30-0-30 ammeter is the best way. On Sat, 14 Oct 2006 19:20:04 -0500, Jim Cathey <[EMAIL PROTECTED]> wrote:
>> I replaced my GPs and the GP relay within the past 3 weeks or so. >> Yesterday, the preglow light came on for only a second or less - even >> though >> it was in the upper 40s and hadn't been started since the night before >> - it >> was stone cold - it started instantly although it runs like one >> cylinder >> isn't firing evenly. Within a minute the engine idles & runs smoothly. > > That's way too quick. No wonder it ran poorly. > >> I'm wondering about the possibility of a GP being bad out of the >> box? > > Certainly. The relay, too. It happens. 'New' relays usually are > new old stock, and the internal components can fail with age, though > not so much as with use. Most likely is the GP, or its wiring. > >> Also - is there a way to check each GP without removing them > > Sure. The quick way is to pull the plug off the GP relay and use a > DMM to measure the resistance to ground of each one. The rated value > is 0.6 ohms, though it can vary with temperature. The important part > is that they all be about the same. > > Even better is to use a hefty ammeter to measure the current to each > one. I just did that on the 190D a couple of days ago. Within a couple > of seconds each one dropped from about 28A to under 20A, except for the > bad one that was drawing about 2x normal current. (_That_ is a weird > failure mode.) Most people don't own an ammeter that is good for more > than 10A, however. > >> The GP's seem to be pretty basic - but I guess the innards could be >> bad in >> one. > > They are pretty basic, but they're not as simple as the old series > plugs. > > -- Jim > -- Luther KB5QHU Alma, Ark '87 300SDL (270,491 mi) head case? '83 300SD (241 kmi) '82 300CD (162 kmi) '82 300D (74 kmi) needs MAJOR engine work
