Rough idle/smoke @ cold start

[adamdrives]

Originally Posted by v8volvo

Good news. Yeah, should start immediately on the first glow cycle, even at very cold temps and even if the engine is pretty tired. Should never take multiple glow cycles and generally you don't even need to wait out the light for the first cycle.

Sounds like you have a wiring issue causing the sticking glow relay. Two wires could cause this, in the 4-wire plug on the bottom of the relay - there's a brown wire that comes from the GP temp sensor and controls glow duration, if it has a bad connection it could cause extended glow time. There's also a starter wire, green I think, that tells the relay when the starter is running and shuts off the plugs a few seconds later. If this wire has a bad connection the relay won't get the signal to cut off. Wire harness problems on this era are common so you might want to inspect the wires, connections, check resistance, etc.

Thanks for the detailed response. The harness is new homemade, so connections and resistance shouldn't be an issue, but if the problem returns I'll look into it. I was looking through the wiring diagrams late last night, but when I started it this morning @ 20 F it fired on the first cycle and the indicator light went out. Hopefully yesterday was just a fluke. It did run a little bit rough (though nothing like before), and oil pressure seems to take a little too long to build, but it does start immediately on the second or third crank which is an incredible improvement. It feels like a real car now, not something I scrapped together . I can't believe they even sell the plugs I had in there before, not the same product. I will play around with cold start rpms and see if that hastens the oil pressure and helps it run smoother.

Originally Posted by ngoma

For the injector spill lines? You may see captive persistent air bubbles at the top of the spill line arcs. They do not necessarily indicate a problem with air intrusion.

I'm not sure on the terminology, I believe they are the fuel return lines. The line I replaced with clear was the small hose from #6 injector to barb on pump. It does have a few small air bubbles on top of the arc, but like you say they are likely trapped from when I removed the line.

Originally Posted by RedArrow

Your original write-up about the no-start/hard-start problem describes *exactly what was happening with mine a few years ago, when 3 of 6 glowplugs suddenly went bad. They were the good Bosch units but probably got tired, idk. If it happens again in the future, I will only use the Bosch Duratherm again.


BTW, where to get the proper, CLEAR, diesel rated hose from?
I see tons of similar items all over the web, but no sellers mention diesel fuel.

It`s nice to see green diesel (without bubbles) in the clear hose! Those banjos need a good cleaning too, I`ll do it next time, when I replace a section of rubber fuel hose junction under the car. I just want to get diesel rated tubing now... any idea?

Nicely done. I only replaced the small fuel return hose as I was under the impression bubbles there could indicate air intrusion (now not sure if this is the case) but the line I got was from Home Depot. It was simply labeled fuel line, it's light translucent pink or orange. It probably won't be a permanent addition. I'm sure you could find something on amazon or by calling your local (not incompetent) parts store. My feed line is pretty discolored too, might be a good project.

The strange thing is all these plugs were within spec for resistance (identical to brand new duraterms) but clearly the quality or design is inferior. They were $4 a pop wholesaler discount from rockauto, so I got what I paid for. Good thing I didn't buy an extra set

[adamdrives]

One more observation was that the car doesn't want to start right away when warm. It started faster when cold. The GPs didn't cycle. Indicator of low-ish compression? I lost the quote, but somewhere in this thread or another a member said that in good condition the car should start immediately on the first spin of the starter. Now I can't settle for anything less At it's fastest, it's still the 2nd or 3rd crank. Maybe that's an indicator of lowish compression as well, although I suppose it could be any number of things in the fuel system. How fast do your cars start up?

[ngoma]

Originally Posted by RedArrow

BTW, where to get the proper, CLEAR, diesel rated hose from?

Remember this post?

http://d24t.com/showpost.php?p=7387&postcount=6

[R.Mojica]

Mine always starts faster and smoother as long as The temperature in the engine is high enough that the glow plugs are not needed.

