Finally got around to testing, and then replacing the glow plugs.. 4 stuck.

DaveBen

Supporting Member
Supporting Member
Joined
Sep 29, 2010
Posts
1,915
Reaction score
632
Location
Ukiah, Ca
You should use a wrench to turn the crankshaft pulley nut. The belts won't be able to turn over the motor if you try to use the fan pulley.
 

MJGenay

Full Access Member
Joined
Mar 20, 2022
Posts
127
Reaction score
25
Location
Leadville, Colorado
Paper towel over the glow plug hole will help catch and absorb anything coming out.
No need to mess with the pump or disconnect anything.
If it's a manual, put it in neutral. If it's an auto, don't do anything.
Just simply put a big ratchet or breaker bar on the big nut at the center of the balancer and bar it over a few revolutions.
Do not use the starter to bar it over. Even with the glow plugs out, depending on how full the cylinders are, it can still hydrolock.

You should be alright, I have faith in you.
Thank you. Which direction am I turning it? When looking at the front of the truck, clockwise? If it does hydrolock while I am turning it by hand, what do I do?
 

Nero

HD Diesel nut
Joined
Jan 3, 2022
Posts
2,198
Reaction score
2,194
Location
OR
If you're standing in front of the bumper looking at the engine, bar it over clockwise.

If you have all 8 glow plugs out, there's literally no reason it will hydro lock. Even then, barring it by hand is so slow you shouldn't be able to damage anything.
 

MJGenay

Full Access Member
Joined
Mar 20, 2022
Posts
127
Reaction score
25
Location
Leadville, Colorado
I had to leave and head down to Denver yesterday mid day... back now. I did manage to get 3 of them out before I left and started on the 4th. Tool works great. Only complaint is access.... it is beyond poor with the fuel lines running from the IP. Hoping will get this wrapped up later today.
 

Norark

Registered User
Joined
Nov 12, 2021
Posts
16
Reaction score
33
Location
Arkansas
I had to leave and head down to Denver yesterday mid day... back now. I did manage to get 3 of them out before I left and started on the 4th. Tool works great. Only complaint is access.... it is beyond poor with the fuel lines running from the IP. Hoping will get this wrapped up later today.
Glad the tool worked for you. I had the same issue getting under the fuel lines, which is why it took me longer than expected. I had to use a small ratchet with a swivel attachment, and could only turn it in small increments before bumping up against a fuel line. The GP in the back on the left side was the one I struggled with the most. But, it’s much easier than removing the heads.
 

MJGenay

Full Access Member
Joined
Mar 20, 2022
Posts
127
Reaction score
25
Location
Leadville, Colorado
Definitely better than pulling the heads. Truck still didn't start that well, took maybe 5 seconds of cranking with the pedal floored. Maybe I still have an issue with the GP system or maybe it is a fuel issue. High idle didn't kick in so I'm not sure what that is about either. Going to check the module next, its pretty new, but who knows. The whole "Wait to Start" light seems to work just fine, stays on for about 15 seconds then kicks off...

To be clear I don't think the temperature is an issue, it was ~3 degrees F outside when I started it, but the truck was in the garage which was probably around 40 degrees F.
 

Olds64

Registered User
Joined
Nov 13, 2022
Posts
65
Reaction score
16
Location
Edmond, OK
Do not use the starter to bar it over. Even with the glow plugs out, depending on how full the cylinders are, it can still hydrolock.

Good to know. I was wondering if the OP could crank her over with the GPs out.

Glad you got those GPs out with the tool.
 

Norark

Registered User
Joined
Nov 12, 2021
Posts
16
Reaction score
33
Location
Arkansas
Mine was still hard to start after replacing the GPs. It turned out the GP relay on the fender was bad too. As soon as I replaced that it started almost instantly. Since you have a 91, you have a different system than I have, so hopefully someone else can weigh in on what you should check next. Starting issues are definitely frustrating.
 

MJGenay

Full Access Member
Joined
Mar 20, 2022
Posts
127
Reaction score
25
Location
Leadville, Colorado
Okay so I did a little digging per this guide:

I checked my power on the terminal with two yellow wires with the ignition off, it is supposed to read 12-14 volts, I had 12.62. Seems okay.

Next I checked my power on the terminal with the red wires, supposed to read 12 volts, I had ~9.06. I figure that might be my issue but I have no idea why I would not be receiving the full 12 volts...

Anyone have any input?

EDIT: I plugged in the block heater this morning as it wouldn't start at 15 degrees. After being plugged in this morning I went outside, went through the glow plug cycle (even though I think they're not working), and it started right up. I pulled it back in the garage to do more digging. Point is I am pretty sure this is a glow plug issue if warming the block allows it to start well.

