M923A2 Starts only with Ether, and stalls when put into gear

Hello All,
This problem is outlined in a troubleshooting post I'm having online with a pay site to try to help me fix my problem. Here is a copy and past of much of the information. Please help if you have an ideas...
Thanks!
Hello, I have an 6CTA8.3 in my former...

Hello, I have an 6CTA8.3 in my former military 5 ton truck. Starting problems slowly went from hard to turn over, to needing ether to start it, to only being able to start it with ether, and now it can only start with ether and seems to run fine, in neutral, but as soon as I put it in gear, it ... view full

06 May 2018 08:58

06 May 2018 09:03​

I have cleaned the fuel injectors by running the truck off a 5 gallon tank of diesel with sea foam and letting it run for an hour, there is no more evidence of contamination in the fuel lines or in the injector pump, the fuel filters were changed before all of this. The truck will NOT start on its own (ether only into the air intake) and then she runs perfectly...BUT, will not move, seems as soon as it is put into gear, even with higher RPM, it will just stall, not even like it's trying. Like it just gets shut off. The fuel is clean, the filters clean, the lift pump primes just fine.

06 May 2018 09:12​

The truck has a transmission neutral switch that prevents the engine STARTER from engaging when not in neutral.
Is there a switch that could have failed that cuts off fuel to the engine when it's put into gear?
There is no ignition on this vehicle as you know, (only compression is required to light off the diesel) so something must be cutting off the fuel to the engine as soon as it's put into gear. Either something electronic, or timing? Perhaps the fuel injector pump is bad? Why would the engine run up to almost 2500 RPM in neutral but not be able to move when put into gear. Is the fuel injector pump failing a duty when it's put into gear, does it need to do something else besides just continuing to give fuel to the engine, something with timing or flow control that could be failed...seems strange that it can REV high, but not provide fuel flow to the engine when it's put into gear...

07 May 2018 04:29​

spankyjr1

Technician
Hi, my name is spanky,thank you for your question.
You mention fuel contamination has this been sitting for extended amount of time?
Did it have a lot of water in fuel?
Did you check fuel pressure?
Did you change filters before or after sea foam?
Did you use fleet guard filters or filters with the correct micron rating?
does this have a electric lift pump or just the normal manual on side of engine?
Let me know

07 May 2018 10:50​

Hello Spanky,
The fuel is clean, in the tank and in the filter
No water in the fuel.
Fuel pressure is fine.
Filters have been changed after seafoam.
Using the same model filters that have worked for years.
manual primer (lift) pump, works fine manually. Engine does not start after manually priming it, (I can see the manual primer works, because I loosen the small bolt on the injector pump when priming, and pump the primer until fuel comes out of that bleed bolt)

07 May 2018 10:53​

...I said the "engine does not start after manually priming it". It doesn't start on its own, it needs ether to kick it over, then it runs and idles fine!

07 May 2018 11:26​

spankyjr1

Technician
I was asking about the fuel since you said no more evidence of fuel contamination so if it did have a lot it could have wiped out fuel injection pump.
I asked about filters only because some filters the micron rating is to small which causes hard start and low power.
Just trying to eliminate everything so you are not wasting time checking things that don't need to be checked.
There is no switch that cuts off fuel when putting in gear.
I think your issue is the torque converter is stuck in lock up
What that does is make the engine and transmission a 1-1 ratio and the engine can't take it so it dies
Try jacking up rear wheels,block front wheels front and back, release brakes, start engine, then feather it into gear.
What I mean is put in and out of gear so it does not slam into gear so hard and see if it will stay running and you will notice wheels spinning fast in lower gears.
Now there is a lock up solenoid in valve body that can be stuck I would try replacing that first before condemning converter but if that does not work trans would need a rebuild as metal from converter went through trans.
That would also cause the hard starting trying to start with the converter (pump) locked up.
Please use the star rating system at top of page so I get credit from the web site for my time,
You may still ask follow up questions at no extra charge after rating.
Thank you

