As a long time VW diesel owner, I've changed my share of glow plugs on both IDI and TDI engines. They will generally last 10 years or more if not run too long, The older (80s vintage) 1.6 IDI diesel on Callisto has a manual button for the glow plugs, and I will try to avoid using more than 5 seconds, which is enough down to 0C, as they glow red hot within 1 second when working correctly. A good test of function is the current draw, each plug should pull about 12A (in my case, yours may differ). Once you know the current draw you can quickly check if they are all good if you have a good ammeter or battery monitor on board (I have a Renogy which uses a shunt). In the case of VW glow plugs, continuous operation more than about 10-15 seconds can quickly shorten their life. I lost all of them a few years ago when the factory timer relay stuck on, so now use a separate 80A relay and a manual button, as changing them is a serious PITA - two are behind the injection pump. A quick test of a plug is to use a spare battery, or any good source of 12V power up to 15-20A. When power is applied they should be red hot within a second or so, if not, replace. They will usually fail open, but sometimes will fail with a higher resistance and only get warm. Use a pair of pliers and gloves for safety when handling hot plugs, and of course use fused conductors for testing. I keep old plugs that have tested ok for spares, which came in handy when I had to change them all while out at anchor.
-- Shawn Wright shawngwri...@gmail.com S/V Callisto, 1974 C&C 35 https://www.facebook.com/SVCallisto On Mon, Sep 12, 2022 at 7:48 AM Jeffrey A. Laman via CnC-List < cnc-list@cnc-list.com> wrote: > For what it's worth -- another data point on glow plugs. I had a 2003 VW > Golf TDI 1.9L (Turbo Direct Injection) and drove it 200k miles. The glow > plugs had to be replaced at 80k and 160k. A good reading was 1 ohm. The > plugs all went together both times (probably) and the car was very > difficult to start. But, the starting issue became obvious only when PA > temperatures dropped, so plugs might have gone one at a time over summer. > With 4 cylinders, all you need is one to start to fire to get the engine > going. > > Jeff Laman > 81 C&C34 > ------------------------------ > *From:* David Knecht via CnC-List <cnc-list@cnc-list.com> > *Sent:* Monday, September 12, 2022 10:32 AM > *To:* CnC CnC discussion list <CnC-List@cnc-list.com> > *Cc:* David Knecht <davidakne...@gmail.com> > *Subject:* Stus-List Glow plugs > > I asked the list a while back about glow plugs (Universal M4-30) and > whether they should be a periodic replacement item. They should have been > testable in place, but I had trouble getting reliable readings from the > meter. So I decided since they were not that expensive ($80 for 4) to just > go ahead and replace them so I had a sense of the state of 30 year old glow > plugs. It turned out to be a pretty easy job as engine jobs go (about an > hour). The only hard part was finding a tool that would grab the circular > knurled nuts on top that held the wires on (Vice grips worked). The plugs > themselves came out without too much trouble with a standard socket > wrench. The old plugs look well used, but not worn out and tested as good > with a Volt-ohm meter (about 1 ohms). The new ones made no difference to > starting the engine that I could detect. It still takes about 15-30 > seconds of glow plug (as the manual recommends) before it starts. So from > my experience, this is not an engine part that needs much concern or > frequent replacement. Also, since the plus sides are all wired together, > my assumption is that if one failed (high resistance), the others would > continue to work fine. Dave > > S/V Aries > 1990 C&C 34+ > New London, CT > > >
