How To Troubleshoot HEUI Systems and IAP faults. 164 Faults. 3126, C7, and C9 Cat Engines. 

got a 3126 in a 2001 freightliner single axle 5 ton. approx 1 million km. Ive been the owner the last 50,000km. The previous owner told me he had the injector cups done once. Personally Ive only changed the oil. Its achieving acceptable blowby and oil use. Really like the engine, its very responsive and generally flawless in terms of operation. Great power for my application. I really like how the power increases through the gears. This aspect seems to be dialed in just right, very smooth and well tuned. I havent noticed the motor miss or skip a beat even once. Loving the cruise control, works very well. The borg warner turbo peaks at 23psi, which seems low, but im only running the 245hp setting. Great turbo good performance for my needs. Although loud at times this engine sounds manly and fun. Also the clutch is very good. Its Super smooth with a bit of practice and can handle a heavy duty sychro transmission just fine. As for some complaints... The 6 speed eaton trans in the truck is long geared. As such im shifting into 1400-1500 rpm often. This is not ideal cause the power output and lifter rattle in this range is not very good. The engine seems to operate best in the 1700-2300 rpm range. Although staying there at all times can be a challenge. And then there are leaks, the turbo side is bone dry at all times. Cant say the same for the intake side. the heui pump leaks from the front cover. The heui supply line leaks. The cam followers leak. The oil pressure manifold leaks. The oil pan leaks. Lets just say it leaks a little. Could fix it if I wasnt too busy making money every day. My attitude could change if I blew the heui system and went broke. But I wouldnt call it a boat anchor. Under the right care it can be considered reliable, and an all around nice engine. Best part is I only paid $8,000 for the truck. Some of my colleagues are $40,000+ into their rigs and spend lots of cash on EGR parts and exhaust filter problems. Not me im banking dollars daily :p

Not a mechanic by trade but do know some maintenance. Your video was straight forward and in layman’s terms Well done

You're correct it is 3126. After changing out fuel actuator which didn't work, I replaced fuel pressure sensor and that fixed the issue. Thanks for the response your videos are great.

Your videos have been very valuable to me in understanding the C7 in my RV; I discovered you when I learned yesterday that I have a HEUI failure with metal in a couple injectors at 87k miles. One thing you haven't mentioned is whether an oil cooler failure or warpage can put metal in the oil supply and THAT failed it, as my CAT shop (which has a good reputation) is suggesting MIGHT.be the source. They point this out because if it is, the $6500 investment in the kit and it's installation can be trashed and the whole exercise re-done with the additional expense of the oil cooler. The cost Delta to do the oil cooler, they say, is about $1500 and they leave it to me to decide whether or not to go that route. I am very inclined to spend the extra money, because while I can afford to pay $8000 to fix this once, I'd rather not Pay a total of about $14,500 to fix it twice. What are your thoughts on this situation? You have not mentioned the oil cooler in your videos. Thanks very much.

These engines seem very familiar to the international 7.3L on how they operate and the injectors look very similar.

thanks for the advice it sat for a year and a half and when i saw that little drip i thought bad the truck is not on the road so the best i could do is give it a good idle every so often and bring temp up till fan kicks on

At start-up C9 oil pressure is very high. With engine pre-heat it's 75 PSI, without it's over 100 PSI. Oil is bypassing the filter with this high pressure, so not good for HEUI pump. CAT 15w-40 oil takes to long obtained operating pressure. I'll received a fault code when engine load is high at high oil pressure. The fault immediately clears when engine load is reduce. When the oil pressure obtains operating pressure about 40 PSI, there's no fault. Still searching for the correct engine oil. Great information. Thank you