07 May 2018 11:41​

Hello Spanky,
"I was asking about the fuel since you said no more evidence of fuel contamination so if it did have a lot it could have wiped out fuel injection pump."
Hmmm...yes, there was a lot of fuel contamination...from Bio fuel. Now it's all gone, but if that could have "wiped out" the fuel injection pump, would the fuel injection pump still be operational in the means that it currently is...once started, will continue to run/idle?
I'll look at the maintenance manual for the torque converter. Is there any way to trouble shoot switch that without jacking the vehicle? It's sitting on dirt, it's a three axle 6 wheel vehicle...hard to simply jack up.
I'm not sure about the rating bit, first time on this site, and concerned that if I rate that means I'm done...what's your motivation to see this through the end if I rate now?
Thanks, please educate me about how this works if necessary.
mark

07 May 2018 11:58​

spankyjr1

Technician
My motivation is I give you my word!
I have never left anyone hanging,, but I have seen others do it so I understand your concern.
It also states rate to close on your end but all you do is refresh the page. I always send a Thank you anyway which keeps the question open as long as you need help to assist with this question.
To rate you click on the stars at the top of page 1-5 stars on how well I assisted you,, without a rating the site keeps all the money you paid and does not share with the expert.
Hope that explains it if you have other questions about it let me know.
Back to your issue
Let me ask when you put in gear and it dies is it almost instant? If it was fuel it would stumble and die
You should only have to jack up one wheel on front drive as long as power divider is not locked,, as long as this only has 2 drive axles,, and one dummy axle for weight.
You just use a bottle jack under a u-bolt to jack up just enough to get a wheel off the ground.
You can try this and if you can rotate the wheel while in neutral with brakes released that would be enough to test.
The only other option would be to take out all the bolts connecting converter to flywheel and see how it starts.
Now that won't tell you about putting in gear and dying it would only tell you that is the cause of hard starting.
I would not do anything about the pump right now I don't think that is the issue but as soon as you can drive it if it smokes or has low power then we could troubleshoot some more
Let me know

07 May 2018 12:17​

spankyjr1

Technician
Also when it dies does it torque the engine Up?
And yes the fuel pump could do this hard start if worn out from contamination. (should not cause it to die putting in gear though)
Just note: for a worn pump you would need to verify pump not sucking air before condemning a pump.
you would put a clear line between T/P and Injection pump get running and rev engine and look for air bubbles if you see bubbles you have a leak before the T/P.
Sucking air would need to be repaired first
Also just so you know I work and have a life so I am not always around so it may take time to reply back
But I always reply.
Are you Military or how did you get truck from auction?
Talk later

07 May 2018 04:04​

Hello Spanky,
I'm a retired Marine, and I use the vehicle for parades and such to bring awareness to the military and to support charities. I have a big event upcoming for Memorial Day, and was hoping it'll be running by then. Of course I want you to be able to extract maximum pay out of the efforts you make and as little go to the middleman as possible
Q: "Also when it dies does it torque the engine Up?"
A: When it dies, it just dies, no sound or any other symptom other than it just dies. Like it gets shut off
I have already checked with a clear line, I see no air at all, I've run it to max RPM and no air at all
I also had a clear return line back to the clean 5 gallon tank I was running the engine from, I can see no contamination anymore coming from the fuel system. All filters are clean and replaced.
So if the injector pump "should not cause it to die putting in gear though" I must have two problems; one that it won't start without ether (perhaps the fuel injector pump) and two that it dies when it gets put into gear. That's been my problem...thinking that there are actually two problems, and not just one. Seems random and coincidental that there are two separate problems because BOTH problems started out together...it got harder and harder to start and then only with ether, and simultaneously it would stall when being put into gear unless the engine was warmed up and held at high idle before being put into gear. I really believe it has to be the SAME problem since both problems came on simultaneously...

