HEUI Troubleshooting - Injection Pressure Desired and Actual Mismatch

[GeneralDisorder]

Well unless oil is gushing around a cracked injector or failed seal

It's certainly worth a look under there with it running since it costs nothing. I would also be very curious to look at the scope traces of the IACV. And to inspect the inside of the HEUI oil supply hose - being that hose is 23 years old - if those have a propensity to shed inner lining that could account for the damaged HEUI pump. Definitely something the community needs to know about and watch out for if that's the case.

His initial symptoms were that the pump was unable to hit the low pressure operating range of 870 psi. I assume this is a high-pressure positive displacement pump and the IACV is dumping pressure back to the pump's inlet or the sump to regulate the pressure down. Since it was fine at higher pressure this always seemed to me like the pump had some kind of partial blockage to the return path (inlet or sump) being regulated by the IACV and thus when it needed to send a large volume of oil back to the sump it was backing up and creating more pressure than the ECM was calling for. At higher pressures the issue vanished as there wasn't the need for the volume of return flow. It then stopped having a problem after changing the IACV and has now returned with worse symptoms...... if that supply hose was coming apart internally due to age this could neatly explain the situation.

 

[aw113sgte]

The supply filter comes with the HEUI pump and injector kit for the C7. Indeed I had to scour the Internet just to find the part numbers to install the filter kit on my C7 because CAT doesn't sell a "kit" for just the filter if you want to install it preventatively - probably because Installation requires compressor removal. I had my compressor off anyway and the filter parts are $200 so it was an obvious upgrade and the original supply hose didn't look that great. The filter parts include a shorter hose, etc.

Do you have those part numbers? I looked out of curiosity a while ago and just saw the kit with the pump too. If you've already done the leg work that's great!

 

[GeneralDisorder]

Do you have those part numbers? I looked out of curiosity a while ago and just saw the kit with the pump too. If you've already done the leg work that's great!

Yeah - one of these days I should make a complete post on that. I've posted it in other threads, but not made a post about the process. I should have taken more pics but I was pretty flustered about the compressor failure and just wanted to get my new toy back together (compressor blew up during the last 100 miles of my 2700 mile trip home with my truck). Here are the parts:

Caterpillar HEUI Filter Parts:

503-7470

503-7469

503-7460

238-5089

 

[aw113sgte]

Yeah - one of these days I should make a complete post on that. I've posted it in other threads, but not made a post about the process. I should have taken more pics but I was pretty flustered about the compressor failure and just wanted to get my new toy back together (compressor blew up during the last 100 miles of my 2700 mile trip home with my truck). Here are the parts:

Caterpillar HEUI Filter Parts:

503-7470

503-7469

503-7460

238-5089

Thanks! Yeah that was a crummy situation for you.

 

[Skyhawk13205]

I was thinking of doing the huei filter or a bypass filtration, sounds like one of the issues of contimated oil if the oil cooler leaking unfiltered oil.

Adept Ape has a good video regarding the secondary filter.

 

[ckouba]

Just realized I posted this to my camper thread and not this forum/thread:

Began a thorough investigation yesterday which effectively ended up with open heart exploratory surgery.

I started the day with checking the harness/connectors to the IAPCV (Injection Actuation Pressure Control Valve- the thing which controls the oil pressure sent to, and used by the injectors to fire fuel into the cylinders). I actually pulled off the intercooler to manifold pipe to make this easier. After that, the task was incredibly easy. There are only about 2 feet of wiring and it appears that it comes directly from the ECU without any intermediate connectors.

There was talk of a degraded block to HEUI pump oil line. Not the case here. It was a steel pipe already and looked in good enough shape.

Rick showed up with his scope around this point, and we started with scoping the signal going to the IAPCV. The first trace we got was with the ignition on but not running. Looked like this:

It's a little tough to read on the screen, but it's showing about 9% duty cycle with a wider pulse followed by 3 or 4 narrow pulses. Over time, the signal was consistent and didn't seem to vary when poking at or jiggling the wires.

Next up we started it and kept the scope running at idle, which looked like this:

For starters, it ran like crap- indicating the problem hasn't miraculously cured itself. It never fully warmed up but after a few minutes of running it was a little bit smoother. Running at idle had it at ~13% duty cycle with the extra spikes on the scope trace. The pattern was quite consistent though, so despite our mutual lack of knowing what the trace should look like and the fact it wasn't changing as we knocked around the wires, we were comfortable enough to say it was running correctly and moved on.

