on my IDA's and they improved a momentary lean spike I was having on hard acceleration from lower RPM.

ive heard that if you have PMO's Richard will provide them free of charge. you also might consider one of the vials for testing squirter volume. if your diaphragms are tired and failing the hatchet wont do any good of course. try a search for hatchet as there are a couple threads on them with photos that show the significant difference in shape between the two differing activation levers. the PMO supplied ones were too thick for the webers initially and I could not cinch them down without restricting the throw action. apparently PMO can supply a sleeve that will allow them to work on webers. I simply took a belt sander to mine and took them down to the same thickness of the weber units and they work great. got rid of the lean spike I noted above.

KTL · 03-07-2019, 01:09 PM

Quote:

Originally Posted by my_911s

Does anyone have a picture of this? one of my acceleration injector nozzle is stuck ... just want to estimate what kind of effort to clear this blockage ...

Thanks,
Jeff

Jeff,

The PMOs are a recreation of the original Weber 40/46 IDA triple throat models but they also use quite a few of the other Weber IDA, DCOE and 48 IDF parts. PMO mentions this about 1/2 way down the features page

https://www.pmocarb.com/features.htm

For instance the emulsion tube stack (includes the E-tube, the air corrector jet and the main jet), the needle valves and the floats are from the two barrel IDF. Pierce Manifolds is a nice site for a lot of carb information and they have good exploded view diagrams.

https://www.piercemanifolds.com/category_s/321.htm

The accelerator pump nozzle is #12 under the carb cover. So you'll need to take the top cover off and then you can remove the hollow screw that secures the nozzle

To make you feel more at home with the triple throat arrangement that are the PMOs, here's what the Weber 40/46 looks like. Either way you're taking the top of the carbs off to get at that nozzle which is #70 in the diagram/link below

https://www.piercemanifolds.com/category_s/249.htm

And if your nozzle got clogged, I think it's a good idea to take the pump body off the side of the carb. Because in order for the junk to get to the nozzle, it had to pass through the accelerator pump housing. It's a good idea to take a look at the pump diaphragm anyway since these seem to get affected by prolonged fuel exposure

Here's some info on the hatchet shaped cams that juanbenae referred to. Gordo's thread is REALLY informative for people who want to learn more about their carbs. Don is really good at documenting what he's working on

Gordo's PMO Carb Tuning

Tuning carbs.

my_911s · 12:15 AM

appreciated the reply. Took the shortcut. I bended a cooper pipe and attached to the air blow gun and removed the screw near the throttle linkage. I inserted the bended copper pipe into the carb and blow into the accelerator nozzle. After a few tries, I freed the stucked nozzle as I could feel air coming from the screw I removed. next I sprayed some carb cleaner into the screw hole to ensure the passage is clean. put back the screw and amazingly that worked! pressed on the throttle linkage and could see fuel squirting out from the accelerator nozzle! Here’s the copper pipe and a short hose attached at the end so I don’t scratch the inside of the carb, and how do looked like inside the carb.

Thanks for you help!

PS. I spoke to Richard Parr at PMO as well and about this. He’s very helpful.

My best,
Jeff

my_911s · 11:22 PM

Here’s the photos

my_911s · 03-09-2019, 12:13 AM

This one shows the acceleration nozzle ...

my_911s · 03-09-2019, 12:40 AM

Quote:

Originally Posted by KTL

Jeff,

The PMOs are a recreation of the original Weber 40/46 IDA triple throat models but they also use quite a few of the other Weber IDA, DCOE and 48 IDF parts. PMO mentions this about 1/2 way down the features page

https://www.pmocarb.com/features.htm

For instance the emulsion tube stack (includes the E-tube, the air corrector jet and the main jet), the needle valves and the floats are from the two barrel IDF. Pierce Manifolds is a nice site for a lot of carb information and they have good exploded view diagrams.

https://www.piercemanifolds.com/category_s/321.htm

The accelerator pump nozzle is #12 under the carb cover. So you'll need to take the top cover off and then you can remove the hollow screw that secures the nozzle

To make you feel more at home with the triple throat arrangement that are the PMOs, here's what the Weber 40/46 looks like. Either way you're taking the top of the carbs off to get at that nozzle which is #70 in the diagram/link below

https://www.piercemanifolds.com/category_s/249.htm

And if your nozzle got clogged, I think it's a good idea to take the pump body off the side of the carb. Because in order for the junk to get to the nozzle, it had to pass through the accelerator pump housing. It's a good idea to take a look at the pump diaphragm anyway since these seem to get affected by prolonged fuel exposure

Here's some info on the hatchet shaped cams that juanbenae referred to. Gordo's thread is REALLY informative for people who want to learn more about their carbs. Don is really good at documenting what he's working on

Gordo's PMO Carb Tuning

Tuning carbs.

Thanks for detailed diagrams! That’s great info that will come handy when I’ve to tear apart the PMO for a rebuild.

I’ve the the PMO now for 15 years and it’s still running great other than occasional blocked passages where I’ve to take out air or mixtures screws to clean them.

I’m running on on a 1968 911S with NGK BPR7EIX, MSD6247CT.