Stalls, then won't crank - then does

[cattlerepairman]

I am looking at this logically and thought I'd poll you for thoughts:

- truck starts as soon as button is hit. Did not have issues in years.
- uneventful 50 mile drive BUT I noticed that the power to the dash came off intermittently (gauges would go to 0). Switching accessory switch on and off seemed to fix it.
- rolled to Stop sign and engine dies. Cranks fine for first restart attempt. When I press the button again, starter clicks, lights dim, just like it would with a low battery.
- accessory switch is ON but I notice 0 fuel pressure at the tank (I have a gauge there). Tank is full, so in tank pump likely off.
- helpful truck driver offers boost (I was in the middle of the road). I am positive that both batteries are good, alternator charges, battery cables are new and tight, but thought...what the heck...and hooked the jumper cables to one battery (12V).
- get into cab, acc switch on, starter button - purrs to life as if nothing had ever happened. I am thinking @#$%^& !!!!!!
- drove her home and she has started as usual ever since. #$%^&*( !!!!

I am thinking the issue is the accessory switch.
Is it possible that it closes "partially" and shuts off part of the voltage? That would explain the low-battery-like behaviour. With the in tank pump off it perhaps decided it did not want to stay idling when I rolled to the stop?

HOUDEL explained the setup of the accessory switch in his post here: https://www.steelsoldiers.com/threads/current-load-in-accessory-master-switch.5638/
First post. If the switch does not reliably supply circuit #27 (starter button and fuel pump) it would explain my symptoms!

I pulled the acc switch and...well...it's a switch. Can't open it. Cleaned contacts, plugged everything back, same with starter. Everything works, but it did so before I pulled it.

Plan is to replace acc switch and starter button (for good measure). Any other ideas from you fine folks?

 

[M37M35]

I think you're on the right track.

Is it possible that it closes "partially" and shuts off part of the voltage? That would explain the low-battery-like behaviour. With the in tank pump off it perhaps decided it did not want to stay idling when I rolled to the stop?

Yeah, it can act like that if the switch contacts are burnt/corroded.
And it makes sense that it may not stay running without the in-tank pump.

I'd also double check every ground you can find.

 

[SCSG-G4]

I've had one of those switches apart and fixed it, but it is a lot easier to simply swap it out. To work on it, it's necessary to pry the can apart to get at the inside stuff - but the real fun comes when getting it all back together after the fixin' is done. It's been eight years or so since I did it, and I did not take any pictures.

 

[fleetmech]

Twice in recent memory, I've found circuits showing voltage but not able to carry any amps. First was on my deuce, the turn signal switch contacts were partially burnt inside and (iirc) would show 24 volts at the flasher, but not carry enough power to actually get the thing to flash. Second was on a marine refrigerator, where a visibly perfect glass fuse was allowing enough power through to light the tiny 'power' light but not enough to run the compressor. The circuit showed 11.5 (12v system, and it was fully charged) volts at the circuit board, but the fuse was 'open' on my DMM.

Electricity is a strange beast.

 

[Jeepsinker]

Check the battery to frame ground to make sure it isn't breaking at the frame connection, and check the #10 wire connection at the magnetic relay above the starter. One of those could cause your intermittent loss of power, but neither should make the truck die. If it won't stay running without the lift pump working you have another serious issue.

 

[cattlerepairman]

Will do and report back.

 

[cattlerepairman]

Check the battery to frame ground to make sure it isn't breaking at the frame connection, and check the #10 wire connection at the magnetic relay above the starter. One of those could cause your intermittent loss of power, but neither should make the truck die. If it won't stay running without the lift pump working you have another serious issue.

Frame ground - check. Feels solid, tight.

Relay, cable #10 - check. Not broken, not loose.

Started as usual on first touch of button, ran fine, after about an hour the gauges flicked off again. I could keep them on by holding the accessory switch up with my thumb while driving.
I am really suspecting it is bad contacts inside the accessory switch.

Jeepsinker, my truck usually idles and runs fine with the accessory switch off. I do not know why it did not the other day. Perhaps it needs the in tank pump when it is sucking a lot of fuel when running wide open (which I did). Maybe it does not get sufficient fuel or at enough fuel pressure when it then suddenly idles down. In any case, this did not happen at all today. I did chenge the fuel filters not too long ago, so they should be fine. Aluminium tank (A3), that I cleaned meticulously and no suspicious fuel went in.