As it was already running, next order of business was to pull the valve cover. This was fairly uneventful, with consistent streams out of each injector. We did a cutout test with each injector, shutting each one down individually and observing the results. In each case, the motor roughed up when we shut one off and smoothed back out when we turned it back on.

Since it was running, one of the suggestions was to pull the plug off the IAPCV, which we did. The motor promptly died, so I guess it passed that test?

At that point we were about out of test procedures and all signs were pointing to HEUI pump. To get a thorough understanding of what may be going on with the whole system, we pulled and cut the filter to see if there were any shimmering warning signs in it. Cutting to the chase, no, there weren't. Everything looked dark and smooth and basically devoid of shiny flakes or particulates.

As we were already pretty deep into this and I really want it bulletproof on the other side of this work, we also pulled out the oil cooler to check it for flatness. There have been occurrences where the gasket in the cooler fails internally and allows dirty oil to cross into the clean side of the filter, without any external sign of a leak. It didn't appear to have an issue (gasket-wise), but putting the cooler on the bench with a straight edge, it is clearly not flat and will need some surfacing work. Will be a hassle but don't want to have to go back in there- especially if there's no external signal for an issue. This was about the end of a productive day (with many thanks to Rick) so I stepped away for the evening.

The cooler warpage (I think lens optics make it look worse than it really is, but it definitely needs some attention):

Seeing as the HEUI pump was still looking like the guilty party, I worked through the steps of its removal this morning. It wasn't too bad since all the crap was off the motor, and it's now resting on a crate with the turbo, oil cooler, and other large parts.

Next steps will be extensive- I have the IFS filter kit on order (HEUI pump to head), an oil bypass kit as well, I want to figure out if the C7 block-to-HEUI pump filter line is adaptable to the 3126, and then I have a whole bunch of crap to replace and reinstall. Good news is the turbo looks good and its bearings spin nicely.

I also pulled the compressor head while removing the HEUI pump, and that will go off for a rebuild while I am assembling other parts.

Basically, I've got a massive boat anchor in the carport at this point. I look forward to getting some parts and putting it back together.

Port:

Starboard:

 

[Ronmar]

Well the control valve pulse width should be inverse of the pressure, the higher the pulse width/duty cycle number, the more the valve is open and the more pressure it vents. so it is good to look at both the duty cycle signal and the pressure. With a low PW/duty cycle number, it was commanding higher pressure. If the pump is not delivering it, then either the valve was not actually cycling at the commanded duty cycle or the pump cannot create the pressure.

That was why I suggested unplugging the IAPCV, if there was a change, like the pressure going high/relief opening, that may have indicated the valve was actually working or not. It may also be that when the ECU no longer detected the circuit, it shutdown the injectors/engine. I guess you could plug in the other PCV and try and start it, but since you have tried 2 valves and the pressure and duty cycle are still both low, that does point toward the pump.

As for the pump, most every hydraulic system has a safety, and i suspect this system is no different. So either the pump cannot provide, or perhaps its safety has failed and is leaking, limiting its pressure… Not finding metal sign and all the injictors still processing oil is a good thing…

 

[MatthewWBailey]

Yeah - one of these days I should make a complete post on that. I've posted it in other threads, but not made a post about the process. I should have taken more pics but I was pretty flustered about the compressor failure and just wanted to get my new toy back together (compressor blew up during the last 100 miles of my 2700 mile trip home with my truck). Here are the parts:

Caterpillar HEUI Filter Parts:

503-7470

503-7469

503-7460

238-5089

Would these work on the 3126b as an upgrade?

 

[GeneralDisorder]

Would these work on the 3126b as an upgrade?

The CAT dealer wanted Chris to talk to CAT engineering to see if that would work or what he would have to do. The 3126 uses the round top HEUI pump and I'm thinking the only difference would be the fitting at the pump and possibly the fitting location relative to the block port. The block port looks to the same. You could likely get the filter from CAT for the C7 and then adapt your existing tubing or hoses to fit it. It's just an inline filter.

 

[MatthewWBailey]

The CAT dealer wanted Chris to talk to CAT engineering to see if that would work or what he would have to do. The 3126 uses the round top HEUI pump and I'm thinking the only difference would be the fitting at the pump and possibly the fitting location relative to the block port. The block port looks to the same. You could likely get the filter from CAT for the C7 and then adapt your existing tubing or hoses to fit it. It's just an inline filter.

