1979 Superliner w/ ENDT676 Maxidyne 300 losing prime

[Joey Mack]

yep.... that's the one... Mark..  good memory...   

[Mark T]

He had a song years ago.  It was Froofie or roofie the dog or something like that.  Who knew it was inspired by starting fluid.  On a serious note, sounds like this dude's truck for some reason has no fuel pressure without some RPMs

[Joey Mack]

fuel pressure issue, is probable,  since it wont fire up after it shuts off while HOT..  compression is at its best at this point, so why... doesnt it fire back up???  and how does the fuel leave the pump so quickly??  and is there more to know?? if you ever put fuel filters on and didnt put enough fuel in them. it will run for a minute, but when fuel gets below the filter pad nipple, well....  there you are ...  dead... so you pull the filter and re-fill it and then pump the primer, if you have one,  and ...  off you go...  call me crazy.... jojo

[Mark T]

After reading this over and over (and factoring in it sat around for a period of time)  makes me think it has something in the governor sticking. Not the ideal thing to ignore.  Watch that video with  that guy that hates the Detroits . Might need it's injection pump looked at by a reputable pump shop.

[MACKS]

I would start with a new fuel pump,not that expensive or at least they weren’t and then go from there..

[theakerstwo]

I like using starting fluid but to put wasp and dirt doubers on the ground.I have used starting fluid for many years and the way any one should start a engine with it is stand back maybe 4 ft from the intake and have some one cranking the engine while you spray and this way you can fan in some air with the starting fluid till you hear if trying to gain some speed.Then go closer with the fluid till it starts but never feed it enough to make it knock or lock up.

[Joey Mack]

I know i made my comments about ether...  however, being from Maine, I have worked on many Mack's with 'propane injection' systems on them..  many were dissabled but some still had the switch in the cab .  it was labeled as... 'for cold starts only'  ...  there was a common propane torch bottle screwed to the injection system..  I know I may be contradicting myself, but I do not like ether in a diesel..   like i said before..  I dont mind learning , if i'm wrong about something..   just saying...  jojo

[theakerstwo]

The injection pump is easy to check for a sticking rack.This pump hear will have 6 screws holding the governor cover on.When you run the engine for awhile and then kill it and if it will not start back up remove the governor cover.You will see a cam like thing resting or close to a ramp that will move forward and back ward when you mash on the gas and then when you pull the stop it will move to the rearward of the pump.It should move back and forward when some one mashes the gas down and then pulls the stop cable.If it dont move then get some one to pull the injection pump and send to a repair shop who does them.

[doubleclutchinweasel]

Kinda off the wall here, but...

An engine with badly worn rings can sometimes be harder to start hot than cold, because of the heating/expansion of the cylinders causing more pressure leakage in the cylinders.  This is particularly noticeable if one or more of the rings is broken.  Have seen this before, but USUALLY is more likely in a gas burner than a diesel.  But, a compression check should rule that out pretty quickly.  Do one cold and another one hot, and see if there is a difference.

Dying when hot and not starting back...still sounds like fuel supply to me.  A silly question; if you warm it up and it dies, and won't start back, can you put the air pressure on the tank right away, and see if it starts back?  If air pressure forces enough fuel into the system to start it, that might indicate something.

I tend to agree with whoever said it before; it's probably something so simple that it's getting overlooked.  Or a pump.

[terry]

6 hours ago, doubleclutchinweasel said:

Kinda off the wall here, but...

An engine with badly worn rings can sometimes be harder to start hot than cold, because of the heating/expansion of the cylinders causing more pressure leakage in the cylinders.  This is particularly noticeable if one or more of the rings is broken.  Have seen this before, but USUALLY is more likely in a gas burner than a diesel.  But, a compression check should rule that out pretty quickly.  Do one cold and another one hot, and see if there is a difference.

Dying when hot and not starting back...still sounds like fuel supply to me.  A silly question; if you warm it up and it dies, and won't start back, can you put the air pressure on the tank right away, and see if it starts back?  If air pressure forces enough fuel into the system to start it, that might indicate something.

I tend to agree with whoever said it before; it's probably something so simple that it's getting overlooked.  Or a pump.