 

[Jeepsinker]

Ok, it is the switch then.

 

[cattlerepairman]

I wanted to provide an update, in case someone experiences similar issues.

- the aux switch ("main switch") was defective; no more sudden switching off of all gauges and the in-tank pump while driving, with the new switch installed. I have not opened the old one (yet) to find out what the innards look like.

- the batteries are only 3 yrs old (stickered 08/17), checked ok for voltage (24.6V), but could not supply the cranking amps needed. I hooked them up individually to my NOCO GENIUS G26000 in battery repair mode and let it do what NOCO does; some sort of pulsing and high voltage charging, not sure, to de-sulfate and fix plate problems. After this, she cranks like a champ. For good measure, I brushed the battery contacts and cable attachment points and put some di-electric grease on everything.

I took her for a 300 km test drive today and she never missed a beat.

Also, the LDS is quite a bit thirstier than the LDT was, FWIW.
I could not get enough of the soundtrack today. On long inclines, the bark of the LDS is simply awesome. It sounds a bit like a straight piped large Cummins. I have a climb that ascends in a V shaped rock cut....my god, did that racket put a smile on my face!

Oh, and when you remember to not trust your fuel gauge and make a mental note to go fuel up AND you switch on the aux switch AND you can hear the in-tank pump wayyyyy louder than it should be.....head to the very nearest fuel station! Alternatives involve 4 way flashers on an awkwardly parked army truck, a fuel can and a friendly person to give you a ride. Ask me how I know that!

 

[Jeepsinker]

Did you figure out why it won't run without the electric pump running? It should run all day with the entire electrical system shut off, including the in tank pump.

 

[cattlerepairman]

Did you figure out why it won't run without the electric pump running? It should run all day with the entire electrical system shut off, including the in tank pump.

It does run without the pump..it actually starts fine without the in tank pump. As far as I can see there is one scenario where it appears to at least occasionally die with the in tank pump off and that is going from a longer stretch of WOT to idle (which is exactly the situation at the intersection it died at). Normally I would think "filters" but they are almost new., with a clean aluminium tank.

 

[glcaines]

I know you've solved your issue with the switch. However, I wanted to share some advice when checking for poor grounds. If I suspect a poor ground, I take a jumper cable directly from the negative pole of the batteries and run it first to the engine and then to the chassis. This eliminates a lot of connections. If the problem goes away, I know where to go next.

 

[Jeepsinker]

Sounds like something in the governor is sticking or worn and its unable to compensate for such a large and quick deviation. I've had this issue before a few times. Sometimes it just does it because of air in the fuel supply side. A small air leak will do it, or having recently opened the fuel system and not ran it enough to purge all the air yet. Sometimes a 30 mile drive isn't enough.
Other times I've seen it is just from trucks that sit a lot or have sat for a long time. Getting them good and hot, fresh oil change, then running them hard will fix it.

 

[cattlerepairman]

Cold start after sitting for three days, with in-tank pump disconnected:

Showing fuel pressure from in-tank pump (about 8 psi):

 

[frank8003]

Did You pull the pump and put a proper OUTPUT hose on it?
One can find all kinds of interesting stuff if one looks into things.

 

[cattlerepairman]

Frank, good point and, yes, only a little while back when I swapped tanks! I cleaned the in tank pump and put a new hose on. Made sure she works.

Sent from my SM-G950W using Tapatalk

 

[frank8003]

Perform the work of the simple stuff first.
Deuce will start and run with a faulty/dead/malfunctioning in-tank pump all the way up to the time one breaks into Her system to change filters or a vacuum leak, or whatever.
Not good for the booster pump but will start + run. She was built to go to war.
Pull it apart and fix it, 5 hours tops.

 

[fleetmech]

Not exactly the same engine, but I had an old 12v Cummins that would occasionally stumble out if you went from heavy load to curb idle in a snap. I've also seen some pulling trucks do it. I can tell ya its not unheard of...

One or another of the fuel governing devices snapping to full close(or at least going past idle), then hanging up slightly as it tries to reopen to idle flow, perhaps.