Hi

I have a 1991 F250 with the 7.3.

My wait to start indicator light has stopped comming on, and now it is getting cold enough (even in Texas) to need the glow plugs. I performed the diagnostics indicated in the Haynes manual, and everything looks good except the control unit. When I turn on the ignition switch with a test light in contact with the test terminal of the control unit, I hear a clicking noise (maybe a solenoid?) and then my test light illuminates for half a second, then clicks off. It was about 50 F outside, and the manual indicates that it should illuminate for 10 seconds at least at that temperature (the engine was cold).

My question is: is this type of failure common? The manul says that I need to replace the entire unit. Where do I get a new one? How much $? Is there another fix?

thanks!

Sam

 

Did you check the ground wire on the control unit?Make sure it is clean and tight.What method was used to check the glo plugs?

 

sfield,

Hopefully I'm not over-complicating your issue but have you pulled the g.p.'s and tested them with a multimeter for resistance reading? I would. I'd also make sure there were no Autolites, Champions, and AC Delcos in the system. Check out Ziggster's experience with glow plugs:

http://www.members.shaw.ca/k2pilot/G...20article.html

Highly enlightening and scary enough to run nothing but Motorcraft/Beru.

The clicking is indeed the G.P. relay (solenoid) engaging. Does it make a series of clicks or just one click? If you pull each g.p., the resistance values for each should be less than two ohms (most likely they will zero out). There is a deception however. Sometimes a g.p. can fail closed, that is, it will read no resistance but the filament will be burned open but merely grounded against the g.p. body.

To test the resistance on a glow plug, put the meter on continuity check, put one lead on the end of the plug where the harness wire connects and the other lead on the threads of the g.p. Make sure no grease (you shouldn't use grease or oil anyway to keep the threads good) interferes with the lead on the threads.

Hope this helps, R.A.

 

I checked the glow plugs by attaching the leads from a test light to the + battery terminal and the terminal of each of the glow plugs (leads were removed). All of them lit up the test light.


Then I checked continuity between each g.p. lead and the test terminal on the control unit. The plastic cover on one of the leads


For the ground wire on the control unit, I attached an ohmmeter to the negative batter terminal and the wire terminal eyelit.

I checked for voltage on the control unit power terminal, as well as on the ignition terminal of the control unit (with ignition switch on).

Everything above seemed to be o.k.

Then I connected a test light to the test terminal and ground, and turned on the ignition switch(my friend did) and heard a single clicking sound, and the test light flashed very briefly, less then a second. It was not repeated, unless the ignition switch was turned on and off.

removing the glow plugs sounds scary. Is it absolutetly necessary in order to test them?

thanks for the helpful info!

Sam

 

Using a test light with one lead on the pos. terminal of the batt. and touching the other lead to the top of the glow plug where the harness connects is the easiest way to see if they are good but the test light method can be fooled if the g.p. filament is burned out yet grounded against the g.p. body.

You can't check the resistance value of the glow plug while it's still in the block. You have to remove it. I was careful my first time also. It shouldn't take much torque to get them out as they aren't put in with much torque. For my van, cyls. 3 and 4 are a P.I.T.A. to get at being under the injector lines but I use a deep 1/4" drive, size 3/8" socket with a special adapter.
The adapter has a 1/4" male socket driver on one end and a 1/4" male hex on the other end.
The 1/4" male socket driver end goes into the 1/4" deep well socket and the 1/4" male hex head is used to apply any torque which might be needed.
To apply the torque/ratcheting action, I use a size 1/4" ratcheting box-end wrench to loosen, and after several minutes eventually get the g.p. out of the block. Usually I can spin the socket with my fingers once I get it loose to a certain point.

If you find that after you've loosened it, and are threading it out, that it stops and no small amount of torque will get it to continue coming out, you can always screw it back in and hook it back up to be dealt with at a later date. At least you would know what you've got.

There are several reasons why it's good to pull the g.p.'s.

