New to diesels, having hard starting issues, glow plugs? Help

[KodiakForge]

hey guys,
I purchased an '88 7.3 last year, which has brought me to lurking this forum and now I am need of some help. Its cooling off here in Oregon (but not cold by any means) and Im starting to notice its harder to start. Ive been having to plug it in at night to get it to start. its been a downward spiral lately where the starter went on me due to more cranking so I replaced that. Got two new batteries in it. I replaced glow plugs with motor craft zd9. ive put new glow plug relay in and replaced fuel return lines and caps. and done a fuel heater delete. i dont think i have air intrusion (based on my limited understanding and late night reading) cuz if its plugged in it starts right up in the morning but it is only in the morning that its an issue also? I noticed my wts light doesnt stay on long and relay just clicks and clicks, even if it cycles more normally its not long enough to matter. the plugs and relay are new so im feeling stumped. it did read about the two yellow wires melting in the connector plug which they were and so i broke them out and reconnected them outside of plug and tapped them up individually. they didnt seem to be corroded of have any reason to not make good contact. any help would be greatly appreciated, this is my daily driver and work truck i rely on 7 days a week. when i bought it it already had some back yard stuff done to it but it worked fine most of this first year only now im hitting some snags. im kind of at a loss as for what to try next other than maybe the manual push button thing. i know there is a lot of knowledge flying around on this forum, so thanks in advance for any and all help.

 

[79jasper]

Glowplugs aren't working. Should check the harness ends at the glowplugs.
Also, could just be the controller.

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[Thatoneguy]

Sounds to me like the controller... But all in all I agree with ^^^

 

[KodiakForge]

Ok I'll check connectors. Forgive me if this is a redundant question but is the controller separate from the relay unit. Or where is it located? I thought It was attatched to relay meaning I replaced it too? I'll check harness ends when I get home today. Thanks

 

[KodiakForge]

Also how do you fix the harness if that's what's going on? I heard something about different caps to connect to glow plugs is there a link someone can share about how to fix.

 

[79jasper]

The controller is what the relay mounts to. The rectangular piece it mounts to.
The blue female bullet connectors are what you want. Or some have modified the 6.0 PSD glowplug harness.

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[KodiakForge]

sorry for my lack of detail in earlier posts the controller and relay i replaced as a unit so both are new. i checked the connectors and the white plastic is brittle but the connectors themselves seem fine. no corrosion oil or anything like that. test light lights up on each plug. ohm test done @ 2k ohms was

Rear
(7) .004 (8) .003
(5) .003 (6) .002 / .003
(3) .004 (4) .004
(1) .003 (2) .008
Front

does this sound right? going to test controller tomorrow morning cold to see if the voltage transfers over when on. not sure if this could have caused this but i dropped a wrench not too long ago and it crossed terminals on the relay mounted horizontally on passenger side fender near top?

 

[bbjordan]

Sounds about right. Just because the Glow Plug relay clicks doesn't mean its working. When the plugs are glowing, you should see your voltmeter drop to around 8-9 volts. The GPs suck a lot of current; about 27 amps/plug! They should also glow for a minimum 4 seconds when its cold.

I carry a can of ether/starting fluid with me as a back up. Just remember to disconnect you glow plug relay or the feed lines to it before you use it. It only take a 1 second blast in the air cleaner. Maybe 2 secs if its really cold. And only use it when your engine is cold.

 

[Pork_Chop50]

I've caused a few sparks with the GP controller that I wouldn't worry about it, but I would certainly check the voltage at the controller. I fought the same issue last winter and it was a long road of alternator, which lead to starter which lead to batters. Both alt and starter were the OEM, batteries had 10 years on them. But if you've gone through all that then I would start looking at your battery cable ends and grounding locations. These can get enough corrosion to drop voltage low enough to also cause a starting issue. Wire age is going to be your enemy, I've been slowly replacing sections of my under hood harness as the wires get old and fail.

 

[snicklas]

Note: this is for the 7.3 style system, this would not work on the 6.9 system with the round controller threaded into the coolant passage in the head.

I would test the relay. The way I would test it, connect your meter on DC Volts and verify you have +12 Volts to the large terminal from the battery. Once you verify voltage to the contactor, I would connect your meter to the other large terminal that is connected to the glow plug harness. When you connect the meter, there should NOT be voltage on that terminal. Now, take a jumper and jump the small terminal with the white wire to ground. At this point, you should hear a nice solid thunk as the relay closes and you should now have voltage present on the terminal your meter is connected to. At first it more than likely won’t be the same as you measured from the battery, it may show 8 or 9 Volts but should climb toward battery voltage as the plugs heat. Do not keep it grounded more than 5 or 6 seconds because you are running the plugs with no controller. They will stay on as long as the white wire terminal is grounded.

Now, if you see no voltage when the white wire terminal is grounded, the relay is bad. If you see the same voltage as measured from the battery immediately, with no ramp up toward battery voltage, then the plugs are not working. Either a bad harness or failed plugs.

If you get the result of the plugs not working, I would verify continuity of each glow plug lead. If you have continuity, I would pop all the connectors from the plugs and make sure they aren’t touching anything. Jump the white wire terminal again and measure voltage at each connector. Since all the connectors are removed from the plugs, you should see close to battery voltage, and since the plugs are disconnected and not being heated, you are not in as much of a rush since you won’t burn out the plugs.

Right now on my IDI, I have a momentary push button connected to the white wire terminal and then to ground. My controller doesn’t work every time so I can manually run the plugs if the controller doesn’t, but it retains the automatic function if it does work.

 

[79jasper]

Remember the golden rule: new doesn't mean good.
Could be a bad controller/relay right out of the box.

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[Thewespaul]

New: never ever worked

 

[KodiakForge]

Thanks guys for your help and suggestions. So this morning everything worked as normal. Cycled for 12 seconds and started right up. I had voltage to relay controller and monitored the voltage drop and climb back up when plugs were heating. While everything worked as it should, I did notice (as I had my girlfriend turned the key and I was under hood) that the two green fusable link wires that come off the starter relay on passenger fender started smoking. So going to replace the yellow wires from controller back to starter relay with larger 6g and hopefully the smoking wire thing will stop. I'm thinking that is the source of my problem And I should start replacing more than just those yellow wires but I'm going to start there. Anyone know what size fusable links I should get to replace with? Or where to get them. Thanks

 

[79jasper]

You can also do slow blow fuses. But total draw is 200-250 amps. Drops off as they heat up.

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