MR 688 electrical trouble shooting. No crank

[Ryanp]

JoeH,

I did fanangle the wire terminals so they get a good grip on the relay. Seems to be pretty secure now.

I believe I have the breakers/ relays/ fuses in correct order to get it going? There are still some missing but I robbed them from spots like the heated mirrors for now. Is there a test procedure to double check power on the eecu? I do have 12v at the CB-40 and I believe I stuck a 20A in there for now.

I had one battery on to test things out and get the starter to engage. I do have 2 more that will get tied in before I plan on starting it.

Blink codes are 2-3, 4-1, and 1-4.

Trans codes are d1-2314, d2-3312, d3-1412, d4-4513, and d5-4512.

When I looked up the trans codes off a PDF I found online there were a few that weren't listed?

 

 

 

 

[JoeH]

2-3 intake air sensor

4-1 vehicle speed sensor (you have trans codes, so this will likely be linked to whatever is going on there)

1-4 ambient air temp sensor

 

To verify EECU power, there's a bolt holding the wiring harness to the engine lock below the EECU.  Takes a 10mm socket. Remove that to create enough slack to undo the 2 plugs into the EECU. They're pretty odd how they unlatch, the end the wires come into needs to lift waaay out once you undo the retainer lever. On the bottom plug, pins 10, 22, and 41 should have 12v power sourced from one of the 4 big relays hanging next to the VECU in the dash. You are probably fine on power to those terminals, I see you have a CB in the #40 slot now.

[JoeH]

https://www.emanualonline.com/material-handling/industrial-equipment-tools/vehicle-parts-accessories/transmissions-gearboxes/allison/4000-series/allison-transmission-4000-series-full-service-repair-manual-emo-171892.html?currency=USD&product_country=US&product_id=171892&placement=&adtype=&keyword=&gclid=CjwKCAiAl-6PBhBCEiwAc2GOVLpvhBeptBaObblZHzI6nRoPzRU1hylOl8ZohDFiQfdTkXVURgzllxoCMOYQAvD_BwE

I believe this is the transmission manual I bought. Worth every penny. There's about 10 or 15 pdf files that it comes with for different books, but the information is very good, and has the DTC codes in it.

 

[Ryanp]

Well kind of made some progress the last 2 days on the truck. Got the fluids topped off and double checked a lot of the sensors and what not. Ive got the batteries pretty well charged up it seems to be rolling over decently quick. Still cant get the thing to fire off good. Im thinking there is a fueling issue? We've got 12v on the eecu. My codes are cleared up from what they were. There was a 9-2 and a 6-3 but I'm back down to the 4-1 and 1-4 now. Also there is a 3-4 that seems to be consistent. I think the 3-4 is to do with the sensor on the timing cover that tells engine speed or cam position? This sensor was missing when i got the truck so I got a new one for it. Now ive read that there are shims to get the sensor the correct distance from the gear? I do not have any shims on it. Wondering if this would affect starting/ running because the eecu might not know the engine position?

We bled the injectors out pretty decent, 1 or 2 of them towards the front of the engine didn't want to bleed,(nothing came out, air or fuel) they would bleed fuel from the bottom of the lines but not at the top. We didn't try too hard to get the lines loose because we were afraid of twisting or hurting the lines. The nuts were backed out decent but the line was froze in the head must be.

Right now it rolls over good and it sounds like one cylinder may be trying to fire. Getting white smoke out the stack and short black puffs I attribute to the one good cylinder. Hit it with ether and it will take off but only as long it has ether. Tach comes up to rpm so i'm thinking the sensor on the front is working?

I am wondering if there is a way to test the coils on the fuel lines or if I need to be looking deeper into the block at the pump/cam set up? Could the timing be off some how? Also I dont think I've completely ruled out the electronics possibly pulling voltage down to 9-10v range when cranking. 3 new batteries and a good jump box. The draw seems like a lot.

[Joey Mack]

No ether!!!!   loosen at least 2 fuel lines at the head, they are tough so pull on them... 2 turns is enough.. then pump the hand primer until fuel/ air bleeds out. lock that one down, pump again til the next one bleeds then lock it down...  youre done.... the cam sensor does have a teardrop shim, however this engine will start and run on either sensor, but wont run good..  check the wires in the sensor plugs and make sure they are healthy.. the one in the flywheel housing is always in bad shape..  make sure the wires arent frayed or brokken, follow it up the loom to find the break, pull gently and hope for a break.. then fix it... jojo

[Ryanp]

Thanks jojo, I will look into that harness further. Mine is definitely dry rotted and sun baked near the flywheel housing. We had 4 injectors bled good, just the front two giving trouble. I will give those last 2 a yank in the morning and get them done.

