Fuel Shut-off Solenoids

[afeustel]

Moved this over from the E3 discussion hoping for more visibility:

Originally thought I had a problem with new fuel pump and regulator, however pressure is solid at 2.7 psi.

Installed Fuel Shut-off Solenoids in a pair of Weber 38's with electric choke. Car does not want to idle with them installed.

Solenoids appear to function properly (retract) when bench tested with 12 V.

On the car, having ZERO luck with both installed, tried to just tinker with one at a time. Now have the car properly tuned and idling just fine without the solenoids installed. Then I installed the front solenoid and restart the car. Idle is poor and low. Then hook up 12V directly from battery to solenoid and no change. Always blip the throttle inbetween to reset the idle but still no joy with the solenoid installed. Then swap the solenoid back out and restart and car runs fine.

On the bench, solenoids appear to function normally when power applied.

Does not make sense that they dont work when installed. Checked that carb provides a proper ground for solenoids as well. The solenoids are new units, I actually have 4 of them.

Am I supposed to change the size of the small brass jet-like object that fits in the end to accomodate the solenoid plunger?

Any thoughts or assistance appreciated.

Seems the problems in the original post were actually caused by the solenoids and not the fuel pump (forgot to mention that I had also made that change at the same time as the install). Should have stuck to the practice of not changing more than one part at a time.
__________________

 

[MMercury]

Installed Fuel Shut-off Solenoids in a pair of Weber 38's with electric choke. Car does not want to idle with them installed.

Solenoids appear to function properly (retract) when bench tested with 12 V.

On the car, having ZERO luck with both installed, tried to just tinker with one at a time. Now have the car properly tuned and idling just fine without the solenoids installed. Then I installed the front solenoid and restart the car. Idle is poor and low. Then hook up 12V directly from battery to solenoid and no change. Always blip the throttle in between to reset the idle but still no joy with the solenoid installed. Then swap the solenoid back out and restart and car runs fine.

Am I supposed to change the size of the small brass jet-like object that fits in the end to accommodate the solenoid plunger?

Your narrative is baffling, because, among other things, the solenoid is designed to prevent run-on. Yet, you are able to get the engine to idle without them installed. This suggests you are bypassing the idle circuits.

You ask whether the small brass-jet like objects should be changed. This may be a simple miscommunication, but if I understand you correctly, the jet-like objects are idle jets. They can be changed and should be changed when necessary to obtain the proper fuel mixture. However, is it possible that you have solenoids without jets affixed? Or is it possible that the jets are separated from the solenoids and sitting in the carb bodies?

Whether they are regulated by solenoids or not (the older Webers did not employ idle solenoids) Idle jets can be clogged or improperly seated. Because they are soft metal and mass produced, they are also susceptible to malformation and can be easily damaged. I have a few that must have been blanks because they were missing holes.

The wrong size jet/s (or clogged or malformed/damaged jets) can all lead to a poor or impossible-to- adjust idle. If you examine a jet carefully, it should have a size marking, e.g., "55." The size can dramatically affect the fuel air ratio at idle through mid-range throttle operation. In my limited experience, Weber carbs have employed two solenoid styles (thin and thick). The jets are not interchangeable between styles. Likewise, idle jets for non solenoid equipped will not work with/fit solenoids.

HTH :smile:

http://www.piercemanifolds.com/category_s/191.htm

http://www.e9coupe.com/forum/showthread.php?t=11370

Solenoid without an attached jet:

Solenoid with jet affixed:

 

[afeustel]

Thanks for the comments MM.

Yep, they are the idle jets (part #34) - still learning the pieces and parts of the carbs.

The idle jets fit perfectly into the ends of the solenoids and by design, if the solenoid plungers retract as they appear to on the bench test, they should not be limiting the proper function of the jets.

The idle jets have all holes visible (including the hole in the tip) so I dont think there is any damage to them or problems otherwise.

