Jump to content

2006 mack ai-427 misfire


Truecountry
 Share

Recommended Posts

This is my first Mack engine I ever worked on ...

I took a job working for a construction company and they have all Mack trucks my old company had all cummins or caterpillars

Ok this problem with 2006 mack with ai-427 happened before I went to work with them .

Heres what I know number one cylinder electric fuel pump came apart and had a misfire on 1

fuel pump was replaced still misfire ..injectors were swapped 1 to 3 and still misfire on 1

Ok now I download service and repair manual for the engine and start checking for fuel at pump check for electrical pulse at pump 

I pull both valve covers and start turning flywheel to do a check on overhead valve adjustment and 4,5,6 rocker shaft is broken seems bolts backed out once and they lock tite them back down .

I get another rocker shaft remember this is 4,5,6 still misfire on 1 after shaft was replaced im not throwing parts at this I want to fix this 

I hook computer to truck and I see only one code over voltage or open engine brake I cant remember code 

can a power leash engine brake cause misfire on number 1 or injector cup? 

 

Link to comment
Share on other sites

So you have replaced the#1 unit pump and injector and still missing in number 1? No fault codes for unit pump? Can you feel the pulse in the injection line in number one?

As far as the rocker, make sure you loosen the 2 rocker stand bolts when you torque the rocker shaft down or it will break the bolts/shaft again.

How about the valve adjustment in number 1? Nothing wacky going on there? I've seen the pins break in the engine brake plunger and cause a miss, but usually it will only miss after the engine brake is activated and a short period thereafter until the oil has time to bleed out.

If you have no electrical issue causing the unit pump to not fire, then you are down to a compression issue. You could always swap the rocker front to rear to eliminate an issue there.

Link to comment
Share on other sites

I didn't replace unit pump another older mech did swap new one and swap it with number 2 and he also swapped injectors 1 and 3 

Nothing wacky on valve adjustment on number one 

I do have spare rockers to swap with number one but this thing is misfire from cold start sounds like exhaust 

Link to comment
Share on other sites

3 hours ago, Truecountry said:

I pulled the pump once that's is ..but couldn't get cup out and I also felt a slot cut in cup oblong which way does that go up or down 

That slot faces the passenger side. There is a pin in the block that rides in that slot. If the pin breaks, the roller can turn sideways which will destroy the roller and the camshaft. 

  • Sad 1
Link to comment
Share on other sites

22 hours ago, Mack Technician said:

You said in your first posting “#1 pump came apart and had a misfire”. Did the EUP (electronic unit pump) shed its spring? Is that what you called “coming apart”. 

yes other mechanic said spring came off ..

 

On 2/15/2020 at 9:05 PM, steeler said:

So you have replaced the#1 unit pump and injector and still missing in number 1? No fault codes for unit pump? Can you feel the pulse in the injection line in number one?

As far as the rocker, make sure you loosen the 2 rocker stand bolts when you torque the rocker shaft down or it will break the bolts/shaft again.

How about the valve adjustment in number 1? Nothing wacky going on there? I've seen the pins break in the engine brake plunger and cause a miss, but usually it will only miss after the engine brake is activated and a short period thereafter until the oil has time to bleed out.

If you have no electrical issue causing the unit pump to not fire, then you are down to a compression issue. You could always swap the rocker front to rear to eliminate an issue there.

swapped out rocker and checked did valve adjustments again on number 1 and still missing ..cracked fuel line at eup and its plenty of fuel pressure there ..even got someone to turn engine by ratchet adapter on flywheel to see the valve train go up and down .pulled eup and cup saw pin you were talking about its there ..turned flywheel to look at cam and I see nothing wrong

I hook computer up and no codes active or unactive even tried to do a engine compression test with computer but it didn't do right ...did cylinder cut out and its #1 

recalibrated the 2 eup that where swapped and still #1

Link to comment
Share on other sites

3 minutes ago, Mack Technician said:

Be careful when putting cam roller followers back in, they’re ceramic. They can crack if you drop them into the bore and they strike the lobe. 

I was but remember im 2nd person to work on this other guy thinks im there to take his job and im not ..im there to fix what he cant help out save money 

Link to comment
Share on other sites

2 minutes ago, Mack Technician said:

It’s really easy to drop the pan for a look and you’ll see any dirty secret. 

ok will do in the morning ...like I said im new to working on macks but I have seen some things with cats and cummins noone could explain

ive called their gurus this is person to talk to and did it and it stumped them hydraulic wise on equipment ….engine is air fuel compression ive seen intake valve break from one cylinder end up in another turned to side making a light tapping sound every tech has seen something none can explain ..yes sir I will drop oil and pan and see 

Link to comment
Share on other sites

I’ve found bad valves without digging too deep. Usually I pull the rocker shaft, let the valves close and pressurize the cylinder through the injector bore with a rubber tip blowgun. Be interesting to see how much blowby slippage you’d observe with pan off pressurizing cylinder.

Wouldn’t stick any limbs in there while engine can spin from air pressure. 

Edited by Mack Technician
  • Like 2
Link to comment
Share on other sites

I just read this 

These ASET engines are really bad an having bad harnesses because of how they lie so close to that exhaust manifold. The shield can only hold back so much heat. I wouldn't be surprised if you remove the shield, use an air gun to blow all the junk that built up there, and lift the harness it will be sticking to the galley that the harness rests in. If so, expect the possibility of a bad harness

Any way to test that ? voltage ?

Link to comment
Share on other sites

4 hours ago, Truecountry said:

I just read this 

These ASET engines are really bad an having bad harnesses because of how they lie so close to that exhaust manifold. The shield can only hold back so much heat. I wouldn't be surprised if you remove the shield, use an air gun to blow all the junk that built up there, and lift the harness it will be sticking to the galley that the harness rests in. If so, expect the possibility of a bad harness

Any way to test that ? voltage ?

You would normally see a fault code if you have broken or shorted eup wires. I've seen a few have chafed wiring where you describe, but all had faults. Those harnesses are actually pretty solid, much more so than the MP engines for sure!

This is smelling more and more of a valve train issue.

 

 

Link to comment
Share on other sites

8 hours ago, steeler said:

You would normally see a fault code if you have broken or shorted eup wires. I've seen a few have chafed wiring where you describe, but all had faults. Those harnesses are actually pretty solid, much more so than the MP engines for sure!

This is smelling more and more of a valve train issue.

 

 

If It were Valves or  a power leash stuck  I would expect to see some smoke of some sort blu fuelly smoke lack of compression  or Black Over fueled  (stuck injector tip!)

Just my opinion!

Edited by fjh
  • Like 1
Link to comment
Share on other sites

Check your fuel pressure too. I’ve had engine misses from low fuel pressure as the engine meets the threshold of stall-out. The cylinder on the end of the lunch line would normally be the first to suffer. Your already poochy running on 5 so you’d be none the wiser by observing engine power performance. 

Be sure to list your fix!!!

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...