EDIT 2: Before I replaced the glow plugs the relay would cycle on and off AFTER the Wait to Start light went out, now, it doesn't cycle at all.
 
Last edited:

franklin2

Full Access Member
Joined
Feb 24, 2009
Posts
5,160
Reaction score
1,384
Location
Va
Okay so I did a little digging per this guide:

I checked my power on the terminal with two yellow wires with the ignition off, it is supposed to read 12-14 volts, I had 12.62. Seems okay.

Next I checked my power on the terminal with the red wires, supposed to read 12 volts, I had ~9.06. I figure that might be my issue but I have no idea why I would not be receiving the full 12 volts...

Anyone have any input?

EDIT: I plugged in the block heater this morning as it wouldn't start at 15 degrees. After being plugged in this morning I went outside, went through the glow plug cycle (even though I think they're not working), and it started right up. I pulled it back in the garage to do more digging. Point is I am pretty sure this is a glow plug issue if warming the block allows it to start well.

EDIT 2: Before I replaced the glow plugs the relay would cycle on and off AFTER the Wait to Start light went out, now, it doesn't cycle at all.
Whenever you get tired of troubleshooting the automatic glowplug system, we can tell you how to convert to a manual switch with one wire and a switch added on the dash. Works much better.
 

MJGenay

Full Access Member
Joined
Mar 20, 2022
Posts
127
Reaction score
25
Location
Leadville, Colorado
Whenever you get tired of troubleshooting the automatic glowplug system, we can tell you how to convert to a manual switch with one wire and a switch added on the dash. Works much better.
Yeah I've considered that... I'd really rather not as I'd like something that someone else can drive too...
 

MJGenay

Full Access Member
Joined
Mar 20, 2022
Posts
127
Reaction score
25
Location
Leadville, Colorado
This truck had about 1.5 years ago a new glow plug module and I'm assuming relay, new bullet connectors, from the previous owner. I'm pretty lost on what else it could be at this point, unless one or more of those has went bad.

EDIT: I just checked the power coming to the bullet connectors... 9V which as far as I can tell is what they should be getting. I'm truly lost at this point. Frustrating me all to hell as by my logic if a human can create this I should be able to fix it.

EDIT 2: The batteries from the PO are about a year or so old but only rated for 650 CCA instead of the recommended 850 CCA. I figure that means it turns over slower when really cold but that shouldn't mean that the glow plugs don't work. Am I maybe not getting enough amperage through the circuit?
 
Last edited:

franklin2

Full Access Member
Joined
Feb 24, 2009
Posts
5,160
Reaction score
1,384
Location
Va
The batteries are not the problem if they are in good shape and it cranks over fast enough.

If you have poor connections anywhere in the system, the controller will not work properly. Yes, a person invented this system, a very smart engineer. But he or she did not take into account the wiring resistance as the connectors get old. If you have a little too much resistance in the wiring to the glowplugs, or just one glowplug is bad, the controller will be fooled and not glow the plugs properly.
 

MJGenay

Full Access Member
Joined
Mar 20, 2022
Posts
127
Reaction score
25
Location
Leadville, Colorado
Okay, understood. I did find a potentially broken fusible link, or at least it broke when I pulled on it. It was under the battery. About 2.5 hrs ago I started the truck up in the garage, with the fixed fusible link and two new 850 CCA batteries (ouch), and pulled it outside and let it sit in the driveway and turned it off immediately. It's been 12 degrees out since I put it out there so I figure it cooled off pretty well. It did actually start, I allowed the Wait to Start to turn off then began cranking. I highly doubt that it would've started before, although it took 10 seconds of cranking before it took off.

Long story short, new batteries, and fixing a possibly broken fusible link seemed to help. Still isn't perfect, so I'm still on the hunt for the issue. I'm going to try it again in the morning, probably get down to around 7 tonight, so I'll wait until its about 10 degrees and then give it another go.

What I'm reading is it should start easy down to about 0 degrees and then struggle below that if everything is working correctly. Is that correct?
 

tradergem

Full Access Member
Joined
Oct 3, 2007
Posts
222
Reaction score
74
Location
Arizona
When I lived in southern Minnesota my 1990 7.3L was hard to cold start when the tempurature got below 40* even with new batteries and glow plugs. When it got below zero I had to add battery blankets to both batteries and keep them and the block heater plugged in or the truck was very hard to start cold. The extreme cold just killed the power from the batteries. I also added Thermocube brand tempurature activated outlet adapters to the plugs of the battery blankets and block heater that would turn them on only when it got cold enough.
 

Forum statistics

Threads
91,217
Posts
1,128,479
Members
24,045
Latest member
Ramtough01

Members online

Top