40 PMO's on 2.4L.....

[Chassis87]

Dear all,

I am lost and cannot understand....and decided to post for some enlightenment.


So a mth or so ago I got my set of 40 PMO's for a 2.4...straight of the box these came assembled and jetted by PMO...with 60 idles, 125 mains, 180air...


anyway i fitted these as per instructions and noticed that this car was excessively rich....the kind that it was fouling plugs left right and center...


i decided to change the idle jets first from 60 went down to 50...noticable improvement but it was tsill rich


then i touched the main jet from 125 i went down to 110's and the car is still a tad rich...but power wise..there is none....


the engine is a 2.4 out of a T model...std to the bone....what do you thing is wrong here please?

Thanks

[al lkosmal]

We will need to know a bit more regarding how you proceeded with the initial set up. The out of the box set up should have been a decent starting point, but did you follow the initial start up adjustments, then adjust vacuum, side to side balance, mixture and idle? Is it possible that you just have your mixture adjustment set too rich?

(from an earlier Pelican post)

Weber Set-up
Part I

STEP 1- Accelerator Pump Volume
Measure the accelerator pump volume at each of the 6 nozzles. Before starting the car, turn the key “on” and energize the fuel pump. Let the pump run a minute or so to fill up the float bowls. The air cleaners are off. Now, lower the vial down the throat of barrel No. 1 and park it directly under the nozzle. Have the assistant in the car depress the gas pedal all the way, nice and easy. Withdraw the vial, record the results on a piece of paper, and dump the contents of the vial. Repeat at each nozzle. (You may have to remove the velocity stacks for cylinders 2, 3 and 6 to gain proper access to the nozzles for those barrels.) Adjust the nut on the accelerator pump rod as necessary. Turning the adjuster nut out will increase the amount injected, and vica versa. You want .6 to .8cc (ml) (.75cc works great). Get them all even.

This procedure can also be done on the bench. Just fill the float bowl that has the brass valve in the bottom that feeds fuel to the accelerator pump. Then activate the pump and measure. The advantage of measuring at this stage, as opposed to when the carburetors are attached to the intake manifolds, is that if there is a blockage, it is easy to get at the check valves, nozzles, pumps, and float bowl valves and clean them out.

This procedure also provides a good opportunity to check that the throttle plates are opening all the way (vertical) with the gas pedal floored. If they are not, turn the plastic adjuster under the gas pedal in to give more travel, or out (less travel) if the throttle plates rotate beyond the vertical position.

STEP 2- Float Level Adjustment
Remove one of the two float bowl plugs on one of the carbs. There are two plugs per carb since there are two float bowls and two floats per carb. Careful- all the fuel in the float bowl will dump out so catch it with a little jar. Now insert the tool and tighten it to prevent leaking, since any leaking at the washer will give false readings. You need to focus on the upper two lines scribed on the vial portion of the tool. The lower two lines are for the Zenith carbs that some 911T's used (70-71). Have the assistant turn on the key to energize the pump but don't try to start the car. Now the float bowl will fill and you'll see gas fill the vial. After the vial is through filling, carefully examine where the meniscus is. You want it right between the top two lines. Turn off the key. Remove the needle valve plug, back out the needle valve and seat and add or subtract washers as necessary to raise or lower the fuel level, respectively. (ADD SHIMS= INCREASE FUEL LEVEL; REMOVE SHIMS= DECREASE FUEL LEVEL). Replace the needle valve and seat and the plug and have the assistant turn on the key. Note the fuel level. Continue to adjust until the meniscus is spot-on. The washers that come with the tool differ in thickness. After you do one, you will develop a sense for how many washers you need to raise/lower the fuel level. Then remove the other float bowl plug on the same carb and repeat the process. Keep at it until you've got them all perfect.

A couple of things- some books say to measure the fuel level with the car running. I've tried it that way and believe me, it's pretty hard to do since the engine is vibrating when it’s running. This vibration makes the fuel is slosh around in the vial and thus it becomes difficult to determine if the level is correct. This is exacerbated by the fact that the two lines scribed on the vial are near the very top of the vial. Second point-- the washers under the float bowl plugs are crush washers that are good for one shot. After you replace the plugs, if you re-use the washers, they are likely to leak. If you have some extra ones, use them. If you don't, don't overtighten the little bastards. Just snug them and move on. You can always order more from PMO and then go back and replace them at your convenience.

