Warm start problems

[ssgtcampbell77]

Ive looked all over this site and the TMs and either Im searching for the wrong thing or its not here but Im having problems with my M1008 starting when the engine is warm. If I shut it down and let it set for 5 minutes, it fires right up. Any longer than 5 minutes and Ive gotta crank 3 or four times for 30 seconds at a time. Ive replaced the glow plugs, bled the fuel system, ran all the circuit tests....nothing. Starts fine on cold starts. Any help would be greatly appreciated.

 

[original]

Turn the key forward and then back again. Then forward, wait, and try starting.

 

[jdemaris]

Ive looked all over this site and the TMs and either Im searching for the wrong thing or its not here but Im having problems with my M1008 starting when the engine is warm. If I shut it down and let it set for 5 minutes, it fires right up. Any longer than 5 minutes and Ive gotta crank 3 or four times for 30 seconds at a time. Ive replaced the glow plugs, bled the fuel system, ran all the circuit tests....nothing. Starts fine on cold starts. Any help would be greatly appreciated.

I've got two 83 Blazers that have been like that since they were new.

They start fine when cold, start fine when hot (within 10 minutes of shutdown) but otherwise need a lot of cranking.

You need to either turn up your fuel delivery - or run your glow plugs longer.

During a time when it's hot and won't restart - have you tried using the glow plugs and . . . if so . . . are you sure they are actually working??

I don't know how you've got your glow-plug circuit wired. Most 6.2 trucks - civilian and military have a "glow plug inhibit" switch that stops the glow plugs from working on a warm engine. That switch can cause a lot of problems and GM finally elimiated it around 1990.

I suspecct all you need is some good burn-out proof glow plugs and a manual push-button control (or over-ride). On my two problematic 83s, I long ago installed a push-button manual override. So, I still have the OEM controllers hooked up - but - I can also push the button and force the plugs to work when needed. Without it, the engine would never start unless it sat for an hour or two.

What you described was a very common problem with 80s vintage 6.2s. In fact, I saw a few get junked when in the hands of "mechanics" who were clueless with diesels.

 

[ssgtcampbell77]

Done that. Nothing. Checked the glow plug wires and Im getting nothing when the engine is warm. Works fine when engine is cold. According to the schematics, there should be a recycle on the gpc but after the first cycle, my gpc doesnt cycle again. I traced and checked for voltage and continuity at all the wires and everything checks out. Except after the first cycle. I have a feeling my glow plug module may be shot. I pulled it out, checked for continuity at all the circuits and its good to go. No burns, no corrosion.

 

[ssgtcampbell77]

I've got two 83 Blazers that have been like that since they were new.

They start fine when cold, start fine when hot (within 10 minutes of shutdown) but otherwise need a lot of cranking.

You need to either turn up your fuel delivery - or run your glow plugs longer.

During a time when it's hot and won't restart - have you tried using the glow plugs and . . . if so . . . are you sure they are actually working??

I don't know how you've got your glow-plug circuit wired. Most 6.2 trucks - civilian and military have a "glow plug inhibit" switch that stops the glow plugs from working on a warm engine. That switch can cause a lot of problems and GM finally elimiated it around 1990.

I suspecct all you need is some good burn-out proof glow plugs and a manual push-button control (or over-ride). On my two problematic 83s, I long ago installed a push-button manual override. So, I still have the OEM controllers hooked up - but - I can also push the button and force the plugs to work when needed. Without it, the engine would never start unless it sat for an hour or two.

What you described was a very common problem with 80s vintage 6.2s. In fact, I saw a few get junked when in the hands of "mechanics" who were clueless with diesels.

When you did your manual override, did you disconnect the light blue wire from the GPC and run it to a switch? Ive seen that on here several times but it doesnt seem to me like that would bypass the module. I will try it though. Since you've dont your override, have you had any trouble starting when warm? My plugs don't cycle at all when its warm, no voltage or anything.

 

[jdemaris]

When you did your manual override, did you disconnect the light blue wire from the GPC and run it to a switch? Ive seen that on here several times but it doesnt seem to me like that would bypass the module. I will try it though. Since you've dont your override, have you had any trouble starting when warm? My plugs don't cycle at all when its warm, no voltage or anything.

Let me first point out that my diesel Blazers are civilian with 12 volt systems, not military with "partial" 24 volt systems. Both civilain and military run the glow plugs at 11-12 volts.

On first generation civilian models, there's a controller and a separate relay. The way to add a manual over-ride is by wiring a push-button to that relay.