I guess I am just wondering if anybody else had experienced challenges with the solenoids or had to change the idle jet size to accomodate their function.

For reference, without the solenoids installed, the engine-side idle mixture screws are about 1.5 turns out while the fender-side idle mixture screws are at about 1.0 turns. The idle speed screws are both just under 1 turn in. Idle speed is set to 800-900 rpm.

 

[61porsche]

Check

for the opposite situation- lean. Big air leak? Carb spray? One design puts a sorta metal cup and washer to seal against the carb on the threads- Mercedes and BMW. Don't see them much any more. make sure you're not tightening too much. Snug and just a bit more.

Second thing is the relation of the butterfly to the orfice in the throat allowing too much air there which really means your out of the idle circuit too far.

Last but not least, duct tape off the air emulisfier which will enrich the mixture. Zeniths have a hole in the casting.

Any way, the point of the excercise is to determine rich or lean?

 

[afeustel]

Great comments. Without the solenoids I think the idle and mixture are right on as the butterflys are not open much and the idle mixture screws are still functional (i.e., if I adjust them the idle changes). Also the settings are about right (1-1.5 turns out).

Agree that the solenoids are causing either way lean or way rich but my question is not so much as which condition, but why the change. Based on the design, it seems to me that I should be able to simply install the idle jet on the end of the solenoid and have everthing else (mixture) work the same, with the exception of the fuel cutoff when ignition is turned off.

By the way, I have the "narrow" solenoids are pictured above from MM.

 

[61porsche]

well

the solenoid could be jamming the idle passage by going in too far. There's actually a cavity there and the holes ( usually two - air and fuel) or passages get restricticed.

So loosen it up a 1/4 turn while running or get your inside micrometers out as the solenoid "slug" or valve could get hung up inside only when the idle jet is inserted and snugged up. Trim a smidge off with a file.

If you're bench testing and listening for the audible click that might get you halfway there. Use a piece of vacuum hose and blow on the end to make sure it 's also opening.

Now the other thing is the ferrul end- if it doesn't seat - no worky.

Back to the butterfly and it's position to the idle opening in the throat- got a vacuum guage? It's a big deal.

Or just go up two jet sizes.

 

[MMercury]

Your initial post states that you installed shut-off solenoids in a pair of Weber 38's with electric choke. Were these replacements? How did the carb/engine combination prior to the installation? Was some modification involved?

The solenoids function properly on the bench but not when installed. Could the issue be related to the 12V source available - on the car? You mentioned using an electric choke. I would assume they are on the same circuit, but there could be a short that you are unaware of when installed?

Perhaps I am dense, but please describe what you mean by getting the engine to run without the solenoids. Are you saying that the solenoids are (1) present but disconnected from a 12V source or (2) present without jets attached or (3) completely removed from the carb leaving an open port. I ask because the only time I can recall seeing this situation is an emergency offloading scenario having lost the entire solenoid assembly with the jet. Something makeshift was jammed into the solenoid orifice in order to prevent the engine (VW) from completely dying.

61P alludes to another problem with the carbs, such as the throttle plates being too far open to permit fully functioning idle circuits. But since this seems to be happening with both carbs, is the linkage over adjusted?

The following may be for Zenith carbs, but the advice is fairly fundamental and may offer more food for thought.

hth

 

[afeustel]

Jerry and MM, thanks for the words, I really appreciate the comments to help sort this out.

For MM, the carbs never had Solenoids before I installed them. The items I purchased are like the narrow versions for 38's shown in your pictures. The idle jets are correct for this style (i.e., no shoulder on the idle jet) and the ferrul seems to seat properly.