STEP 3- Initial Start-up Adjustments
Make the initial adjustments to the screws as per PMO and fire it up.

Initial adjustments (PMO) are as follows:
Idle air correction: 1/8 turn out*
idle screws: ½ turn in after touching throttle arm on each carb
idle mixture screws: 2 turns out

(*I suggest turning all the idle air correction screws in (gently!) until they hit their seats, and lock them down for the initial start up. You want a nice rich mixture for starters to avoid excessive popping which is really distracting, and then work from there.)

Here is where it gets tricky- while your assistant in the car keeps the motor running by judicious applications of throttle so that the engine warms, you have to diagnose in a grossly rough way, what is going on and what you need to do to smooth out the idle so that you can get the car running tolerably well enough to begin the real work of balance, synchronization, mixture adjustment and idle speed adjustment.

If the engine idles (regardless of speed) with the initial settings, do the following: if any barrel is spitting, slowly open the mixture screw- like 1/8 of a turn at a time. This should reduce the incidence of popping/spitting. Once the popping is reduced, quickly measure vacuum on each barrel with your STE. Are the barrels of each carb pulling roughly the same vacuum? If not, and vacuum is all over the place, determine which carb is pulling, on average, more vacuum than the other. Then open up the idle stop screw on the carb that pulls less vacuum, or turn in the idle stop screw on the carb that pulls more vacuum, or both, so as to get both sides roughly equal. Keep engine speed close to idle speed (900 rpm).

If the engine won’t idle, have the assistant hold it at a faster speed and adjust the mixture screws to avoid excessive popping. Once the engine runs smoothly, release the gas pedal and see if it idles. Check vacuum and make any adjustments to the idle stop screws that are necessary to get the car to run at idle. Once the car is warm (140 degrees or better) and holding an idle, it is ready for accurately setting balance, sync, mix and idle speed.

END PART I

[al lkosmal]

Weber Set-up
Part II

STEP 4- Vacuum Adjustment- (balance)
Disconnect the right and left carbs from the crossbar by undoing the short press rods on each carb. Use an 8-mm wrench to pop the ball cups free of the throttle arms. You don't want the linkage affecting this adjustment. Pick a carb. At 900 rpm, measure vacuum at each barrel and record results. Determine which barrel pulls the most vacuum (“reference barrel”). Lock down the jam nut on that barrel’s idle air correction screw. Now, carefully and slowly turn out the idle air correction screw on one of the two barrels that doesn't pull as much vacuum as the reference barrel. Get the vacuum exactly equal to the reference barrel. As you open the idle air screw to equalize vacuum, you are going to experience popping, since you are leaning out the mixture by introducing more air into that barrel's idle mixture. DON"T PANIC! Just open the mixture screw up a hair to compensate so that the popping doesn't distract you, or if it's just occasional popping, you can leave it alone for the moment. When vacuum is equal to the reference barrel, lock down the jam nut. Equalize vacuum in the remaining barrel the same way.

Now, you have all three barrels on the one carb pulling equal vacuum. Repeat the process for the other carb.

Step 5- Side-to-Side Balance @ Idle (synchronization)
Using the STE synchrometer, determine which side is pulling more vacuum. Turn the idle stop screws out or in a hair until both sides are pulling equal vacuum and you have 900 rpm idle. Turn the idle stop screws in to speed or out to slow, keeping each side balanced with the other. Now, the engine should be running at 900 rpm with each barrel pulling exactly equal vacuum. You are probably getting an occasional pop since your mixtures are all off.

Step 6- Side-to-Side Balance @ 3000 RPM (synchronization)
Reattach the press rods. Check the side-to-side balance at idle to make sure that the linkage isn't off at idle. If the press rods disturb the idle balance, adjust them so that they exert no preload on the carb throttles. Now you are ready for balance at 3000 rpm. Have the assistant hold the engine at 3000 rpm. Quickly run the STE over each barrel and record the results. Each barrel of each carb will match. But, your linkage could be off, causing the right carb to be out of sync with the left—that is, one carb may be pulling more vacuum than the other at 3000 rpm. If one carb is pulling more vacuum than the other @ 3000 rpm, lengthen or shorten the right/left press rods to compensate. When you get vacuum to balance at 3000 rpm, check that the linkage adjustment hasn’t screwed up idle balance. When vacuum balances at idle and at 3000 rpm, you are synchronized and ready for the "artful" part of this process, where it helps to have the ear of a musician.

