Please Help Double Check 603 Glow Plugs

[mj_sid]

Hello All,
On my 87' SDL I've thought that there may have been some glow plugs out for awhile. Then on Friday and Saturday mornings (about 50D F) the car took two or three glow cycles to start. I knew that my problem had worsened and yesterday morning (and afternoon) she would not start at all. I did the tests and the results are: Resistance from ground to glow plug wires all wires but 3 and 6 are 1; 3 is .8 and 6 is .7. I then tested to make sure the strip fuse was ok; it is fine. I then tested the relay for voltage (the big old nut (I think the manual calls it number 30) and it tests fine. I then tested using a test light and 3 and 6 light up all the rest remain dark.

The questions are as follows:
1. I'm assuming that all glow plugs but 3 and 6 are bad; I will replace all. Should I be concerned that the glow plug indicator light continued to work until Sunday morning? Am I missing something?

2. Assuming bad glow plugs; I'm going to remove the intake manifold (I've got big hands and don’t think I could get to them otherwise I know some say it can be done without removal) what gaskets do I need to order to reinstall.

3. Is there anything I should look for while all that junk is out of the way? I think I’ve heard about cleaning out the pipe that runs over the valve cover.

4. Any knowledge that would make this experience more enjoyable?

Thank You,
Matt

[Brian Carlton]

Originally Posted by mj_sid

I then tested using a test light and 3 and 6 light up all the rest remain dark.

The questions are as follows:
1. I'm assuming that all glow plugs but 3 and 6 are bad; I will replace all. Should I be concerned that the glow plug indicator light continued to work until Sunday morning? Am I missing something?

You found good resistance values for all six glow plugs.

You then used a test light and confirmed voltage at glow plugs 3 and 6, but no voltage at plugs 1,2,4, and 5.


The questions are as follows:

1) Did you make your voltage check at each individual glow plug when you confirmed this voltage?

2) If so, you only have 35 seconds before the relay drops out and the voltage at the plug goes to zero. Are you aware of this?

3) If you have good resistance for all glow plugs and no voltage at the glow plug, the problem is not the glow plug. Are you aware of this?

[mj_sid]

Originally Posted by Brian Carlton

You found good resistance values for all six glow plugs.

You then used a test light and confirmed voltage at glow plugs 3 and 6, but no voltage at plugs 1,2,4, and 5.


The questions are as follows:

1) Did you make your voltage check at each individual glow plug when you confirmed this voltage?

2) If so, you only have 35 seconds before the relay drops out and the voltage at the plug goes to zero. Are you aware of this?

3) If you have good resistance for all glow plugs and no voltage at the glow plug, the problem is not the glow plug. Are you aware of this?

Hi Brian,
Maybe I’m getting myself confused. I followed the instructions at diesel giants site as well as some instructions I found in past posts here. As to your questions:

1. I connected the test light to the strip fuse and then to the glow plug socket (the wires which run to each of the plugs. Should I try to connect to each of the plugs themselves? If yes don't you have to hit a pretty specific spot on the plugs?

2. I am aware of this; I did it all before the relay clicked.

3. I don't understand this. According to the instructions 1 is not good resistance. I am reading 1 (open right) on all of the plugs except for number 3 and number 6.

What am I missing???

Please let me know what further information would be helpful or what other tests I can perform.

Thanks,
Matt

[Brian Carlton]

Originally Posted by mj_sid

1. I connected the test light to the strip fuse and then to the glow plug socket (the wires which run to each of the plugs. Should I try to connect to each of the plugs themselves? If yes don't you have to hit a pretty specific spot on the plugs?

This does not test whether the plug gets power from the relay. This simply confirms that the glow plug is grounded.

The best test is to check the tip of each plug with the voltmeter. However, getting to them is difficult. If you are able to confirm this on a couple of plugs, I'd say that the relay is performing properly and the chances of bad wiring to any specific plug are slim.

Originally Posted by mj_sid

3. I don't understand this. According to the instructions 1 is not good resistance. I am reading 1 (open right) on all of the plugs except for number 3 and number 6.