I have a 1999 Newmar Dutchstar Motorhome with 170K miles and a Cat 3126 Diesel. On a return trip from ND this summer it suddenly slowed to 40mph while travelling down a freeway. I could not get it above 40. I could slow down and speed back up to 40 but nothing faster. I decided to pull over and it died and would not start again. Afterr about a 1/2 hour of calling around, it did start but again would only go 40 max. I limped it to the next exit and called for a tow. The towing company also did minor servicing and suspected clogged fuel filters, which they changed, numerous times but did not fix the situation. They noticed the diesel fuel was dark with oil and suspected blow by from a cracked piston, o-rings or cracked head. They replaced the o-rings which seems to have helped the discolored diesel, but did not fix the speed or starting issue. I should mention that the RV would start with ether and if I was lucky and could get the vehicle moving, I could limp down the road but it seemed after the engine was warm and it died, it would not start until some time passed or ether was used. Also the OBDC is not producing errors. When the 40 mph govenor kicks in the Engine light does come on but does not pass any codes. After apparent cooling down, the Check Engine light goes out as if nothing is wrong only to reappear after a while. The shop now suspect the HUEI. They are not a highly knowledgeable professional diesel service/shop but are trying to help me by keeping my costs down. Although trial and error and parts changing may work, it's been 2 1/2 months now and would like to get this resolved. Any help, thoughts, comments, kick in the pants would be greatly appreciated. Thanks in advance!

Ok thanks for your help. I'm going to take the injector out to see if the o- rings are bad. video helped me out a lots

I have a c7 in a freightliner that only show's .5 gph fuel rate. I performed the actuation pressure and cutout tests that looked great. I have extended crank, miss, fuel knock, hesitation etc. No codes except for low cranking pressure but its an old code.

I have an rv with a 04 cat c7. It is a 350 hp engine. Upon start up when it sits overnight, it will throw the ck engine and engine protect light upon start up. Codes 164-2 and 164-0 are the only codes in the system. When it starts it will seem to run a little rough and seems more black smoke than usual but I never paid much attention upon start up because I am inside. It stalled twice on me. Both times when the lights were on. I had to turn the key off and try to start it again because it would not start until I shut the key all the way off. Once I did that it started right back up. If the light come on when I start it, I turn the key off and start it again and the lights are off. It never had low power and still doesn't once those light are out. I put my scanner on it to test the actuation pressure, and it did go all the way up and down, but seemed a little delayed in response. Any suggestions? PLEASE!!! Supposed to leave for vacation in 2 weeks and need a vacation not a vacation to HELL though. Thanks in advance

Got i C9 giving 42-05 current below normal in crane operation. 1.replace ECm,wiring harness, injectors,HUEI pump Engine hunting when ramp up to 1800rpm.

Awesome video! Its been some time since Ive worked with the CAT HEUI systems. Great refresher course and thanks for the help.

Awesome intel as usual. 👍 Another video another lesson learned. 😎

im actually thinking about going to uti diesel program and work on these cats instead of driving them plus knwoledge is good keep up with the excellent videos // wood like too see a cat rebuild video some day but there are none // your diagnostic videos help new guys for theyre schooling career alot

Great video!!! Good explanation of heui systems!!!

I just replaced my 3126b with a reman that I bought off a shop from Florida. It's in a Vermeer bc2000xl wood chipper. I have only ran it 50hrs. It looks like I received a freshly painted truck engine. Maybe partially rebuilt, I don't know. Today we lost oil pressure. It went down to around 3psi and shut itself down. Oil level is fine. The motor starts normally, but shuts itself down within a minute. Went to replace the oil filter and it was not full of oil when we took the old one off. We stuck our finger in the oil filter housing tube and pulled out some type of plastic tape or film. Don't know what that came from. Then we replaced the oil filter with a new one. Then started the motor for a minute again to see if the oil filter would fill up again. It did fill up. Although, we are still not getting more than 4psi oil pressure at idle. Would this be a HEUI pump problem? I also read that there might be a problem with the filter housing. Any help would be appreciated. Thanks

Hey man it would be very interesting if you did a day in the life i would love it im in highschool and i want to be a diesel mechanic at CAT. Thank you pleas keep up the great work!

Thank you sir! 🙏 great advice!

CAT 3412E, at full throttle under load fuel position intermittently goes to 0. Replaced heui pump and inspected all orings on injectors and high pressure oil elbows. Cylinder cutout test all injectors firing but a few are weak. All cylinder have good compression. There’s a knocking sound coming from the pressure regulator on the new and old HEUI pump. Thank you to anyone who has any ideas.

