Choctaw H140 sending too much fuel to burner

[dwade154]

Won at auction.

Cleaned out the tank and blew out all lines/new filter and ran new fuel to burner- as previous posts suggested.

Upon inspection/operation of the H140 I was getting raw unburnt fuel coming out the exhaust pipe in “all” settings-Ventilation, Cool down and Heat mode. Made a mess of things.

Initially, I tried to verify ignition arc through the glass port and could see a small flame in there trying to get going in the cool down setting and heat mode. It was a faint flame I observed. I was sure I had too much fuel overwhelming the arc igniter.

The unit was producing a bit of heat.

I disassembled the front of the heat exchanger and observed raw fuel in the bottom of combustion chamber. A lot. About an inch deep.

I removed/cleaned the burner assembly and verified arc ignition was present outside the unit. Arc ignition was present in the cool down and heat modes only, outside the unit, with the doors and top on. I learned via the diagram- The internal air pressure switch (electrically) must be closed so the arc ignition functions.

Upon further diagnostics, the fuel line to the burner had active constant fuel pressure in all settings-Vent, cool down and heat mode. I had the fuel line to the nozzle disconnected and draining in a bucket inside the burner. The burner assembly was removed at this time.

I’m assuming the fuel solenoid (L1) is stuck in the open position and supplying fuel at all times to the burner??!

But what is unclear in the Manual (pg 0003 00-3) is how fuel gets to the burner after the fuel solenoid (L1). I’m not sure if this is a pump issue or not.

My assumption is that the burner only requires fuel in the heat mode but my unit is getting constant fuel in all settings. Is this correct?

Does the fuel solenoid supply fuel to the nozzle and the selector switch controls the fuel solenoid? If not, what controls the flow of fuel to the burner?

The solenoid did not show a short upon checking the ohms and I could not get a voltage readin any setting. I stripped the black wires to the solenoid back and put alligator clips on the wires.

I can get a new solenoid for 19$ on eBay


I’d appreciate any experience or advice


https://www.liberatedmanuals.com/TM-9-4520-271-14.pdf

Thank you,

Daniel

 

[155mm]

I’m assuming the fuel solenoid (L1) is stuck in the open position and supplying fuel at all times to the burner??!
L1 is normally open and would have to be stuck closed to provide fuel to the burner, verify S2 is functioning properly as it also controls L1, see schematic right side center above K1 controller,

I would speculate as to foreign material blocking L1 before it would fail



But what is unclear in the Manual (pg 0003 00-3) is how fuel gets to the burner after the fuel solenoid (L1).
L1 closes and forces fuel to burner


My assumption is that the burner only requires fuel in the heat mode but my unit is getting constant fuel in all settings. Is this correct?
Correct


Does the fuel solenoid supply fuel to the nozzle and the selector switch controls the fuel solenoid? If not, what controls the flow of fuel to the burner?
L1 provides back pressure to force fuel to the nozzle

What is fuel pressure?
Verify previous owner did not bypass d1 at tb3-1 and tb3-2, search flame detector or read thru baby its cold outside thread, many items are the same between h82,83,130,140 heaters
you can test almost any wire or part from the bottom of the control panel on the terminal blocks (TB), marked as tbx-x on schematic, so you dont have to skin back wires

 

[dwade154]

thank you for your response.

Here are my findings.

Just to be more clear, The fuel supply at the nozzle is a trickle in all settings at all times the unit is running. I did manually put 120v to L1 and the fuel solenoid closed and provide WAY more fuel to the nozzle. It was no longer a trickle when manually applying 120v.

I did order another “new” L1 on eBay and installed it. Same issue. Leaking fuel at the nozzle in cool down and Vent mode.

However in heat mode L1 is not closing and it’s not providing more fuel to burner. (Without manually applying 120 volts). But maybe this may have something to do with the burner being out?! I’m not sure yet.

Someone appears to have been chasing this issue before. L1 has previously spliced in brown wires from TB 1-8 and TB2-7 connecting to L1. I think these are the right TB locations based on the schematic?!

The fuel pressure gauge shows approximately 85psi in all settings according to the units Fuel pressure gauge. Is that about right? I’m in southern, Mo.

There is not a bypass (jumper wire) in between TB3-1 and TB3-2. The flame detector is completely closing in heat mode. However, in vent and cool down the resistance is dependent on how much light is on the flame detector. (I used a flashlight.)

The overheat thermostat (S2) seems to be working properly as it is always closed in all settings. It provides current across the switch

Again, with all these tests, the burner assembly is removed and top is on and the doors are closed.

What do you think my next step should be?

Is it likely it’s a bad fuel pump that is bleeding fuel to the burner?

Any ideas as to why L1 isn’t closing in heat mode and providing more fuel to the burner?

Thank you.

 

[155mm]

my guess is pump failure or foreign material

 

[cancunlarry]

I have seen another thread where someone moved the L1 or L2 solenoid. I think the L1 to the fuel outlet side of the fuel pump. so right as the fuel exits the pump it hits a L1 solenoid. I am not sure if they ADDED a L1 solenoid to the fuel pump exit and left the old one in OR they just moved L1 solenoid to the fuel pump exit side of the pump.
I think he was having the same issue, fuel dumping into the combustion chamber.
In theory if you put a solenoid on the fuel pump exit "to the burner" and the solenoid only turns in heat mode. You should not get fuel flow in the other modes. I did see someone with the same problem post this finding.

 

[dwade154]

That makes sense. I have the extra 19$ solenoid and will make an attempt at an install tomorrow. I will post back with my findings. Thank you.

 

[dwade154]

That was the issue. I added a solenoid in between the fuel pump and the burner assembly and wired it in series with L1. This stopped my fuel going to the burner in all modes. This was my main issue. I just used about a foot of 1/4" copper tubing and flared the ends with a flaring tool. Pretty straight forward.

With the top and doors open I jumped across air pressure regulator and confirmed I had fuel to the combustion chamber only in the heat mode. I put the burner assembly back together and top on. While testing it and had both fuel and ignition-but no combustion. Bummer. I removed the sight glass to confirm.

I again removed the burner assembly and followed the TM to set the electrodes the proper distance from the spray nozzle. I should have checked this ahead of time.

I again cleaned up the raw fuel inside the chamber and reinstalled everything.

I FINALLY have heat. It smoked a lot.

While I was inspecting the unit, I observed one of the heat exchangers steel runner tubes was red hot while in operation. My guess is it was the remaining unburnt diesel fuel I could not see or get to.

I shut the unit down, but it continued to burn in vent mode for 30 minutes. I again removed the sight glass so I could get a better look and it was just unburnt fuel.

Thanks for all the help. I hope this thread is able to help someone. I will attempt to add a picture of the solenoid I added.

Amazon.com: U.S. Solid 1/4inches Brass Electric Solenoid Valve 110VAC Normally Closed VITON : Industrial & Scientific



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