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Unread 04-25-2013, 02:23 PM   #1
CliffordsJeep
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1987 FSJ Wagoneer 
 
Join Date: Mar 2013
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AMC 360 Dieseling

Hi Guys,
My 87 GW with the amc 360 is dieseling when I turn off the engine. Last month I rebuilt the carb (motocraft 2150) and set the timing to the specs suggested in my chilton's manual. The dieseling started shortly (not immediately) after I worked on those things. Could improper adjustments have led to this problem? For what its worth when the engine is cold it shuts down nice and smooth, just like it should. From what I have been able to find online, that is typical of an engine that diesels. A friend recommended removing the air cleaner and dribbling just a tiny bit of water into the carb to help remove the carbon build up on the heads. That just strikes me as a bad idea and am curious what your thoughts are on it. He also said that a high speed long distance drive may take care of it. Anyway, has anyone here experienced this and found a solution? Thanks guys!

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Unread 04-26-2013, 07:32 AM   #2
muddy93
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1987 FSJ Wagoneer 
 
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Location: Templeton, Indiana
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Just a little info.

The 87's (among other years) had an "anti diesel solenoid". The solenoid is supposed to extend when the key was turned on, and open the throttle to the idle position. Then it was supposed to retract when the key is turned off, and allow the throttle blades to fully close, which basically chokes the engine. And, according to the book, idle speed adjustmens are made by moving the solenoid.

The thing is, you don't really need the solinoid. When I rebuilt the carb on my 87 (a little over a year ago), I removed the anti diesel solenoid and it's been running great ever since.

I'd go through it again and check all of the adjustments, mixture, idle speed, timing, etc...... Just to make sure that everything has stayed where it's supposed to be.

Your friend is correct. It's common for dirty engines with a lot of carbon buildup to have "hot spots". These hot spots can cause the air/fuel mixture to ignite even though the ignition is off, which is what dieseling is. The "little bit of water down the carb" trick does work, It's the DIY version of seafoam. Basically the water hits the hot intake, flashes to steam, and steam cleanes the cylinders. It brakes up any carbon deposits, and they simply blow out the exhaust.
Just use extreme caution, pour the water to fast and you could hydrolock the engine.
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Unread 04-26-2013, 07:55 AM   #3
CliffordsJeep
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Thanks Muddy93.

I have a couple cans of seafoam sitting on the shelf, I may go ahead and run that through. Should I add it to the crankcase or the fuel? This was the first time I have ever set the timing in a vehicle, and was the firs time I have ever worked on a carburetor, so i will go back and double check my settings and look into the anti-dieseling solenoid. Thanks!
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Unread 04-26-2013, 08:45 AM   #4
CSP
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If you're going to use an additive to clean the cylinders, spend the $30 on a can of BG 44K. It's by far the best fuel system cleaner out there.

Does the engine ping at all when it's under a load like going up a hill? If so, your timing is too far advanced. Back it off two degrees at a time until the pining stops, if applicable.
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Unread 04-26-2013, 11:00 AM   #5
CliffordsJeep
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Quote:
Originally Posted by CSP
If you're going to use an additive to clean the cylinders, spend the $30 on a can of BG 44K. It's by far the best fuel system cleaner out there.

Does the engine ping at all when it's under a load like going up a hill? If so, your timing is too far advanced. Back it off two degrees at a time until the pining stops, if applicable.
Yes, I did notice just a very slight ping that I had not noticed before. It was running pretty poorly before and sounds much better now, but there is a ping. I will play with the timing and see if that makes a difference. It just occurred to me that I may want to rethink using the specs in the chiltons manual. I have after market ignition (jacobs and an ultra coil) and that may impact where I should have the timing/idle set. I will dig around and see what other guys have been doing that may have similar set ups.
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Unread 04-26-2013, 12:59 PM   #6
CSP
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Altitude also plays a part in timing as well as engine condition. Start at a spec listed and adjust as necessary. Vacuum is also a good way to set timing.
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Unread 05-20-2013, 09:23 AM   #7
CliffordsJeep
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Well, I finally had time to tinker with the Jeep this past weekend. I should note up front, this was my first ever attempt at adjusting the timing of a vehicle on my own. I started by marking the shaft of the distributor with some red nail polish, compliments of the wife. I then started the vehicle, used the timing light to see where the timing mark was. I knew I would need to retard the timing, so I killed the engine, backed off the timing and re-checked with the timing light. This went on for about 5 for 6 tries, before it sounded good to my ears. I drove to town on three occasions to see if I had made an impact with the dieseling. The first two times were both frustrating trips, as the engine kept cutting out and dying when it would idle in park. The first trip it even backfired a few times too. Finally, on the third trip the everything seems to be correct. Idle in both park and in drive sounds good, and the dieseling seems to have disappeared! This whole experience helped me understand the sound of my engine better. I would like to know one thing, is it safe to adjust the distributor while the engine is running? It sure seems like that would have sped things up, but I didn't want to take a chance of making things worse. Thanks for all the input guys!
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Unread 05-20-2013, 09:50 AM   #8
CSP
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It's absolutely safe to adjust it while it's running. The first thing that came to mind when you mentioned shutting it off is this guy is doing it the hard way.

Leave the clamp just tight enough that it won't move on it's own while you're making adjustments.
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Unread 05-20-2013, 11:12 AM   #9
muddy93
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I'd pull the vacuum line off of the power valve and check it for fuel. More often than not, a backfire will blow out the diaphram in the power valve. Seeing that you had multiple backfires, it wouldn't hurt to check it out. If there is fuel in the vacuum line, the power valve has ruptured.
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