1. You get to see what brand you have in there and replace any necessary with Motorcraft/Beru.
2. You can check the resistance value and any which are showing more than two ohms ought to be replaced. (When I first removed the g.p.'s from my new, used vehicle, I had four Autolites and four Motorcraft. Two of the Autolites had burned up but had not distorted, a third was showing 70 ohms, and the fourth was okay but got drop-kicked out anyway. All the Motorcrafts were still good.)
3. You can tell a bit about the condition of each cylinder by looking at the deposits on the end of the g.p. IE whether you've got excessive oil in a cylinder, how completely the fuel is burning.
Check out:

http://www.beru.com/english/produkte...gnosehilfe.php

Download the .PDF called "Brochure>Glow Plugs<" at this page:

http://www.beru.com/english/produkte...id=gluehkerzen

Will give you more info about the current glow plug technology. Hope this helps, R.A.

 

doesn't the test I ran on the control unit indicate that the unit is bad? It does sound like a good idea to pull the g.p., but it looks like I am going to have to get a new control unit anyway (or fix the old one).

 

Easiest and cheapest way to go would be pulling the gps 1st.If there are a few gone the control unit will short cycle as it is doing.

 

The amount of time the controller applies current to the glow plugs is directly related to how much resistance it sees through the glow plug circuit. This means that if just one glow plug has become more resistive to current flow, the controller will shorten the time it applies current to all the glow plugs.

Which is why checking the glow plugs for resistance values is necessary. And why pnose is right when he says to check the glow plugs first to make sure they're good as they are the cheapest place to start (and most logical, really). Motorcraft g.p.'s cost around $9.00 each. The relay costs around $18.00 and the controller will set you back around $120.00.

The controller would be virtually impossible to repair as the circuit board is embedded in epoxy to ward off engine vibration damage.

So in summary:

1. Checking g.p. resistance values will allow you to see:

a. what brand you have in the block
b. the resistance
c. if you have any plugs which may have, diety forbid, a distorted tip

Then you may save yourself some money and just replace g.p.'s which are bad. You can always thin your wallet on a controller later.

pnose has already said to check the controller ground, making sure it is clean and tight. Apply some dielectric grease, too.

I'd clean all the other relay contacts and apply dielectric to them as well.

I'd get some Q-tips and spray the swab with Brake-clean and swab out the harness connectors which go on each glow plug. You may have to take a bit of the cotton off to get it to fit inside. I was amazed at the gunk which came out. Then apply some dielectric inside them as well with Q-tips or toothpicks.

Before pulling the g.p.'s out of the block, I'd use a vacuum in the injector/glowplug valley (which the intake manifold surrounds) and suck up all the dirt and bug bodies which have probably accumulated.

Hope this helps, R.A.

 

dieselzen and pnose,

thanks for your informative responses. I will definitely, carefully, remove the g.p.s. I checked for continuity between each lead and the test terminal (and they checked out), but the plastic cover on one of my leads completely disintigrated when I pulled if off, so it may not be making good contact with the g.p.. Is there a place where I can get replacement leads?


thanks,

sam

 

Yeah, the insulation will disintegrate over time and heat. People have had great success with heat shrink tubing to insulate the connector.

R.A.

 

well, I have pulled 5 out of 8 glow plugs.


I can't pull two of them because they are underneath the fuel lines. I will have to get another tool.

one of them came apart on me as I was racheting it out. The outside, metal cover with the threads turned independently of the heating element and the glow plug terminal. I was able to pull the outside cover completly off, leaving the interior parts of the g.p. in the cylinder! There is still a long, solid looking piece of the g.p. sticking out, but some light tugs on it did not free the g.p. from the cylinder. I hesitate to pull too hard, concerned that some of it will fall inside the cylinder. It seems like this g.p. is probably the source of my problems.

I am kind of stuck with this one. Not sure what to do. I suppose I could make sure that the cylinder is top dead center, and then pull on what is left of the g.p.hard. If it breaks apart, I'll vacume it out the pieces through the injector hole (as is described in an article posted on this web site).


