Testing the Pilot Jet Valve

This article began as a “simple test” to determine if a particular part was viable or faulty.

It continued to evolve—maybe “morph” would be a better term.

My wife, Neva, watched me struggling with a couple of aspects, trying to come up with terms and where to, actually, draw the line on the discussion.

We really got into it.  I mean—she began to grill me.  I explained and re-explained my objective for writing the article.  But, she was convinced that there needed to be more explanation about the particular aspect—one lone aspect—which I wanted to talk about.

She reminded me of the MANY times people have called with stalling VWs—then she told me that I could not explain just the one aspect.  That drew us into ever deepening conversation, confusing at times because we weren’t always talking about the same things.

Folks—I am amending this discussion to please Neva!  I cannot afford to have her leaning over my shoulder asking question after question, so here goes nothing….!  LOL

For some background you can read from the two Links given here.  There will be quite a bit of over-lap:

Idle Cut-off Valve

30 Pict-1 Carburetor Differences

Sometimes, when a vintage VW Carburetor is not performing well, small things get overlooked.  Let’s examine a couple of things which deserve our attention when troubleshooting a Carburetor.

The Pilot Jet Valve is a small canister which screws into the Carburetor.  It combines the Brass Idle Jet with an Electro-Magnetic Valve (Solenoid).

Depending upon the Model of Carburetor, it may screw into the generator side or into the driver’s side of the Carburetor.

If you have the German Solex 30 Pict-1 (VW 105-1 for the 1967 Beetle), the Pilot Jet Valve is located on the Generator (Passenger’s) side of the installed Carburetor.  If you have a Solex H30/31 Brosol, the Pilot Jet Valve is located on the driver’s side of the installed Carburetor.  (see Notes at Article’s end)

The function of the Pilot Jet Valve is to immediately stop the flow of gasoline through the Idle Jet into the Carburetor as soon as the Ignition Switch Key is turned to the Off Position.  It is an anti-dieseling device to keep the Engine from continuing to run (called dieseling) after the Key is switched to Off.

This Valve can mal-function.  In such a case, the Engine may continue to run but at Low Idle the Engine tends to die due to the inhibited fuel flow.

The Valve is an electro-magnetic process.  When the Key is turned to the On Position, the Valve becomes electrified and activates a “plunger” inside the Valve to the open position.  Thus, gasoline can flow through the Idle Jet and thus, through the Carburetor.

IF—the Valve malfunctions, no matter that it still is connected to electricity, the Valve will not open.  This inhibits the flow of gasoline.  And, as I say above, the Engine MAY continue to run if the Idle Speed is sufficient, but will want to die at the first opportunity—such as when pulling to a stop.

Here’s a simple test to determine the viability of the Valve.

Chock either front or rear wheels.

Place the car into neutral.

Turn the Key in the Ignition Switch to the ON Position.  (Do NOT turn the Key to the Start Position!  It is NOT necessary to start the Engine for this test.)

Go to the Engine Compartment and open the Lid.

Remove the wire from the Terminal of the Pilot Jet Valve. 

Now—touch the Wire to the Terminal on the Valve.  As soon as you touch the Wire to the Valve’s Terminal, you should hear a click.  This is the Magnetic Mechanism activating.

Remove the Wire—it should click.

Touch and remove—touch and remove.  Each time there should be a click.

If this is the case, we have shown that the Valve is in working order.

Replace the Wire, making certain that it is firmly installed, and turn the Key to the Off Position.  Test Completed.

There is another thing which we should check while we are testing the Pilot Jet Valve.

The Key should be in the OFF Position during this test.

IF—the Pilot Jet Valve is not properly screwed into the Carburetor, but is loose—air can be drawn around the threads and into the Carburetor.  Make certain that the Pilot Jet Valve is screwed tightly into the Carburetor.  NOT over-tightened, but snugly tight.

Please use the correct size of open end wrench to tighten the Valve.  The temptation is to use a pair of pliers to do the job. This not only makes ugly marks in the soft case of the Valve but can squash the case and damage the internals.

I must interject a short anecdotal account here:  about 35 years ago, I was working out front when a neighbor from the extended neighborhood drove up and parked on the parking strip.  I must have been working on one of our VWs because I had a red rag in hand.  We were known in the area as “the VW people” since we always had a bevy of them sitting out front.  John got out of his Ruby Red ’67 Beetle and told me that it was not running quite right.  He had left the engine idling.  I opened the engine compartment and casually used my red rag to clean the top of the air breather as I surveyed the engine and listened to its cadence.  Out of habit, I reached around the 30 Pict-1 Carb and grasped the Pilot Jet Valve and gave it a twist.  It was a bit loose.  John was bending over the car watching.  When I gave that little twist—the engine suddenly responded by smoothing its idle. 

