Rough idle/smoke @ cold start

[adamdrives]

The car had the same hard starting issue this morning, so I went ahead and put the Bosch plugs in. The whole process only took about two hours, I could have cut that down by half an hour atleast if I would have put the 8mm nut on the 6th plug before installing it into the head. Wasted a bunch of time trying to get the little bastard on before I realized the only reasonable way to do it is before installation. Having the right length 12mm wrench makes all the difference, actually screwing the plug in only really takes a few minutes once you have the right position. Tightening the 8mm nut with the plug installed is of course fiddly as well, but not too bad with a long handled open wrench. The most time consuming part is probably getting the plug into position in the head, using a combination of a magnet tool to get it in position from behind the pump bracket, leveraging it forward with a long handled screwdriver, and then rotating it a few times with a magnet took some patience. In any event, they all went in without issue, and the car started right up. Leaving it overnight will be the real test. In temperatures around freezing, is it typical to have to cycle the plug multiple times to get a quick start? I've seen some videos of d24ts being started after months of sitting and starting up quickly, but it's not clear how long the plugs are energized. I don't think I've had a quick, trouble free cold start in any condition just letting the plugs energize once.

I'm still curious about if my voltage drop was acceptable, but thinking about it I believe that a voltage drop of about a volt could make sense considering the plugs are drawing nearly 80 amps. I took a DC theory class in college a few years ago but can't remember the equation to calculate what the "ideal" drop should be or if it would be the same from a power source like a battery.

I also picked up some clear fuel line to install between the injectors and pump to see if I have any air bubbles if the starting problem persists.

[adamdrives]

Went for a drive this morning in ~25 F weather and she started right up on the second cycle. Very cool. Issue now is that my GP relay is sticking, indicator light wouldn't shut off. Had to unplug it. My old relay would stick occasionally but would click off if I gave it a tap, no dice. Not sure why that could be or if I messed something up while testing the system. Either way, it was definitely the plugs that were the issue. Pretty crappy that brand new plugs were no good.

[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.

[ngoma]

Originally Posted by adamdrives

I also picked up some clear fuel line to install between the injectors and pump to see if I have any air bubbles if the starting problem persists.

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.

Originally Posted by adamdrives

Pretty crappy that brand new plugs were no good.

Champion GPs are problematical, so are Autolite.

[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.


Getting that clear fuel line replaced is always a good idea. I have been hating to see the old, discolored (fully dark brown) hose between the filter and the IP, so I fixed it today.
Thanks for the `quick project` idea... although I will have to redo it asap because I used vinyl clear tubing, that, I`m sure, is not tolerating diesel for too long.

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 took some time to do this fix, bc the old fuel line lost all of its flexibility, completely hardened, became brittle so it did not give up easily.
I decided to not risk disturbing the pump AND hurting, scratching, denting the banjo nipples by using tools; so I removed both fittings with the hose. After that, I simply torched the old hose endings a lot until I could pull them right off.

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?

[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.