'98 Jetta, testing glow plugs, harness, etc.

\'98 Jetta, testing glow plugs, harness, etc.

Hi all
it's been awhile since I've visited here, but needed some advise. I've had several of the older style VW diesels and have had opportunity to rebuild three of them, so I'm familiar with the diesel system, BUT that's the older system & there are some big differences. For one major thing TO ME the glow plug wiring harness is no longer an easy to access/check bare wire or conductor. It sure looks prettier with a plastic 'boot' over all of the plugs, but not as convenient to test. Which brings me to my point. A few months ago when I started having starting issues ( dipped below 32F) I immediately took time to pop off the boot and check each GP with an amp meter that I still have from my previous diesels- checks +/- 60 amps and the older plugs were usually good if they read ~15 amps each. When I checked these several months ago they each read ~15-20 amps. I figured they read different because of slightly different style and figured they were all good. I have since replaced(reluctantly) the GP relay because it was indicated by the VAG-COM codes, and i just failed emissions test for the FIRST time ever with a diesel. Now my problem is that when I tried to remove the GP boot it was pretty stuck and I while I was able to get the 1st plug leg off, i was afraid to break the boot removing it in the cold weather without 1st removing the fuel pipes 1st. Any ideas/suggestions on removing the boot and especially on testing the boot and other components of this newer system?? I do have the Bentley manual for what its worth. My VAG-COM is currently not functional, because I switched laptops and haven't reloaded it on another unit, but I could reload it - only that it wouldn't be 'activated' until I was able to get in touch w/ Ross-Tech. I am also interested in thoughts on what others have done to protect the fuel pipes, & the individual injectors when removing pipes temporarily for maintenance, etc? Very much looking forward to replies, and will be back in a few hours to check this forum. I'm in the southwest Ohio area of the US, by the way. Thanks everyone!

\'98 Jetta, testing glow plugs, harness, etc.

The harness is kinda stuffed in there, but I was able to get my fingers under it and yank it off. I agree, it is tight, though. As for how to support the fuel lines, many just loosen the bolt at the fuel pump and rotate them towards the front of the car to get them out of the way.

As for testing the glowplugs, you have the right idea, but are measuring the wrong thing. Read up the FAQ we have here. The glowplugs should test within a certain range of RESISTANCE. I can't remember the exact range, but it is in the FAQ. If you think the harness might be a problem, stuff some rolled up sandpaper in there or something, and get any oxidation off of the terminals. The harness is on surprisingly tight, so you will have to yank a little to get it off the GPs.

As for the emissions, I don't think this is GP related. The GPs only fire to help to start the car...that's it. Once the car is running the GPs shut off.

\'98 Jetta, testing glow plugs, harness, etc.

each GP shouuld be the same resistance value, 1 to 1.5 ohms dependent on engine temp. book states amp. check should be minimum of 6 amps with inductive pickup. pull the GP connectors off "gently". if they have not been off for quite a while you amy want to turn and pull..they will come off, be persistant. clean end of GP and harness connection, i use .22 cal cleaning brush for connector and apply a small amount of OX-Guard (OX-100)made by GB Electrical, inc. to the GP connection tip. a little dielectric grease on the boot only is also a help in keeping moisture out. /images/graemlins/smile.gif

\'98 Jetta, testing glow plugs, harness, etc.

You shouldn't need to remove the fuel pipes to remove the wiring harness. This topic has been discussed ad nauseum here and information is in the FAQs.

The glow plugs should be less then 1.5 ohms when measured from contact tip to engine ground. Typically they measure .6-.8 ohm on my cheap DMM. I haven't bothered measuring with my more expensive DMM as the accuracy is not required.

If they check out, then the harness probably has sufficient corrosion or charring in the contact area to cause the glow plug relay to report a fault. It's not the relay itself that is bad, it is just the component that reports back to the ECM about the GP circuit needs attention. You may get by with unplugging/plugging the GPs several times to scratch off enough of the corrosion/charring to get a good contact. Then you have to clear the fault code to quickly verify if the situation is corrected. However, the longer term cure is to replace the wiring harness section.