Yeah I'm doing this on a priority. This thread makes me pucker. Got the amsoil bypass filter already. Just need that ifs kit but it's hefty$. Doing a synthetic oil change once I get the goods from Amsoil.

 

[ckouba]

Following up on this work:

• Motor is back together and running wonderfully. Desired and actual are running within ~10psi across all ranges.
• IFS filter is installed between HEUI pump and cylinder head. This went well with the filter being mounted where the driver side kneeling cylinder was located.
• The IFS lines weren't ideal for the location- one too short, the other too long, so I had new ones made locally.
• The CAT block oil to HEUI pump filter was way too bit to fit into the available space, so the filter and C7 hard feed line are still in a box.
• I have the Amsoil bypass filter ready to install but will not get to it until back from our next trip.
• The oil cooler had about 0.025" runout on it so I had it decked locally.
• All in all, the work was pretty straightforward- just expensive!

Yeah it was a lot of work, but things are running very smoothly now. We are lining up to do a shakedown trip sometime this coming week, then we leave for UT again the following week.

 

[hike]

Following up on this work:

• Motor is back together and running wonderfully. Desired and actual are running within ~10psi across all ranges.
• IFS filter is installed between HEUI pump and cylinder head. This went well with the filter being mounted where the driver side kneeling cylinder was located.
• The IFS lines weren't ideal for the location- one too short, the other too long, so I had new ones made locally.
• The CAT block oil to HEUI pump filter was way too bit to fit into the available space, so the filter and C7 hard feed line are still in a box.
• I have the Amsoil bypass filter ready to install but will not get to it until back from our next trip.
• The oil cooler had about 0.025" runout on it so I had it decked locally.
• All in all, the work was pretty straightforward- just expensive!

Yeah it was a lot of work, but things are running very smoothly now. We are lining up to do a shakedown trip sometime this coming week, then we leave for UT again the following week.

Thank you for sharing.

It would be nice to see photos of your modification progress—

 

[Skyhawk13205]

Following up on this work:

• Motor is back together and running wonderfully. Desired and actual are running within ~10psi across all ranges.
• IFS filter is installed between HEUI pump and cylinder head. This went well with the filter being mounted where the driver side kneeling cylinder was located.
• The IFS lines weren't ideal for the location- one too short, the other too long, so I had new ones made locally.
• The CAT block oil to HEUI pump filter was way too bit to fit into the available space, so the filter and C7 hard feed line are still in a box.
• I have the Amsoil bypass filter ready to install but will not get to it until back from our next trip.
• The oil cooler had about 0.025" runout on it so I had it decked locally.
• All in all, the work was pretty straightforward- just expensive!

Yeah it was a lot of work, but things are running very smoothly now. We are lining up to do a shakedown trip sometime this coming week, then we leave for UT again the following week.

Good work, sounds like quite a bit of work and thinking. The oil cooler warping is a really frustrating, it may be why your huei system was having trouble, hopefully fixing that will resolve your issues.
I was wanting to use the Amsoil bypass kit, the filter has the micron rating that I wanted. I was trying to decide where to install, the oil feed I was thinking of either using the oil sample line or the port off the oil filter housing. Cat supposedly had provisions for an additional oil filter for the 3126 see item 26 on the attached picture. For the return I was thinking of using one of the oil dipstick ports. Thanks for the update.

 

[ckouba]

Initial install, should be pretty obvious why the universal lines weren't a good match here:

For the record, the forward one rubbed against the cab mud flap and pushed it out. The aft one had ~1/8" clearance between the coolant hard lines and the cab body seam, maybe 3/8" after I hammered on the seam. Not a good set up.

With a shorter line and a longer line, routed more appropriately:

Close up of fliter mount (filter housing is beefy):

Good work, sounds like quite a bit of work and thinking. The oil cooler warping is a really frustrating, it may be why your huei system was having trouble, hopefully fixing that will resolve your issues.

Based on the "printout" of the gasket on the cooler faces, it appeared as though it was sealing, but I'll never really know at this point. It is a little annoying that design has the possibility with no external indication of failure.

I was wanting to use the Amsoil bypass kit, the filter has the micron rating that I wanted. I was trying to decide where to install, the oil feed I was thinking of either using the oil sample line or the port off the oil filter housing. Cat supposedly had provisions for an additional oil filter for the 3126 see item 26 on the attached picture. For the return I was thinking of using one of the oil dipstick ports. Thanks for the update.

I was thinking the sample port as well. I will take a better look for the 2nd filter provision. Would appreciate any insight or detailed suggestions...