“What did you do?  What did you do? John yelled.  I should not have said so, but I blurted it out:  “I tightened the loose Pilot Jet Valve!”  And, my secret fix was out!

What to do if the Pilot Jet Valve on your 30 Pict-1 tests as inoperative?  That would be the time to search for a new or a good used Valve.

An alternative would be to remove the inoperative Jet Valve and to install a substitute Brass Idle Jet into the same location.  This Idle Jet should be #55 value.

If your Carburetor is the H30/31 Brosol, purchase a replacement Valve for it.  Discard the inoperative Valve and install the new Valve.

But wait—there is one more thing which we should look at.  It is possible for the Jet itself to become clogged.  Maybe the car has been sitting for a long period of time.  Maybe there has been debris from the tank which has made its way to the Jet and has become lodged in the orifice of the Jet.

Unscrew the Jet from the ElectroMagnetic portion of the Valve and examine it carefully.  If debris is present, it can be removed by soaking the Jet in Carburetor Cleaning Solution and/or blowing compressed air backwards through the Jet.

Resist the urge to run a small wire through the Brass Jet.  This can enlarge the Jet’s orifice.  Use a toothbrush or other soft brush to clean the outer surfaces of the Jet.  When it is shiningly clean, reinstall it onto the Valve and tighten it snugly.

If you are running a Stand-alone Brass Idle Jet and suspect that it may be plugged with debris, remove it and follow the above cleaning procedure.

Notes: 

There is a Mexican Solex 30 Pict-1 replacement Carburetor.  Some of you may be using this Carburetor.  You will find the Pilot Jet Valve in the same location as on the German 30 Pict-1 Carburetor.  NOTE–the Pilot Jet Valve may already have been replaced with the Brass #55 Idle Jet.

There also is an EMPI replacement 30 Pict-1 with the Pilot Jet Valve.

I do not recommend buying either the Mexican or the EMPI versions.   If at all possible, strive to locate a German Solex 30 Pict-1 (VW 105-1) and restore it, or have it restored.

For those who may have interest in further discussion, I am going to quote David Brown, a now retired, former Volkswagen of America employee in Parts Management.

David says:

“The Jet in question is called a Pilot Jet.  I believe that it is so named because it acts like the ‘pilot light’ in a Gas Stove or Water Heater (or in an old-fashioned ‘Pot’ Type Oil Furnace).  It is a Jet that runs the Idle Circuit.  Sort of a mini-Carburetor all its own.  Vacuum supplies Air and pulls Fuel from the Float Bowl and mixes it for consumption at Idle (when the throttle is closed). The Electric Solenoid portion, the Valve, cuts off the flow of Air and thus also stops the pull of Fuel through the Jet. If you pull the Wire off the Valve while the car is Idling, it should stop the Engine.  This is assuming that the Carburetor is set correctly. Too much Throttle opening at Idle will defeat this system. (this is why we don’t make the car run by turning up the Idle Screw) I don’t think that VW described the thing very well in their literature. If you look at the business end of several differently sized Pilot Jets, you will see a variety in the placement and size of the drillings. The quality of Idle can be tailored by changing Pilot Jet Sizes. The Jet also acts like an Emulsion Tube, for bubbling the Fuel through the Air for mixing. The regular Pilot Jets and “Fuel Cut-off” units are about the same at the tips, just the addition of the threaded portion and an internal seat for the Valve Plunger are different.  If you remove the Jet portion from the Valve and solder the outer end closed, you have a standard, non-electric Pilot (Idle) Jet. The real purpose of the Electric one is to stop “run-on” after you shut the Ignition off. I’m sure that you have experienced this “run-on” in hot weather and maybe you’ve had questions about it.”

If you have a Pilot Jet Valve which has a tiny set screw in the electric connector end, David has this comment:

“I cracked open the factory “Fuel System” book and the very page I opened  showed a picture of removing the Jet from the Solenoid for cleaning.  Just below was: ‘Note:  If Solenoid is defective the Valve can be opened and held in position by means of the small Set Screw’ !

It also says that the Solenoid can be checked by switching the power on and off and listening for the ‘ticking’ noise which indicates that the Plunger is moving in and out.

So there you have it. A piece of knowledge for both of us today. So easy…….. Thanks to Neva for the question. “  David Brown

My Thanks to both Neva Salser and to David Brown for their valuable input.