[Joey Mack]

well if you had fuel bleed at 4 of them , thats enough..  when the engine starts just hold the throttle down a little and wait for it to clear out, it will!..jojo

[Joey Mack]

do you have any 8-? codes present?  8-1 through 6 is the EUP's.. 8-9 is basically all of them faulting..  jojo

[JoeH]

[JoeH]

[JoeH]

[Joey Mack]

ok.... 9-2 code is a bitch but simple to start with... clean all grounds,, dash panel grounds, starter ground, engine block ground, left side in front if the starter), frame ground, behind left steer tire, the ground breaker,, jojo

[JoeH]

Appears your VECU power is dropping out.  This is likely the trigger for the 6-3 code, as the VECU dropping out will obviously disrupt data communication.

[Joey Mack]

grounds......

[Joey Mack]

great postings, JoeH...  jojo

[JoeH]

3-4 is engine position sensor, located on the timing cover. Camshaft.

[Joey Mack]

I wish I knew MR's like I do CH,RD,Cl ect..  fuse 41 is the EECU fuse in the trucks I know,  25amp, check your's...  jojo

[JoeH]

Go to your dealer and order book # 8-211!

[Joey Mack]

https://newsmanuals.com/download/mack-iii-8-211-v-service-manual/

[Ryanp]

All right the grounds and power wires have all been cleaned up. I have a wire wheel on a cordless drill that is great for shining those things up. Frame ground and engine grounds are wire wheeled up and tight.

Tested continuity on the wires from the timing sensor and flywheel sensor back to the eecu and they seem to work. Both (4) wires seemed happy.

Batteries hooked back up and it seems to be mostly happy. 9-2 went away, 6-3 went way, 3-4 went away. The only codes that are still on seem to be the 1-4 and 4-1. Nothing that would keep it from starting is it?

Now we've been bleeding the injectors at the head and I understand these are difficult to bleed but I feel like were missing something. I can get one cylinder firing and sometimes two will grab but it just doesn't want to take off. Its got so I can let off the starter and It will chug along for a good 10 seconds maybe but it doesn't keep running. Mostly a decent amount of grey/white smoke out the stack, seems when the other 2 cylinders fire we get a good puff of black. We can get 5 of the lines to bleed good at the head, the 6th seems a bit set up and we didn't want to twist it off.

Pulled one of the EUPs to see what I could see and it looked pretty happy. Nothing dirty really, thought I might see rust from it sitting before I got it. Pics attached. I did manage to get the dirt/ oil out of the bore before I put the EUP back in.

I am considering my issues now might be injector related? This truck did sit for probably 5 years or so without being ran. What issues could that cause on an engine like this. Haven't pulled any injectors yet, I understand they have issues with the holders in the head or something?

Also I will have to download that 8-211 manual to my laptop! Thanks for the link, looks like there should be a ton of info in it.

[Joey Mack]

I believe 1-4 is 'ambient air temp sensor'  4-1 is the speed sensor in the tranny tail shaft.  I see you took an EUP apart, I dont know any one who has the 5 pointed torx bits that I have, too funny...  Mack has a repair kit for that..  as far as getting fuel to bleed out of the lines at the head, it shouldnt be hard to do, loosen real good, pump hand primer til it bleeds, lock it down, go on to the next.  Check voltage at fuse 41 while cranking the engine, if it gets below 10 volts, the EECM wont fire the EUP's..  so for now keep it simple, if voltage is low, I have a trick for that..  Jojo

[JoeH]

That you have it chugging along somewhat means the EECU must be working to some degree.  Pull the valve covers, time to check mechanical bits.  Check slop on rocker arms. Bent pushrods? This engine could have been over revved.

 

Oil pan gets you a view on bottom of the engine: camshaft, debris in bottom of pan, etc. Valve covers tell you what's going on above.

Edited February 7, 2022 by JoeH

[JoeH]

Though I'm not sure if it's possible to over rev an automatic? Unless the engine came from a different truck...

[Onyx610]

Check fuel pressure and fuel system for obstructions/sucking air. 

[Ryanp]

Well kind of made some progress today. Ran through the valves and they were all pretty close. A few were maybe 3-4 thou off. Ran It again, basically the same. Ive got probably 3 cylinders firing. This afternoon we fired it up and I shorted some of the EUPs as it was stuttering and trying to run. We thought it would show us what injectors were firing and what ones were not. Shorted cylinder 1 and it shut off immediately. #2 no change, #3 shut it off again immediately. Cant remember what the rest did but I plan to take the 5 that I haven't had off yet to verify the little parts inside move. Probably let them soak and get freed up? Not sure how sensitive the EUPs are but I've been keeping things clean inside. Got #2 off and sure enough that little square inside is froze up.

Currently running on 3 ish and fills the shop in thick black smoke in about 2 minutes. I read that these things can get stuck open is that right? Or am I more likely looking at a set of injectors?

Thank you all for the help, Its been great to have things to try. Learned a lot more about Mack engines and controls than I probably care to Lol.