GP tips gone

[jayro88]

Hi all. So I went to replace my GPs today. I had noticed harder cold starts and less of a voltage drop when glowing them than before. All GP were zd-9. All of them came out easy, but the ones from my rear 2 cylinders were missing their tips. I have no idea how long they have been like this and I have had no issues with the motor or performance. I DD the van and just got back from a 6hr round trip towing my 7500lb camper. So I know the “real” fix would be to pull the heads, but that really isn’t an option right now.

So is this one of those things where I am just on borrowed time if I keep driving it, or is it one of those things where if it was gonna cause an issue it already would have?

What do y’all think?

At some point I do plan on pulling the motor and studding the heads, but that won’t be for a little bit.


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[Selahdoor]

Can you give us a pic of the GPs?

 

[The_Josh_Bear]

Sounds more like they eroded than broke off clean? Just a guess since you said no noises or odd running. If so your timing is likely too advanced. Happen to have a meter?

 

[jayro88]

Can you give us a pic of the GPs?

Here you go. Middle one it a full plug. 2 others are the broken tip ones.

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[jayro88]

Sounds more like they eroded than broke off clean? Just a guess since you said no noises or odd running. If so your timing is likely too advanced. Happen to have a meter?

I don’t, but I will be replacing the pump and injectors in the near future. I already have them sitting in the garage. When I do that I will make sure timing is good. 7.5 + or - 1 BTDC, correct?


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[Thewespaul]

The spec is 8* +/- 1.5*

Jayro, since you’re going to replace the injectors down the road, would you mind taking note of which injectors coresponded to the missing injector tips, and if you don’t mind, could you send those injectors to me and I’ll do a post autopsy on them? My theory is the injector pintles have worn unevenly and are shooting at an angle contacting the gp tip.

 

[jayro88]

The spec is 8* +/- 1.5*

Jayro, since you’re going to replace the injectors down the road, would you mind taking note of which injectors coresponded to the missing injector tips, and if you don’t mind, could you send those injectors to me and I’ll do a post autopsy on them? My theory is the injector pintles have worn unevenly and are shooting at an angle contacting the gp tip.

Sure. I am hoping it will be done in the next 1-1.5 months. The pump and injector replacement goes along with a turbo kit install.


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[IDIBRONCO]

Sounds more like they eroded than broke off clean?

This is my guess too. I believe that another cause of this is from an injector that still bleeds fuel after it fires. I know that I always had one glow plug that would burn the end off like yours before I bought my Moose Jr. and BBs from Mel.

 

[Agnem]

Eroded tips are traditionally a sign of advanced timing, so possibly the injectors in those cylinders are popping lower than the others, which would advance the timing there. The spray pattern is not much of a factor, as in my IDI cutaway head which is in the Moose Museum, you can clearly see that the injector basically is aimed at the glow plug tip anyway, more so in the 6.9 then the 7.3 where they moved it slightly out of the way.

 

[Thewespaul]

I know that’s been the traditional belief but I’m looking for evidence that points towards that, I’ve run injectors that had 26* of injection duration and I’ve run them up to 14* in my testing to get most the fuel out before the exhaust stroke, and never had issues with eroding glow plugs. Justin has run IDIs up to 18* of timing with his stage ones and never had this issue, so I think there’s something else causing the erosion. Advancing the timing is going to increase cylinder pressure and decrease egts, I’ve run enough cylinder pressure to shatter idit pistons, and enough egts to split cylinder heads lengthwise across all the valves, and on that engine all the glow plugs tested great and were used again in the next engine. So either there’s a group of factory defected zd9s that are all having this issue or the injector is firing onto the tip of the plug eroding it off over time.

 

[Agnem]

Perhaps. I know the only reason we have traditionally adhered to this belief is that it is stated somewhere in the IH or Ford service literature.

 

[Thewespaul]

I’ll have to look through some of my books and see if I see any reference to it

 

[Black dawg]

Never had that in a 6.9-7.3, but a 6.2 and a 6.5 (with zd9s in them). Burned 50/50 wmo/diesel in them year round. Hard white stuff would build up on the injector tip, and make the spray pattern just a solid stream. If the injector tips were kept clean it wouldn't happen.