Could it be the glow plug selonoid?

[Poorman]

Been fighting this smoky startup (bad) for awhile on my "86" 6.9 f350. I'm on a manual switch, last week I pulled the glows out and I had 5 bad ones, they were only 1.5 years old with 5000 miles on them, they were Beru. I needed to get the truck going to deliver some wood. I could only find AC Delco 8g locally so I bought 5 and put them in thinking I would do more research and order more online. Putting the 5 new plugs in didn't make much difference. I ordered in a set of Bosch 80034 and installed them last night. I was surprised that 4 of the 5 AC delco plugs I installed last week were dead but all three of the Beru's that were old were still good? I put new connectors on the harness to match the Bosch 80034"s (narrow spade) and installed them. Cycled them for 10 seconds and it fired up, smoking terrible and missing so bad I could hardly keep it running, I tried a few after glows but didn't change anything. The symptoms I've been having were much worse after installing the Bosch plugs. After thinking it over I remembered there's been a few times over the last year that I've hit the glow button and my ninth plug in the cab didn't light up, but always would on the second try. I didn't have a 9th plug in last night. Could it be that the solenoid relay is acting up? (rhetorical) Can a solenoid work but not pass on the proper amperage? Intermittently? And I think the Beru's are 6 volt and the Bosch I think are 12volt, would that put more work on the solenoid and make it more prone to failure? I'm going to replace the relay but would like to better understand what might be going on! Compression is good and if I leave it on the heater for 4 hours it starts pretty clean. THANKS

 

[Kdo58]

It could be the solenoid or even the switch, I use a warn winch solenoid ,you need to use Motorcraft glow plugs, most from Amazon or eBay are fakes.

 

[Lumberjackchuck]

Did you test your glow plug harness? Do you have a good connection to the plugs?

 

[IDIBRONCO]

You can't mix and match the Berus and the Bosch and expect good results. The Bosch plugs need a longer glow time than the Berus do. It's possible that the same thing could have happened with the Delco plugs too. I would get all 8 matching glow plugs and see how it starts. Then go on to other possible issues.

 

[gnathv]

Check the voltage drop across the glow plug relay. With a voltmeter set to dc, put the leads a the two large lugs on the relay. Have someone push the button and read the voltage. Should be less than 1 1/2 volts. If it’s more your relay is bad.

 

[Poorman]

So I tried jumping across the solenoid just to take the solenoid out of the equation and no difference, even jumped direct from the battery. The harness is two years old with new connectors to match the bosch plugs, tested to make sure voltage is getting to plugs. IDIBRONCO,I didn't mix and match beru's and bosch, I mixed beru's and delco's but only while I was waiting for the bosches to arrive. GNATHV, I will try testing across the solenoid while engaged, don't understand why it would be 1.5 volts?
I've been reading a lot tonight, a lot of what I read makes me think the bosch plugs will heat faster and a lot makes me think slower and that I need a longer glow time. In the morning I'm going to try 20 second glow time and see what happens (instead of 10). It's been said that you can't burn them out, I hope that's right. Thanks

 

[Rdnck84_03]

Yes the contacts in the solenoid can get burnt and not always make contact. With the 12 volt plugs you need to double (if not possibly a little more) the glow time.

James

 

[gnathv]

The voltage shouldn’t be more than 1 1/2v. 1 1/2v would be contacts beginning to pit.

 

[Lumberjackchuck]

I will try testing across the solenoid while engaged, don't understand why it would be 1.5 volts?

Ideally you’d want almost no voltage drop across the contact on the relay, you want it all to drop across the glow plugs in the circuit. But everything has a little resistance and the glow plugs have such little resistance you’ll have a significant amount of voltage drop before you even get to the glow plugs.

It’s just Ohm’s law, current multiplied by resistance equal voltage. So the higher the voltage drop across your relay, means the higher it’s resistance through that contact.

I do have a DC inductive ammeter, I’ve never tried reading what these glow plugs pull as far as amperage and how much variation but maybe I’ll try and report back.

 

[BeastMaster]

I know I am waking up a stale post but upon reading it, I would like to leave my personal experience which is almost identical to Poorman's experience.