Love your video, you did a good job explaining things.

thanks Ill check; I had a bad injector before but my mechanic fixed it, the control valve of heui has 9 ohm and the sensor gets 5 volts in, .9 volts at idle when rev it up going up, and ran well but it show those codes ..thanks Iam learning a lot of mechanic with you and your videos are helpful and interesting thanks for your time body

Great video mate! Thank you

Excellent video

Great video.

Huei pump and injectors were replaced. Updated filter kit is installed on feed to humidity pump

thanx josh you helped me again

why does my Check engine light does not comes on and the OBD indicate NO ENGINE.???????? PLZ THANKS.

A question about: the fuel flow from the filter thru the pressure regulator on the Cat 3126 2001\2002 build. Question: Would installing an electric fuel pump between the fuel filter and the fuel transfer pump allow the bleeding of air from the head in the event of the failure to prefill the fuelfilter\filters? Would the additional pump allow any air to pass thru the pressure regulator and allow fuel to be circulated bank into the fuel tank?

Thanks for the videos... need help. 1997 3116 Heui... Starts easily, runs great, low power. No boost to speak of. I just got the J1708 rewired to a regular truck connector and can talk to it now. Without Cat ET I only see fuel pressures, not requested (yet) working on codes for that data point... Pulled the Fuel actuator IACP and pulled it apart, and cleaned it. no change. Checked the intake air pressure sensor, clean. I only see up to ~20psi boost then it drops back to 18 even on the floor. can't get over 40 mph. Heeelllppp. suggestions are welcome.

Have a 02 , 3126 no codes engine idles fine at cold start , but afterwards engine warmed up engine surges on idle , once you increase rpm to 1000 rpm runs fine.

This is very helpful. Thanks for making the video. What kind of software do I need to troubleshoot the 3126. I have been having issues and the dealership around me is terrible at helping even finding the right issue. Thank you.

Great video. Working on a 04 IC DT466. Starts great and runs great until it gets hot. Injection control pressure drops way off and it wont start again once engine is shut off. Then when it cools off BAM starts and runs great until it gets hot again. Should I look under the valve cover PITA, or suspect the HPOP. Thanks again!

Hai thanks for the video, can you explain about the injection current based on the load percentage, will be helpful

why does my C7 cat engine CHECK ENGINE light does NOT comes on ....and why my OBD screen show me ,,,,NO ENGINE.....???? PLEASE and Thanks

Thanks!

Hi there I'm having trouble with a 336d running a c9 that refuses to start when warm unless it gets a squirt of ether I'm thinking huei pump or faulty injector am I on the right track?

My 3126 wouldn't start. Turned over fine. I replaced the injection actuation pressure sensor and it fired right up without further issues.

My question is this what fails in the Heui pumps on the 3126e

I really enjoy yiyr Cat videos I have a car c9 in a bus. I was having surging read the dipstick correctly or GLASSES I’m old. I was 7 quarts low now runs excellently. I wonder can o make an immune filter system for a cat c9 or can get them now. Thanks for any reply

thanks

fluctuation right ? great vids man thumbs up to you

hi friend, I have a c7 that runs fine but sometimes It starts to shake and miss powerwith white smoke and the flash code are 15 ; 39 thanks for your comments...

Need Help... I have two rollbacks with the Cat. 3126 Turbo deisel.. takes fuel fine, unless you have pedal all the the way down with the weight of the rollback going up hill.... down to 30mph on some hills.. blue smoke, no power under strain... even it's own weight up hill.

Hi Adept Ape... Thank you so much for your videos. They are very helpful. But I was wondering where I can buy that software? I have several C7 engine trucks and have paid my mechanics a lot of money every time they hook the computer up. I would like to know where I can buy it and what are the prices. if there are several different versions, which would you recommend? I would highly appreciate your advice. Thank you

Can you tell me what you said from 5:30 to 5:33 in the video it sounds like you said you have never seen that be the cause unless it says injection actuation pressure sensor( forward chime) What is forward chime...or did I mishear something

Your videos are great.keep up the awsome work you do. quick question, at the dealer i work we have access to CAT software and to the manuals. for some reason i have a hard time finding trobleshooting info for engine DTC's you think you could make a video about where to find the info.

