M1009 Understanding Warm Start Woes

[tgtaylor64]

My CUCV has started the dreaded warm start problem. Starts fine when cold (winter) or just after sitting overnight in summer or after 6 or so hours after being driven. Other than a manual glow plug button, all electronics are stock. Starts up fine within a few minutes of shutting down but not so well if sitting say 10 minutes to and hour. Lots of cranking to get it to catch and fire up. I have good 31C batteries that have been load tested and are jam up. I have a fuel back-flow preventer installed before the stock fuel filter which was recently changed. And for the final ta da: IF you cycle the glow plugs for 5 or so seconds manually, the beast will start right up! What is going on? The engine and chambers are hot, fuel is there, the IP is injecting, why the hard start-up? I really need to understand this issue! Someone please talk me through this....

 

[cucvrus]

I am pointing at the injection pump. Try pouring cold water on the pump and see it that helps. Also check the throttle shaft seals on the side of the injection pump. Are they leaking? As you know a warm diesel does not require or signal the glow plugs to engage. It could be dropping fuel under the truck. With out seeing it it is hard to diagnose any further.

 

[tgtaylor64]

I have tried the cold water but with no effect. No fuel leaks. If the IP is going, then why does cycling the GPs work? I do not understand nor see any commonality.

 

[antennaclimber]

I have 2 trucks that do the exact same thing. The only way to get them to start (when the engine is warm) is to heat the glow plugs some and then they both start right away.
The M1009 has a new IP in it and all the cylinders passed a compression test.

The latest revision on the GPD2 (C revision) glow plug card has an option jumper (pictured below) to fire the glow plugs when the engine is slightly warm. The card will turn the GP's on for a short period of time based on the resistance from the temperature sensor. The Wait light will NOT come on for the short period of time during a warm engine start up however it will come on when you need to Wait for the GP's to heat up a cold engine.

I have been using a card with the option enabled for a few months now with good results. The warm start up issue is gone it you wait just a couple of seconds for the modified card to heat the GP's. Using this option may shorten the life of the glow plugs by heating them more often. My thinking is that I would rather change the glow plugs on a regular basis than change out a starter due to excessive cranking.

Or you can use a manual switch to add some heat to the cylinders as needed.

It may also be possible that your GP temperature sensor is not functioning properly. If the GP card does not see a certain resistance from the sensor, then it will not turn on the GP's.

 

[Keith_J]

Check cranking speed, a worn starter can be sluggish when warm. Diesels need cranking speed, even when warm. The last 1009 I saw that had the same issue had nubbins for brushes and bushings worn plumb out. An overhaul kit brought it back to life.

 

[tgtaylor64]

The starter sure seems to have the necessary umph to get it going. I have heard that somewhere in the 600 to 700 RPM range is what is needed. How can I have this tested (RPMs) at start-up?

 

[Keith_J]

I have an optical tachometer, made for the model airplane hobby. It is for measuring prop speed, switchable from 2,3 and 4 blades. I put two squares of aluminum foil tape on the crank pulley and set it for a two blade prop. Works like a champ. Should be under $20, mine is a Hangar 9 brand.

 

[tgtaylor64]

You mentioned the newest rev on your cards some time back and I am glad to see that they are progressing nicely! Although it does work, I want to understand why. The GP temp sensor appears to be working and I know how to check for the feed resistance so I might do that. Again, on a 20°F morning, the GPs will fire for say 10 to 15 seconds and it fires up immediately. I cannot understand that the engine, while hot to the touch, will not crank but firing the GPs for 5 seconds gets it to start right up! I am not complaining and maybe I should be thankful (and thankful I am) that this is the only issue I have! I have always enjoyed CUCVs for going on 5 years or so and I am always wanting to better understand how they operate. Somethings I have been taught, some things I have learned, and others things have come from the vast experience and wisdom of this forum. I deeply appreciate the knowledge found on this board. "The best, Jerry, the best!"

 

[tgtaylor64]

What RPMs are you turning at crank? I would like to invest in one to also check my idle and high idle speeds. Thanks!

 

[Keith_J]

300+ rpm! running dd starter 24 v with dual purpose marine batteries.

 

[tgtaylor64]

I thought about the post concerning the warm starter being sluggish. I don't think that is the case here. When the starter is hottest, right after being driven, it starts up just fine. An hour or so later, it is still warm but cooler than it was so why the problem? My thinking would dictate that a hot or warm starter should perform better than one that is cool or cold. Someone help me see this differently.

So far, nothing makes sense but a root cause for this is waiting out there....

 

[Warthog]

Some Diesel engines are just temperamental and need the extra heat. Barrman is in south Texas and is running three 6.2Ls. One starts just fine and another needs some extra GP heat, even in 90+ weather.

 

[Barrman]

Anytime the inside of the engine is below 150˚, it is considered cold. The glow plugs normally kick in below 125˚. You could just be in the dead zone between the two.

 

[cucvrus]

I am still saying injection pump. Unless I missed it here. I did not read where a fresh gone over injection pump was installed on this unit. I had one like this and it was hit and miss. Mostly miss. But I changed out the injection pump and that fixed the issue. My question do you know when the pump was last replaced? If not that is where I am going to put my vote. On the pump. And I am not talking a take off pump. Or a used pump. Unless you are 100% sure it is a good pump and has no problems it is not worth the time to install it. That is my final diagnosis on this issue.

 

[antennaclimber]

Anytime the inside of the engine is below 150˚, it is considered cold. The glow plugs normally kick in below 125˚. You could just be in the dead zone between the two.

Our GP card testing has confirmed this "dead zone"as well.
There is a temperature window where the GP card does not always come on.

 

[Keith_J]

Definitely check starter cranking speed, the higher the crank speed, the hotter the air at time of injection and the least delay in igniting the injected quantity (Cetane index here also helps). When the engine is just warm, considerable heat is lost to the precombustion chamber, slower cranking speed allows more heat loss.

 

[tgtaylor64]

I recently had the injectors replaced due to another issue (rough idle) but that did not fix the problem. The diesel guy said that the IP had been rebuilt at Ft. Bragg but could not say when or how deeply. So no, I cannot say that it is not the problem or a contributor. I do fail to see the link between 5 or so seconds of GP heat into a warm engine equates with a failing or faulty IP. I should also say that this did not used to be a problem at all for this truck. I want to know what is happening. Interestingly, I am waiting to get the 'beating a dead horse' emoticon anytime! However, in the spirit of this thread, I hate to accept 'that's just the way it is' and move on.

An issue with the temperature sending unit to the GP card seems to be a likely source of my issues although it works fine for a cold engine....

 

[Warthog]

Have you done a compression test? Diesel ignites with heat. There are different ways to make that heat. GPS or compression. The higher the compression the higher the heat.

 

[tgtaylor64]

I just rebuilt the IP and it now runs the way it should! Gone are the warm start issues, vibration, sluggishness, and overall lack of power.

 

[Warthog]

Thanks for the follow up. Always good to find out the outcome.