[adamdrives]

Cold starts have been much better since new GPs, but yesterday it ran a little rough after starting. It had snowed overnight and gotten into low double digit temps, so I attributed it to that. This morning it started well after only one cycle, but quickly started to run rough, bouncing rpms, similar to before with bad GPs. I wonder if there is some issue with my control unit that is making the GPs wear out really fast, or if it's just the colder than usual temps. Odd that it initially starts fine they quickly runs crappy. I haven't made any changes to the car except driving it a little harder than usual up some hilly areas. It's supposed to be cold all week so I'll see if the issue stays the same or gets worse.

[ngoma]

Is the cold start waxstat functioning? Is the cold start lever and ball set correctly?

[adamdrives]

The waxstat looks to be functioning, there is much tension on the cable when the car is cold (hard to disengage CS for setting timing) and when warm it is relaxed. I believe there is a procedure to test precisely but this seems adequate.

I'm not sure what you mean by cold start lever. Do you mean the lever on the pump? I haven't touched that. The ball stud has been moved around a few times, I need to get that fine tuned. The odd thing is that my cold start RPMs start lower and raise in the first minutes of driving. Then when the car is hot, they drop back down. Usually I just keep them up with my foot until the idle clears up.

I tested the entire GP system and everything works exactly as it should. I didn't realize that in certain temps the controller keeps the plugs on for a few moments after the indicator light goes off. I have yet to test it, but my theory is in very cold temps the controller isn't holding them on long enough. That's why it starts strong, then takes a dump after a moment or two. Will have to get out the test light one morning. Not really my cup of tea first thing in the cold but only way to be sure.

Also lost 1st and 2nd gear right before the snowstorm here in NY, the bushings at the bottom of the shifter rod were missing and broken. In a pinch cut up some 240 endlinks I had in the scrap bin to make solid bushings

[ngoma]

The cold start mechanism does two things:
1. Pulls a lever that internally advances low-rpm IP timing
2. The same lever has a ball stud (item #2 in this diagram) that nudges open the IP's "throttle" lever slightly off its normal resting position on the idle speed set screw.

So you get smoother idle when cold, as well as higher idle.

Check the IP throttle lever position at idle when warmed up. It should be resting on the idle set screw. Compare that to its position when cold. When cold, you should see the same throttle lever several mm away from the idle speed set screw. (Correlating to approx. 1100-1200 rpm.) Note how the ball stud on the CS lever is pulling the throttle lever open. You can adjust that ball stud on its slot mount for higher cold idle speed.

NOTE: The cold start lever is extremely hard to manipulate by hand while the engine is not running (i.e. IP is not spinning.)

HERE is a great CS troubleshooting checklist. Highly suggested you follow it.

Here are a couple of forum threads on the subject. There are more.

d24t.com/showthread.php?t=822

d24t.com/showthread.php?t=1201

[adamdrives]

Thanks for the link. Unfortunately I don't see any green dash in the pic (colorblindness or it's just unclear), so I'm not sure about the arm resting on the pump body. My cold idle was around 1000 so I bumped it up to 1200 by adjusting the ball stud. I'll see how it starts tomorrow after sitting overnight with corrected CS idle. When warm it idles right at 900.

I don't have a pic of the pump with CS connected in front of me right now, but it seems to me that if the ball stud was adjusted to be too far away from the throttle tab (as it was in my case) then the CS lever on the pump would be allowed to move more and advance timing excessively (?). Maybe that can affect cold starting as well.

[ngoma]

Green dash? sorry, you lost me there.

Originally Posted by adamdrives

...it seems to me that if the ball stud was adjusted to be too far away from the throttle tab (as it was in my case) then the CS lever on the pump would be allowed to move more and advance timing excessively (?). Maybe that can affect cold starting as well.

No, the CS lever moves only a small amount anyways (guessing less than 20deg?) and advances the IP timing only a small amount (few degrees?). The location of the ball stud on its slide (in any position) does not control the amount of timing advance. It DOES control how much idle RPM boost at cold start (and at all temps if the waxstat has failed).

Many have found, that for a reasonably sound engine, that the CS mechanism is not required for starting, at least for temps down into the teens F. Might take marginally more cranking, and a few more seconds of rough running, but will start relatively quickly w/o the CS. We're talking an engine with decent compression, good cranking speed, and all 6 functioning GPs.