Thanks for the video. I have a 2009 f750 7.2l it starts ,run and shutdown after 1 minutes and will start right back and there is a sign on cluster stop engine. .I need some help please. Thanks

Have c7 10 oms good. If I clear codes and history engine not running. I get the flashing light on the dash. I haven't even started the motor. Would this indicate a wiring issue. I had to put injector seals they were gone. The harness to injectors was in bad shape and 1 injector failed on test. I can't get the flashing to stop. I need advice on what to do. Please. Great video!

I have a cat engine 3412E showing the following defect in the first cold start the engine runs but in the second start the engine does not work only by applying ether in the turbine What can be thank you

the heui pump om at 10.1 the pressure was bouncing from 2400 to 5200 as we werechecking conections we lost pump data

I've got a 3126 crank no start. I recently tested the driver and it tested out at 10ohms. Would you lean toward the HEUI pump or a possible electrical communication issue? I dont have the software to plug the truck in. I appreciate it and love all the vids, especially about the cat motors.

On the C7 sensor you said 6 to 10 ohms is that 6k to 20k or judt 6 to 10 also the sensor has 3 pins so test both outside pins to the center I'm currently working on a royal pain in the axx lol c7 truck is surging after it warms up with no codes it did have some events for low cranking pressure and I did reseal the injectors they where leaking using the primer pump any help would be much appreciated

I have a Cat C-7 eng# WAX54111 I have extreme high pressure oil pressure at crank and idle approximately 4000-4500 psi changed IPC sensor HEIU pump ecm traced and inspected wiring any other ideas as to why this issue is occurring advice would be much appreciated.

Hey adept , I’m having an issue with a c7 in a motor home, lost power on a trip and died , I have a video showing the injector act. Pressures in cat et while cranking,I was hoping I could send the vid to you and see what you think

My freightliner cat c7 it's returning oil to the fuel tanks? I was advised by mechanic that the HEUI pump it's the cause of my oil "disappearing". Around 2 gallons of oil consumed on a day (450 miles). When looking at the tank it's black and we're advised it's oil. I'm not sure about it, what are your thoughts?

great video your presentation and info are super! any chance of video about using et. i have it at work but would like some of your input

You're saying it's more common to replace the whole HUEI pump, than the seals going bad on the injectors? ( 5:18 )

Hello, I have a C7 "JTF". Excessive oil consumption complaint , about 8 L in a 12 hour shift.. Found oil in the fuel so replaced injector o-rings and cups about 6 months ago. The lift pump looks new, HEUI looks new, Turbo is not leaking oil, no oil in the exhaust no smoke, air compressor carrying oil out so disabled it. Wondering if you have any methods for testing oil in fuel? Any help would be appreciated.

it has a new IAP and what i call ipr for the heui pump. i work with powerstrokes and i know that they are alike. i don't a scanner to check my pressure, so I'm not sure how to go about to see if i have desire pressure that it needs to fire the injector.

I have a motor home with a C7. Sat for couple years. I did start it and run once in a while. I can’t seem to get fuel to the inlet of primary filter. I drained tank and added fresh fuel. Replaced both fuel filters. I did replaced the fuel regulator today. Have a hand prime pump but it never gets hard to push after priming 100’s of times. Cat dealer replaced HUI pump and injectors a few years ago so I’m hoping it’s not that. Any ideas as to why no fuel to the primary fuel filter?

Excellent Thanks you. What is a good scan tool for occasional use？

My problem with a cat c7 is low oil pressure, change the pistons, all the metals inside the new oil tank and the head rubbers, and nobody understands why there is no pressure. question ? can be heui pressure pump

I have a bus with a 3126 the buss has a hard time starting and loss of power I’m getting flash codes they are 39 and 15 what do you think is the problem ? Thanks a lot for all your videos!

