2000 M1088A1 w/3126 no start

[ckouba]

I am about to start tearing through the troubleshooting routines but if anyone has any quick check recommendations, here's the situation:

I went to work on it this afternoon and it started fine. Ran it about 8 min, just to move it slightly and air up. Raised the cab.

Finished working on what it was that I was doing. Lowered the cab.

Started next task, needed to move it slightly again.

No start.

Dash lights up as usual, looks like ignition is on and things are normal, and I hear a relay click when I hit the starter. Nothing happens with that click of the starter though, and I need to figure out if I am hearing just the one in the cab or the one on the starter too.

It has always started well- the starter sounds strong and batteries spin it well. Has always started on the first push of the button, was nervous about a lot of things but a no start wasn't one of them.

Drop a line with suggestions if you have them.

Thanks in advance...

 

[NDT]

I would grab my voltmeter and soldier b and have them press the start button while I measure for voltage present at the starter solenoid and relay.

 

[Ronmar]

What NDT said, but add to check the voltages at the PDP test points While the button is being pushed.

there should be 2 clicks when you push the button, a relay in the PDP and the aux start solenoid under the cab on the drivers side frame rail near the power steering reservoir. It is about the size of a tennis ball and when it clicks it should send 24V to the starter solenoid. I would measure for 24V to ground from both the large terminals on that aux relay. If y0u have 24v on one, try jumping the large contacts with a screwdriver. Doing that should spin the starter. If it dosnt, you may have a bad connection or a problem with the starter.

y0u can try rapping on the starter with a hammer to possibly free it up.

 

[Third From Texas]

To date I had this happen once with both my trucks.

On the M1078A0 it was a battery that had a bad cell and was under-volt (11.7v). The others were fine. I pulled the bad battery and the other one outboard, and just ran with dual batteries.

Just yesterday I resolved the "no start click" on my M1079A. After it was driveway bound for three weeks, and $500 pair of batteries, it turned out to be a grounding strap with a rather suspicious end that was bolted up inside the frame rail.

But I just started at the batteries and worked my way out from there. When we found nothing out of place after screwing with it for two weeks, I caved and purchased batteries. And of course, when that didn't resolve it (all four batteries that were on the truck were showing 12.3v but some folks said even that isn't enough) I went back thru every connection from the batteries to the starter.

Have someone press the start button while you listen with your head in the wheel well. See exactly where the click is coming from...

 

[ckouba]

Thanks for the suggestions.

In an effort to determine if it was starter side or wiring side, I jumped the solenoid input and the starter spun the motor. Just for laughs, I tried the dash starter button and it worked. Truck starts again as normal. I feel like I still need to confirm that it's getting 24v at the solenoid and check the wiring back from there.

Might it also might be indicative of the solenoid going bad?

 

[Suprman]

I find a lot of ground issues in these trucks. The main ground goes thru a current shunt up by the polarity box. I usually add a large ground wire from the batt negative to the main frame rail. If you lift the relay panel there are ground wires that go to the dash. Good to clean upwhere they bolt up and use a lock washer.