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AMC 360 cranks slow when hot |
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jeep9393guy 
AMC Fan 
Joined: Jul/08/2018 Location: Mansfirld PA Status: Offline Points: 15 |
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 Topic: AMC 360 cranks slow when hotPosted: Jul/08/2018 at 12:06pm |
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I have a 1984 jeep j20 with a 306 v-8 . Timing is set a 10 BTDC ,starts great when cold . When it get hot you shut it down , if you immediately got to restart it it cranks fine but wait 10 seconds it will crank real hard and slow and will not start . If you remove the coil wire it will crank fine. Retard the timing to 0 it will crank fine and start hot . Starter has been replaced with a new one , Distributor has been replaced with a new one .Same issue . The plugs are black like its running rich . The guy I got it from did some work to it .A lot of things he did I had to correct . Now he put a timing chain and gears on it , which has me wondering if he got the timing on the gears a tooth off . Thoughts ? Thanks Frank
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billd
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Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Posted: Jul/08/2018 at 12:38pm |
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It sounds as if the timing at 10 is just too much. What's the spec for that engine? Too much timing sounds cool, but can be destructive, COUNTER-PRODUCTIVE, and make 'em hard to crank.
You sort of proved there's a push-back issue with your remove the coil wire test. If it was just a bad starter it wouldn't make much difference, some but not much. Is ten degrees the spec or is that just what someone said you should do? Be aware that "one size fits all" is BS in timing - each engine size and configuration will be happier with its own timing setting. Book spec is often fine or close enough, but can be tweaked, depending on what else has been done. Be more concerned with TOTAL timing and not so much base timing, again, depending on the engine. MAYBE 10 degrees is a bit much for your engine for initial timing. Now to other ideas - rich causes oil to we washed from the cylinder walls. You don't mention the engine's operating temperature. You don't mention the oil you are running. And when you say "new starter" - do you really mean parts store remanufactured?
Same for distributor - new? Or parts store reman, and was the timing curve on that distributor checked by a pro? Timing chain should have pretty much no impact on cranking speed. If it's a tooth off it's VALVE timing, not ignition timing, that will be impacted. (and if it starts and runs fine, I doubt the timing chain is "off a tooth". Not impossible, but still, it won't impact ignition timing. |
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jeep9393guy
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Joined: Jul/08/2018 Location: Mansfirld PA Status: Offline Points: 15 |
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Posted: Jul/08/2018 at 12:58pm |
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!0 BTDC is factory spec.With vacuum hose to the distributor disconnected. Engine temp 180 . 10/30 oil shell . Starter brand new . distributor brand new . When its first started and set on 10 btdc I have good engine vacuum 19 ins . When it retarded to 0 vacuum falls to 16 in vacuum. Vacuum reading is steady .
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304-dude
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Joined: Sep/29/2008 Location: Central Illinoi Status: Online Points: 9082 |
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Posted: Jul/08/2018 at 1:24pm |
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Heat will make more current demands on electronics. The hotter the more current. Some electronics can go into thermal runaway and shut down or fail. The starter can consume more current than the factory cables can provide if not proper in connection.
Check and clean the cable ends to the starter, as it is very long and it's connections need a good contact, and check and clean the ground cable end to the engine head. Simple checks and maintenance can keep odd issues from happening. |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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billd
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Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Posted: Jul/08/2018 at 1:37pm |
EXCELLENT information - and with that vacuum reading, it's unlikely there's a problem with timing chain or your ignition timing. That was VERY helpful. Do you have a way to check the starter DRAW on that engine??
That would be my next step if it was in my shop. I would feel for hot connections at the battery, and check for ENGINE to chassis GROUND strap - it must have one. Check all connections at the battery (not looking, but removing and cleaning if you have not already, maybe you have....) and check that the cables are sufficient for the engine. Cheap replacements are often smaller and not always made well. Voltage drop across a bad connection can cause a spike in amperage draw. |
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401MATCOUPE
AMC Addicted
Joined: May/20/2010 Location: Salisbury, MD Status: Offline Points: 5368 |
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Posted: Jul/08/2018 at 2:15pm |
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If you live near an Autozone or Advance they will bench test the starter for free......I can tell you that most rebuild starters from chain stores are VERY POOR quality......every time I have had a slow crank after heat soak problem, it has been the starter.........
One thing I have found more of an issue these days is the cables look great, but when you bend or twist them they sound "crunchy".....unbelievable internal corrosion.....the cables took not swelled or anything wrong but after I cut them open it was really bad. I think part of that is Chinese Copper used in the Chain Store cables.......just more junk...... Don't rule out the starter, even if you replaced it once, I have gone through 4 in a row from Autozone for a neighbor's Ford (same basic unit as AMC used)...the last one the Bendix drive just shattered and took chunk out of the flexplate.....I was not happy about that. No good deed goes unpunished sometimes!
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Ross K. Peterson
68X,GoPac,343,AT,52A(1stCar) 68X,GoPac,390,4sp,52A 69X,GoPac,390,4sp,64A 70X,GoPac,390,4sp,87A,8 70X,GoPac,390,4sp,BBO,8 70 Jav SST,390,AT,BSO 74MatX,401,AT,Prototype 74MatX,401,AT |
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billd
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Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Posted: Jul/08/2018 at 3:35pm |
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Yup. Ross has some thoughts there. I sill bet the starter is NOT new. It's remanufactured. I would bet on it.
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one bad rambler
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Joined: Jan/09/2008 Location: On The Island Status: Offline Points: 2007 |
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Posted: Jul/08/2018 at 8:35pm |
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Is the balancer correct??? I run 14 deg on one engine and 16 on another no issues...
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 68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8
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billd
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Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Posted: Jul/08/2018 at 9:55pm |
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Every engine is different so it's not possible to compare what one runs vs. another engine, different build, different gas, different elevations, many factors, etc. Those settings may be fine for your engine, but I have a couple that would self-destruct with those initial timing numbers, or i'd never get them started - at the very least, I'd LOSE horsepower going that far. My 360 is ok with 10 but any more and it balks and isn't as strong. My 390 I don't dare go that high initial - but it's got good timing total at speed.
Anyway, it does actually sound like a starter issue since his vacuum seems to match timing that's pretty close at least. You don't go into a parts store and buy a "new" starter these days. (unless it's for a 4.0 and then you could as of a year or so ago buy BRAND NEW, not reman, starters but that's another topic) It's likely a remanufactured starter - and like the fellow who had to go to a third or fourth alternator to get his issues resolved, just because it's from a parts store and guaranteed doesn't mean it's good. I could show some of the alternators and starters I have on my shelves that are "reman" and some were only on the car for days, weeks at the most - and it's scary what I see inside 'em, or even outside of them.
This is but one reason I do electric parts myself and refuse to rely on parts store reman stuff when I can totally avoid it. |
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Boris Badanov
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Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4209 |
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Posted: Jul/09/2018 at 5:32am |
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Hot starter and or bad cables.
Try it near a garden hose. Hose down the starter and try it again. Hint it takes a few seconds for the cooling water to have an effect. |
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Gremlin Dreams
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jeep9393guy wrote: