Poor starting with block heater

[Ray Walkerdine]

I have just joined this group, and hope that someone will be able to restore my faith in diesel engines. I'm not sure where to start, but in bried here goes.

I own a 95 Chev 3500 Dually CrewCab with about 130,000 kms (81,000 miles) In July I had to install an entire new engine because the turbocharger blew and completely ruined the engine. The repairs, including the re and re have exceeded $16,000 Canadian. Here is a list of what was replaced...Long block engine, oil switch, temp sensor, air filter, injection pump, new injectors, new glow plugs, re-conditioned turbo , oil cooler hose, thoermostat, heater hose... After receiving the truck back, there was still an unacceptable amount of white smoke on startup, so I went back to the mechanic. After having the truck for over 1 month, and checking every conceivable part, including the computer, it was believed the problem had been narrowed down to a problem with inconsistant connections in the wiring harness. ( Which were fixed)
This now brings us to several weeks ago, when I noticed that the truck started better cold, than when I plugged in the block heater. So, after losing faith in my mechinic I went to my local GM Dealer and had them check it. This is a summary of their evalutaion
Fuel pressure and flow - good
TDC off set - good
Scan check, History Codes 65, 84, 88, 99 Clear codes, Run and Scan
Temp normal all parameters, Good started good after sitting a few minutes. No code repeats Has weak left hand batery, failed batt test. Rechecked after sitting overnight with block heater plugged in. Scan Check starting temp
85 deg Celsius (185 deg F) Started and stayed running if accel pedal applied 1/3 down. Glow plugs cycled only once. Tried changing TDC set was .08, to 0 deg was worse, went to -1.14 about the same, Accelerator pedal codes reset, May need to replace accelerator pedal assembly.
REPLACED accelerator pedal assembly ($617.00 Can)

After all this, the problem still wasn't solved. The truck starts better cold, been as cold as - 12 C (10 deg F.), than it does with block heater plugged in. (As you can tell from above diagnosis). No one can figure out what may be the cause. The engine has been checked by a local diesel fuel injection business, the diesel engine rebuilders and the GM dealer and still no success. I am just about ready to give up all hope, I have now invested over $17,000 into a 1995 Chev truck, and can not ever recover my losses.

Does anyone have a suggestion about what may cause this problem. My concern is that if the truck doesn't start correctly with the block heater, what will happen in the summer when the engine is at the same temperature. It should be noted that when the engine is at operating temperature it starts like a charm.

Sorry for being so longwinded, but I felt that the full background may be of assistance.

This group is my last hope. If you need any more info, just ask.

Thanks so much for any help.

Ray Walkerdine
Enderby, BC

[norm]

It seems like glow cycling times could be to blame here. What do you notice about how long the glow plug light stays on in various temp situations? Do you know what part # glow plugs were used? You have checked all that wiring?

I wonder if you have an incorrect temp. sensor that is not allowing the right glow plug time. Some others may chime in on how the computer determines glow time.

[Ray Walkerdine]

Norm,
In response to your input here is what I know.

- When cold, the glow plugs are activated for 11 seconds. When warm from block heater, about 6 seconds.
- I didn't check the wiring, but the fellow who is supposedly a diesel "expert" has checked every relay, switch, and electrical connection under the hood.
- Not sure of the glow plugs, other than that the part number states 8 glow plugs 80034 (my cost $140.00 Canadian)
- I asked about the temp sensor, and was assured it was not the problem.

Again, thanks for the response. I am a computer person, not a diesel expert, so anything you guys offer is much appreciated. Even the GM dealer said that if I can find an answer to the problem they would be more than happy to explore the option.

Thanks,
Ray

[eracers999]

Ray:

I had the exact same problem, i have one simple test for you to perform.

When the truck is in the state where it is most difficult to start, unplug the coolant temp sensor. It is located on the water manifold to the left of the upper hose, it's a two wire plug.
Try a start like normal, report you finding's .

Kent

[Beedee]

Welcome to the DP's Ray
Don't give up, there are some extremly smart people that belong to this forum. If you are patient and keep with it and give lots of feed back, someone out there will help.
Good luck
Brian

[Ray Walkerdine]

Kent,
I just went outside and plugged in the block heater and disconnected the temp sensor. I will let you know what transpired tomorrow when I start truck up to go to work.
Fingers (and toes) crossed.

Ray

[eracers999]

Ray:

If it starts right up and you plan to drive it right away be shure to plug the sensor back in!!

