Potential new owner, need help with no start truck!

[MrGoldman]

I have been looking for my first LMTV for about a year and want to start with a "cheap" truck as a toy for now and then buy a C7 variant in a year or 2

I have found a semi local truck and made a tentative deal to purchase it at a great price pending me getting it running first. I'm not a formal mechanic but I play one most days for fun, I buy and sell a lot of generators and drash trailers currently, the big trucks are new to me.

The truck is a 1998 with 20k miles on it and the CAT 3116.

The truck was driven into its current storage location and sat with no batteries for about 8 months.

When trying to start the start button causes a loud click in the lower driver engine area but the starter does not turn over. I've checked the following:
1. Batteries are good. load tested.
2. One battery cable needs a new end, but I sanded and clamped it on.
3. Oil looks good, does not smell like fuel.


My tentative plan of action on Tuesday is the following, please let me know what else I should be looking for:
1. Fix battery cable and put truck on 24v 60a charger
2. Clean off starter area with Hotsy and dielectric the connections to the starter and check grounds.
3. Check stater solenoid, Does anyone have a part number for a new one at Napa or anywhere I could get one in Denver Monday?
4. Pull glow plugs and make check cylinders with camera scope, are these easy to remove?


The truck has some "creative" mount for the alternator, can anyone tell me what is missing here? Part number for replacement part would be great.

Anything else to look out for once I get it running apart from/ blowby and alternator charging?
What model would this be? anyone have the link to the TM?

 

[Third From Texas]

loud click in the lower driver engine area

99.99% of the time, that's low voltage/bad battery.

Batteries are good. load tested.

Seems like that's often the story.
Then it turns out to be low voltage/bad battery(s)

 

[Third From Texas]

And that would be an A0.

The TM's are here:

M1078 TM's

Listed below are a number of the TM's for the M1078 trucks. To save them to your computer, right click, select "save as" m1078_TM 9-2320-365-10.pdf TM 9-2320-365-10 for the M1078 series trucks. m1078_TM 9-2320-365-20-1.pdf TM 9-2320-365-20-1 for the M1078 series trucks. m1078_TM...

www.steelsoldiers.com

 

[Ronmar]

Ok, it looks like a 98 M1078 A0
that looks like the standard alternator mount, it is missing a drive belt…

should be a couple of things going click when you turn on the ign switch, and when you push the button. The loud click under the cab is a good sign that is probably the aux start solenoid. That means you have neutral start from the trans as well as the other interlocking circuit in the start circuit Driven by the low oil pressure switch(should also have a low oil P idiot light).

the aux start relay on the drivers frame completes a circuit from the main 24V lead attached to the start solenoid. They also added a starter overtemp sw in some models and that sw is in that circuit. If your starter has one there is a plug/receptical on the front end of the starter motor. And an associated plug from the adjacent wiring harness. If it doesn’t have a thermal sw receptical connector on the starter the wire harness plug is still there on the A0, it just has a jumper in it…

bad electrical connections are a common issue on these trucks. I would start with ground , 12 and 24 batt connections at the batts,

ground and 24 at the starter motor and solenoid. The main chassis ground strap runs from front end of starter motor to drivers frame, make sure these are clean.

behind cab between spare and air filter there is a polarity box with 6 large wires on in. 24 and 12 battery and alternator on the top and bottom terminals and 24 and 12 load feeding up to the cab power panel. There is a dedicated 24v line from battery to solenoid, and a ground lead from battery to a device called a shunt(used to measure current flow) just to the rear of the polarity box, and from there to the starter motor housing. There is a recent thread showing these two devices… they are out in the weather and bad connections here are common.

resistance resists current flow , so you can have full voltage at the end of the circuit until you start to do some work and pull some current thru it and like a kink in a garden hose the voltage falls on its face. Rapid clicking or a single big click when you use a switch is a common symptom, enough current flows to make the click, but not enough to spin the starter… a voltmeter will show this clearly. Hookup a meter to the ground and 24v testpoints in the power panel. Turn on ign, how much does the voltage drop?
press the starter button again how much does it drop?
connect your meter to the ground and 24v terminals on the starter and do the same thing. What does the voltage do when you push the button and things go clunk. Stays steady maybe the starter solenoid is bad, voltage falls on its nose bad connections back thru the circuit to the batteries…

the grounds on these trucks are all trash, they installed them after paint, and relied on a star washer to pierce the paint and make a circuit. Strip them all to bare metal around the bolt/stud, chuck the star in the trash and re-assemble with copper coat or dielectric grease, lock washer, nut and paint over them when done.

starter motor to drivers frame.
alt to pax frame.
pax frame to cab tunnel behind grill
inside cab from tunnel to dash extreme right end(behind grab handle)
cab end to ground test point in power panel.

Good Luck!

 

[Ronmar]

The schematics in the manual are in an unusual format and can be a little hard to follow As the start circuit hops around between several pages. Here is the A0 start circuit condensed to one page…

 

[hike]

Tuesday's plan:

item 4— CAT 3116 doesn't have glow plugs. She uses an inlet air heater—

 

[MrGoldman]

Thanks everyone for the help! Ill change my plan a bit based on the info provided.
-Bring new batteries, does it need 4D or will it start on group 31's?
-Bring disc sander to clean grounds
-Bring remote multimeter leads to check voltage drops.


@Ronmar when you say its missing a belt is it supposed to be a double belt system? Where does the belt tension come from? the shelf bracket mounting the top of the alternator is a fixed hole, so it has no adjustability.


The real question is for $5k running and driving is this a good deal, or should I keep looking? Some nicer ones coming out of Yermo this week but dont know what they will go for yet, I know this one will take more than that to maintain but its a cheap starting price.

 

[Ronmar]

A pair of group 31’s in series will work just fine, it is what cat specced for these engines. The 4 batts were to meet a milspec requirement, but the alt was too small to support them properly. A pair of 31’s is what I use, and are a great match for the alt.

Yes 2 alternator belts, there is a tensioner pulley and adjustable bracket located below the alternator. You can just see it at the bottom of your alternator picture…

As mentioned no glow plugs, and this model did not have a intake grid heater. They put in a direct ether injection system for really cold starts.

at 5K if you can drive it away, it is probably worth that in parts…

 

[MrGoldman]

A pair of group 31’s in series will work just fine, it is what cat specced for these engines. The 4 batts were to meet a milspec requirement, but the alt was too small to support them properly. A pair of 31’s is what I use, and are a great match for the alt.

Yes 2 alternator belts, there is a tensioner pulley and adjustable bracket located below the alternator. You can just see it at the bottom of your alternator picture…

As mentioned no glow plugs, and this model did not have a intake grid heater. They put in a direct ether injection system for really cold starts.

at 5K if you can drive it away, it is probably worth that in parts…

Good to know, that makes it much easier. Ill bring a fresh set of Napa 31's with me.

Ill bring a second belt as well, do you happen to know the easiest way to find the part number? I could always get it on tuesday with the other belt in hand.

thanks for the insight, figured I could have my fun with it at 5k and sell it at a later time with some leaks fixed and buy a nicer one.

 

[Ronmar]

I wouldn't worry about the belt right away, there is a parts spreadsheet link at the top of this LMTV forum...

 

[Third From Texas]

Here's the set up dual batteries.