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Glow Plug issues...UGH

3K views 7 replies 4 participants last post by  0lee 
#1 ·
Okay, I've had my '83 blazer for a few months now, and it was doing this thing where sometimes it would start fine, and other times it wouldn't start at all, unless I used some wd-40. So, after a couple months, I finally replaced the glow plugs-started up fine. BUT, the glow plugs kept cycling on and off about every 20-30 seconds. So I got a new controller and installed that. Now if it's cold, it starts up fine, but if I run it and it gets warm and then turn it off, then it won't start back up again until it is cold. The glow plugs don't cycle, so I thought maybe it had something to do with the relay, so I replaced that, and it still does the same thing. When it is not starting warm, I can hear something click in...I don't even know what it is! It is right above the fuel injector pump...It has a plastic cover with three coils inside...I'm not sure, I am so new to diesels and my head is spinning. I would really like to get this thing running correctly so I can begin to convert it to waste vegetable oil, but I am starting to wonder if it is worth it. Someone pleeeeaaassseeeee help me!
 
#2 · (Edited)
There is probably (I`m not sure for that year) a temperature sensor on the rear passenger side (under the air filter housing). The sensor is supposed to prevent the glow plugs from being powered when the engine is supposed to be warm enough to be started without glowing first.

You can do something to have manual control over the glow plugs, see this thread: http://dieselplace.com/forum/showthread.php?t=186870.

The clicking you hear from the injection pump may be the fuel shutoff solenoid. You can verify that by taking off the thick pink wire that goes to the contact on top of the IP. When this wire is taken off, the fuel shutoff solenoid can not be energized and keeps the fuel supply shut off.
 
#3 ·
Now if it's cold, it starts up fine, but if I run it and it gets warm and then turn it off, then it won't start back up again until it is cold. The glow plugs don't cycle, so I thought maybe it had something to do with the relay, so I replaced that, and it still does the same thing. When it is not starting warm, I can hear something click in...I don't even know what it is! It is right above the fuel injector pump...It has a plastic cover with three coils inside...
The coils with covers that you see are probably the EGR and EPR solenoids and have nothing to do with the glow plugs or starting.
Many of the 82s to 85s did what your's is doing. Eliminate the glow-plug inhibitor sensor by unplugging the wires and connecting them together. If that doesn't work - install a manual pushbutton to use during those times when you need it. I have one on all my older 6.2s (with the old control system). The glow-plug inhibitor sensor is a little two-prong unit and it scews into the passenger-side cylinder head at the rear - just above the exhaust manifold.
 
#4 ·
Thanks for all the help. I installed a manual push button switch today, and it seems to work much better, but it still sometimes it is taking a while to turn over. Also, will standard glow plugs swell and get ruined by using the manual switch? I have Wellman automotive glow plugs right now...should I look into getting more heavy duty plugs? Thanks again.
 
#6 ·
Thanks for all the help. I installed a manual push button switch today, and it seems to work much better, but it still sometimes it is taking a while to turn over. Also, will standard glow plugs swell and get ruined by using the manual switch? I have Wellman automotive glow plugs right now...should I look into getting more heavy duty plugs? Thanks again.
In regard to the glow plugs - it's not a matter of heavy duty, or not - some are PTC (positive temperature coefficient) and some are not - regardless of brand. It depends on what specific system design is used. Your 6.2 calls for the PTC type plug - which includes the Delco 60Gs and Wellman GO50s. Military 6.2s do NOT use PTC type plugs.

The PTCs are have built-in, heat-sensitve current limiters. But, I still wouldn't use them more then 10 seconds at a time. The AC 60GS - in 10 seconds reach 1600 degrees F, whereas the Wellman GO50s heat up to 1950 degrees F in 10 seconds.

In regard to what Olee mentioned - i.e. hot starting not being a glow-plug issue - that's not always the case. I've worked on many 6.2s that are like that - some since new. Shut the engine down - and 10 minutes later it starts fine - but let sit for 15-20 minutes - and some need glow plugs. Especially if the injection pump is a little worn and has trouble making proper fuel delivery at engine -cranking-speed. Glow plugs can make up for that and get it started.

Here are some specs on the plugs. The Wellmans heat up faster - but overall don't seem to result in a better starting engine if used with an automatic controller.

Wellman GO50 plug for 6.2 and 6.5 diesels
2 seconds - 10.2 volts, 13.6 amps and 1500 degrees F
5 seconds - 10.3 volts, 11.7 amps, and 1560 degrees F
9 seconds - 10.3 volts, 9.66 amps, and 1905 degrees F
12 seconds - 10.4 volts, 8.6 amps, and 2000 degrees F

AC60G (Beru) plug for 6.2 and 6.5 diesels
2 seconds - 10 volts, 8.6 amps and 807 degrees F
5 seconds - 10 volts, 8 amps and 1145 degrees F
9 seconds - 10 volts, 7.3 amps and 1545 degrees F
12 seconds - 10 volts, 7 amps, and 1716 degrees F
 
#5 ·
Does the manual switch energize the glow plug relais?

For manual operation, AC Delco 60G plugs are recommended. They are supposed to be self-limiting so that they don`t overheat, but they take longer to heat up so that they don`t work as well for automatic operation as the "faster" plugs.

Other things to check are the batteries and the battery connections, the mechanical lift pump, the fuel filters and the starter. If the starter turns too slow --- due to bad batteries/battery connections or wear --- the engine won`t start at all.

If the engine is actually warm, like after driving for a while, and then it won`t start after sitting for like 10 or 15 minutes, your problem is probably not related to the glow plugs. You can start a warm engine without glowing at all, and without excessive cranking. So if the engine is warm/hot and you can`t start it, either the starter turns too slow or there is some problem with the fuel supply.

How old are the fuel filters (there should be two of them, on the firewall on the drivers side on the intake)?
 
#7 ·
Right on, JD. My pickup starts great when cold. When warm, it needs glow plugs. The suburban is the other way. Cold, slower to start, needs more glow plug, warm, starts right up without glow plugs, even after sitting for an hour.

The pickup has an additional 100,000 on it's engine but it has done this since new. It's worn, using some oil, needs a watchful eye but still runs smooth. The suburban has a replacement GM crate engine with just over 100,000 miles and has started the same way since installation.

From years in the dealership, I've grown to realize they are all different!
 
#8 ·
Oh, ok --- then I`m lucky to have one that behaves "normally" :)

BTW, since I fixed the power supply to the plugs, it starts pretty well. But after sitting over night, to start I have to push the pedal down like 1/8 inch and hold it there for a bit until things have warmed up a little. If I get off the pedal immediately after starting, the engine cuts off. After that, it starts fine all day.

Is that just the way they are, or could I do something to improve on this?
 
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