Young man my motorhome has a 3126 and it was running ok and it just started losing power and at times it would die I can let it idle and run at full throttle and it will start losing rpm and then start smoking real bad is that a sign the pump might b bad it might run fine for a couple miles then it starts acting up no engine light and no codes I'm lost

Will the pump throw this 164-4 code had at 2 shops 1 of witch said motor needed new rings I had put new injector seals in it replaced pressure sensor on head still have crank no start or really bad running when does start engine protect light and engine light comes on lose of all power

Excessive smoke and sluggish performance on 2006 c7 475 hp marine Is thus indicative of injectors hanging up?

Sir, what to check clutch pressure alarm in caterpillar engine.

Hey there. I am working on a C9 that surges while accelerating until it gets above 1600 RPMs. I’ve noticed the actual injection pressure is higher by 2-600 psi while it’s doing this and once it calms down it read close to the desired. Where do I even start. I have CAT ET and am familiar with the heui system but never seen one do this.

Hi there I have a C7 that has injector 1 and 2 not firing. I have since confirmed its not the injectors we I swoop them around and they fire. I suspect it could be the ECM because all injectors squirts oil and if I pull out the plug it stops squirting. I tried the cylinder cut out test but you can hear there's no change in sound or rpm or fuel pressure unlike injectors 3 - 6. Can you please help with any advice. Our big problem is we don't have another test ECM so I want to make sure before buying one. Thank you

working on a c7. runs like crap. 102-4 was active but after a few minutes of running, went logged. inside logged events, 164-11 code found. cylinder cut out test shows to have 2 inactive injectors. should this be the 164-11 event?

Hey adept have you come across working on perkins engines

I Have a 2006 c7 and it is surging badly when accelerating under load.It shakes the truck badly. It also surges or has a "choppiness" when revving the engine in neutral. It does have a light unevenness when you let go of the throttle from a rev. Have any thoughts???

on the video u said to take off the valve cover to see if oil was coming out of the injector, is that another way to determine if my heui pump is working if the if oil shoots out? how would you determine if the injector themselfs are leaking? i wanna say thank you for help me out on this cat engine.

a 1998 Kodiak with a 3116 HUI. I used it to move parked it 3 years ago and want to start it. Fuel evaporated from the tank, added 5 gallons. Tried pressurizing the fuel tank with 15 ish psi and no fire. What should I be doing? tia

Have one running like it's got a cam in it at idle... running it feels like a miss. On the test drive I go into Injection Actuation Pressure Test, Start Test, runs smooth as butter immediately. At 870 it ain't got the power to drive the mountains of course. I push up the pressure to max and she runs like a scalded dog. Pressures max, expected to actual match up. Ran like that for a bit. Cut off the test and the engine runs normal. Drove around a bit and still no problems. It was recently serviced. Any chance there was debris in the injectors and pushing the pressures blew it out or should I be looking into this more?

I have a 3126 with a bad HEUI. It looks like the one I -this video with the filter housing/reservoir on top. (Not sure what it is) so if I were to replace the pump do I need to do anything with the computer to reset it?

Hey brother thanks for Information I have a 05 freightliner with a c7 that currently has a slight miss at low idle my fuel pressure is good and oil pressure so I removed valve cover and I can see that 2 of my injectors are squirting oil from the actual injectector itself and nor from the seals below it , is that a sign my injectors are failing ? Also had injector harness unplugged while I cranked to prevent mess?

Have a 2001 renegade with a cat 3126, cranking but doesn’t start, runs off starting fluid but doesn’t continue to run, It’s been sitting for years so I think it’s either the transfer pump or the heui pump but both are expensive and idk how to tell which one, what kind of scanner do I need to check for codes?