Kent

[Ray Walkerdine]

Kent,
The good news is that this morning the truck started like a charm. No smoke, and almost instantly.
The bad news is that the temp sensor has been changed several times before, and checked at the last visit to GM. In fact, the diesel mechanic who originally installed the engine wanted to put a bypass sensor on to help with starting, but I declined, as this isn't how the engines came from GM.

Anwyway, I called GM and they said it could be the computer. Is there a way to tell if I need a new computer? I already paid the money to replace the accelerator pedal sensor, and worried about another fishing expedition.
Do you have any suggestions?

Thanks again for all your help with this issue.

Ray

[eracers999]

Ray:

In my opinion it is going to come down to 2 things.
What you did by disconecting the temp sensor was tell the pcm that it was -40 temp, it responded by advancing the pump timing all the way.

Back to the place that set your pump timing.
It is a 2 step process. Timing learn and tdc offset learn. There is a ton of info on this, but i suspect that may not be the problem.

I had to run one of the coolant temp wires to a cab controlled switch, key on, glow cycle, swich on, start. Worked perfect, but, it was a nagging imperfection in the back of my mind that i would figure out one day. All settings and data were perfect. I had suspect the timing chain being too loose, hence, retarding the valve timing and causing compression loss. Motor had 50k on it at that time.

Long story short the motor is out and tore down.
A new gm timing chain is suppose to have .500 slack when new, with a service limit of .800 .

When i took the front cover off i was looking for a loose chain, boy did i find it. Measured 1.200 and that my friend is rediculas.

When this goes back together it will have a gear set installed in place of the chain set up.

70k is what this supposed new chain had on it and had the symtoms as yours as soon as i was doing warm starts in the morning, ( sitting all nite on a warm summer morning ) When cold it started much better (not plugged in).

My recomendation to you is to take up your friend on installing a cab controlled switch in the .05v wire in the sensor circut.

Going to have to get some sort of sense of how loose is the chain is in your truck. Was it replaced?? Was it a el cheapo??

Kent

[Ray Walkerdine]

Kent,
Really appreciate your expertise. I just got off of the phone with GM and they are of the opinion that the block heater may be too hot. It is at 85 deg Celsius (185 deg F.). The diesel tech feels that if the block heater is changed it may solve the problem. The thought is that the disparity between the temperature of the coolant and that of the rest of the engine is confusing the temp sensor/computer/ What is your concept of this? What temperature does a block heater usually heat to? I checked the local parts store and they sell a 600 watt and 1000 watt block heater for the 6.5.

This would be a cheap fix, and I am prepared to give it a try, unless you think I am wasting my money.

As for the timing chain, I can only assume that it was brand new along with the engine. I do know that the mechanic did adjust the timing at least once, when there were other starting issues.

Back to work until 5:00 pm.

Thanks,
Ray

[eracers999]

Ray:

You do have 2 good batterys in the truck ???
Absolute must have.

When your done driving your truck and it's warmed up. After it cools down 1 hour i'll bet you can jump in it and it will start, with no glo plug cycle??

I need to know what make of scanner your mechanic used to set the timing on your 6.5?? If he is knowlegable on setting the timing on a electronic 6.5 he should be able to tell you his procedure he used, becase there definatly is one. Please relay his responces.

I noticed that you had it to the dealer and they were resetting the offset learn, you say you wound up at -1.14 You will get better cold starting if you go to -1.94 tdc offset. Did the dealer do a pump timing learn procedure,that is NOT the same as TDC offset learn.

We will leave it at that for now so as not to confuse you.

Good luck/ Kent

Lots of guys on the board run at that offset

[DmaxMaverick]

....and they are of the opinion that the block heater may be too hot. HOGWASH!!

By the time the heater heats up the engine enough to be too hot, according to your tech, it doesn't need glow plugs to start.

Convince your tech to chase another wild goose. That one won't fly.

[Ray Walkerdine]

Kent,
I will check into the questions you asked, but I do have one quick question. You mentioned that I must have two good batteries. The mechanic did say the the left hand battery failed the battery test, but if the battery is a problem why wouldn't cold starts be affected? It was about 15 degress here today, and the vehicle started ok when not plugged in.

Just a bit confused about the battery issue.

Ray

[eracers999]

Ray:

Just covering all the bases. When the system commands the glow plugs on, the glow plugs are going to get hotter if it has 2 good batterys. When the system is working right the glow plugs pull down the batts pretty good. If you are going after a starting problem then the basics have to be covered.