Regarding the 12V source, I tested all possible options (power from the choke circuit, and then direct from battery, grounded through carb, grounded direct to block, etc.). Its not the power supply since no power source/ground combination made any difference (and all were tested with multimeter as well).

w.r.t current tuning, the car idles "purrrrrfectly" in the stock configuration without the solenoids installed and the idle jets installed in their screw/base holders. So for MM, this means that without the solenoids, there is no open hole, rather the idle jets are installed normally. It may be a poor assumption, but further evidence that I may be close for non-solenoid tuning is evidenced by the number of turns for the idle mixture screws being more than 1, but less than 2 out at peak idle speed, which seems to be supported by documentation I have read on these carbs.

I think Jerry might be on to something with the seating of the idle jet while on the end of the solenoid. One thing I did notice is that the screw that holds the idle jet (w/o solenoid) will tighten until it seems to hit a "hard stop". Whereas when the jet is on the solenoid, the solenoid never seems to bottom out. So it may not be seating the jet properly into the carb body.

 

[MMercury]

A few more disorganized thoughts?

If the carbs were not originally equipped with solenoids, then you are, in effect, retrofitting them?

I suspect therein lies the problem. It sounds as though your issue is one of fitment. I wonder whether the solenoid jets are seating exactly the same as their non-solenoid counterparts. (I didn't think you could "easily" fit the idle solenoid into a non-solenoid body because the solenoid's threads were different/larger. Yet perhaps I am confusing the two style of solenoids, since admittedly, I have dealt with a great number of carbs, but not for some time.)

Parenthetically, I used to have an inventory of spare jets kept for tuning purposes. I also had a close coterie of acquaintances who occasionally "borrowed" tools and parts, including jets. Some of the jets were returned with "ridged" or slightly modified noses. I mention this because they were returned since "they didn't work right" or were the wrong size - and it was obvious that the borrower overtightened them attempting to get them to seat properly. I would encourage you to get out your magnifying glass to compare the jets you have and make sure they are the same depth and have the same taper as both are essential. Both the carb body and the jets are soft enough so that they could be "persuaded" to conform. Still, this may possibly result in other unforeseen damage, which would outweigh the benefits of the solenoids.

While I ordinarily do not give up easily, and have the scars to prove it, in your case I would likely return to the original non-solenoid idle jet status. If everything purrs, as you state, the only advantage to the solenoids would be to prevent or reduce run-on/dieseling. That is the subject of another thread, e.g., reducing idle speed, different petrol blend . . .

 

[afeustel]

That is pretty much where I am at...back to no solenoids and dumping the clutch in 4th gear with e-brake and A/C on when I shut down the car. Run-on seems to be an issue with these carbs even with all else adjusted properly.

I will take a closer look at how the jets seat in the carb with the solenoids installed.

 

[Mike Goble]

What is your timing at idle? Do you have vacuum advance with full manifold vacuum?
With my Webers I find that using full manifold vacuum to the vacuum advance allows me to close the throttle blades enough to prevent run-on. I have over 18inhg at idle, so the VA is essentially all in.

 

[afeustel]

Timing is set at about 12 deg at idle. "All in" looks to be around 3K rpm. Hitting the 22 degree advance mark around 1,600 rpm.

No vacuum advance on the distributor. PO installed pertronix and the vacuum mech hole is blocked out.

Solenoids seem to be working now. Per Jerry's suggestions I started trying them at varrying number of turns in and there definately seems to be a sweet spot where they work (too far in and they stop working, as well as too far out). Odd, but that is the way it is. Now it runs the same with Solenoids installed as without them, and when I pull the power supply from them it is obvious that the fuel gets cut off.

I had the timing set a little higher (~14 degrees at 900 rpm) to allow me to back off the idle speed (i.e., close the butterflys down) but that makes it a little tough to start. Also I think it was contributing to the run-on (which it still seems to do occasionally) so I backed it off to 12 degrees and figured I would live with the slightly lumpy idle around 700 rpm if it helps to shut it down without run on.

Going to drive it a while to see how it goes but seems to be better than before.

Thanks for all the comments.

 

[Mike Goble]

I would suggest getting a vacuum advance can installed. You will find it helps the engine run cooler and more efficiently, resulting in improved fuel mileage.