Black Box

[79GLIDE]

94F350 7.3 turbo, What is the black box on top of the passenger valve cover near the fire wall. Makes a loud clicking noise sometimes and seems to hang up briefly on occasion causing high RPM's. Hard starting when cold, then smells flooded with cloud of white smoke when it fires. Otherwise runs great, idles smooth, decent power and no smoke normally. I'm no idiot, just new to diesels. Thanks.

 

[The Warden]

Do you have a picture by chance?

Offhand, it sounds like the glow plug controller...

 

[Pipeliner_86]

But a GP relay shouldn't have any effect on rpm. Only the high idle solenoide or your right foot should change engine speed.

 

[79GLIDE]

I don't have a picture, but it looks like some kind of electrical relay, vented housing.

 

[Diezel_Cowboy]

You mean this? It is the GP controller.....it is a piece of junk see tech articles about how to bypass.

 

[Diezel_Cowboy]

It is not actually controlling the rpm's.......that is controlled by the high idle solenoid completely seperate thingamabober even though they do come on together in cold weather

 

[79GLIDE]

Since there is no computer control, is the fast idle solenoid controlled only by a sender, or is it mechanically controlled by the accellerator similar to a carbuerated vehicle.

 

[79GLIDE]

Yep, that's the unnecessary part i'm looking at. I'll check the article to bypass. I have a feeling it's not lighting the glow plugs up all of the time because my cold starting problem is intermittent. Thanks for the info.

 

[dbarilow]

Dont be so quick to bypass the controller. A properly working G.P. controller will start the truck just fine. My truck fires like a champ at 11 deg.

 

[Mr_Roboto]

Well that is supposed to click, it's a solenoid.

I would suggest replacing all of your glow plugs before fooling with the controller. If one or more glow plugs are bad the controller will not cycle properly.

There is NOTHING inherently wrong with the 7.3 GP controller. It is the 6.9 controller that is recommended to bypass.

 

[Diezel_Cowboy]

yeah it will start the truck if the system is in tip top shape (all glow plugs are good) but if one is bad you are out of luck, HOWEVER, bypassing it will still yield good results with a few bad plugs not to mention the plugs dont come on or cycle when they are not needed which prolongs their life

Bypassing the controller may not be your cup of tea but I would and have recommended it to everyone because it makes perfect sense to me and I have had zero problems with glow plugs since i bypassed the controller a couple of years ago.

 

[The Warden]

Dont be so quick to bypass the controller. A properly working G.P. controller will start the truck just fine. My truck fires like a champ at 11 deg.

What he said. I know that some don't like the 7.3l style controller, but it seems to me that failures of those systems are rather rare...certainly rare compared to the 6.9l system. And, a push-button system is not foolproof by ANY means.

Even with carefully timed cycles, I went through two sets of plugs in a year with a push-button system on my truck...compared with never burning out a set, even with the original 6.9l system (even though the controller stuck on once, but I was able to get the relay disconnected in time). I scrapped the push-button system in favor of the 7.3l system, but I'm still working out the bugs (I made my own wiring harness, finding out after the fact that resistance in the wires is crucial...and, I think I actually made the wires too big!)...

I'm not saying that the 7.3l system is perfect, but like dbarilow, I wouldn't be so quick to dismiss it either...

 

[79GLIDE]

Sounds like a compromise is in order. I don't know the maintenance history on this truck, 230k on the clock. May be best to replace the glow plugs and save the good ones in the truck now as spares. The idea of being able to manually activate the glow plugs only in cold start situations makes sense. I've read about the risk of over heating the glow plugs with a bypass/manual type system. I just don't want to face daily hard starting headed into winter. Thank you all for the input.

 

[ttman4]

Mine looks like Diezel_Cowboy's, except his looks washed, waxed, buffed & shined compared to mine
Well I don't know what everybody else thinks, but on my 7.3 controller thingie....I clipped that controller black ground wire that's about 4-5" long that goes down & grounds under/thru the bolt that holds the controller in place.
These 7.3 controller thingie works by closing/conecting the ground anyway. I clipped, spliced, then ran wire up to, & thru my pushbutton switch, then just find a good ground past the pushbutton.
Works great....turn key on, pushie the button, count 6-8-9, hit starter.....smoke & roll!!!
Had mine redone for 2+yr & no glowplug changing....before that new set every 6-8-10mo.
If it's real cold I may turn key off 2-3-4 seconds, then do it again.
If the key is on & I'm pushing button, & it warm enough to not need all 7-8-9 count, it'll kick off & start cycling on it's own till I release button. Works just like it used to before I got to cutting & splicing.....except now it doesn't keep cycling & wear out glowplugs.

& yes, 1 plug out= hard to start, 2 plugs out= nearer to impossible to start, 3 plugs out you better get the canned glowplugs out & start spraying.....about then rolling down a big hill helps too

On edit....now that I think things over, I don't know why I bought that big handfull of ZD9's while back...these'll last till I'm gone!!!

 

[Compu Doc]

If the wait to start light is going off before 10-15 seconds then you have one or more bad GP's. I had 3 bad ones. Replaced all 8 with Motorcraft (beru's) and all is well. I'd sya leave the controller on the truck and replace the GP's.