hard cold starts with white/blue smoke

[sths]

I have a 1995 Chevy with the 6.5L turbo diesel. I have replace the glow plugs (with ac-60g's), replaced the glow plug controller, and have 11-12 volts at each plug wire. In the mornings I have to try 3-4 times to start the engine and when it starts it stumbles, idles rough and then smooths out. This comes with a large amount of white/blue smoke from the tailpipe. I noticed when I plug in the blocker heater overnight or run the truck for awhile, it will start up just fine and a very small amount of smoke. Can anyone help me with this frustrating issue!?? Thanks, Sean

[93GMCSierra]

check to see if your lift pump is working correctly.

[DaveNY]

Where are you and how cold is it when you start up. Cause it sounds like you missed something in the glowplug dept? Smoke means there is fuel, white is unburned. I would recheck GP votage and then GP themselves. Dave

[rustyk]

Also check the fuel return lines...

[Ken9665]

Did STHS find the problem? I have also replaced the injectors and glow plugs recently. The hard starting black smoke was replaced by the white/blue smoke; looked like progress to me. But, the starting was still hard. I was looking at the glow plug connectors (which seemed way to easy to wiggle and pull off) and decided to replace the easy side, which seems to have helped a little. I think the frame mounted lift pump is working, I hear it running. The relay was the next target. Can the relay work intermittantly? Can someone recommend a volt meter that has all the bells an whistles for working on these engines? It runs fine after it fires up on all 8. Winter is on the outskirts of town and I would like to get all the glow plugs working so I can get home at the end of the coming cold days!

[Mark Rinker]

I battled with two high mile 1994s for a few years - same problems. Worse yet, they were snowplow trucks, so had to be ready to go whenever the weather was crap.

Both got new glows, new controllers, new lift pumps, but would not dependably start in even moderately cold weather (anything below freezing temps).

Finally gave up and kept them plugged in 24x7, with a 110V trickle charger mounted under the hood to maintain the batteries, also carrried a small 1100w portable generator during really severe weather, or when away from 110V plug to run block heater and top off batteries.

Check all battery connections and grounds, you might consider a new starter, if its not spinning fast enough, you'll never get good cold starts...the OEM Delco starters are the best in my experience. Expensive, but they crank faster than remans or generics.

[Robyn]

This is a common issue with these engines when they get some serious miles on the IP, injector nozzles and the glow plugs.

Glow plugs are the first place to check. If this does not result in resolving the issue then the injectors need to be checked for POP pressure and spray pattern.
If the POP is low and the spray is sloppy the engine is going to be hard to start and cough up copious quantities of blue smoke.

When the injectors start peeing off over into the corner of the Precup things just dont work well at all.

If the glows and the injectors dont do the trick then the ugly finger is pointing at the IP.
If the IP cant make enough pressure at cranking speed then things go south real quick.

***** NOTE**** be sure that the starter is a whippin that little monster over at a good clip. In cold weather if the cranking speed is slow the whole program goes right out the window.

Slow cranking equals lower compression and when that happens all bets are off.
In summer time this issue can go almost unnoticed and the rig can start fairly easily no matter.

1 Be sure the cranking speed is good. (battery cables, batteries, starter)
2 Glow plugs working and glowing cherry red all the way to the tip (new is better)
3 Injectors working properly. (POP and spray pattern)
4 The IP is the last stop when all else has been checked.
5 If the filter has not been checked or changed lately, toss in a fresh fuel filter.
*** Check #6 *****
6 Another sometimes overlooked issue can be the coolant temp switch in the water crossover. If this little beast has gotten hinky and is not sending the proper signal the cold advance may not be working right and this can cause poor cold start quaility. Unplug the thing to fool the ECM and try the start up. If it starts good then there is the gremlin.
The coolant temp switch sends different voltages to the ECM depending on the engine temp and if the voltage is wrong the ECM may think the engine is warm and the cold start characteristics will be real sour.

A scan tool is very handy for checking things like the CTS as you can see exactly what the ECM is getting. After sitting all night the engine coolant temp shown on the tool should be very close to ambient.

BY disconnecting the switch the ECM will think the outside temp is like -30F and give the engine all the advance there is available. (IT MAY RATTLE A LOT) no worries though as soon as it starts plug the sensor back in.

Hope these items get you going

Robyn

[Ken9665]

Can you cite a reference I for the procedures? I can find the coolant temp sensor to try that.

The injectors are new Bosch as are the glow plugs 60G. I hope I haven't installed the one in a thousand part that should not have passed quality control.

The spray pattern and POP, I'm guessing here, would need to be checked on a test bench. The glow plugs could probably be checked with a multimeter. The "glow red" test would probably check the melting temp of my fingers.

The IP was replaced under warranty in 2005. I had them reinstall the new PCM on a heat sink from US Diesel.

Is a scanning tool a necessary tool? Can it determine problems with every sensor on the engine? How often would it pin point most engine starting and running problems?

[DmaxMaverick]

Glow plug cycle. Simple as that. I may be going out on a limb, and could be wrong, but it is most likely just that simple. Check this before continuing onto any other diagnosis.

When you installed 60G plugs, you installed a plug that requires twice the glow cycle time to reach near the temp of your original plugs. Pulling the temp sensor connector (like Robyn described) will give maximum glow time designed into the system (which was not designed to use 60G's or similar rated plugs), and may make your cold start issue disappear. If the situation improves, but still isn't quite up to what it should be, you'll have to jumper the GP relay for a longer glow time. After you confirm the problem is the GP cycle time, you can modify the system for a more permanent solution.

[Ken9665]

Yup, the coolant temp sensor was disconnected and it cold started like before, like before, when it was starting without all the smoke.

Anyway, the Peninsular Marine folks have a deal/kit to make the time adjustable. It comes with instructions, I like instructions.

I'll head down this path and see how it goes.

I hope STHS is reading this, it was his thread that caught my eye and got me to this point. Thanks to everyone for your willingness to help.

[DmaxMaverick]

The Peninsular controller is a good one. A little more costly than other solutions, but certainly the best for someone who likes instructions. Just don't try to overcomplicate it. It is what is, and does no more than you already know.