All of the g.p. that I have seen, including the broken one, are
Beru plugs.

One of them had a fair amount of oil on the threads

a few had white chalky ends

I check the resistance on each with an digital multimeter. Not very experienced using one. Many of those that I tested seem to settle on .2 ohms. One of them jumped all over the place, while another seemed to settle on a little higher resistance, . 5 or .7 ohms. I test the resistance by placing one lead on the threads and the other on the terminal.

any suggestions, pointer very welcome!

 

That's the first thing I gotta say!

You said:
"I can't pull two of them because they are underneath the fuel lines. I will have to get another tool."

Check out the tool I described. The difficult part of that set up is to find the 1/4" socket driver by 1/4" male hex driver adapter. You can usually find one in a cheap ratcheting screwdriver set which has the female hex end to accept different types of screw bits (including a bit which has a 1/4" socket driver for 1/4" drive sockets).

You said:
"one of them came apart on me as I was racheting it out. The outside, metal cover with the threads turned independently of the heating element and the glow plug terminal. I was able to pull the outside cover completly off, leaving the interior parts of the g.p. in the cylinder! There is still a long, solid looking piece of the g.p. sticking out, but some light tugs on it did not free the g.p. from the cylinder. I hesitate to pull too hard, concerned that some of it will fall inside the cylinder. It seems like this g.p. is probably the source of my problems."

So you're saying the glow plug body which has the threads and hex facets machined on it came out BUT the glow tube (which holds the glow filament) and the parts joining it to the bullet connector were left in the block?!

Which cylinder was this g.p. on? (FYI, whether you know it or not, cyl. 1 is the front cyl. on pass. side behind alt. so there are cyl. 1,3,5,7 on pass side and beginning with front driver's side, 2,4,6,8.)
If it's a cylinder you can easily reach, can you shine a light to see what's fusing the glow tube(causing the glow tube to stick) to the pre-combustion cup. It may be only a carbon build up, but then again, it may be a swollen tip. Did the whole glow plug begin to rise out of the hole just before the body broke loose, or were you not able to see due to the socket being in the way?

When this happens to a glow plug (if I understand what you're saying correctly) there are two schools of thought on how to proceed.

I've read of some who will crank the engine and have had success with the plug being blown out of the hole from the compression of the engine. You need to protect whatever is over it's direct path out as it's supposed to come out like a bullet.

Then there are those who take the course of putting the cylinder in question at TDC and do like you say, pull hard. If you were to go that route, you might want to soak everything in that g.p. hole with WD-40 or whatever's your favorite to help it ease out.

You said:
"All of the g.p. that I have seen, including the broken one, are
Beru plugs."

I'm astounded, Sam, that a Beru plug could cook like that, THEN break off like that, simply astounded.

The oil on the threads of a g.p. isn't a good sign. Did you make a note of which cyl. it came out of? Also oil on the threads will insulate the threads from a proper ground and will show up as resistance to the controller.

On your multimeter when checking for resistance on a plug, use the "continuity" function. It usually has the schematic of a diode representing it on the multimeter position switch. One lead firmly on the threads and the other firmly on the bullet-style connector.

I hope this helps 'cuz I feel real bad about you having this experience. Please write for my questions and your progress. R.A.

 

you wrote:

If it's a cylinder you can easily reach, can you shine a light to see what's fusing the glow tube(causing the glow tube to stick) to the pre-combustion cup. It may be only a carbon build up, but then again, it may be a swollen tip. Did the whole glow plug begin to rise out of the hole just before the body broke loose, or were you not able to see due to the socket being in the way?

the stuck g.p. is in cylinder #5. easy to access.

I will look closely at the g.p. this evening.

Although the socket obscured what was going on, it seems like the inner part of the g.p. never moved. The outer part resisted turning a little more then the other g.p.s I removed (for a few turns), but I didn't think much of it at the time (obviously).


you wrote:

So you're saying the glow plug body which has the threads and hex facets machined on it came out BUT the glow tube (which holds the glow filament) and the parts joining it to the bullet connector were left in the block?!