Step 7- Mixture Adjustment
Speed the car to 1200 rpm using the hand throttle in the car to hold it there. (This is the BA method- put rock on gas pedal. PMO advises to disconnect the right press rod and speed the engine with the idle stop screws. I use the BA method.) Now start with barrel 1. Slowly turn the mixture screw in until you hear slight popping in the muffler- a little more and the idle speed drops. You may get an occasional BIG POP while doing this- this is normal. As soon as the idle speed drops, slowly turn out the screw until idle speed comes back up- this should take about 1/8 of a turn. You may hear that faint popping in the muffler at this point. If you do, turn the screw out a bit more until the popping disappears and the engine runs smoothly. (NOTE: Slow turns on the screw are warranted. Reaction to changes in the screw’s position is not immediate.) Now, note the position of the screw and slowly give it 1/2 a turn more. This is the initial setting. If it continues to pop or spit up before moving on to the next barrel, turn out the mixture screw an additional 1/8 turn. All should be well with that barrel for the moment. Proceed to barrel 2- same process- then 3, 4, 5 and 6. If it took ½ plus 1/8 of a turn to get barrel 1 to behave, then turn out the mixture adjustment screws for all of the other barrels the exact same amount.

After you run through them once, you will have some doubts as to whether you got the mixture on the first few barrels equal, since as you move through this process, you will begin to develop the "ear" and the "feel." Start over with barrel 1. Make sure that each screw is turned out the same amount from that point where the idle speed returns without faint exhaust popping after it has dropped as a result of turning it in. The point here is to get them all equal. Run through them as many times as it takes to smooth out all popping and spit ups and to get satisfied that you have them all open the same.

Step 8- Idle Speed Adjustment
Release the hand throttle and let the engine return to idle speed. If idle speed is off, disconnect the right and left press rods. Adjust the idle speed to 900 rpm with the idle stop screws. Make sure that side-to-side vacuum remains equal. The engine should be running smooth- no popping and holding a nice idle. Reconnect the press rods and check balance at idle and at 3000 rpm again just to be sure!

Step 9- Test Drive
Take the car for a test ride. Is there any surging between 2000 and 3000 rpm? Is it popping on deceleration? Is it transitioning seamlessly between idle and main circuits? That is, no flat spots, right?

Return to home base. Make any final adjustments that you feel are necessary to the mixture screws. In other words, if it popped occasionally or surged, turn all mixture screws out an extra 1/8. Repeat test ride. Make any further adjustments that are necessary.

If the mixture screws are turned out more than 3 ½ turns from full in, the idle jets are too small. If the engine stumbles on acceleration or is slow to return to idle, the idle jets are too small.

End Part II

[Chassis87]

Wow....that's a lot of stuff to do haha....

I'm installing a pressure regulator and fuel pressure gauge at the moment to check out whats going in....

What fuel pump would you guys recommend?

What sort of jets are you guys running?

What would be the expected gain in performance on a standard 2.4t?


Thanks

Jeremy

[al lkosmal]

Jeremy...good move on getting a fuel pressure regulator and gauge. I would return the setup to the configuration that you received from PMO, ensure that you have 3-5psi, and walk down through the steps listed above. The key to getting these running properly is to have patience and enough discipline to follow the tune up steps. Seems like a lot of stuff to do.........but it will be the shorter path to a good running engine in the long run. Once you get it running well, following these steps, you will then be in a position that you can fine tune, as required.

As far as your fuel pump goes....I've used everything from Facet, Holley (low pressure, carb pumps)..and fuel injection pumps from CIS engines. They all work fine as long as you can regulate to the proper pressure.

Was your 2.4T engine an MFI engine or the 73.5 early CIS engine? If MFI...I would expect no increase in performance................If CIS you will feel a quicker, snappier response to the throttle input that will "feel" like a boost in horsepower.


regards,

Al

PS: I have a few fuel pumps for sale.

Fuel pumps

[Chassis87]

Hi Al,

Did all as told...put on rolling road and car working like clock work...

Managed to get 141bhp....however i have no idea if car is T/E or S


would have loved to buy one of your pumps..however I am based in the Mediterranean on a little island named Malta hehe...would take forever to arrive


Thanks

Jer

[al lkosmal]

Jer,
Congratulations! Your 1st post mentioned that the engine was out of a T and at 141hp...I expect that is what you have. I'm glad that you have it running well now. Carburetors are a good thing....Have fun.......terrorizing the streets of Malta.

regards,
Al