Anything between .6 ohms and 1.2 ohms is fine. The question is whether you have 1 ohm or whether the meter is showing open which is infinite resistance. Please check again.

[mj_sid]

Thanks again Brian,

I checked all but one of the glow plug tips (the 3rd one from the front was not easily reachable). They all test around 11.9V.

I then retested the Ohms readings. The results were the same using the 200 setting (I don’t really understand what the different settings mean). I also took measurements at the 2K and the 20K settings with the results listed below.

Plug 1: 200=1; 2K=1; 20K=10.58
Plug 2: 200=1; 2K=1; 20K=6.69
Plug 3: 200=.7; 2K=.001; 20K=0
Plug 4: 200=1; 2K=1.258; 20K=1.26
Plug 5: 200=1; 2K=1; 20K=6.89
Plug 6: 200=.8; 2K=.002; 20K=0
*plug is counted from front of radiator and in order toward back of engine. (Not sure if I should have used the firing order ???)

I’m not sure if the numbers other than the 200 are actually useful but I figured that since I was there it would only take a couple of extra seconds. I was hoping that you could just adjust the decimal point but that does not seem to be the case looking at the results.

What would you recommend testing next?

Thanks,
Matt

[Brian Carlton]

Originally Posted by mj_sid

Plug 1: 200=1; 2K=1; 20K=10.58
Plug 2: 200=1; 2K=1; 20K=6.69
Plug 3: 200=.7; 2K=.001; 20K=0
Plug 4: 200=1; 2K=1.258; 20K=1.26
Plug 5: 200=1; 2K=1; 20K=6.89
Plug 6: 200=.8; 2K=.002; 20K=0
*plug is counted from front of radiator and in order toward back of engine. (Not sure if I should have used the firing order ???)

I'm quite sure that you are not getting proper results from that meter due to "operator error".

However, plugs 3 and 6 do make some sense to me. .7 and .8 ohms on those plugs would be proper and the meter can read this level on the 200 ohm scale. On the higher 2K and 20K scales, the meter effectively sees no resistance and, hence, the very low values.

Now, on the other four plugs, the value of "1" for each of them tells me that something is amiss with the meter or the procedure. Also notice that the value of "1" appears on the 2K scale as well. Only when you get to the 20K scale are you getting some measureable values.

So, I conclude, without sufficient knowledge of the meter or the operator, that plugs 1,2,4, and 5 are NG.

Pull one of these plugs and carefully do a bench test and see what you get.

[mj_sid]

Originally Posted by Brian Carlton

I'm quite sure that you are not getting proper results from that meter due to "operator error".

The truth hurts sometimes.

I will pull one of the plugs and see what happens. How are the plugs numbered? I want to make sure that I do not pull a plug that is good by mistake. Are the numbered 1-6 from the front of the engine back or are they related to the firing order?

--Matt

[Brian Carlton]

Originally Posted by mj_sid

The truth hurts sometimes.

I will pull one of the plugs and see what happens. How are the plugs numbered? I want to make sure that I do not pull a plug that is good by mistake. Are the numbered 1-6 from the front of the engine back or are they related to the firing order?

--Matt

1-6 from the front.

[mj_sid]

Ok; I pulled the number one glow plug. Only a mild pain but I can see how much fun the rest will be. There was some black stuff on the tip of the glow plug. It did not look like oil and it is still on my hands where i rubbed it off. Is this carbon or do I need to start panicing that something really bad has happened?

I tested the plug hooked up to a vice. I placed the meter on the 200 setting and applied the red terminal to the silver metal part at the bottom of the glow plug. I then placed the black wire on the silver part on the top of the glow plug (one tip on each side of the copper seperator like the picture I have shows). The result was 1 (open). Then trying to rule out operator error I hooked up a set of jumber cables and attempted to make it glow with power. No glow.

So I take it that the glow plug does not work.

Now I understand that the best way to procede with glow plug removal is to remove the intake manifold and the cross over pipe. Is this correct? I've also heard that you should check the cross over pipe for some sort of build up. Is this correct?

Am I missing anything?