My glow plug relay was welding itself ON! Erratic at that. Sometimes it would clear by itself but at first I did not know what to look for. With 20-20 hindsight, watch your voltmeter like a hawk while your engine is starting up and familiarize yourself on its typical antics.

The glow plug controller cycles upon starting and should stay open after a few seconds after starting. The glow plugs take about 200 amps, and the voltage drop is noticeable.

When the engine catches, it starts powering the alternator, then the alternator will try to hold the battery rail at about 14 volts. The alternator will not be able to supply enough current for the glow plugs, so the battery rail voltage won't make it to normal engine run voltage.

A few seconds after starting, my voltmeter continued to wag as the still cycling glow plugs were switched on and off by the glow plug controller.

However, the voltmeter gave up the wagging as I subsequently discovered I no longer had any operable glow plugs! ( I no longer had a 200 amp load either! ).

If those contacts weld shut, you have just a few minutes to get your battery disconnected ( Suggest disconnect Both battery negatives, so a slipped wrench contacting the frame doesn't result in yet another unwanted weld ).

Even though I had been chasing this bogey for several months, and knew exactly what to look for, when I noticed the unexpected wag in the voltmeter, I lost two more glow plugs before I got the batteries disconnected.

There is no power shutoffs for the glow plugs. That relay IS the only thing between battery and plugs. If it fails ON by contact weld, turning the key off doesn't help. The relay coil can't undo a welded shut contact.

Being a battery disconnect switch is a helluva lot cheaper than a set of glow plugs, I would suggest putting one in the glow plug feed circuit.

If you can make up a test light, wire up one on the glow plug rail so the lamp will illuminate upon glow plugs being powered ON.

That gives you a "heads-up" for things like this. Snake it to where you will you will notice it should it come on while you are driving, and leave it in place until you get to the bottom of this.

I am always repurposing "bad" dual filament brake/turn lights (1157 type ) so I can still use the remaining filament for test purposes. I end up giving these things away every time I make one. I wire them in...semi permanently...and leave it be until I find the gremlin, even then leaving it there until I am sure the gremlin has gone. Also, if you put a new bulb in there, you will not only have a test lamp in your trouble bag, you also know where you have a good lamp stashed!

Anyway, I had been away for a while, saw your post, and leave this in the hopes it helps someone else researching the posts here, just as I do when trying to fix my beast.

This was one gremlin who gave me a lot of aggravation before I got to the bottom of it.

A lot of people are seeing this. It appears someone has cheapened a manufacturing design, and multiple re-branders are selling the same pretty gremlin in a shiny case. I ended up going all manual for glow plug control, with a completely different power contactor. It's a much heavier industrial power contactor...White-Rodgers model 586-902. Thewespaul ( https://www.oilburners.net/threads/classic-diesel-designs.83766/ ) on this forum kits these up for us. It's not a cheap contactor, but then, neither are sets of glow plugs, alternators, batteries, and starter motors, all of which are pretty heavily taxed when the glow plugs fail. Although I used my own design, I am very impressed with the Classic Diesel Design kit and I can't do any better...he has best stuff out there from what I've seen.

That White-Rodgers ( Now an Emerson part ) is a top-of-the-line industrial power contactor with impressive specs. ( I use the same one I use to build Arduino interfaces to hazardous things where a fail-on would result in a personal disaster. Triacs often fail ON! I still want that old-school air gap in case lightning or nasty inductive kickbacks visit me through the power line. ).

Glow Plug Solutions from Classic Diesel Designs

Thank you again to everyone who participated in the preorder sell! I was blown away by the amount of interest in these kits, so Id like to take some time here to showcase some of the interesting details with the various versions, as well as post the new prices now that our sale has ended. Our...

www.oilburners.net

I killed my gremlin three years ago. It hasn't been back. But he sure cost me a pretty penny to evict.

 

[IDIBOBS]

Yup. I can not stress enough to just buy new plugs, and controller every year or so and move the controller the the passenger fender. AND re wire your plugs. It’s so cheap and easy.

 

[Nero]

Every year?? You madman... I still have most of my original plugs from when I got my rig in 2011, just replace them as they go bad. My original GPC is still working, but I did relocate it.