That is a whole lot of injector pulling to test all six cold then hot.   terry 

[Joey Mack]

I guess heat it up first, do the hot test, leave them out and tomorrow do the cold test...    jojo

[fjh]

On 7/10/2022 at 3:25 PM, theakerstwo said:

The injection pump is easy to check for a sticking rack.This pump hear will have 6 screws holding the governor cover on.When you run the engine for awhile and then kill it and if it will not start back up remove the governor cover.You will see a cam like thing resting or close to a ramp that will move forward and back ward when you mash on the gas and then when you pull the stop it will move to the rearward of the pump.It should move back and forward when some one mashes the gas down and then pulls the stop cable.If it dont move then get some one to pull the injection pump and send to a repair shop who does them.

I will suggest this once again Before you throwing a big bag of money at this! go to a parts store get some standyne fuel conditioner and Overdose the fuel tanks with it ! I" ve seen this stuff perk up pumps before its worth a try before pulling the the pump in my mind! As Glen is saying here if you have the cover off Providing this is an AMBAC Pump   you will be able to see if the rack is sticking by simply looking pulling the stop back if the rack does not return to idle after the stop is pulled and released there is definitely a issue in the governor or rack area! the The standyne lubricity formula MAY Help  free things Up !

Just sayin!

Worth a try!

[theakerstwo]

My 1 ton has a ISB cummins and it was surging and i used the additive and it was doing better in half hour.

 

 

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[Truckie Harbison]

Haven’t updated in a while cause I’ve been too frustrated. I tried several different things. I replaced the Fuel line from the tank to the filter and the filter to the lift pump. I bypassed the auxiliary filter, I eliminated the fuel tank and ran the line into a jug of diesel. I removed the lift pump, cleaned it, it has new check valves, and a rebuilt a primer and put on it. I just had the truck running ( had to start with a small squirt of ether) and cracked open the injector lines at the engine and made sure each one had fuel. Shut it off, and it wouldn’t restart. 
 

here’s what I noticed. When I crack each injector line open at the pump with the truck running, the engine makes a definite change in the way it runs and sounds, except when I crack open the the line for the third cylinder from the front. There is no change at all with that line. That leads me to believe that cylinder isn’t firing and could be the reason it doesn’t want to start or idle at 600 or so rpm’s. 
 

Any thoughts?  I figure I’ll pull the injector and have it tested m, hoping that it’s plugged, and also do a compression test. 

[mrsmackpaul]

Well a few thoughts here from a bloke that knows SFA

I dont think the injector would be blocked, the diesel system is postive displacement, what goes into the injector line feeding the injector must come out 

So am wondering if that injector is really faulty and just dribbling away or stuck and letting the fuel return straight to the tank

Compression test wouldn't hurt and only takes time to perform and the correct compression tool

I am a loud mouth that said its nothing more than a fuel leak so perhaps don't listen to a word I say 🤔

I guess report back when you have some more findings

I would expect to find around 450 psi when checking the compression and all within 50 psi of each other 

Maybe pull the suspected dud injector and clamp it on the fuel line upside down and see what the spray or dibble is like, just keep your face and fingers etc away from the firing line, or for that matter all your body parts 

 

Paul

[Truckie Harbison]

Thanks for the input. I’ll have to do some searching online to see how to pull the injector and do a compression test.  

[Dave K]

I always like to have a fuel pressure gauge permenetly installed on each  truck or machine it predicts and prevents so many problems when out on the job..  D K

[BOBWhite]

Compression test and injector test. You can send them off to someone who knows what their doing but if your cheep and stubborn like I am I'd rig up a tester yourself. There are several articles about how to turn an old hydraulic pump jack into one or you can buy one off amazon for a reasonable price. 

When testing you're looking for 1. Spray pattern, I have a great video that explains what your looking for here: 

Next your looking for injector cracking pressures, its best to find a book describing what these pressures are but if you can't its more important that there within about a 5 to 10 pound difference between injectors (the less difference the better)

Not too sure what brand of injector Mack uses but I would imagine its the same brand as the pump, there may still be kits available and you could rebuild them yourself if you have the proper specs and your wife doesn't mind the smell of diesel fuel in the clean house. Injectors might not be the problem but their old and its something to look into on older diesels, well balanced injectors make a world of difference. 

 

 

[Truckie Harbison]

I haven’t updated this post in quite a while.  Swapped the injector pump and the truck runs like a champ now. 

[doubleclutchinweasel]

Thanks for the update. Glad you got it sorted out. 

[fjh]

Yup good on you For posting your fix! All these type of posts spread the wealth of knowledge of stuff to try when chasing down issues like this! The post indicates that the injector was stuck open in my brain compression being pushed back into the fuel system! GOOD JOB!