Most 6.2 trucks and Blazers, up to around 1990 have a temperature switch that stops the controller from energizing the glow plugs when the engine is warm. it is the switch with two terminals on it. That can cause many warm-start problems. When it is working properly, it prevents the glow plugs from working at all when the engine is 125 degrees F or warmer. Even on some brand new trucks, it prevented them from starting when warm. Many repair shops just unplugged it and tied the two wires together.

On mine that won't start warm with the controller - all it takes is 5-7 seconds of glow plugging and they start fine. Been that way for many years.

I'll add that even when all is working as it should - new glow plugs can render the controller useless because they have a different amp draw then the original design. Especially the Beru plugs that Delco puts into their AC60G boxes. They will not work properly with an OEM civilian controller unless it gets reprogramed.

 

[doghead]

How do you reprogram the controller? could you show me pictures of this programable controller?

 

[jdemaris]

How do you reprogram the controller? could you show me pictures of this programable controller?

The guy that owns and runs the 6.2/6.5 diesel website posted full specs and pictorial years ago - on how to do it. He first posted it when Delco first started selling the Beru AC60Gs.

His website (if Jim still runs it) is at:

http://www.62-65-dieselpage.com/

I reprogramed two of my controllers years ago and they worked great with the AC60Gs. But then I switched to the Wellman G050 plugs and the controllers again - did not work pefectly. But at that point I didn't care since I've got push button over-rides on all my 6.2 trucks and Blazers.

Automatic controllers are usually finely calibrated to only work correctly with a specific amp-draw and heat-up time. Once a new plug comes out that works a little different, the controllers have problems. The Wellman WAP G050s heat up faster then the AC60Gs.

By the way, reprogramming involes pulling the card out of the contrller and replacing a few resistors.

 

[doghead]

The military GP controller cards do not seem to be so "fussy" about the GP resistance or whatever other variables exist between GP manufactures products.

Are you familiar with the GP controllers in CUCVs?

 

[Shankem-Deep]

Another thread that wasn't finished....Did you fix the problem?

 

[Keith_J]

Speed of cranking can cause this problem, often it is the brushes in the starter motor. Rebuild kits are only $14

 

[Shankem-Deep]

What am I looking for in a rebuild kit? 24V starter rebuild kit? Where did you get yours?

 

[Warthog]

Depends on the starter. Here are full rebuild kits. Individual items are also available.

27MT direct drive
http://www.aspwholesale.com/index.php?act=viewProd&productId=6174

or 28MT gear reduction

http://www.aspwholesale.com/index.php?act=viewProd&productId=5977

 

[Shankem-Deep]

Depends on the starter. Here are full rebuild kits. Individual items are also available.

27MT direct drive
http://www.aspwholesale.com/index.php?act=viewProd&productId=6174

or 28MT gear reduction

http://www.aspwholesale.com/index.php?act=viewProd&productId=5977

I believe I have the direct drive. Is there a visual differance so I can make sure of what I have?

 

[Warthog]

28MT Gear reduction on the left and 27MT direct drive on the right

When you order the kit, specify that is for a 24v starter.

 

[Shankem-Deep]

Well I stand corrected. I have the one on the right, gear reduction. My M1028 and M1009 both have that style. Thanks Warthog!!

 

[Keith_J]

28MT have less issue with brush wear since they draw less current. If the engine isn't turning over fast enough, you can bet it is the starter. I got the rebuild kits from ebay.

 

[Shankem-Deep]

I've only had this 09 for a few weeks. I suspect that the batteries don't have enough cranking amps as well. I have a lot of things to check yet. All the swellman (although non where swollen) glow plugs checked out good but I replaced them with AC60G's. Did the doghead relay. I'm doing the resistor bypass. GP relay checks out fine. GP card seems to be working. I'm replacing the fuel filter base with a NOS one that some kind stranger left on my driveway in a cardboard box. Still not sure who did that! Very cool though! I'm also going to replace the "inhibit switch" or glow plug temp switch. Like I said lots of things yet to check and do. Thanks for all the help. Just to restate the problem, my 09 starts fine when cold. If you shut it off after it's warm it will start right back up within say 5-10 min. If it sets any longer it is a bear to start until it cools completly down.

 

[Warthog]

Okay I'm a dunce.

28MT Gear reduction on the Left - smaller starter
27MT Direct Drive on the right - Larger starter

That's what I get for typing and taking a support call on the phone at the same time

 

[Shankem-Deep]

Okay I'm a dunce.

28MT Gear reduction on the Left - smaller starter
27MT Direct Drive on the right - Larger starter

That's what I get for typing and taking a support call on the phone at the same time

Well then, I retract my previous statement! I have the Direct Drive starters on both my MV's