I'm located up in Outville, a couple hours drive from you at most, and can fix this if you need a hand.

\'98 Jetta, testing glow plugs, harness, etc.

thanks for the replies. I looked thru the FAQ's, initially and didn't find anything on removing the GP boot. Anyway my main concern on the boot is breaking it in the cold weather. I just had it off a few months ago. It seems to be giving me a much tougher time this go around. When we refer to the contact area I presume we're talking about the interior of each leg of the boot and the neck of each of the GPs itself. Also when we refer to the 'harness' is this including everything, because I'm merely refering to the 'boot' over the GPs themselves at least with reference to removal. I'm also assuming that when it comes to possible replacement of the 'boot' it is not available or impossible to just replace it without the rest of that whole nest of wires?

\'98 Jetta, testing glow plugs, harness, etc.

to MOGolf
I may just take you up on that offer. It would be nice to have an experienced TDI owner for assistance(somewhat concerned about screwing this up compared to an old mechanical diesel that I've been so familiar with). Outville huh...northwest Ohio?

\'98 Jetta, testing glow plugs, harness, etc.

Middle OH. East of Columbus.

\'98 Jetta, testing glow plugs, harness, etc.

Dave, see this thread.

\'98 Jetta, testing glow plugs, harness, etc.

Thanks,
I took a brief look before I head out for some errand running and fun in what they call snow here( I like snow - originally from the N.E. area ). I'll look more when I get back. Thanks again.

\'98 Jetta, testing glow plugs, harness, etc.

Hey thanks for the info and thread links. Very informative stuff. I will have to work on the plugs/harness thing over the next few days as I have time. I wish I hadn't bought that relay now, but who knows it may end up being replaced someday anyway and if so I already have it. I'll be back with feedback on how things go. Thanks again.

\'98 Jetta, testing glow plugs, harness, etc.

dunno if it is mentioned in the FAQ, but when you try to measure the resistance against the engine, remember to clean off the oxidation on there. First time I tried, I couldn't get contact...then I realized the oxidation isn't too conductive. /images/graemlins/rolleyes.gif

\'98 Jetta, testing glow plugs, harness, etc.

Ok,
I've tested all 4 GPs and they were nearly 'perfect' matches. All measured .6 to .7 ohms. I also tried to get a voltage reading off of the harness with my daughter in the vehicle, flipping the ignition switch back forth and apparently didn't have good contact OR there was no voltage, which I find rather difficult to believe so I'll try the voltage readings again 1/29/04 or 1/30/04 I hope. (Oh, yea the harness came off pretty easily when it was warmed because of the engine.) Will report back the results. Any other ideas?
Oh yes by the way, concerning the GPs being emissions related...while I realize they don't 'run' the vehicle, if one or two aren't working, then there would be a difference in the initial emissions at startup and in the state of Ohio as of 1/5/04 the E-check (required in MY county ) on ' 97 or ' 98 ( I can't remember the dividing line) they check emissions by OBD not by exhuast. They say that the Ohio EPA got the emissions related error codes from VW, and that the intermittent GP relay is one of them. That's why I failed e-check.

\'98 Jetta, testing glow plugs, harness, etc.

hey MOGolf
I'm starting to give thought to taking you up on that help offer. It would appear that the GPs AREN'T the problem and neither is the relay (now that I already bought one). I would like to diagonos this problem definitively, without buying more parts that won't neccessarily fix it. Anyone have other ideas for harness checking or other possible items? I did notice this big red fuse looking device in the area of the relay block that look rather wrong -like it was blown or at least stressed. It was marked 50Amps, 32V if I remember correcly. Anyone know what this goes for? GP related? It's going to get rather nippy this weekend and I'm getting rather tired of these long starts, not to mention wear and tear on my system. Looking forward to any thoughts. Thanks again, everyone.