I have generator c7 and I would like to know the maximum and minimum injector pressure

I'm using a gallon of oil each day i run my truck. 3126. going into fuel . How to check Heui or injectors.

sorry to bother u again. so took off the valve and cranked it over and i notice that one of the injector was shooting out oil through the side does that mean i have a bad o rings on the injectors? and when it start up that was the only one with oil shooting out. thanks

I have a 3126 i put a new heui pump on it it still will not start I have loosened the fuel lines one at a time and not fuel is coming in new fuel filter already installed

I have a3126heui that wont start after setting for 7 months, ran perfectly, when parked. thought that possibly air in injector lines, removed valve cover to get to lines, cracked lines one at a time starting at front of engine, nearest to radiator, very little fuel or air at injector line, and one of the lines no fuel came out. fuel filter pressure pump on fuel filter is pumped up. What do I need to check next? thank you.

Hello, how about I changed one of my injectors (#5) and vehicle is still losing power. Not sure if the ECM is bad or the HEUI pump is bad. Please help... Thank you!

Question: Is there a CAT ET or something equivalent for DYI'ers to help with things like this?

My truck has a misfire I have no way to communicate with the ecm I’ve replaced tue huei pump and stil cuts off when Im after 3rd gear ⚙️ check remove the valve cover to check for leaks seems like a lot of oil is coming out of the injectors but don’t know if that’s normal any ideas 💡

I have a 31-26 that is putting motor oil back into the fuel tank nude leaks no oil in the air no oil in the water but when you run it the oil goes from the engine back into the fuel tank any suggestions would be appreciated I have changed the O ring kit on the injectors no help

I have a motorhome with the C7 and having a fuel problem. Do you know how the ecm works in the 2006 winnebago? Where it is?

So, I have a 3126 with a intermittent issue. While under way, i hear will the engine "grunting", then for no apparent reason will stop grunting and smooth out. When it smooths out, I can hear the turbo more clear and it runs like a top. Most times it will not clear up, and for better words is a complete dog! I have done injector cups, and have changed the fuel filters 20 times or so.(in hopes it will run like it should). I have no check engine lights. I noticed the other morning, I started it and the rpms jumped to 1000 rpms or so as if I patted the pedal a couple times. It ALWAYS STARTS, and has never left me stranded. KOW. Any help would be great. I appreciate your videos. Where are you located?

I need some help here. My 3126 is down and its the system i think. Fires on ether. Crank no start. Just died on me backing out the garage fixing issue none related to this. Had a computer on it saying it met desirables on pressure while cranking. Found a 164-3 code. High voltage to iap sensor. Replaced iap and ipr(iap valve on pump). Any ideas

I have about 20 psi idling on a C7 with 20000 hours it starts very hard when it is hot. Could the oil pressure be the problem? the injection pressure test seems to be ok.

Hi there I have 3126b in an 2001 fl70, the engine is sputtering if the outside air temp is hot. Doesn’t matter if the engine is cold or hot. But on a colder day. The engine will run nice and smooth until I have to really put it work(climbing a hill loaded or something like that), i have changed the Heui pump, fuel transfer pump, the actuator on the heui pump, the oil pressure sensor, the check valve on the rear on the engine, the fuel pump in tank, and of course new filters and oil and lots of fuel. the truck doesn’t have any codes and doesn’t have any kind of smoke coming out of it. Do you have any suggestions for me to check next? Thank u

I bought a 2000 gmc 7500 box truck and it came with no ecm can i buy any ecm for the 3126 cause that’s the motor thats in there to get it to drive?

My cat cylinder no 3 ive changed theinjecto but to no avail so what could be the problem

Hey Adept I noticed that many youtube videos of 3126 engines use meui not heui. so does the 3126 use heui or meui?

So I'm getting a no-start issue after engine warms. Start when cold but after warmed up a can't restart it. Could that be a Heui pump?

I did that pressure test like you did and mine will to 3300 psi but when at that pressure the engine is surging or hunting is this normal? Thanks

My 2000 gmc topkick C6500 keeps cutting off when i hit around 60mph what could it be someone said maybe the pressure control valve.What do you think?

Ok I have a 3126 pulled the valve cover off no oil when u crank on it. So do I need to change the heui pump or is there something else to check before I order a pump???