Interesting HEUI Discovery

[discovery39s]

Inspected a 3126E today that stumped me at first. Threw many different codes that didn't make sense before I started on it as DOA when it arrived. Owner stated it shut off like you turned the key to OFF. I first checked all the normal items for a no start: HEUI coil current, IAP and other sensors before I checked the lift pump. Strangely I found the lift pump had zero flow while cranking. I pulled the fittings off the inlet, looked at the gear while my partner cranked the engine. The lift pump gear was not rotating. First thought was that the tang may have broken off the drive shaft of the lift pump to the HEUI shaft.

So, I removed the HEUI to find the nut had loosened off the drive gear. On the bench I tightened the nut, after cleaning the thread and applying Loc-tite) to find the lift pump was now turning.

The taper of the drive gear to HEUI shaft, large OD tapered shaft, turns the swash plate of the HEUI pump only. The threaded shaft that the nut threads to is a separate shaft that runs through the center of the HEUI swash plate. When the shaft nut is tightened it locks the two shafts together by the tapers that in turn turns both the HEUI swash plate and the lift pump. If the nut comes loose then the two shafts disconnect causing neither the lift pump or HEUI swash plate to turn.

Someone may diagnose this as a defective HEUI. It was but not because the HEUI came apart inside as they can. This was simply a matter of $1.00 worth of loc-tite to repair. This is now the second one I have come across where the nut came loose and caused this issue.

So, before you diagnose the HEUI being defective and replacing it OR someone convincing you it needs replaced, you may want to inspect or request this to be checked. This saved the owner $1,800.00 and three days of hotel costs.

[FIRE UP]

Thanks for that really great tid-bit but, VALUABLE amount of info on the HEUI pump and related components. I'd sure like to see the inside of what you were/are talking about so I'd know my HEUI pump better.
Scott

[discovery39s]

Originally Posted by FIRE UP

Thanks for that really great tid-bit but, VALUABLE amount of info on the HEUI pump and related components. I'd sure like to see the inside of what you were/are talking about so I'd know my HEUI pump better.
Scott

Hey Scott,
You bet. I have a HEUI on my bench that I have taken apart to do some training. I'll take some pics and detail each component that has a propensity to fail. We take apart every failed unit to inspect the specific failure. It's been interesting to find several areas that can fail. Three areas have proven to fail. 1- Broken piston return springs. 2-Metal transfer from piston to bore. 3- Radial main shaft bearing. These are catastrophic failures that take out the injectors.

The final issue is not damage, metal to metal damage/particulate, it is just worn piston to piston bore diameters. This causes low pressure conditions and "Low Power" condition the owner experiences. Once you see the inner's you may then realize the things that can go bad.

I'll be back to you in a couple days.
George

[wclogger1]

You may have mentioned this before but what do you use to check engine codes? Thanks

[discovery39s]

Originally Posted by wclogger1

You may have mentioned this before but what do you use to check engine codes? Thanks

VMSpc and no-share software I wrote myself.
VMSpc will provide many codes, just not all.

[wclogger1]

Ok thanks for the response.

[discovery39s]

Originally Posted by wclogger1

Ok thanks for the response.

You are welcome.

Stay safe

[FIRE UP]

Originally Posted by discovery39s

Hey Scott,
You bet. I have a HEUI on my bench that I have taken apart to do some training. I'll take some pics and detail each component that has a propensity to fail. We take apart every failed unit to inspect the specific failure. It's been interesting to find several areas that can fail. Three areas have proven to fail. 1- Broken piston return springs. 2-Metal transfer from piston to bore. 3- Radial main shaft bearing. These are catastrophic failures that take out the injectors.

The final issue is not damage, metal to metal damage/particulate, it is just worn piston to piston bore diameters. This causes low pressure conditions and "Low Power" condition the owner experiences. Once you see the inner's you may then realize the things that can go bad.

I'll be back to you in a couple days.
George

Hey George,
I most certainly appreciate your answer here. I've been around diesels my whole life (35+ years as a fireman in 4 different fire departments) but, have never really gotten into how they work. I know the basics but, things like the HEUI pump, well, that's a bit over my head, 'till I can learn more.
Scott

[discovery39s]

Originally Posted by FIRE UP

Hey George,
I most certainly appreciate your answer here. I've been around diesels my whole life (35+ years as a fireman in 4 different fire departments) but, have never really gotten into how they work. I know the basics but, things like the HEUI pump, well, that's a bit over my head, 'till I can learn more.
Scott

Well Scott,
I have many pictures to share. However, every time I attempt to upload I get "file size exceeds 500kb". This is regardless of the size.... Any clue?
George

[discovery39s]

Lets see if this works....

[discovery39s]

Okay, figured it out, DA. Here is the main pic of the HEUI internal components. Not shown is the coil and pressure control valve. I wanted to show the components that fail.

[discovery39s]

This photo shows one failure area. It is not due to "dirty oil" but more due to age. The shoe is a socket on the piston ball that swivels. When new, the shoe to piston ball is .002/.0025" clearance. When this joint fails, like you hip socket may as you age, the clearance begins to increase as this hammers the joint back and forth. When this joint finally fails you will experience debris and substantial noise in the pressure reading. This is sure death of the injectors in short order.

[discovery39s]

Here is a pic of the pistons on the shaft and swash plate.
And the related piston bores in the housing. The ARE very much related to "Dirty oil" failures due to scouring in the bores, thus creating low HEUI pressure output or "Low Power" conditions.

It is important to note that in the very end of the piston bores are discharge checks. Once the piston advances, pushing oil out of the HEUI, the checks must close to now draw oil back into the piston for the next discharge cycle. If one or more of these discharge checks fail then that piston will not deliver oil to the common oil rail. At times this is a common miss-diagnoses of a bad HEUI. If you remove the plugs opposite of the piston bore you can remove any debris and or replace the spring.

[discovery39s]

This is what I spoke of originally regarding the lift pump not turning while cranking the engine. The small center shaft turns the lift pump with the slot and tang. If the nut comes loose on the input shaft then the taper disengages and neither the HEUI nor the lift pump will turn.