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# Generator fuel solenoid5

## Generator fuel solenoid

(OP)

This 255kW Volvo based generator has a fuel solenoid bolted on the side of the engine block. It's at an angle, if I recall correctly. It's silverish-pinkish and about six inches long, two inches in diameter. This is all from seeing it about last October.

It has three wires going to it. Why?

Whenever the system is turned on the wires promptly melt clear back to the controls. Apparently the wires melted so it was assumed the solenoid was toasted so they replaced it. The wires promptly melted again. Any ideas?

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Generator fuel solenoid

Wrong voltage? When they replaced the solenoid, did they check why 3 wires and what is the rated voltage?

Muthu
www.edison.co.in

### RE: Generator fuel solenoid

The voltage supply to the coil is excessive. then, for three wires,they are for hot(live), neutral and earth lines depending the color code. check if they were terminated correctly

### RE: Generator fuel solenoid

SWAG:
Some solenoids have a pull in coil and a holding coil.
Most have an internal switch to cut out the pull in coil.
This may have had an external switch to cut out the pull in coil.
The pull in coil is momentary duty only.
If the pull in coil is staying in the circuit, either due to a failed external switch or being miswired, bad things will happen.
Or, as edison123 suggested, a 12 Volt coil on a 24 Volt system.
Any two wire, normally closed solenoid of the proper voltage should work.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

(OP)
edison; The original solenoid had this happen. The wires are color coded. They procured an identical replacement with the same part number.

Oyebisi; This is a DC solenoid that has to work before the engine can start and any AC becomes available.

Bill; I'm suspecting a pull-in, hold-in scenario. Any chance they did something like DC pull-in and (eventual after starting) AC hold-in?

There has never been an external switch. Perhaps a control timer that stops the pull-in coil. I will ask them.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Generator fuel solenoid

They need to check the DC power that activates this, did they maybe loose a regulator or diode and overdrive this?
The other thing that comes to mind is ground issues if this is grounding back through one of the wires.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy

### RE: Generator fuel solenoid

By external switch, I meant external control rather than the common internal switch.
Something in the control cabinet. Possibly a timer.
Some way of cutting the pull in coil out of the circuit.
If this external to the solenoid switching has failed, it would explain the solenoids failing as fast as they are changed.
Or, something else. Without seeing the set first hand.........

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

That vintage engine could have one of two style fuel solenoids, pretty much as Bill described, both were three wire, in the diagrams they are usually called out as,
Ground
Pull
Hold

On the style with an internal switch, usually the contact is on the inside of the solenoid body, most common problem when they burn like that is that the linkage is not coming back far enough to break the pull in coil contact, so your "electrical" problem could actually be mechanical in nature. If you pull the solenoid plunger out of the body you should be able to see the contact pin. This style is usually the longer of the two and most I come across are made by Bosch or Dynalco, and most are branded with the engine manufacturers name and part number

On the style with the external switch, the pull in coil was usually wired to a relay that is energized when the starters crank, so while cranking the pull in coil is active, and the hold in coil is controlled by the keyswitch or genset controller. This style is usually shorter than the one with the internal switch.

Hope that helps, MikeL

### RE: Generator fuel solenoid

#### Quote:

Bill; I'm suspecting a pull-in, hold-in scenario. Any chance they did something like DC pull-in and (eventual after starting) AC hold-in?
Very unlikely.
Another possibility is an internal switch with a panel mounted relay to insert a series resistor in the cut out coil circuit.
That set will have a prime mover of close to 400 HP.
If the batteries are good enough to start the set, they will keep the voltage within range for the solenoid despite a regulator failure.
This sounds like a control panel issue.
I would consider a generic 12 Volt solenoid, but first you should sort out the panel.
Let me guess; This customer doesn't want to pay for a service call if he can get free information over the phone to fix it himself.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

(OP)
With all your great suggestions here's where I'm at now.

Walking them thru the controls one wire is grounded to the engine block within 12" of the solenoid.

The second wire goes to the key ON/OFF switch.

The third wire goes to a control relay.

Going thru the motions;
The control relay closes when the START button is pushed.
And only opens when the STOP button is pushed.

My logic:
That relay is acting like the HOLD coil should be operating.
If this is a PULL, HOLD solenoid (thanks Mikel) then the wire going to the KEY switch must be the PULL coil.

Since the smoke shows up soon after the key switch is turned ON I believe the PULL wire is incorrectly hooked to the KEY switch and have directed them to move it to the START button.

### RE: Generator fuel solenoid

(OP)
Dave; The maintenance guy died. Then his replacement died. Then his replacement quit due to medical reasons. The current one is trying to fix this and is a buddy of mine. The generator is running daily. They have to manually operate the fuel rack wiring it ON then unwiring it.

They've used it for about twenty years.

