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300GD Engine Troubleshooting

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300GD Engine Troubleshooting

Post#1 » Mon Sep 03, 2012 11:08 pm

So last week, I snapped my shifter in half while driving. Guido came to the rescue and shipped me a new part, and I'm waiting for that in the mail.

So the 300GD has been sitting for a few days and in the mean time, I've replaced the Brake Master Cyl. Not complete yet, as I stripped the 11mm bolt for the front brake hard line. Holiday weekend here in the US, so I have to get a new line with a new nut made in the next few days at a machine shop.

In the mean time, I've started the G up a few times, but have been noticing an issue: despite it being over 90 degrees outside, my 5-cyl has had issue starting up. I've tried with and without the manual glow plugs warming up (original owner was a DIY guy who used some weird fixes). Starter motor works fine; battery is new; have a rebuild alternator in; filled up the tank with diesel 2 (horray California), but it now takes me a few tries to get her to start up.

I'm not leaking any fuel anywhere, and my vacuum lines are all intact.

Any ideas?

VolvoC303
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Re: 300GD Engine Troubleshooting

Post#2 » Mon Sep 03, 2012 11:44 pm

You need to eliminate the glow plug issues first. They need to be taken out and tested/inspected. It's easy to do and not expensive to fix if needed. Though you may have answered your own question with the "do it yourself" news. I wouldn't trust that wiring in the least. I'd set it up like it's suppose to be, if not it will never be right. If after all of that is done and it still has issues, look into doing a compression test.

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jonathan joseph
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Re: 300GD Engine Troubleshooting

Post#3 » Tue Sep 04, 2012 5:27 am

Definitely check out the glow plugs, get them returned to original or better wiring. They are essential. Even in higher temps.
Start there as it's a known deficiency. Also make sure your fuel filters are clean. If that doesn't do it we can move further but take care of those things first.

Jonathan

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ontum
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Re: 300GD Engine Troubleshooting

Post#4 » Tue Sep 04, 2012 6:36 am

To get a good quick idea of your glow plugs, simple unplug them from the relay. Now that your glow plugs are dicconected from your relay you can test the continuity by placing a test light on a positive terminal and the other pointy end into the wiring harness for each plug or the end sticking the glow plug. The idea is that a functional glow plug will be grounded through the threaded end of it. All glow plugs are is a big resistor that gets hot but doesn't burn up. There shouldn't be a need to remove them unless they lose their continuity.

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Craig
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Re: 300GD Engine Troubleshooting

Post#5 » Tue Sep 04, 2012 2:10 pm

Thanks for all the info guys.

The original owner of my G made the glow plugs manual by flipping a switch on the dash... I haven't even begun to sort out how they're connected, so I'll look into this shortly.

VolvoC303
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Re: 300GD Engine Troubleshooting

Post#6 » Tue Sep 04, 2012 2:48 pm

I think you should take them out because the engine is a complete unknown. It could have massive build-up and plugs can be in poor shape but still show "ok" when simple testing. It's just such a critical thing that is worth the time and trouble, in my opinion!

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vadimivanovich
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Re: 300GD Engine Troubleshooting

Post#7 » Fri Sep 07, 2012 9:59 pm

Unplug the big plug from glow plug relay & use an ohm-meter to read the resistance between each pin and ground. Plugs should all ohm-out under 10 ohms, otherwise they're bad. There are millions of other reasons for starting and/or running trouble. Can you describe the symptoms and conditions when they occur? Have you checked for a leaking fuel primer pump? Any leaky/restricted hoses? How about new fuel filters (all 3)? When were your fuel injectors last changed (I recommend Monarks)? When was your last valve adjustment & injection pump re-timing? Do you know how much timing chain stretch you have? Check that using the 2mm valve lift method (google it), and adjust using an offset woodruff key or new timing chain. A compression check would be wise too. Shall I continue???

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bratwurst
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Re: 300GD Engine Troubleshooting

Post#8 » Sat Sep 08, 2012 10:26 am

Ya definitely check glow plugs first.

The manual override done by the PO is a bit of a clue- the glow plug relay was possibly dead and they saw this as a cheap/quick fix. I would go to the wrecker, pull a relay from a 300d which should only cost a couple of bucks, and try to get things closer to stock. I would guess the glowplugs would burn out if left on accidentally which might be your problem.

The second thing is the valve adjustment. You need to make a couple of wrenches with a bend in them (or buy a set if you really want to spend the $$$). The first valve adjustment you do is a PITA. The second is a lot easier. The third is a breeze...

The good news is that most starting problems are cheap to solve. The only one that isn't is a plain old worn out motor- which is really rare. Mine for example has about 510,000 km and will start within 5 seconds of cranking with no glow plugs. With gp's working normally, it fires up in less than a full crank.

Cheers,

Michael

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Re: 300GD Engine Troubleshooting

Post#9 » Sat Sep 08, 2012 6:40 pm

vadimivanovich wrote:Can you describe the symptoms and conditions when they occur? Have you checked for a leaking fuel primer pump? Any leaky/restricted hoses? How about new fuel filters (all 3)? When were your fuel injectors last changed (I recommend Monarks)? When was your last valve adjustment & injection pump re-timing? Do you know how much timing chain stretch you have? Check that using the 2mm valve lift method (google it), and adjust using an offset woodruff key or new timing chain. A compression check would be wise too. Shall I continue???


I'm new to diesels, so there has been a lot of searching so far.

As for symptoms, it takes a good deal of cranking time (when activating the glow plug switch and not) when cold, sometimes two or three times turning the key, including a quick push to the pedal. It'll start up just fine when warm (as in was used in the previous couple hours).

No leaks anywhere along the fuel lines, and the vacuum lines are all intact. I'm unsure of when all the fuel filters were replaced last (as I just bought this a couple weeks ago) but I'm not seeing any sediment in the secondary filter (the clear one).

I have no clue about the last time the injectors were changed, or the last valve adjustment, but based on previous ownership, these were done in the last year or so.

Timing chain may be an issue... I hear a noise coming from the front of the engine that sounds suspicious... but starting right up when the engine is warm leads me to believe it's fine.

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Re: 300GD Engine Troubleshooting

Post#10 » Sat Sep 08, 2012 6:42 pm

bratwurst wrote:The manual override done by the PO is a bit of a clue- the glow plug relay was possibly dead and they saw this as a cheap/quick fix. I would go to the wrecker, pull a relay from a 300d which should only cost a couple of bucks, and try to get things closer to stock. I would guess the glowplugs would burn out if left on accidentally which might be your problem.

The second thing is the valve adjustment. You need to make a couple of wrenches with a bend in them (or buy a set if you really want to spend the $$$). The first valve adjustment you do is a PITA. The second is a lot easier. The third is a breeze...

The good news is that most starting problems are cheap to solve. The only one that isn't is a plain old worn out motor- which is really rare. Mine for example has about 510,000 km and will start within 5 seconds of cranking with no glow plugs. With gp's working normally, it fires up in less than a full crank.


The previous owner included the Valve Adjustment tool in the sale, so I'll have to go through the manuals for all the specs, but it does seem like the manual glow plug override (like much else in the truck) was a shoddy DIY fix by the original owner. I'm finding lots of little bits that don't belong.

I'll start checking around with some junkyards here in SoCal for 300D setups. I'll learn a lot by seeing how it's supposed to look in the engine bay.

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