08 May 2018 04:16​

spankyjr1

Technician
Thank you for your service!
I would like you to check power going to the shut down solenoid with key on and during cranking, making sure voltage is at least within 1 v of battery voltage, then put in gear and see if voltage is dropping out.
I have seen something shorting out wiring when put in gear that causes loss of power to solenoid which would cause shutdown.
You should have 3 wires on shutdown, one is ground, one is power with key on, and one power during cranking.
If you have a single wire solenoid power all the time with key on and cranking
The solenoid can also cause hard start if it is not being pulled all the way in.
With this type of injection pump and nozzle set up return fuel air is not a issue, it would only cause a miss on one cylinder, now if this was a electronic engine air would effect multiple cylinders at once.
Let me know

08 May 2018 04:25​

spankyjr1

Technician
If your solenoid has outside linkage make sure it is going full travel both directions with stop lever.

08 May 2018 11:55​

Hi Spanky,
Solenoid has been bypassed, it failed years ago and I took it off. Truck has been working great without it.
See attached photo. That cable is called "CABLE – Connects modulator to fuel pump". Is there a solenoid here?
I still think that since both the putting into gear and stalling was intermittent, and the hard starting was intermittent, then both problems are caused by the fuel injector pump...if I fix the start problem first, perhaps the putting into gear problem will be fixed at the same time?
I want to ensure that you get paid properly here, do they only pay a flat fee?
I tried to attach the maintenance manual, but the software here doesn't all the attachment for some reason.
mark

• Screen Shot 2018-05-08 at 11.49.29.png

08 May 2018 12:29​

spankyjr1

Technician
Yes it is a flat fee I get paid when a rating is made of 3-5, after you rate they do allow tips
Make sure your shutdown cable is releasing all the way at pump and it's not holding it part way on.
I see 2 cables I assume one is for shutdown and one for throttle hold?
The electric going down by trans goes to a potentiometer (probably looks about the size of a can of beer) that tells trans throttle position for shift points
I don't think it's a fuel issue or pump since you can get more fuel by revving up engine and it still dies putting in gear, seeing it doesn't have a shutdown solenoid that can't happen.
Still think it's the converter that is the only other thing that explains both issues coming and going then stayed all the time.
When the converters go bad they can be locked when hot then after you cool down would start working okay until hot again, that explains issue coming and going, after a time doing this they stay locked.
When you rev engine it it a fast response up to 2500 or slow?
Any smoke out exhaust if so what color?
I see 2 cables I assume one is for shutdown and one for throttle hold?
send manual to mustang spanky@rocketmail.com and I'll take a look.

08 May 2018 01:13​

spankyjr1

Technician
Just to make sure have you tried starting while holding throttle down?

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08 May 2018 02:57​

Spanky, see below...
Yes it is a flat fee I get paid when a rating is made of 3-5, after you rate they do allow tips

Great, I'll take care of you! Promise...this isn't an easy one, I know...

Make sure your shutdown cable is releasing all the way at pump and it's not holding it part way on.

Shutdown cable is releasing all the way. It takes a very long pull to engage it.

I see 2 cables I assume one is for shutdown and one for throttle hold?

Exactly, manual throttle by hand to adjust idle high and walk away

The electric going down by trans goes to a potentiometer (probably looks about the size of a can of beer) that tells trans throttle position for shift points

Could this be failed?

I don't think it's a fuel issue or pump since you can get more fuel by revving up engine and it still dies putting in gear, seeing it doesn't have a shutdown solenoid that can't happen.

But the "modulator connection to fuel pump" in the diagram, could that, if failed, shut down the engine?

Still think it's the converter that is the only other thing that explains both issues coming and going then stayed all the time.

Not sure what you mean by the "converter"...which part is that or is that slang? I don't see a converter on the manual. I will attach and send to you

When the converters go bad they can be locked when hot then after you cool down would start working okay until hot again, that explains issue coming and going, after a time doing this they stay locked.

Ok, gotta find that part...but still curious why the engine won't start without ether? Would the converter have that as a symptom as well?

When you rev engine it it a fast response up to 2500 or slow?
FAST

Any smoke out exhaust if so what color?
Exhaust is clear and perfect

I see 2 cables I assume one is for shutdown and one for throttle hold?
Yes

That sounds legit to me. Torque converter in the transmission is locked somehow. Only thing I could come up with from your symptoms.