I suspect the last machinate guy or the generator repair service may have miswired it. No connector just three flying wires, Red, Black, White. They voltage can't be wrong as it's simply two 8D batteries in series.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Generator fuel solenoid

I really was after that the voltage was applied to the expected wires at the expected times. I'd still bench test and put in the fuses.

Still - how long have they been jumpering this? I'm missing how they can manually operate if the solenoid is toast. Is this a fuel cutout solenoid?

Like you, I am puzzled how what is ordinarily an item that is generally bullet proof ends up burning all the wiring. One winding is intended to be on the entire time so its wire should be fine. It is said this happens without delay so if the other winding shorted it would take some time to develop enough heat to cook the second one enough to also short.

Have the solenoids been taken apart to see what has failed? There are at least two of them now.

### RE: Generator fuel solenoid

(OP)
I think your idea of fuses is a good one but I'm not sure they have the chops to come up with the right fuse that won't blow during the course of a normal start but blow on excessive abuse.

It's a giant solenoid that works a lever that allows fuel into the engine. Without the solenoid they simply mechanically coat-hanger the lever. Their attitude is that they're not going to idle 70 people because of a missing solenoid.

The smoking is that they turn the key ON then walk around to the other side of the generator enclosure (large) and press the START button. About the time they get to the other side the wire/solenoid starts to emit the magic. It's my belief that that's a way longer application of the PULL coil than what would occur if the pull coil was energized during just the time the START button is being pushed. I'm not sure if the user has to hold the start button or a controller sees the signal and runs the start evolution. With the latter the solenoid PULL signal would only be about a second verses the entire cranking period. On the other-hand I suspect the voltage may sag enough to require the PULL to continue during the entire crank period and the coil seeing several volts less anyway.

I don't know about the solenoids. I'm 50 miles away. I'll be visiting next week for other projects so no doubt I'll get more info and hear how my 'move the wire to the start button' worked out.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Generator fuel solenoid

This is bringing my curiosity to a boil. 255kW is about 340 HP; even if the losses are terrible, like a 1200 HP input, how big a lever does this need to cut off the fuel flow?

Even without a wiring error, if there is a failure of the control on the pull-in winding, it could still cook the relay. It should have been obvious if it was wired so the key operated the pull-in winding that the solenoid would give a big clunk as it operated the lever, which should only happen when the Start button was pushed. Perhaps what ever the Start button is operating isn't releasing correctly.

### RE: Generator fuel solenoid

OK. Got it.
Dave; This is not a fuel valve.
The combination injection pump/governor has a mechanical shut down lever and the solenoid operates the lever.
Probably the pull in coil is not taking too much current.
It is taking the proper current for too long.
Given that the pull of a magnet decreases as the square of the distance, it takes a lot of current to pull in the solenoid and very little current to hold it in.

#### Quote (3DDave)

Perhaps what ever the Start button is operating isn't releasing correctly.
A possible scenario:
The circuit or relay that controls the pull in coil failed. open circuit.
Someone found that by switching the wires, he could get the solenoid to pull in.
Shortly after another problem developed.
To his mind unrelated, so there is no need to mention that the wires were swapped.
I don't think that you will be able to talk them through this on the phone.
On the other hand I am confident that when on-site you will be able to find the control problem in a few minutes.
How long does it take for the solenoid to pull in? I'm thinking between 100 milliseconds and 500 milliseconds.
That is the on time of the pull in coil.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

Keith,

Take a look here, https://www.sbmar.com/articles/fuel-shutoff-soleno...

Pretty much all the smaller engines that use an ETR (Energize To Run) fuel solenoid with external relays use a connection like this. So other than the color coding the wiring function will be the same. Not sure which wire is which? Best bet is ask the supplier for a diagram, if that doesn't work then use an ohm meter, the two coils will have a large difference in resistance value, a little bit of Ohm's Law applied will tell you which is the Pullin vs. the Holdin coils. Also in newer versions of the solenoids by many manufacturers the pull in coil will have an internal flyback diode.

Another problem that crops up in these a lot is the relay used for the pull in circuit, usually a small Bosch relay but its contacts are rated for 30 amps, the relay fries and someone grabs a similar looking relay without paying attention to the contact rating, it fries and then someone start jury rigging wiring to make it work.

Hope that helps, MikeL.

### RE: Generator fuel solenoid

(OP)
That's correct Bill. As far as I'm told there are no other "relays" than the one that is behaving as a HOLD relay. Hence my thought of using the START button. It's essentially like a two button motor starter. Pushing the start button pulls in a motor starter contactor that once in closes the AUX contact keeping it in. Then the STOP button is in series with the coil interrupting it to drop the contactor. This is sort of the same. Push the START button and the PULL coil sucks in the armature while the HOLD keeps it in. Pressing STOP interrupts the HOLD just as turning all the control power OFF would also stop everything dropping out the HOLD.