Later / Kent

[Ray Walkerdine]

Kent,

Tonight I performed a little test to see what effect the block heater was having on the engine. Here are the results.
Block heater on: Glow Plugs Light: Starting
20 mins 11 secs Immediate, Great
40 mins 9.5 secs Slight stumble,Ok
50 mins 9 secs Stumble, rough,
60 mins 9 secs About the same
80 mins 9 secs About the same
100 mins 7 secs
*** Failed to start on 3 attempts, required throttle to state, then very rough and smokey.
120 mins 9secs (Note: This time I squeezed the rad hose numerous times in an effort to circulate the warm coolant thoughout the block.) As you can see the glow plugs stayed on 2 secs LONGER, despite the block heater being on an extra 20 minutes. This is only speculation, but could a circulating type of coolant heater resolve the issue of inconsistant heating, and the temp sensor confusion.

Obviously the duration of the glow plugs is shortening as the coolent temperature rises. I am probably going to change the block heater just to cover all the bases, altough I don't hold much hope it this option.

After that I am weighing the options you mentioned I think I may install a cab controlled switch in the .05v wire in the sensor circut. I have read the article by Todd Smith regarding improving cold starts in the 6.5, but I think a simple switch would be adequate for my needs. The obtaining of the variable 12 volt relay is becoming a bit of an issue here in Canada, but one can be ordered for about $50.00 Canadian.
If you could give me some direction about how you installed the cab controlled swithch it would be most appreciated. I did a search of the board, but couldn't find a complete explanation. I think I should be able to do this

What is your opinion? Am I out in left field.

Thanks,
Ray

[eracers999]

Ray:

Super easy to install switch. Here goes.

Unplug your coolant temp sensor.
Using a volt ohm meter capable of reading .5v turn the key on and probe the 2 wires 1 of them will show .5 voltage one wont.
Cut that wire that has the .5 volt, strip the ends, and all you are doing is connecting a long enough wire to to each of the stripped ends to go inside the cab to a switch. You can use a but connector to connect your wires, but you should know the method of choice and 1 that i do is solder and heat shrink.
The switch choice should be a normally closed type switch one that you flip up to disconnect the circut and when you let go of it it comes back on its own to normal. I think they call that a momentary switch. You can use any type of switch you want, with me i cant remember to turn things on or off and you dont want to leave that on and drive.
When doing this circut it has to be protected and durable.
With mine i use it right before i turn the key to start, works great.

Good luck

Kent

[Ray Walkerdine]

Kent,
I just wanted to thank you for all your help. I installed the switch on the temperature sensor this weekend, and it seems to have solved the problems of starting when the block heater is plugged in. Barely even a wisp of smoke at -15 deg Celsius. I am still thinking about putting on the relay with the adjustable delay , but this will be fine for now. I have noticed that even when not using the block heater the engine starts better if I use the switch for 5 or so seconds when starting. Runs smoother with the slight timing advance. A mechanic told me the other day that I can ruin my computer, is this true?
Thanks again,
Ray

[eracers999]

Ray:



A mechanic told me the other day that I can ruin my computer, is this true?The mechanic that told you this did'nt tell you why did he? Cause he cant, cuase it wont hurt a thing. Glad to help.

Kent

[Billman]

Ray

Like DMax said, I don't believe your block heater is heating up too good. That's absurd.

What were outside temps when you found the blockheater warming the engine to 185F?

I don't use mine much, but I did notice with a Tech II that the coolant temp was approx 110F on a 25-30* day.

185 sounds like a lot...

[Ray Walkerdine]

Biily,
You are so right. I reviewed my post, and it should have read 85 deg Farenheit, which is not too how in my opinion either. The outside temp would have been around, 22 or so degress Farenheit.

The switch has seemed to have resolved the problems, but I still wonder why it is needed. Something must be out of whack somewhere in the system. But what? is the question!

Ray

[Ray Walkerdine]

Kent or any of you other knowlegable persons.
The toggle switch that I installed on the engine temperature sensor is working great. I was just wondering; is it ok to use the switch even in warmer termperatures, say 40 F to 50 F. I find that the engine starts with almost no white smoke and idles much better if I turn the switch on for at least 10 seconds.
Can I damage the motor by leaving the switch on for this length of time. I don't want to damage a brand new motor. Just for the record, any idea why I need to bypass the temperature sensor on a new motor to make it start right.
Thanks again,
Ray

[eracers999]

Ray:

You can use the switch any time any place any temp, just not when driving. I suspect a loose timing chain is your problem. You never did clear up the question of exact procedure that your mechanic used to set timing, before i say anything else i need to know this. Where was the pump set in the timing learn mode ? and what was the TDC offset set to??

Kent