[Airweld]

The image below shows temperatures I recorded while troubleshooting. Specifically, note the ambient temperature. The readings were taken just prior to the 129 fault code. What is missing from when I originally did this image is the reading where the output port meets the pump body, when it reached 80°F the 129 fault would occur, even when it is really cold out. Note that the perspective of the photo is confusing and the exhaust pipe was nowhere near as close to the pump as it looks but was still part of my problem. Both are in different locations now.

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You may have the wrong version of the fuel pump if you have the larger inlet port.

The incorrect replacement pump I got from (and returned to) Esparparts is 22.4519.01.xxxx which had the larger inlet side and a different electrical connector than my original pump and harness has. Apparently this is the pump for the original B4 heater version.

I got the proper fuel pump from Heatso. The M2 B4L fuel pump is part number 22.4552.03.xxxx.

Your pump is mounted exactly how mine was when I was experiencing the my problem with the P000129. My thinking was that it is a nice protected area. The new location for the pump below the frame rail resolved my issue.

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Our symptoms are not identical, so all this info may not be useful. Hopefully, your new sensor resolved this.

OK. Here's the latest and it's not good. At this point I can't say I was very optimistic but went ahead and made the changes anyway.
Dropped the fuel tank and put in new 2mmID fuel line from the dip tube to the pump. Made sure the lines were butted up tight end to end and clamped good. Moved the pump while I was at it to a very similar location as this one in the picture.AND TA DA........NO CHANGE in behavior. Solid fuel into pump, bubbles coming out, same as before. And that's from start up when cold. No possible heat related issues. Same as before. What's left? I have now replaced everything from the fuel tank to heater with the "correct" parts, "corrected" pump position, flashed ECU, replaced combo sensor, replaced burner screen, "corrected" combustion intake. I'm assuming the fuel pump generating bubbles is the issue so what else is there to do? Do all these heater installations' pumps generate bubbles?

 

[Airweld]

I don’t know if mine generates bubbles or not. But i do know the thing works fine. Starts up every time and heats with no errors. Do you still get error codes?

If so, maybe it is not even the bubbles that are causing the codes.……

When it won't make it through the start cycle it's always the same fuel related (ie temperature) codes. Sometimes after multiple tries it will run a full cycle ( I have it set to run 60 minutes). I haven't tried very many start cycles since the latest changes. I actually have other stuff to do. I have been told bubbles are bad yet when it does run a full 60 minutes it's still making bubbles. So, how do you stop making bubbles?

 

[Airweld]

My understanding is that downstream of the pump it is normal for there to be a stream of very small, uniform bubbles spaced abut 1/2" apart. That is how my properly-operating D5 works.

However, if you look around the Web, you find a diversity of views on this topic.

Interesting that the diesel heater also makes bubbles. I have one (diesel fired heater) but it has always worked fine so I never looked to see.

 

[Airweld]

On the first test with partial blockage of the output was positive. Ran through the start cycle for the first time at 36F ambient. Can't believe this hasn't been common knowledge for all the heaters with no output ducting. Will take time to verify but looks promising.

 

[Airweld]

What did you do to the output? ( fuel output?)

In order to raise the temperature of the combo sensor to satisfy the ECU requirement I partially blocked off the hot air output. Seems that without a duct to provide some back pressure, the temp requirements are so narrow that on a cold morning it can't do the complete start up cycle. At least that's my current working theory.

 

[Airweld]

Awesome news that you now have a definitive cause & solution, even if the solution is a bit of a hack. Maybe bring this up in the automation thread to develop a temperature activated baffle on the heater warm air output since anyone that installs the heater in this location is likely to have the same problem.

Had another successful cold start up this morning. Since I have a "spare" combo sensor I'm thinking I could change the resistance on the low temp side and try to get it to satisfy the ECU at a lower temp. Can't believe Espar isn't aware of this issue????

 

[Airweld]

I updated the Espar troubleshooting post on my website and sent a note to Mike on this. Hopefully, we can get the word out for other folks dealing with this and maybe Espar will address it. This seems like a worse issue than I experienced since the fault codes in this situation are actually misleading and detrimental to the troubleshooting process.

Good on you. I hope we can spare others the long frustrating troubleshooting process we have been through.

 

[Airweld]

I went back & forth with Mike a bit yesterday. He's not buying the working theory we have here. His first explanation is that on the cold start mornings, the heater goes into boost mode and boost mode is more susceptible to the fuel cavitation. On warmer mornings, the heater doesn't go into boost mode and can better tolerate the cavitation bubbles in the fuel line. He's trusting the fault codes and still believes that it is a fuel supply issue (cavitation).

So why would the warm air exhaust back pressure affect this? The heater heats up faster and gets out of boost mode.

With our very small sample, we see a correlation of folks with the cold start issue that have no warm air duct and those with ducting not having the issue. He didn't have an explanation for this.

Anyway, I don't know that we'll get to the bottom of this unless someone with the issue gets hooked up to the EasyScan diagnostic tool to watch the sensors in real time. In my case, this was very enlightening.

At least there seems to be a workaround.

Interesting. There are bubbles on the pump output ALWAYS. Cold, warm, and in between, before and after all the changes I've made. If there is a fix for that, I'd love to hear it. And I'd love to hook up a scanner. Tell me where? Bottom line is, it needs some better engineering!

 

[Airweld]

Is it possible to have an installation (gasoline) that sucks fuel up a standpipe, even a 2mm ID Espar, that does not cavitate and make some bubbles downstream of the pump? If it"s as difficult to do as it seems, then what is the downside to lowering the temp threshold so the **** thing works for less than perfect installations. Is the goal "I don't want it to work unless the installation gods are happy?" Or "Let's make the majority of customers happy by allowing it to work in less than "perfect" installations? How difficult would it be for the factory to make that adjustment? Either send out a replacement combo temp sensor or recall and reflash the ECU?

 

[Airweld]

Here is a video of what my fuel line looks like between the pump and heater, lots of bubbles and no errors (anymore). Does yours look better or worse?

I have a video of mine but it's too large and I haven't figured out how to cut it down so I might have to shoot another at lower quality. But my bubbles are similar, maybe even fewer.

 

[Airweld]

Here is a video of what my fuel line looks like between the pump and heater, lots of bubbles and no errors (anymore). Does yours look better or worse?

How do I load an MP4 file?

 

[Airweld]

Check out my bubbles.

 

[Airweld]

That looks much better than mine. I shared it with Mike, I'll let you know what he comes back with.

Tell Mike to send me an EasyScan and I'll show him what's going on. Espar Parts has them, $1463.86 each.

 

[Airweld]

My high tech solution:

Vent Open

Vent closed

 

[Airweld]

Update after a two week road trip at altitudes mostly 7k to 9.2k and nighttime temps in the 20's and 30's.
The brick is the key. With the output closed the heater runs when started in the AM. (Had to restart two times). If I open the vent too soon the heater quits and does a restart and if I put the brick back it will restart and run again. With a data logger and temp probe I could tell you at what temp it quits. You can leave the vent closed and it will run for hours but I was trying to find the sweet spot for cfm and temp. It is pretty obvious to me that the if you have too many cfm the internal temp drops and the temp sensor tells the ECU to shut down.
I have a 2018 short wheelbase tall roof with a fixed bed, big garage, two reefers, and lots of cabinets, so not a lot of volume. The heater runs full speed for a couple hours in the morning and does not come close to overheating the interior. Insulated with rock wool. Overnight interior temps in the 40's. So I can't see anything fuel related in spite of the error codes it throws when it quits and the BTU's are marginal for the application. YMMV.