My one concern in telling them to move the wire to the START button is that maybe they did something dumb and the START button isn't plumbed with 24Vdc. I'll be confirming it is before they try it.

Mikel; Thanks. Sounds about right. Internal flyback.. Had no idea. This thing is at least 20y.o.

I think this is what it looks like and even has RED/WHITE/BLACK wires. But, no connector.

Theoretically I'll be going there Tuesday as long as they get certain tasks completed.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Generator fuel solenoid

LPS, Bill and Mike. (sounds like a cop show).

Muthu
www.edison.co.in

### RE: Generator fuel solenoid

See if you can find a 24 Volt version of this.
This is on Ebay.
The cut-out switch is internal.
COMPARISON.
Internal cut-out switch: If the internal switch fails, replace the solenoid and done.
External cut-out switch/ circuit: If the external circuit fails, solenoids will fail as fast as they are replaced until the cut-out circuit is repaired.
I've learned something new.
All of the many generators that I have worked on have had solenoids with internal switches.
The most common failure was an internal switch failing to close.
With a failed switch, the engine won't start automatically but it may be started and run manually.
While cranking, push the solenoid ALL the way in. Even with a failed switch the solenoid will hold in and the engine will run until it is intentionally stopped.
After changing the oil I would pull one wire from the solenoid and crank until I saw oil pressure.
Then I would reconnect the solenoid and let the engine start.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

It could be a mechanical problem also. If the linkages to the solenoid are not adjusted correctly, the solenoid may not be allowed to move enough to close the magnetic circuit completely. It will then burn out. Read the yellow caution label on the picture above.

### RE: Generator fuel solenoid

These are DC Compositepro.
With the DC solenoids an incomplete stroke on a three wire solenoid will result in not enough force to hold in.
An incomplete stroke on a two wire solenoid will result in burnout as the internal switch will not operate and will leave the pull-in coil in the circuit.
But, the burnout of a DC solenoid is not the result of an incomplete magnetic circuit, it is the result of the pull-in coil staying in the circuit.
An AC solenoid has a low inductive reactance and low impedance when de-energized.
This causes a high current and a high pull in force.
As the solenoid moves towards the closed position, the air gap shortens and the inductive reactance increases, dropping the impedance and the current.
If an AC solenoid does not complete the stroke, the inductive reactance will be too low and the solenoid will draw excess current.
A DC solenoid does have inductance but it does not have inductive reactance.
Keith, does this help?

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

(OP)
Regardless, Comp's right that the two-wire will 'automatically' toast itself if allowed, whereas the three-wire will not - if correctly wired.

If the HOLD coil is only run as long as the start button is pushed then it shouldn't be toasting.

I can't switch to a two wire because the HOLD is controlled by a puny relay that would weld-shut the first time it had to power the PULL coil.

But, I do see your point about the utility of the solenoid still manually workable if the switch has failed open though a failed closed would.. not. be. good.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Generator fuel solenoid

The internal switch is opened by the solenoid itself and failed closed is extremely unlikely. Possible but the odds go the other way.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

(OP)

I explained how to do it and what to check.
Instead they put this one, number 3, in yesterday and promptly burned it to a crisp.

They said, "they found a schematic on the internet and hooked it up that way, instead".

I told them to get a fourth one and to NOT install it but call me when they had it.

Bill I'm loving that schematic you posted, have you got a full page shot of that page of your road lighting generator?

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Generator fuel solenoid

Did any of them previously work for Lucas Electric?

### RE: Generator fuel solenoid

lps for that one, Dave.

Keith, that is a photo of the inside of the side cover.
When I get a chance I'll trudge through the snow and take a wider shot.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

Here's a picture off the net.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

(OP)
Thanks for the try.
Had to take the star back off your schematic post since it's too blurry to make out much.

Keith Cress
kcress - http://www.flaminsystems.com

### RE: Generator fuel solenoid

Service Manual
Take a look at page 51.
This is an alternate method.
Instead of a dedicated terminal on the ignition switch, the pull in coil is connected to the starter.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

Is this engine hard starting?
Extended cranking times may fry the pull in coil.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: Generator fuel solenoid

(OP)
Dang! Nice manual. I should be so lucky.

Don't know about the cranking times. I'll check that out!

I'm trying to understand your HOLD circuit. It's not making total sense to me.

The relay contact providing HOLD is NC??
Low oil pressure while starting would energize the relay OPENing its coil circuit removing HOLD?
I guess the PULL coil seats the solenoid while cranking and as the engine starts the oil pressure rises.
The low oil switch OPENs the HOLD relay deenergizes.
The NC contact closes and the solenoid is held in?

So too the engine overheating OPENs the HOLD contact.

Not fail-safe but fail-catastrophic. LOL

Weird, but I better consider this could be the case on this Volvo.

Keith Cress
kcress - http://www.flaminsystems.com

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