I think this is an accurate description of what happened.


you wrote:

The oil on the threads of a g.p. isn't a good sign. Did you make a note of which cyl. it came out of? Also oil on the threads will insulate the threads from a proper ground and will show up as resistance to the controller.


The g.p. with the oil on the threads came from cylinder #2. I am pretty sure the oil was causing a problem, because after I wiped off the oil, the resistence reading on the ohmeter went down. This g.p. might have also been a problem.

Oil in the cylinder doesn't sound good, but the engine seems to run fine (when it runs). No sign of burning oil.


Thanks very much for the answers to my questions. I'll continue to post this emerging disaster story.


Sam

 

In order make sure the piston on the #5 cylinder is t.d.c. I need to :

To do this, you need to find the timing pointer, and the line scribed into the side of the harmonic balancer.


where is this on the engine?

 

Sam,
Thanks also to you for answering my questions.
First, discussions regarding the "easy" stuff regarding your glow plug experience.
The oil on the threads of the glow plug may have come from a leaking valve cover gasket.
Now, some links which may help:
This one is of a tool made by OTC specifically for removing stuck glow plugs BUT I think it requires the g.p. body to be intact around the glow tube and inner glow plug to do any good. The first link is a .pdf file from the maker regarding how to use it (you'll have to allow some time for it to load; just two pages):

http://www.otctools.com/brochures/201-1.pdf

This link is to a internet retailer, best price I could find:

http://www.sjdiscounttools.com/otc6005.html

May not be worth the price even if it would work.

The next are some links are of people's experience with the same problem:

Not a whole heck of a lot of solution on this one:

https://www.ford-trucks.com/archives...o=&fpart=1.htm

Here is cdnarsguy's solution to a stuck g.p., scroll down to middle of page and look at "This is my tool...."

http://forums.ford-trucks.com/ubbthr...ue#Post1159909

Here is a guy's experience which is more hopeful if it's merely a carbon build up in the hole/pre-cup:

http://forums.ford-trucks.com/ubbthr...ue#Post1154482

and the happy result:

http://forums.ford-trucks.com/ubbthr...ue#Post1159183

This one is for a GM 6.2 by a guy named Greg and his experience with a swollen plug so there is corroboration for Ziggster's method (not that I would doubt him in the least):

http://www.dieseldoctor.com/messageboard/data/472.html

Now regarding my thoughts:

I asked if the core came out slightly with the body as if it Did, then that might denote a swollen tip.
If it Didn't, then it might denote that it is merely carbon build up which is keeping it in place.

Take one of the g.p.'s which you've pulled. Look closely at the area between the hex facets and the bullet-style connector. Do you see the hard rubber grommet/washer? It is responsible for bringing the g.p. core out when you ratchet the g.p. body. Apparently, your grommet was heat damage enough to give way and allow the body to slip past it, as the body was threaded out.

My considered solution (Remember, to put the #5 cylinder at TDC):

The space which the rubber grommet/washer takes up between the top of the g.p. body and the bottom of the bullet-style connector is 1/16". If you could get a small steel washer and cut it so the hole and cut area creates a slot which will allow the steel washer to be slid into place between the g.p. body and the g.p. core There must be a close tolerance for the slot to g.p. core. An alternative material could be strong, small gauge(pref. 1/16") wire wrapped around the core in the 1/16" groove.
Procedure:
1.You would clean the lower core and upper body of any rubber/grommet material.
2.You would clean the hole of debris so the g.p. body will thread down as far as possible.
3. You would soak the hole of the g.p. with your favorite chemical rust-breaker.
4. You would thread the g.p. body back into the hole as far as you could.
5. You would then install the the washer or the wire where the rubber grommet/washer used to be.
6. You would then slowly, while continuing to soak the hole, thread out both the g.p. core with the g.p. body.

R.A.