Thanks for your help,

Matt

[Brian Carlton]

Originally Posted by mj_sid

So I take it that the glow plug does not work.

Now I understand that the best way to procede with glow plug removal is to remove the intake manifold and the cross over pipe. Is this correct? I've also heard that you should check the cross over pipe for some sort of build up. Is this correct?

Am I missing anything?

Thanks for your help,

Matt

Yep, one down, three to go.

If you have a decent set of extensions and universal joints, you can pull them from underneath the manifold. But, if you are pulling the manifold to clean it, then the plugs are a five minute job with the manifold off.

It will take you some time to remove and clean the manifold, however. The buildup inside the tubes is a project to remove.

[mj_sid]

Thanks again for all of your help. I will post again in a couple of days once the project is done and hopefully (fingers are crossed) the car is clattering away.

--Matt

[Brian Carlton]

Originally Posted by mj_sid

Thanks again for all of your help. I will post again in a couple of days once the project is done and hopefully (fingers are crossed) the car is clattering away.

--Matt

I have no doubt that when you change those four plugs, it will immediately start.

I'm still not understanding the meter when it reads "1" for an open circuit???

[sixto]

Matt, getting the fuel lines into the clips is a PITA. Best to release the lines at the IP and injectors and leave them attached to the intake manifold.

Technically you need an intake manifold gasket and the gasket that goes between the crossover pipe and the intake manifold. I don't know how many miles are on the car now but in the past I've reused both gaskets. The intake manifold gasket is as new as the head and has been reused once or is still in place from when the new head went on. I don't know about the crossover pipe gasket. It's possibly the one that came with the car. Even if it was new when the head went on, I pulled the crossover pipe a number of times. I put a thin layer of gray RTV when I install it, mostly so it stays in place while parts come together since it has a tendency to slip between the block and IP. The bolt that holds the angle bracket at the round end of the crossover pipe is stripped. The crossover pipe isn't going anywhere when it's bolted to the manifold so I don't think it's a big deal. Maybe you can get a Helicoil in there if it matters to you.

An alternative to pulling the manifold is pulling the cruise actuator. In fact you probably have better access to the plugs if you don't mind working under the manifold.

Sixto
93 300SD

[bozemanbiofuels]

I spent the afternoon changing my plugs as the car was starting rough and missing for the first 20-40 seconds, worse in colder weather. I had tried all the glow plug tests and they seemed to come out good (good plugs) but I didn't know what else to try so I put in Beru plugs.

2 of the manifold hex bolts were stripped so I had to leave it in place and remove other obstructions like the throttle cable mount. It took a good 6 hours and a telescoping magnet along with a wide assortment of 1/4" and 3/8" sockets, universals and extenstions. Don't know which is worse, removing manifold or stretcing my fingers out to get the job done.... Hopefully I'll never know!

They all looked decent with some blackening and shrinkage of the heating element, until #6 which came out in 2 pieces. It could have been damaged when I removed the wire connection but I'll never know. When I started the car I heard the strip fuse blow, and found where I probably grounded some plug wires at the glow plugs, bent them away with a screwdriver, didn't have a new strip fuse so I tested for shorting across the strip fuse terminals. No short so I went out on a limb and installed a temporary wire between the terminals, so I need to know where to get a new strip fuse. Also, isn't the manifold aluminum and so why would it short out?

Today was 25F and it started better but still coughed about like it did in summer. It could be a glow plug wire so I'll test those today, but if there is voltage to each plug what should I try next? Injectors?

Thanks for the advice!
Paul

[P.E.Haiges]

mj,

Did U remove the GP cable from the GP relay? If U didn't, U may get parallel readings when taking readings at the GP terminals.

Best way is to remove the GP cable and take the readings thru the female connectors in the GP cable connector holes. This also tests the GP wires and screw on connections. A "banana" plug works best to plug into the GP cable connectors holes.

U should always test the GP resistance on the lowest setting of the meter because GP resistance is low: about 1 ohm. You should test any resistance, voltage or current on the scale that is closest to the value U are testing.

P E H