I didn't read all the back and forth.

In think the fuel lines are leaking, allowing air entrainment. Or it may possibly be sucking air at the manual primer pump.

I have seen this exact thing with fuel pump replacements I'm willing to bet the timing is off. If his pump was replaced and not properly torqued to the proper torque as I remember its some high number like 125 ftlbs over time the gear can move on the shaft and one will experience hard starting and poor performance. That said first ensure you have a good fuel supply hoses and fuel pump than check timing I would bet its off.

I've seen this exact set of symptoms with an air leak progressing.

Hard to start, till you crank it enough to purge the air.

Air leak gets worse. Now cranking it isn't enough to purge the air, but starting it with ether is enough to prime it.

Air leak gets worse. Ether will get it running, but it's running on froth. It stalls when put in gear.

I still think it is air entrainment.
Whatever it turns out to be, post the results - I want to be able to say "I told you so" if I'm right, but more importantly I want to learn if I'm wrong. ...

Take a fuel can that is clean and put a new line directly to your IP (no breaks or joints). Keep it high so it does not need to suck fuel up (set it on the cowl). That will take you around all of the fuel lines, filters and tank pickup to see if air is the problem. Should you want to run more than a couple of minutes, you will need to plumb the return line back to your tank, otherwise fuel just gets put back into the truck tank. This takes about 5 minutes but gives much valuable information.

In the "conversations", you stated that the fuel pressure is "fine". What does "fine" equate to in a measurement? That is an important measurement. Start with basics, Check the timing, if that's gtg, make sure the fuel shut off that was removed is being pulled up to the proper distance, if too far up, symptoms you describe have happened, wiring it up is a get home out of the dirt patch. Didn't see where you answered the person as to if it starts with the pedal on the floor, does it?

All of the symptoms you describe point to a fuel system issue, could be low pressure, out of time, air, a failed pump. You need to troubleshoot it by taking measurements. We can give you ideas, but it will be up to you to pin point the problem.

Do you know how to check pump to engine timing? To check the fuel pressure you need to buy/make a fitting that will accept a gauge to measure the low pressure fuel going into the fuel pump.

Timing check is easy, use the pin on the back side of the gear housing, push it in and slowly rotate the engine until the pin "snaps" into a hole in the back of the cam gear. Remember to pull it back out. Remove the cap on the lower left of the governor housing on the fuel pump, there is oil there, you will make a mess. there is a white nylon pin in that cap. First, look in the hole to see if you see a tab directly in the center of the hole. If it is there, take the pin out of the cap and there will be a forked looking end on it...the other end is just a round metal pin. Put the forked end into the pump, the pin should seat at the shoulder on the pin. If not, it is out of time, if the tab in the pump isn't in the window or not centered, out of time.

Start there and let us know, we'll go from there

Just reading one problem fuel related hard starting. The stalling would it not be the TQ lock up button on the range control?

Oh yeah, be easy on starting fluid, it likes to soften the carbon in the ring land area and will cause the compression rings to stick after the carbon gets hard again. The result is no compression and the fix is a re-ring

Hello All,
Here's the latest:
I've removed the "lock up solenoid" on the transmission, simply bypassed it as per instructions from Memphis Equipment.
Now I can get the truck to "lurch" forward before stalling, and if I put it into reverse, it will keep going backwards until I take my foot off the accelerator or put on the brake, then it will stall.
What's up with this? Transmission modulating valve? It's is a cable connected from the transmission to the engine idle lever on the transmission. It controls shifting, but not sure how much it controls or prevents it. Not much to find on the web in this regard, not for a CABLE controlled modulating valve, (vs a vaccum driven valve, which there is plenty of info about)

Did you try putting your transfer case in neutral and seeing what your transmission will do? I mean see if it will go thru all the gears or if there is any abnormal jump or movement of the output shaft into the jackshaft. Just a thought cause if your transfer case is burned up it wont move either but a little bit before it kills the motor.

