Got a question for you guys. Last year something with my glow plugs went on the fritz...initially one of them shorted out, then they started not cycling correctly. I hooked up a push button switch and apparently burned out one or two because the truck was idling rough right after I started it even when it was warm. I accidentally burned out pretty much all of them by cycling them too long in the spring, so I replaced 7 of the 8 (didn't even try the one under the turbo) and didn't cycle them as long with the button.

Anyway, I noticed that the WTS light seemed to be staying on the appropriate amount of time (7-8 sec) when I turned on the key, even with the pushbutton. I decided to hook the GP controller back up, and it cycles the GP's correctly (7-8 seconds at first, then alternating cycle after the light goes off).

But, since it has started to get colder in the morning the truck idles very rough on first start, even if I have it plugged in for 3 hours in the morning. In fact it seems to start about the same, plugged in or not, but the nice thing about it not being plugged in is that I can kick on the fast idle and that smooths it right out (if it's plugged in, fast idle won't come on). So it idles rough and blows a whole bunch of bluish-whitish smoke.

Why does it idle so rough? If the glow plugs are cycling correctly I don't understand why it doesn't idle better.

 

Im new to diesels, but from reading (our 6.9 is doing the same thing) several people have suggested that there could be air leaking into the fuel system overnight.

I am gonna put new tee's and return lines, o-ring in mine and se if that helps.

You can unscrew your fuel filter in the morning, and If it is NOT plumb full, then you have an air leak, at least from what i've read.

Hopefully someone smarter than me will be along shortly to offer more assistance!

good luck!

 

glow plugs should come on for 10-15 seconds. mine come on for about 10. 7-8 seconds plus rough idle/smoke on start up tells me you may have one glow plug burnt out. check all the glow plugs. it one is bad replace it and they should come on for atleast 10 seconds.

 

Well, I just did the return lines last year too because one of them was dripping fuel at one point. I can't imagine I'd have air getting in there, it certainly doesn't act like it any other time except on a cold start, but I may have to check the fuel filter.

I recently put a fuel pressure gauge on the filter head inlet, and at idle I'm only seeing a max of 1.5 psi, so I may also have a weak lift pump.

edit: Really? Dammit. It's too hard to find one bad glow plug. I bet it's the one under the turbo.

 

unplug the wires off the top of the GP's and hook a test light to the positive battery post and touch the probe of the test light to the glow plug terminal. If it light ups, the plug is good, if it don't its bad!

 

i would lean towards one bad g/p. i fought the same exact symptoms on my 93idi non turbo last winter. not saying for sure you have the same problem but sounds like you have the same symptoms. i noticed when one of my g/p's went bad they would only cycle for 7 to 8 seconds. the truck would be hard to start becuase the g/p's werent hot enough. the truck would smoke becuause one cylinder wasnt' igniting. i tried to replace the bad glow plug only to find out it was stuck. i left it in. after a few weeks another g/p went bad and they would only cycle for 3 seconds or so. fortunatly i was able to replace the second faulty g/p and keep limping along. ultimatly it was a combination of a bad glow plug controller and freaking autolite g/p's. everyone told me not to buy them but i did because they were half the price of motorcrafts. i ended up buying 10 autolites before i wised up.

has anyone told you how to test the glow plugs? take a test light and put the clamp on the positive battery post, unhook the glow plug and take the pointy end of the test light and put it n the exposed tip of the glow plug. if it lights up its a good g/p. if it doesnt light up the g/p is bad.

 

one other thing, if you don't see a difference when you plug your block heater in maybe its not working. last winter when i was having all these troubles i tried plugging my block heater in and discovered it wasn't working. it wasn't working because it was leaking antifreeze onto the electrical plug and corroded it. i bought a new cord and it worked for all of 2 days. when it did work all i had to do was bump the starter and the thing fired right up. when i took it to the mechanic to replace the glow plugs/controller i had him replace the block heater. of course this was in march so i no loner needed the block heater. i haven't tested it yet but i'm fixing to as soon as i figure out how to tap into an outside lamp at the appartment parking lot.

 

I knew about the test light method, it's just difficult to do sometimes because the glow plugs can be so difficult to get at.

Oh, and yes the block heater works as the truck blows warm air out of the vents right after you start it when it's been plugged in.

Ah well, guess I'll have to get to testing those GP's, though I have a suspicion I know exactly which one it is.

 

Come on man, you knew it was going to be the one under the turbo.

 

Murphy's Law 548.

If your vehicle has multiple copies of the same part, the one that fails first is the one that is the hardest to get to.

On a turbo engine, number 7 cylinder glow plug is his favorite since it is under the turbo.

 

Yep, I was right. That was the only one I checked and, surprise...it's dead. I couldn't get it to work via the test light method at least, and the connector was fubared (someone did a backyard fix on the connector and I have a sneaking suspicion I'm going to find an Autolite GP in there, same as was on the rear cylinder on the driver's side....)

 

G-Man, I know you know, but be careful pulling out that back GP especially if it is an Autolite. Shoot a little PB Blaster around the threads just to let it soak and losen it up if it is stuck. Then when you replace that glow plug or any others for that matter, put some anti-seize gray grease stuff on the GP threads so they never lock in.

 

Yeah I know, the driver's side autolite came out fine and it was burned out too but not swollen, so I'm hoping this one will be alright (it's gonna be a bitch enough to get at anyway)

The plug looks pretty corroded and there's a bunch of crap laying around it that I will have to get out of there also.