Hello and thanks Simp5782.. I'll try what you discussed above when I can (I'm out of town until Thursday)
I have a new primer pump on the way, hoping that addresses the starting only with ether problem, but seems there's a coincidental transmission problem which is the big head scratcher now...
Also, Foridiansan, thanks, the solenoid that you reference is located in the shifter housing IN the cab/shift lever assembly?

You might want to consider taking the driveshafts off to the front and rear for more diagnosis.

Hello,
I jacked up the back of the truck. Started it with ether. (One tiny shot and it starts and runs fine).
FYI, the gear shift is set up like this: Auto transmission, the "top" or front of the shifter is Reverse, then Neutral, then 1-5, 1-4, 1-3, 1-2, 1.
I shifted the truck into 1-5, it stalled (all four back wheels were off the ground). The parking brake was set.
I restarted it, released the parking brake. I brought the shifter all the way down to 1. The wheels spun, engine kept running. I ran it through the gears, although shifting from gear to gear, it seemed like it always stayed in first. Why do I say this? The engine RPM and the speedometer were the same in every gear, i.e. 1500 RPM in first was the same speed, 8 MPH, as 1500 RPM when in gear 1-5.
The truck seemed less likely to stall when put in Reverse with some brake application.
Someone asked above if I could put the transfer case in neutral...there is no neutral that I read in the manual for the transfer case.
Shifting the transfer case to LOW auto locks the front wheels into drive. In other words, unless I jack the whole truck up, I can't test the transfer case in low...only while it's fully on the ground so it doesn't jump the jacks.
Perhaps I should take the truck off the jacks, put the transfer case in low, and see if I can get it to move forward without stalling? Will that help out the troubleshooting, or not.
Thoughts everyone?
Thanks all!

Transfer case - down is high, up is low, and there's a N in between.

Same speed in 1-5 that you're getting in 1 because you're in 1 either way.

I still say it's air entrainment in the fuel lines.

Take the front and rear driveshafts off at the transfer case so your not turning the axles.

Sounds to me like the transmission if you are only getting one gear. Still betting torque convertor.

1 Patriot-of-many said:

Sounds to me like the transmission if you are only getting one gear.

Click to expand...

Only one gear. On jackstands. At 1500rpm, well below the shift point.

Transmission doesn't explain the requiring ether to start.

Fuel problem explains all the symptoms. I've experienced these exact symptoms on more than one truck. It has always been a fuel problem. It has either been pinholes in the soft lines, air leak at the primer pump, or air leak at the tank selector valve on vehicles so equipped.

The truck is almost certainly running on froth.

Conceivably I'm dead wrong and there's multiple complex problems all lining up to mimic a fuel problem. By all means start with placing the truck on jackstands instead of just shifting the t-case to neutral. By all means pull the driveshafts.

But eventually, after exhausting all the complex difficult options, you'll get around to the air entrainment in the fuel and resolve it.

When you hear hoofbeats, think horses and not zebras.

When you encounter flu-like symptoms, it's far more often the flu than ebola.

Bet the odds. A simple single common easy frequently-encountered fail that explains all the symptoms, or multiple rare complex failures interacting to mimic it. Add to this the distortion caused by the description coming from someone who doesn't really know the truck ("my t-case doesn't have a neutral")

Again, it's possible his truck is unlike any of them I have ever seen. Conceivably his doesn't have a N in the t-case. But it isn't the way to bet. The way to bet is operator error and the t-case is just like the other 69,998 of them.

I look forward to seeing a resolution. I either get to sing the "I TOLD YOU SO" song, or I will readily admit to being dead wrong.

1 Patriot-of-many said:

Sounds to me like the transmission if you are only getting one gear. Still betting torque convertor.

Click to expand...

Torque convertor is plausible, but doesn't explain requiring ether to start.

Just using a small, say 1 gal. tank and line direct to your IP can tell you if it's a fuel issue. Bypass all of the potential leaks.

I'm not one to want to run one up speed with the wheels spinning but I do like having it engaged so the transfer case output spins, not simply in neutral with no output shaft spinning.